1	accept_memory=  [MM]
2			Format: { eager | lazy }
3			default: lazy
4			By default, unaccepted memory is accepted lazily to
5			avoid prolonged boot times. The lazy option will add
6			some runtime overhead until all memory is eventually
7			accepted. In most cases the overhead is negligible.
8			For some workloads or for debugging purposes
9			accept_memory=eager can be used to accept all memory
10			at once during boot.
11
12	acpi=		[HW,ACPI,X86,ARM64,RISCV64,EARLY]
13			Advanced Configuration and Power Interface
14			Format: { force | on | off | strict | noirq | rsdt |
15				  copy_dsdt | nospcr }
16			force -- enable ACPI if default was off
17			on -- enable ACPI but allow fallback to DT [arm64,riscv64]
18			off -- disable ACPI if default was on
19			noirq -- do not use ACPI for IRQ routing
20			strict -- Be less tolerant of platforms that are not
21				strictly ACPI specification compliant.
22			rsdt -- prefer RSDT over (default) XSDT
23			copy_dsdt -- copy DSDT to memory
24			nocmcff -- Disable firmware first mode for corrected
25			errors. This disables parsing the HEST CMC error
26			source to check if firmware has set the FF flag. This
27			may result in duplicate corrected error reports.
28			nospcr -- disable console in ACPI SPCR table as
29				default _serial_ console on ARM64
30			For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
31			"acpi=nospcr" are available
32			For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force"
33			are available
34
35			See also Documentation/power/runtime_pm.rst, pci=noacpi
36
37	acpi_apic_instance=	[ACPI,IOAPIC,EARLY]
38			Format: <int>
39			2: use 2nd APIC table, if available
40			1,0: use 1st APIC table
41			default: 0
42
43	acpi_backlight=	[HW,ACPI]
44			{ vendor | video | native | none }
45			If set to vendor, prefer vendor-specific driver
46			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
47			of the ACPI video.ko driver.
48			If set to video, use the ACPI video.ko driver.
49			If set to native, use the device's native backlight mode.
50			If set to none, disable the ACPI backlight interface.
51
52	acpi_force_32bit_fadt_addr [ACPI,EARLY]
53			force FADT to use 32 bit addresses rather than the
54			64 bit X_* addresses. Some firmware have broken 64
55			bit addresses for force ACPI ignore these and use
56			the older legacy 32 bit addresses.
57
58	acpica_no_return_repair [HW, ACPI]
59			Disable AML predefined validation mechanism
60			This mechanism can repair the evaluation result to make
61			the return objects more ACPI specification compliant.
62			This option is useful for developers to identify the
63			root cause of an AML interpreter issue when the issue
64			has something to do with the repair mechanism.
65
66	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
67	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
68			Format: <int>
69			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
70			debug output.  Bits in debug_layer correspond to a
71			_COMPONENT in an ACPI source file, e.g.,
72			    #define _COMPONENT ACPI_EVENTS
73			Bits in debug_level correspond to a level in
74			ACPI_DEBUG_PRINT statements, e.g.,
75			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
76			The debug_level mask defaults to "info".  See
77			Documentation/firmware-guide/acpi/debug.rst for more information about
78			debug layers and levels.
79
80			Enable processor driver info messages:
81			    acpi.debug_layer=0x20000000
82			Enable AML "Debug" output, i.e., stores to the Debug
83			object while interpreting AML:
84			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
85			Enable all messages related to ACPI hardware:
86			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
87
88			Some values produce so much output that the system is
89			unusable.  The "log_buf_len" parameter may be useful
90			if you need to capture more output.
91
92	acpi_enforce_resources=	[ACPI]
93			{ strict | lax | no }
94			Check for resource conflicts between native drivers
95			and ACPI OperationRegions (SystemIO and SystemMemory
96			only). IO ports and memory declared in ACPI might be
97			used by the ACPI subsystem in arbitrary AML code and
98			can interfere with legacy drivers.
99			strict (default): access to resources claimed by ACPI
100			is denied; legacy drivers trying to access reserved
101			resources will fail to bind to device using them.
102			lax: access to resources claimed by ACPI is allowed;
103			legacy drivers trying to access reserved resources
104			will bind successfully but a warning message is logged.
105			no: ACPI OperationRegions are not marked as reserved,
106			no further checks are performed.
107
108	acpi_force_table_verification	[HW,ACPI,EARLY]
109			Enable table checksum verification during early stage.
110			By default, this is disabled due to x86 early mapping
111			size limitation.
112
113	acpi_irq_balance [HW,ACPI]
114			ACPI will balance active IRQs
115			default in APIC mode
116
117	acpi_irq_nobalance [HW,ACPI]
118			ACPI will not move active IRQs (default)
119			default in PIC mode
120
121	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
122			Format: <irq>,<irq>...
123
124	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
125			use by PCI
126			Format: <irq>,<irq>...
127
128	acpi_mask_gpe=	[HW,ACPI]
129			Due to the existence of _Lxx/_Exx, some GPEs triggered
130			by unsupported hardware/firmware features can result in
131			GPE floodings that cannot be automatically disabled by
132			the GPE dispatcher.
133			This facility can be used to prevent such uncontrolled
134			GPE floodings.
135			Format: <byte> or <bitmap-list>
136
137	acpi_no_auto_serialize	[HW,ACPI]
138			Disable auto-serialization of AML methods
139			AML control methods that contain the opcodes to create
140			named objects will be marked as "Serialized" by the
141			auto-serialization feature.
142			This feature is enabled by default.
143			This option allows to turn off the feature.
144
145	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
146			   kernels.
147
148	acpi_no_static_ssdt	[HW,ACPI,EARLY]
149			Disable installation of static SSDTs at early boot time
150			By default, SSDTs contained in the RSDT/XSDT will be
151			installed automatically and they will appear under
152			/sys/firmware/acpi/tables.
153			This option turns off this feature.
154			Note that specifying this option does not affect
155			dynamic table installation which will install SSDT
156			tables to /sys/firmware/acpi/tables/dynamic.
157
158	acpi_no_watchdog	[HW,ACPI,WDT]
159			Ignore the ACPI-based watchdog interface (WDAT) and let
160			a native driver control the watchdog device instead.
161
162	acpi_rsdp=	[ACPI,EFI,KEXEC,EARLY]
163			Pass the RSDP address to the kernel, mostly used
164			on machines running EFI runtime service to boot the
165			second kernel for kdump.
166
167	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
168			Format: To spoof as Windows 98: ="Microsoft Windows"
169
170	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
171			of 2 which is mandated by ACPI 6) as the supported ACPI
172			specification revision (when using this switch, it may
173			be necessary to carry out a cold reboot _twice_ in a
174			row to make it take effect on the platform firmware).
175
176	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
177			acpi_osi="string1"	# add string1
178			acpi_osi="!string2"	# remove string2
179			acpi_osi=!*		# remove all strings
180			acpi_osi=!		# disable all built-in OS vendor
181						  strings
182			acpi_osi=!!		# enable all built-in OS vendor
183						  strings
184			acpi_osi=		# disable all strings
185
186			'acpi_osi=!' can be used in combination with single or
187			multiple 'acpi_osi="string1"' to support specific OS
188			vendor string(s).  Note that such command can only
189			affect the default state of the OS vendor strings, thus
190			it cannot affect the default state of the feature group
191			strings and the current state of the OS vendor strings,
192			specifying it multiple times through kernel command line
193			is meaningless.  This command is useful when one do not
194			care about the state of the feature group strings which
195			should be controlled by the OSPM.
196			Examples:
197			  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
198			     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
199			     can make '_OSI("Windows 2000")' TRUE.
200
201			'acpi_osi=' cannot be used in combination with other
202			'acpi_osi=' command lines, the _OSI method will not
203			exist in the ACPI namespace.  NOTE that such command can
204			only affect the _OSI support state, thus specifying it
205			multiple times through kernel command line is also
206			meaningless.
207			Examples:
208			  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
209			     FALSE.
210
211			'acpi_osi=!*' can be used in combination with single or
212			multiple 'acpi_osi="string1"' to support specific
213			string(s).  Note that such command can affect the
214			current state of both the OS vendor strings and the
215			feature group strings, thus specifying it multiple times
216			through kernel command line is meaningful.  But it may
217			still not able to affect the final state of a string if
218			there are quirks related to this string.  This command
219			is useful when one want to control the state of the
220			feature group strings to debug BIOS issues related to
221			the OSPM features.
222			Examples:
223			  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
224			     '_OSI("Module Device")' FALSE.
225			  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
226			     '_OSI("Module Device")' TRUE.
227			  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
228			     equivalent to
229			     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
230			     and
231			     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
232			     they all will make '_OSI("Windows 2000")' TRUE.
233
234	acpi_pm_good	[X86]
235			Override the pmtimer bug detection: force the kernel
236			to assume that this machine's pmtimer latches its value
237			and always returns good values.
238
239	acpi_sci=	[HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode
240			Format: { level | edge | high | low }
241
242	acpi_skip_timer_override [HW,ACPI,EARLY]
243			Recognize and ignore IRQ0/pin2 Interrupt Override.
244			For broken nForce2 BIOS resulting in XT-PIC timer.
245
246	acpi_sleep=	[HW,ACPI] Sleep options
247			Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
248				  s4_nohwsig, old_ordering, nonvs,
249				  sci_force_enable, nobl }
250			See Documentation/power/video.rst for information on
251			s3_bios and s3_mode.
252			s3_beep is for debugging; it makes the PC's speaker beep
253			as soon as the kernel's real-mode entry point is called.
254			s4_hwsig causes the kernel to check the ACPI hardware
255			signature during resume from hibernation, and gracefully
256			refuse to resume if it has changed. This complies with
257			the ACPI specification but not with reality, since
258			Windows does not do this and many laptops do change it
259			on docking. So the default behaviour is to allow resume
260			and simply warn when the signature changes, unless the
261			s4_hwsig option is enabled.
262			s4_nohwsig prevents ACPI hardware signature from being
263			used (or even warned about) during resume.
264			old_ordering causes the ACPI 1.0 ordering of the _PTS
265			control method, with respect to putting devices into
266			low power states, to be enforced (the ACPI 2.0 ordering
267			of _PTS is used by default).
268			nonvs prevents the kernel from saving/restoring the
269			ACPI NVS memory during suspend/hibernation and resume.
270			sci_force_enable causes the kernel to set SCI_EN directly
271			on resume from S1/S3 (which is against the ACPI spec,
272			but some broken systems don't work without it).
273			nobl causes the internal blacklist of systems known to
274			behave incorrectly in some ways with respect to system
275			suspend and resume to be ignored (use wisely).
276
277	acpi_use_timer_override [HW,ACPI,EARLY]
278			Use timer override. For some broken Nvidia NF5 boards
279			that require a timer override, but don't have HPET
280
281	add_efi_memmap	[EFI,X86,EARLY] Include EFI memory map in
282			kernel's map of available physical RAM.
283
284	agp=		[AGP]
285			{ off | try_unsupported }
286			off: disable AGP support
287			try_unsupported: try to drive unsupported chipsets
288				(may crash computer or cause data corruption)
289
290	ALSA		[HW,ALSA]
291			See Documentation/sound/alsa-configuration.rst
292
293	alignment=	[KNL,ARM]
294			Allow the default userspace alignment fault handler
295			behaviour to be specified.  Bit 0 enables warnings,
296			bit 1 enables fixups, and bit 2 sends a segfault.
297
298	align_va_addr=	[X86-64]
299			Align virtual addresses by clearing slice [14:12] when
300			allocating a VMA at process creation time. This option
301			gives you up to 3% performance improvement on AMD F15h
302			machines (where it is enabled by default) for a
303			CPU-intensive style benchmark, and it can vary highly in
304			a microbenchmark depending on workload and compiler.
305
306			32: only for 32-bit processes
307			64: only for 64-bit processes
308			on: enable for both 32- and 64-bit processes
309			off: disable for both 32- and 64-bit processes
310
311	alloc_snapshot	[FTRACE]
312			Allocate the ftrace snapshot buffer on boot up when the
313			main buffer is allocated. This is handy if debugging
314			and you need to use tracing_snapshot() on boot up, and
315			do not want to use tracing_snapshot_alloc() as it needs
316			to be done where GFP_KERNEL allocations are allowed.
317
318	allow_mismatched_32bit_el0 [ARM64,EARLY]
319			Allow execve() of 32-bit applications and setting of the
320			PER_LINUX32 personality on systems where only a strict
321			subset of the CPUs support 32-bit EL0. When this
322			parameter is present, the set of CPUs supporting 32-bit
323			EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
324			and hot-unplug operations may be restricted.
325
326			See Documentation/arch/arm64/asymmetric-32bit.rst for more
327			information.
328
329	amd_iommu=	[HW,X86-64]
330			Pass parameters to the AMD IOMMU driver in the system.
331			Possible values are:
332			fullflush - Deprecated, equivalent to iommu.strict=1
333			off	  - do not initialize any AMD IOMMU found in
334				    the system
335			force_isolation - Force device isolation for all
336					  devices. The IOMMU driver is not
337					  allowed anymore to lift isolation
338					  requirements as needed. This option
339					  does not override iommu=pt
340			force_enable    - Force enable the IOMMU on platforms known
341				          to be buggy with IOMMU enabled. Use this
342				          option with care.
343			pgtbl_v1        - Use v1 page table for DMA-API (Default).
344			pgtbl_v2        - Use v2 page table for DMA-API.
345			irtcachedis     - Disable Interrupt Remapping Table (IRT) caching.
346			nohugepages     - Limit page-sizes used for v1 page-tables
347				          to 4 KiB.
348			v2_pgsizes_only - Limit page-sizes used for v1 page-tables
349				          to 4KiB/2Mib/1GiB.
350
351
352	amd_iommu_dump=	[HW,X86-64]
353			Enable AMD IOMMU driver option to dump the ACPI table
354			for AMD IOMMU. With this option enabled, AMD IOMMU
355			driver will print ACPI tables for AMD IOMMU during
356			IOMMU initialization.
357
358	amd_iommu_intr=	[HW,X86-64]
359			Specifies one of the following AMD IOMMU interrupt
360			remapping modes:
361			legacy     - Use legacy interrupt remapping mode.
362			vapic      - Use virtual APIC mode, which allows IOMMU
363			             to inject interrupts directly into guest.
364			             This mode requires kvm-amd.avic=1.
365			             (Default when IOMMU HW support is present.)
366
367	amd_pstate=	[X86,EARLY]
368			disable
369			  Do not enable amd_pstate as the default
370			  scaling driver for the supported processors
371			passive
372			  Use amd_pstate with passive mode as a scaling driver.
373			  In this mode autonomous selection is disabled.
374			  Driver requests a desired performance level and platform
375			  tries to match the same performance level if it is
376			  satisfied by guaranteed performance level.
377			active
378			  Use amd_pstate_epp driver instance as the scaling driver,
379			  driver provides a hint to the hardware if software wants
380			  to bias toward performance (0x0) or energy efficiency (0xff)
381			  to the CPPC firmware. then CPPC power algorithm will
382			  calculate the runtime workload and adjust the realtime cores
383			  frequency.
384			guided
385			  Activate guided autonomous mode. Driver requests minimum and
386			  maximum performance level and the platform autonomously
387			  selects a performance level in this range and appropriate
388			  to the current workload.
389
390	amd_prefcore=
391			[X86]
392			disable
393			  Disable amd-pstate preferred core.
394
395	amijoy.map=	[HW,JOY] Amiga joystick support
396			Map of devices attached to JOY0DAT and JOY1DAT
397			Format: <a>,<b>
398			See also Documentation/input/joydev/joystick.rst
399
400	analog.map=	[HW,JOY] Analog joystick and gamepad support
401			Specifies type or capabilities of an analog joystick
402			connected to one of 16 gameports
403			Format: <type1>,<type2>,..<type16>
404
405	apc=		[HW,SPARC]
406			Power management functions (SPARCstation-4/5 + deriv.)
407			Format: noidle
408			Disable APC CPU standby support. SPARCstation-Fox does
409			not play well with APC CPU idle - disable it if you have
410			APC and your system crashes randomly.
411
412	apic		[APIC,X86-64] Use IO-APIC. Default.
413
414	apic=		[APIC,X86,EARLY] Advanced Programmable Interrupt Controller
415			Change the output verbosity while booting
416			Format: { quiet (default) | verbose | debug }
417			Change the amount of debugging information output
418			when initialising the APIC and IO-APIC components.
419
420	apic_extnmi=	[APIC,X86,EARLY] External NMI delivery setting
421			Format: { bsp (default) | all | none }
422			bsp:  External NMI is delivered only to CPU 0
423			all:  External NMIs are broadcast to all CPUs as a
424			      backup of CPU 0
425			none: External NMI is masked for all CPUs. This is
426			      useful so that a dump capture kernel won't be
427			      shot down by NMI
428
429	apicpmtimer	Do APIC timer calibration using the pmtimer. Implies
430			apicmaintimer. Useful when your PIT timer is totally
431			broken.
432
433	autoconf=	[IPV6]
434			See Documentation/networking/ipv6.rst.
435
436	apm=		[APM] Advanced Power Management
437			See header of arch/x86/kernel/apm_32.c.
438
439	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
440			Format: { "0" | "1" }
441			See security/apparmor/Kconfig help text
442			0 -- disable.
443			1 -- enable.
444			Default value is set via kernel config option.
445
446	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
447			Format: <io>,<irq>,<nodeID>
448
449	arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
450			32 bit applications.
451
452	arm64.nobti	[ARM64] Unconditionally disable Branch Target
453			Identification support
454
455	arm64.nogcs	[ARM64] Unconditionally disable Guarded Control Stack
456			support
457
458	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
459			Set instructions support
460
461	arm64.nomte	[ARM64] Unconditionally disable Memory Tagging Extension
462			support
463
464	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
465			support
466
467	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
468			Extension support
469
470	arm64.nosve	[ARM64] Unconditionally disable Scalable Vector
471			Extension support
472
473	ataflop=	[HW,M68k]
474
475	atarimouse=	[HW,MOUSE] Atari Mouse
476
477	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
478			EzKey and similar keyboards
479
480	atkbd.reset=	[HW] Reset keyboard during initialization
481
482	atkbd.set=	[HW] Select keyboard code set
483			Format: <int> (2 = AT (default), 3 = PS/2)
484
485	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
486			keyboards
487
488	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
489			Format: <bool> (0 = real, 1 = synthetic (default))
490
491	atkbd.softrepeat= [HW]
492			Use software keyboard repeat
493
494	audit=		[KNL] Enable the audit sub-system
495			Format: { "0" | "1" | "off" | "on" }
496			0 | off - kernel audit is disabled and can not be
497			    enabled until the next reboot
498			unset - kernel audit is initialized but disabled and
499			    will be fully enabled by the userspace auditd.
500			1 | on - kernel audit is initialized and partially
501			    enabled, storing at most audit_backlog_limit
502			    messages in RAM until it is fully enabled by the
503			    userspace auditd.
504			Default: unset
505
506	audit_backlog_limit= [KNL] Set the audit queue size limit.
507			Format: <int> (must be >=0)
508			Default: 64
509
510	bau=		[X86_UV] Enable the BAU on SGI UV.  The default
511			behavior is to disable the BAU (i.e. bau=0).
512			Format: { "0" | "1" }
513			0 - Disable the BAU.
514			1 - Enable the BAU.
515			unset - Disable the BAU.
516
517	baycom_epp=	[HW,AX25]
518			Format: <io>,<mode>
519
520	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
521			Format: <io>,<mode>
522			See header of drivers/net/hamradio/baycom_par.c.
523
524	baycom_ser_fdx=	[HW,AX25]
525			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
526			Format: <io>,<irq>,<mode>[,<baud>]
527			See header of drivers/net/hamradio/baycom_ser_fdx.c.
528
529	baycom_ser_hdx=	[HW,AX25]
530			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
531			Format: <io>,<irq>,<mode>
532			See header of drivers/net/hamradio/baycom_ser_hdx.c.
533
534	bdev_allow_write_mounted=
535			Format: <bool>
536			Control the ability to open a mounted block device
537			for writing, i.e., allow / disallow writes that bypass
538			the FS. This was implemented as a means to prevent
539			fuzzers from crashing the kernel by overwriting the
540			metadata underneath a mounted FS without its awareness.
541			This also prevents destructive formatting of mounted
542			filesystems by naive storage tooling that don't use
543			O_EXCL. Default is Y and can be changed through the
544			Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
545
546	bert_disable	[ACPI]
547			Disable BERT OS support on buggy BIOSes.
548
549	bgrt_disable	[ACPI,X86,EARLY]
550			Disable BGRT to avoid flickering OEM logo.
551
552	blkdevparts=	Manual partition parsing of block device(s) for
553			embedded devices based on command line input.
554			See Documentation/block/cmdline-partition.rst
555
556	boot_delay=	[KNL,EARLY]
557			Milliseconds to delay each printk during boot.
558			Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
559			and you may also have to specify "lpj=".  Boot_delay
560			values larger than 10 seconds (10000) are assumed
561			erroneous and ignored.
562			Format: integer
563
564	bootconfig	[KNL,EARLY]
565			Extended command line options can be added to an initrd
566			and this will cause the kernel to look for it.
567
568			See Documentation/admin-guide/bootconfig.rst
569
570	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
571	bttv.radio=	Most important insmod options are available as
572			kernel args too.
573	bttv.pll=	See Documentation/admin-guide/media/bttv.rst
574	bttv.tuner=
575
576	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
577			firmware feature for flushing multiple hpte entries
578			at a time.
579
580	c101=		[NET] Moxa C101 synchronous serial card
581
582	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
583			Sometimes CPU hardware bugs make them report the cache
584			size incorrectly. The kernel will attempt work arounds
585			to fix known problems, but for some CPUs it is not
586			possible to determine what the correct size should be.
587			This option provides an override for these situations.
588
589	carrier_timeout=
590			[NET] Specifies amount of time (in seconds) that
591			the kernel should wait for a network carrier. By default
592			it waits 120 seconds.
593
594	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
595			the system trusted keyring to be used for certificate
596			trust validation.
597			format: { id:<keyid> | builtin }
598
599	cca=		[MIPS,EARLY] Override the kernel pages' cache coherency
600			algorithm.  Accepted values range from 0 to 7
601			inclusive. See arch/mips/include/asm/pgtable-bits.h
602			for platform specific values (SB1, Loongson3 and
603			others).
604
605	ccw_timeout_log	[S390]
606			See Documentation/arch/s390/common_io.rst for details.
607
608	cgroup_disable=	[KNL] Disable a particular controller or optional feature
609			Format: {name of the controller(s) or feature(s) to disable}
610			The effects of cgroup_disable=foo are:
611			- foo isn't auto-mounted if you mount all cgroups in
612			  a single hierarchy
613			- foo isn't visible as an individually mountable
614			  subsystem
615			- if foo is an optional feature then the feature is
616			  disabled and corresponding cgroup files are not
617			  created
618			{Currently only "memory" controller deal with this and
619			cut the overhead, others just disable the usage. So
620			only cgroup_disable=memory is actually worthy}
621			Specifying "pressure" disables per-cgroup pressure
622			stall information accounting feature
623
624	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
625			Format: { { controller | "all" | "named" }
626			          [,{ controller | "all" | "named" }...] }
627			Like cgroup_disable, but only applies to cgroup v1;
628			the blacklisted controllers remain available in cgroup2.
629			"all" blacklists all controllers and "named" disables
630			named mounts. Specifying both "all" and "named" disables
631			all v1 hierarchies.
632
633	cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
634			Format: { "true" | "false" }
635			Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
636
637	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
638			Format: <string>
639			nosocket -- Disable socket memory accounting.
640			nokmem -- Disable kernel memory accounting.
641			nobpf -- Disable BPF memory accounting.
642
643	checkreqprot=	[SELINUX] Set initial checkreqprot flag value.
644			Format: { "0" | "1" }
645			See security/selinux/Kconfig help text.
646			0 -- check protection applied by kernel (includes
647				any implied execute protection).
648			1 -- check protection requested by application.
649			Default value is set via a kernel config option.
650			Value can be changed at runtime via
651				/sys/fs/selinux/checkreqprot.
652			Setting checkreqprot to 1 is deprecated.
653
654	cio_ignore=	[S390]
655			See Documentation/arch/s390/common_io.rst for details.
656
657	clearcpuid=X[,X...] [X86]
658			Disable CPUID feature X for the kernel. See
659			arch/x86/include/asm/cpufeatures.h for the valid bit
660			numbers X. Note the Linux-specific bits are not necessarily
661			stable over kernel options, but the vendor-specific
662			ones should be.
663			X can also be a string as appearing in the flags: line
664			in /proc/cpuinfo which does not have the above
665			instability issue. However, not all features have names
666			in /proc/cpuinfo.
667			Note that using this option will taint your kernel.
668			Also note that user programs calling CPUID directly
669			or using the feature without checking anything
670			will still see it. This just prevents it from
671			being used by the kernel or shown in /proc/cpuinfo.
672			Also note the kernel might malfunction if you disable
673			some critical bits.
674
675	clk_ignore_unused
676			[CLK]
677			Prevents the clock framework from automatically gating
678			clocks that have not been explicitly enabled by a Linux
679			device driver but are enabled in hardware at reset or
680			by the bootloader/firmware. Note that this does not
681			force such clocks to be always-on nor does it reserve
682			those clocks in any way. This parameter is useful for
683			debug and development, but should not be needed on a
684			platform with proper driver support.  For more
685			information, see Documentation/driver-api/clk.rst.
686
687	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
688			[Deprecated]
689			Forces specified clocksource (if available) to be used
690			when calculating gettimeofday(). If specified
691			clocksource is not available, it defaults to PIT.
692			Format: { pit | tsc | cyclone | pmtmr }
693
694	clocksource=	Override the default clocksource
695			Format: <string>
696			Override the default clocksource and use the clocksource
697			with the name specified.
698			Some clocksource names to choose from, depending on
699			the platform:
700			[all] jiffies (this is the base, fallback clocksource)
701			[ACPI] acpi_pm
702			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
703				pxa_timer,timer3,32k_counter,timer0_1
704			[X86-32] pit,hpet,tsc;
705				scx200_hrt on Geode; cyclone on IBM x440
706			[MIPS] MIPS
707			[PARISC] cr16
708			[S390] tod
709			[SH] SuperH
710			[SPARC64] tick
711			[X86-64] hpet,tsc
712
713	clocksource.arm_arch_timer.evtstrm=
714			[ARM,ARM64,EARLY]
715			Format: <bool>
716			Enable/disable the eventstream feature of the ARM
717			architected timer so that code using WFE-based polling
718			loops can be debugged more effectively on production
719			systems.
720
721	clocksource.verify_n_cpus= [KNL]
722			Limit the number of CPUs checked for clocksources
723			marked with CLOCK_SOURCE_VERIFY_PERCPU that
724			are marked unstable due to excessive skew.
725			A negative value says to check all CPUs, while
726			zero says not to check any.  Values larger than
727			nr_cpu_ids are silently truncated to nr_cpu_ids.
728			The actual CPUs are chosen randomly, with
729			no replacement if the same CPU is chosen twice.
730
731	clocksource-wdtest.holdoff= [KNL]
732			Set the time in seconds that the clocksource
733			watchdog test waits before commencing its tests.
734			Defaults to zero when built as a module and to
735			10 seconds when built into the kernel.
736
737	cma=nn[MG]@[start[MG][-end[MG]]]
738			[KNL,CMA,EARLY]
739			Sets the size of kernel global memory area for
740			contiguous memory allocations and optionally the
741			placement constraint by the physical address range of
742			memory allocations. A value of 0 disables CMA
743			altogether. For more information, see
744			kernel/dma/contiguous.c
745
746	cma_pernuma=nn[MG]
747			[KNL,CMA,EARLY]
748			Sets the size of kernel per-numa memory area for
749			contiguous memory allocations. A value of 0 disables
750			per-numa CMA altogether. And If this option is not
751			specified, the default value is 0.
752			With per-numa CMA enabled, DMA users on node nid will
753			first try to allocate buffer from the pernuma area
754			which is located in node nid, if the allocation fails,
755			they will fallback to the global default memory area.
756
757	numa_cma=<node>:nn[MG][,<node>:nn[MG]]
758			[KNL,CMA,EARLY]
759			Sets the size of kernel numa memory area for
760			contiguous memory allocations. It will reserve CMA
761			area for the specified node.
762
763			With numa CMA enabled, DMA users on node nid will
764			first try to allocate buffer from the numa area
765			which is located in node nid, if the allocation fails,
766			they will fallback to the global default memory area.
767
768	cmo_free_hint=	[PPC] Format: { yes | no }
769			Specify whether pages are marked as being inactive
770			when they are freed.  This is used in CMO environments
771			to determine OS memory pressure for page stealing by
772			a hypervisor.
773			Default: yes
774
775	coherent_pool=nn[KMG]	[ARM,KNL,EARLY]
776			Sets the size of memory pool for coherent, atomic dma
777			allocations, by default set to 256K.
778
779	com20020=	[HW,NET] ARCnet - COM20020 chipset
780			Format:
781			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
782
783	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
784			Format: <io>[,<irq>]
785
786	com90xx=	[HW,NET]
787			ARCnet - COM90xx chipset (memory-mapped buffers)
788			Format: <io>[,<irq>[,<memstart>]]
789
790	condev=		[HW,S390] console device
791	conmode=
792
793	con3215_drop=	[S390,EARLY] 3215 console drop mode.
794			Format: y|n|Y|N|1|0
795			When set to true, drop data on the 3215 console when
796			the console buffer is full. In this case the
797			operator using a 3270 terminal emulator (for example
798			x3270) does not have to enter the clear key for the
799			console output to advance and the kernel to continue.
800			This leads to a much faster boot time when a 3270
801			terminal emulator is active. If no 3270 terminal
802			emulator is used, this parameter has no effect.
803
804	console=	[KNL] Output console device and options.
805
806		tty<n>	Use the virtual console device <n>.
807
808		ttyS<n>[,options]
809		ttyUSB0[,options]
810			Use the specified serial port.  The options are of
811			the form "bbbbpnf", where "bbbb" is the baud rate,
812			"p" is parity ("n", "o", or "e"), "n" is number of
813			bits, and "f" is flow control ("r" for RTS or
814			omit it).  Default is "9600n8".
815
816			See Documentation/admin-guide/serial-console.rst for more
817			information.  See
818			Documentation/networking/netconsole.rst for an
819			alternative.
820
821		<DEVNAME>:<n>.<n>[,options]
822			Use the specified serial port on the serial core bus.
823			The addressing uses DEVNAME of the physical serial port
824			device, followed by the serial core controller instance,
825			and the serial port instance. The options are the same
826			as documented for the ttyS addressing above.
827
828			The mapping of the serial ports to the tty instances
829			can be viewed with:
830
831			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
832			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
833
834			In the above example, the console can be addressed with
835			console=00:04:0.0. Note that a console addressed this
836			way will only get added when the related device driver
837			is ready. The use of an earlycon parameter in addition to
838			the console may be desired for console output early on.
839
840		uart[8250],io,<addr>[,options]
841		uart[8250],mmio,<addr>[,options]
842		uart[8250],mmio16,<addr>[,options]
843		uart[8250],mmio32,<addr>[,options]
844		uart[8250],0x<addr>[,options]
845			Start an early, polled-mode console on the 8250/16550
846			UART at the specified I/O port or MMIO address,
847			switching to the matching ttyS device later.
848			MMIO inter-register address stride is either 8-bit
849			(mmio), 16-bit (mmio16), or 32-bit (mmio32).
850			If none of [io|mmio|mmio16|mmio32], <addr> is assumed
851			to be equivalent to 'mmio'. 'options' are specified in
852			the same format described for ttyS above; if unspecified,
853			the h/w is not re-initialized.
854
855		hvc<n>	Use the hypervisor console device <n>. This is for
856			both Xen and PowerPC hypervisors.
857
858		{ null | "" }
859			Use to disable console output, i.e., to have kernel
860			console messages discarded.
861			This must be the only console= parameter used on the
862			kernel command line.
863
864		If the device connected to the port is not a TTY but a braille
865		device, prepend "brl," before the device type, for instance
866			console=brl,ttyS0
867		For now, only VisioBraille is supported.
868
869	console_msg_format=
870			[KNL] Change console messages format
871		default
872			By default we print messages on consoles in
873			"[time stamp] text\n" format (time stamp may not be
874			printed, depending on CONFIG_PRINTK_TIME or
875			`printk_time' param).
876		syslog
877			Switch to syslog format: "<%u>[time stamp] text\n"
878			IOW, each message will have a facility and loglevel
879			prefix. The format is similar to one used by syslog()
880			syscall, or to executing "dmesg -S --raw" or to reading
881			from /proc/kmsg.
882
883	consoleblank=	[KNL] The console blank (screen saver) timeout in
884			seconds. A value of 0 disables the blank timer.
885			Defaults to 0.
886
887	coredump_filter=
888			[KNL] Change the default value for
889			/proc/<pid>/coredump_filter.
890			See also Documentation/filesystems/proc.rst.
891
892	coresight_cpu_debug.enable
893			[ARM,ARM64]
894			Format: <bool>
895			Enable/disable the CPU sampling based debugging.
896			0: default value, disable debugging
897			1: enable debugging at boot time
898
899	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
900			Format:
901			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
902
903	cpuidle.off=1	[CPU_IDLE]
904			disable the cpuidle sub-system
905
906	cpuidle.governor=
907			[CPU_IDLE] Name of the cpuidle governor to use.
908
909	cpufreq.off=1	[CPU_FREQ]
910			disable the cpufreq sub-system
911
912	cpufreq.default_governor=
913			[CPU_FREQ] Name of the default cpufreq governor or
914			policy to use. This governor must be registered in the
915			kernel before the cpufreq driver probes.
916
917	cpu_init_udelay=N
918			[X86,EARLY] Delay for N microsec between assert and de-assert
919			of APIC INIT to start processors.  This delay occurs
920			on every CPU online, such as boot, and resume from suspend.
921			Default: 10000
922
923	cpuhp.parallel=
924			[SMP] Enable/disable parallel bringup of secondary CPUs
925			Format: <bool>
926			Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
927			the parameter has no effect.
928
929	crash_kexec_post_notifiers
930			Only jump to kdump kernel after running the panic
931			notifiers and dumping kmsg. This option increases
932			the risks of a kdump failure, since some panic
933			notifiers can make the crashed kernel more unstable.
934			In configurations where kdump may not be reliable,
935			running the panic notifiers could allow collecting
936			more data on dmesg, like stack traces from other CPUS
937			or extra data dumped by panic_print. Note that some
938			configurations enable this option unconditionally,
939			like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
940
941	crashkernel=size[KMG][@offset[KMG]]
942			[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
943			upon panic. This parameter reserves the physical
944			memory region [offset, offset + size] for that kernel
945			image. If '@offset' is omitted, then a suitable offset
946			is selected automatically.
947			[KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
948			under 4G first, and fall back to reserve region above
949			4G when '@offset' hasn't been specified.
950			See Documentation/admin-guide/kdump/kdump.rst for further details.
951
952	crashkernel=range1:size1[,range2:size2,...][@offset]
953			[KNL] Same as above, but depends on the memory
954			in the running system. The syntax of range is
955			start-[end] where start and end are both
956			a memory unit (amount[KMG]). See also
957			Documentation/admin-guide/kdump/kdump.rst for an example.
958
959	crashkernel=size[KMG],high
960			[KNL, X86-64, ARM64, RISCV, LoongArch] range could be
961			above 4G.
962			Allow kernel to allocate physical memory region from top,
963			so could be above 4G if system have more than 4G ram
964			installed. Otherwise memory region will be allocated
965			below 4G, if available.
966			It will be ignored if crashkernel=X is specified.
967	crashkernel=size[KMG],low
968			[KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
969			When crashkernel=X,high is passed, kernel could allocate
970			physical memory region above 4G, that cause second kernel
971			crash on system that require some amount of low memory,
972			e.g. swiotlb requires at least 64M+32K low memory, also
973			enough extra low memory is needed to make sure DMA buffers
974			for 32-bit devices won't run out. Kernel would try to allocate
975			default	size of memory below 4G automatically. The default
976			size is	platform dependent.
977			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
978			  --> arm64: 128MiB
979			  --> riscv: 128MiB
980			  --> loongarch: 128MiB
981			This one lets the user specify own low range under 4G
982			for second kernel instead.
983			0: to disable low allocation.
984			It will be ignored when crashkernel=X,high is not used
985			or memory reserved is below 4G.
986
987	cryptomgr.notests
988			[KNL] Disable crypto self-tests
989
990	cs89x0_dma=	[HW,NET]
991			Format: <dma>
992
993	cs89x0_media=	[HW,NET]
994			Format: { rj45 | aui | bnc }
995
996	csdlock_debug=	[KNL] Enable or disable debug add-ons of cross-CPU
997			function call handling. When switched on,
998			additional debug data is printed to the console
999			in case a hanging CPU is detected, and that
1000			CPU is pinged again in order to try to resolve
1001			the hang situation.  The default value of this
1002			option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
1003			Kconfig option.
1004
1005	dasd=		[HW,NET]
1006			See header of drivers/s390/block/dasd_devmap.c.
1007
1008	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
1009			(one device per port)
1010			Format: <port#>,<type>
1011			See also Documentation/input/devices/joystick-parport.rst
1012
1013	debug		[KNL,EARLY] Enable kernel debugging (events log level).
1014
1015	debug_boot_weak_hash
1016			[KNL,EARLY] Enable printing [hashed] pointers early in the
1017			boot sequence.  If enabled, we use a weak hash instead
1018			of siphash to hash pointers.  Use this option if you are
1019			seeing instances of '(___ptrval___)') and need to see a
1020			value (hashed pointer) instead. Cryptographically
1021			insecure, please do not use on production kernels.
1022
1023	debug_locks_verbose=
1024			[KNL] verbose locking self-tests
1025			Format: <int>
1026			Print debugging info while doing the locking API
1027			self-tests.
1028			Bitmask for the various LOCKTYPE_ tests. Defaults to 0
1029			(no extra messages), setting it to -1 (all bits set)
1030			will print _a_lot_ more information - normally only
1031			useful to lockdep developers.
1032
1033	debug_objects	[KNL,EARLY] Enable object debugging
1034
1035	debug_guardpage_minorder=
1036			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this
1037			parameter allows control of the order of pages that will
1038			be intentionally kept free (and hence protected) by the
1039			buddy allocator. Bigger value increase the probability
1040			of catching random memory corruption, but reduce the
1041			amount of memory for normal system use. The maximum
1042			possible value is MAX_PAGE_ORDER/2.  Setting this
1043			parameter to 1 or 2 should be enough to identify most
1044			random memory corruption problems caused by bugs in
1045			kernel or driver code when a CPU writes to (or reads
1046			from) a random memory location. Note that there exists
1047			a class of memory corruptions problems caused by buggy
1048			H/W or F/W or by drivers badly programming DMA
1049			(basically when memory is written at bus level and the
1050			CPU MMU is bypassed) which are not detectable by
1051			CONFIG_DEBUG_PAGEALLOC, hence this option will not
1052			help tracking down these problems.
1053
1054	debug_pagealloc=
1055			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1056			enables the feature at boot time. By default, it is
1057			disabled and the system will work mostly the same as a
1058			kernel built without CONFIG_DEBUG_PAGEALLOC.
1059			Note: to get most of debug_pagealloc error reports, it's
1060			useful to also enable the page_owner functionality.
1061			on: enable the feature
1062
1063	debugfs=    	[KNL,EARLY] This parameter enables what is exposed to
1064			userspace and debugfs internal clients.
1065			Format: { on, no-mount, off }
1066			on: 	All functions are enabled.
1067			no-mount:
1068				Filesystem is not registered but kernel clients can
1069			        access APIs and a crashkernel can be used to read
1070				its content. There is nothing to mount.
1071			off: 	Filesystem is not registered and clients
1072			        get a -EPERM as result when trying to register files
1073				or directories within debugfs.
1074				This is equivalent of the runtime functionality if
1075				debugfs was not enabled in the kernel at all.
1076			Default value is set in build-time with a kernel configuration.
1077
1078	debugpat	[X86] Enable PAT debugging
1079
1080	default_hugepagesz=
1081			[HW] The size of the default HugeTLB page. This is
1082			the size represented by the legacy /proc/ hugepages
1083			APIs.  In addition, this is the default hugetlb size
1084			used for shmget(), mmap() and mounting hugetlbfs
1085			filesystems.  If not specified, defaults to the
1086			architecture's default huge page size.  Huge page
1087			sizes are architecture dependent.  See also
1088			Documentation/admin-guide/mm/hugetlbpage.rst.
1089			Format: size[KMG]
1090
1091	deferred_probe_timeout=
1092			[KNL] Debugging option to set a timeout in seconds for
1093			deferred probe to give up waiting on dependencies to
1094			probe. Only specific dependencies (subsystems or
1095			drivers) that have opted in will be ignored. A timeout
1096			of 0 will timeout at the end of initcalls. If the time
1097			out hasn't expired, it'll be restarted by each
1098			successful driver registration. This option will also
1099			dump out devices still on the deferred probe list after
1100			retrying.
1101
1102	delayacct	[KNL] Enable per-task delay accounting
1103
1104	dell_smm_hwmon.ignore_dmi=
1105			[HW] Continue probing hardware even if DMI data
1106			indicates that the driver is running on unsupported
1107			hardware.
1108
1109	dell_smm_hwmon.force=
1110			[HW] Activate driver even if SMM BIOS signature does
1111			not match list of supported models and enable otherwise
1112			blacklisted features.
1113
1114	dell_smm_hwmon.power_status=
1115			[HW] Report power status in /proc/i8k
1116			(disabled by default).
1117
1118	dell_smm_hwmon.restricted=
1119			[HW] Allow controlling fans only if SYS_ADMIN
1120			capability is set.
1121
1122	dell_smm_hwmon.fan_mult=
1123			[HW] Factor to multiply fan speed with.
1124
1125	dell_smm_hwmon.fan_max=
1126			[HW] Maximum configurable fan speed.
1127
1128	dfltcc=		[HW,S390]
1129			Format: { on | off | def_only | inf_only | always }
1130			on:       s390 zlib hardware support for compression on
1131			          level 1 and decompression (default)
1132			off:      No s390 zlib hardware support
1133			def_only: s390 zlib hardware support for deflate
1134			          only (compression on level 1)
1135			inf_only: s390 zlib hardware support for inflate
1136			          only (decompression)
1137			always:   Same as 'on' but ignores the selected compression
1138			          level always using hardware support (used for debugging)
1139
1140	dhash_entries=	[KNL]
1141			Set number of hash buckets for dentry cache.
1142
1143	disable_1tb_segments [PPC,EARLY]
1144			Disables the use of 1TB hash page table segments. This
1145			causes the kernel to fall back to 256MB segments which
1146			can be useful when debugging issues that require an SLB
1147			miss to occur.
1148
1149	disable=	[IPV6]
1150			See Documentation/networking/ipv6.rst.
1151
1152	disable_radix	[PPC,EARLY]
1153			Disable RADIX MMU mode on POWER9
1154
1155	disable_tlbie	[PPC]
1156			Disable TLBIE instruction. Currently does not work
1157			with KVM, with HASH MMU, or with coherent accelerators.
1158
1159	disable_ddw	[PPC/PSERIES,EARLY]
1160			Disable Dynamic DMA Window support. Use this
1161			to workaround buggy firmware.
1162
1163	disable_ipv6=	[IPV6]
1164			See Documentation/networking/ipv6.rst.
1165
1166	disable_mtrr_cleanup [X86,EARLY]
1167			The kernel tries to adjust MTRR layout from continuous
1168			to discrete, to make X server driver able to add WB
1169			entry later. This parameter disables that.
1170
1171	disable_mtrr_trim [X86, Intel and AMD only,EARLY]
1172			By default the kernel will trim any uncacheable
1173			memory out of your available memory pool based on
1174			MTRR settings.  This parameter disables that behavior,
1175			possibly causing your machine to run very slowly.
1176
1177	disable_timer_pin_1 [X86,EARLY]
1178			Disable PIN 1 of APIC timer
1179			Can be useful to work around chipset bugs.
1180
1181	dis_ucode_ldr	[X86] Disable the microcode loader.
1182
1183	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
1184			this option disables the debugging code at boot.
1185
1186	dma_debug_entries=<number>
1187			This option allows to tune the number of preallocated
1188			entries for DMA-API debugging code. One entry is
1189			required per DMA-API allocation. Use this if the
1190			DMA-API debugging code disables itself because the
1191			architectural default is too low.
1192
1193	dma_debug_driver=<driver_name>
1194			With this option the DMA-API debugging driver
1195			filter feature can be enabled at boot time. Just
1196			pass the driver to filter for as the parameter.
1197			The filter can be disabled or changed to another
1198			driver later using sysfs.
1199
1200	reg_file_data_sampling=
1201			[X86] Controls mitigation for Register File Data
1202			Sampling (RFDS) vulnerability. RFDS is a CPU
1203			vulnerability which may allow userspace to infer
1204			kernel data values previously stored in floating point
1205			registers, vector registers, or integer registers.
1206			RFDS only affects Intel Atom processors.
1207
1208			on:	Turns ON the mitigation.
1209			off:	Turns OFF the mitigation.
1210
1211			This parameter overrides the compile time default set
1212			by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1213			disabled when other VERW based mitigations (like MDS)
1214			are enabled. In order to disable RFDS mitigation all
1215			VERW based mitigations need to be disabled.
1216
1217			For details see:
1218			Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1219
1220	driver_async_probe=  [KNL]
1221			List of driver names to be probed asynchronously. *
1222			matches with all driver names. If * is specified, the
1223			rest of the listed driver names are those that will NOT
1224			match the *.
1225			Format: <driver_name1>,<driver_name2>...
1226
1227	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1228			Broken monitors, graphic adapters, KVMs and EDIDless
1229			panels may send no or incorrect EDID data sets.
1230			This parameter allows to specify an EDID data sets
1231			in the /lib/firmware directory that are used instead.
1232			An EDID data set will only be used for a particular
1233			connector, if its name and a colon are prepended to
1234			the EDID name. Each connector may use a unique EDID
1235			data set by separating the files with a comma. An EDID
1236			data set with no connector name will be used for
1237			any connectors not explicitly specified.
1238
1239	dscc4.setup=	[NET]
1240
1241	dt_cpu_ftrs=	[PPC,EARLY]
1242			Format: {"off" | "known"}
1243			Control how the dt_cpu_ftrs device-tree binding is
1244			used for CPU feature discovery and setup (if it
1245			exists).
1246			off: Do not use it, fall back to legacy cpu table.
1247			known: Do not pass through unknown features to guests
1248			or userspace, only those that the kernel is aware of.
1249
1250	dump_apple_properties	[X86]
1251			Dump name and content of EFI device properties on
1252			x86 Macs.  Useful for driver authors to determine
1253			what data is available or for reverse-engineering.
1254
1255	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1256	<module>.dyndbg[="val"]
1257			Enable debug messages at boot time.  See
1258			Documentation/admin-guide/dynamic-debug-howto.rst
1259			for details.
1260
1261	early_ioremap_debug [KNL,EARLY]
1262			Enable debug messages in early_ioremap support. This
1263			is useful for tracking down temporary early mappings
1264			which are not unmapped.
1265
1266	earlycon=	[KNL,EARLY] Output early console device and options.
1267
1268			When used with no options, the early console is
1269			determined by stdout-path property in device tree's
1270			chosen node or the ACPI SPCR table if supported by
1271			the platform.
1272
1273		cdns,<addr>[,options]
1274			Start an early, polled-mode console on a Cadence
1275			(xuartps) serial port at the specified address. Only
1276			supported option is baud rate. If baud rate is not
1277			specified, the serial port must already be setup and
1278			configured.
1279
1280		uart[8250],io,<addr>[,options[,uartclk]]
1281		uart[8250],mmio,<addr>[,options[,uartclk]]
1282		uart[8250],mmio32,<addr>[,options[,uartclk]]
1283		uart[8250],mmio32be,<addr>[,options[,uartclk]]
1284		uart[8250],0x<addr>[,options]
1285			Start an early, polled-mode console on the 8250/16550
1286			UART at the specified I/O port or MMIO address.
1287			MMIO inter-register address stride is either 8-bit
1288			(mmio) or 32-bit (mmio32 or mmio32be).
1289			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1290			to be equivalent to 'mmio'. 'options' are specified
1291			in the same format described for "console=ttyS<n>"; if
1292			unspecified, the h/w is not initialized. 'uartclk' is
1293			the uart clock frequency; if unspecified, it is set
1294			to 'BASE_BAUD' * 16.
1295
1296		pl011,<addr>
1297		pl011,mmio32,<addr>
1298			Start an early, polled-mode console on a pl011 serial
1299			port at the specified address. The pl011 serial port
1300			must already be setup and configured. Options are not
1301			yet supported.  If 'mmio32' is specified, then only
1302			the driver will use only 32-bit accessors to read/write
1303			the device registers.
1304
1305		liteuart,<addr>
1306			Start an early console on a litex serial port at the
1307			specified address. The serial port must already be
1308			setup and configured. Options are not yet supported.
1309
1310		meson,<addr>
1311			Start an early, polled-mode console on a meson serial
1312			port at the specified address. The serial port must
1313			already be setup and configured. Options are not yet
1314			supported.
1315
1316		msm_serial,<addr>
1317			Start an early, polled-mode console on an msm serial
1318			port at the specified address. The serial port
1319			must already be setup and configured. Options are not
1320			yet supported.
1321
1322		msm_serial_dm,<addr>
1323			Start an early, polled-mode console on an msm serial
1324			dm port at the specified address. The serial port
1325			must already be setup and configured. Options are not
1326			yet supported.
1327
1328		owl,<addr>
1329			Start an early, polled-mode console on a serial port
1330			of an Actions Semi SoC, such as S500 or S900, at the
1331			specified address. The serial port must already be
1332			setup and configured. Options are not yet supported.
1333
1334		rda,<addr>
1335			Start an early, polled-mode console on a serial port
1336			of an RDA Micro SoC, such as RDA8810PL, at the
1337			specified address. The serial port must already be
1338			setup and configured. Options are not yet supported.
1339
1340		sbi
1341			Use RISC-V SBI (Supervisor Binary Interface) for early
1342			console.
1343
1344		smh	Use ARM semihosting calls for early console.
1345
1346		s3c2410,<addr>
1347		s3c2412,<addr>
1348		s3c2440,<addr>
1349		s3c6400,<addr>
1350		s5pv210,<addr>
1351		exynos4210,<addr>
1352			Use early console provided by serial driver available
1353			on Samsung SoCs, requires selecting proper type and
1354			a correct base address of the selected UART port. The
1355			serial port must already be setup and configured.
1356			Options are not yet supported.
1357
1358		lantiq,<addr>
1359			Start an early, polled-mode console on a lantiq serial
1360			(lqasc) port at the specified address. The serial port
1361			must already be setup and configured. Options are not
1362			yet supported.
1363
1364		lpuart,<addr>
1365		lpuart32,<addr>
1366			Use early console provided by Freescale LP UART driver
1367			found on Freescale Vybrid and QorIQ LS1021A processors.
1368			A valid base address must be provided, and the serial
1369			port must already be setup and configured.
1370
1371		ec_imx21,<addr>
1372		ec_imx6q,<addr>
1373			Start an early, polled-mode, output-only console on the
1374			Freescale i.MX UART at the specified address. The UART
1375			must already be setup and configured.
1376
1377		ar3700_uart,<addr>
1378			Start an early, polled-mode console on the
1379			Armada 3700 serial port at the specified
1380			address. The serial port must already be setup
1381			and configured. Options are not yet supported.
1382
1383		qcom_geni,<addr>
1384			Start an early, polled-mode console on a Qualcomm
1385			Generic Interface (GENI) based serial port at the
1386			specified address. The serial port must already be
1387			setup and configured. Options are not yet supported.
1388
1389		efifb,[options]
1390			Start an early, unaccelerated console on the EFI
1391			memory mapped framebuffer (if available). On cache
1392			coherent non-x86 systems that use system memory for
1393			the framebuffer, pass the 'ram' option so that it is
1394			mapped with the correct attributes.
1395
1396		linflex,<addr>
1397			Use early console provided by Freescale LINFlexD UART
1398			serial driver for NXP S32V234 SoCs. A valid base
1399			address must be provided, and the serial port must
1400			already be setup and configured.
1401
1402	earlyprintk=	[X86,SH,ARM,M68k,S390,UM,EARLY]
1403			earlyprintk=vga
1404			earlyprintk=sclp
1405			earlyprintk=xen
1406			earlyprintk=serial[,ttySn[,baudrate]]
1407			earlyprintk=serial[,0x...[,baudrate]]
1408			earlyprintk=ttySn[,baudrate]
1409			earlyprintk=dbgp[debugController#]
1410			earlyprintk=mmio32,membase[,{nocfg|baudrate}]
1411			earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
1412			earlyprintk=xdbc[xhciController#]
1413			earlyprintk=bios
1414
1415			earlyprintk is useful when the kernel crashes before
1416			the normal console is initialized. It is not enabled by
1417			default because it has some cosmetic problems.
1418
1419			Use "nocfg" to skip UART configuration, assume
1420			BIOS/firmware has configured UART correctly.
1421
1422			Append ",keep" to not disable it when the real console
1423			takes over.
1424
1425			Only one of vga, serial, or usb debug port can
1426			be used at a time.
1427
1428			Currently only ttyS0 and ttyS1 may be specified by
1429			name.  Other I/O ports may be explicitly specified
1430			on some architectures (x86 and arm at least) by
1431			replacing ttySn with an I/O port address, like this:
1432				earlyprintk=serial,0x1008,115200
1433			You can find the port for a given device in
1434			/proc/tty/driver/serial:
1435				2: uart:ST16650V2 port:00001008 irq:18 ...
1436
1437			Interaction with the standard serial driver is not
1438			very good.
1439
1440			The VGA output is eventually overwritten by
1441			the real console.
1442
1443			The xen option can only be used in Xen domains.
1444
1445			The sclp output can only be used on s390.
1446
1447			The bios output can only be used on SuperH.
1448
1449			The optional "force" to "pciserial" enables use of a
1450			PCI device even when its classcode is not of the
1451			UART class.
1452
1453	edac_report=	[HW,EDAC] Control how to report EDAC event
1454			Format: {"on" | "off" | "force"}
1455			on: enable EDAC to report H/W event. May be overridden
1456			by other higher priority error reporting module.
1457			off: disable H/W event reporting through EDAC.
1458			force: enforce the use of EDAC to report H/W event.
1459			default: on.
1460
1461	edd=		[EDD]
1462			Format: {"off" | "on" | "skip[mbr]"}
1463
1464	efi=		[EFI,EARLY]
1465			Format: { "debug", "disable_early_pci_dma",
1466				  "nochunk", "noruntime", "nosoftreserve",
1467				  "novamap", "no_disable_early_pci_dma" }
1468			debug: enable misc debug output.
1469			disable_early_pci_dma: disable the busmaster bit on all
1470			PCI bridges while in the EFI boot stub.
1471			nochunk: disable reading files in "chunks" in the EFI
1472			boot stub, as chunking can cause problems with some
1473			firmware implementations.
1474			noruntime : disable EFI runtime services support
1475			nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1476			attribute may cause the kernel to reserve the
1477			memory range for a memory mapping driver to
1478			claim. Specify efi=nosoftreserve to disable this
1479			reservation and treat the memory by its base type
1480			(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1481			novamap: do not call SetVirtualAddressMap().
1482			no_disable_early_pci_dma: Leave the busmaster bit set
1483			on all PCI bridges while in the EFI boot stub
1484
1485	efi_no_storage_paranoia [EFI,X86,EARLY]
1486			Using this parameter you can use more than 50% of
1487			your efi variable storage. Use this parameter only if
1488			you are really sure that your UEFI does sane gc and
1489			fulfills the spec otherwise your board may brick.
1490
1491	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1492			that is to be dynamically loaded by Linux. If there are
1493			multiple variables with the same name but with different
1494			vendor GUIDs, all of them will be loaded. See
1495			Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1496
1497
1498	eisa_irq_edge=	[PARISC,HW]
1499			See header of drivers/parisc/eisa.c.
1500
1501	ekgdboc=	[X86,KGDB,EARLY] Allow early kernel console debugging
1502			Format: ekgdboc=kbd
1503
1504			This is designed to be used in conjunction with
1505			the boot argument: earlyprintk=vga
1506
1507			This parameter works in place of the kgdboc parameter
1508			but can only be used if the backing tty is available
1509			very early in the boot process. For early debugging
1510			via a serial port see kgdboc_earlycon instead.
1511
1512	elanfreq=	[X86-32]
1513			See comment before function elanfreq_setup() in
1514			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1515
1516	elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY]
1517			Specifies physical address of start of kernel core
1518			image elf header and optionally the size. Generally
1519			kexec loader will pass this option to capture kernel.
1520			See Documentation/admin-guide/kdump/kdump.rst for details.
1521
1522	enable_mtrr_cleanup [X86,EARLY]
1523			The kernel tries to adjust MTRR layout from continuous
1524			to discrete, to make X server driver able to add WB
1525			entry later. This parameter enables that.
1526
1527	enable_timer_pin_1 [X86]
1528			Enable PIN 1 of APIC timer
1529			Can be useful to work around chipset bugs
1530			(in particular on some ATI chipsets).
1531			The kernel tries to set a reasonable default.
1532
1533	enforcing=	[SELINUX] Set initial enforcing status.
1534			Format: {"0" | "1"}
1535			See security/selinux/Kconfig help text.
1536			0 -- permissive (log only, no denials).
1537			1 -- enforcing (deny and log).
1538			Default value is 0.
1539			Value can be changed at runtime via
1540			/sys/fs/selinux/enforce.
1541
1542	erst_disable	[ACPI]
1543			Disable Error Record Serialization Table (ERST)
1544			support.
1545
1546	ether=		[HW,NET] Ethernet cards parameters
1547			This option is obsoleted by the "netdev=" option, which
1548			has equivalent usage. See its documentation for details.
1549
1550	evm=		[EVM]
1551			Format: { "fix" }
1552			Permit 'security.evm' to be updated regardless of
1553			current integrity status.
1554
1555	early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
1556			stages so cover more early boot allocations.
1557			Please note that as side effect some optimizations
1558			might be disabled to achieve that (e.g. parallelized
1559			memory initialization is disabled) so the boot process
1560			might take longer, especially on systems with a lot of
1561			memory. Available with CONFIG_PAGE_EXTENSION=y.
1562
1563	failslab=
1564	fail_usercopy=
1565	fail_page_alloc=
1566	fail_skb_realloc=
1567	fail_make_request=[KNL]
1568			General fault injection mechanism.
1569			Format: <interval>,<probability>,<space>,<times>
1570			See also Documentation/fault-injection/.
1571
1572	fb_tunnels=	[NET]
1573			Format: { initns | none }
1574			See Documentation/admin-guide/sysctl/net.rst for
1575			fb_tunnels_only_for_init_ns
1576
1577	floppy=		[HW]
1578			See Documentation/admin-guide/blockdev/floppy.rst.
1579
1580	forcepae	[X86-32]
1581			Forcefully enable Physical Address Extension (PAE).
1582			Many Pentium M systems disable PAE but may have a
1583			functionally usable PAE implementation.
1584			Warning: use of this parameter will taint the kernel
1585			and may cause unknown problems.
1586
1587	fred=		[X86-64]
1588			Enable/disable Flexible Return and Event Delivery.
1589			Format: { on | off }
1590			on: enable FRED when it's present.
1591			off: disable FRED, the default setting.
1592
1593	ftrace=[tracer]
1594			[FTRACE] will set and start the specified tracer
1595			as early as possible in order to facilitate early
1596			boot debugging.
1597
1598	ftrace_boot_snapshot
1599			[FTRACE] On boot up, a snapshot will be taken of the
1600			ftrace ring buffer that can be read at:
1601			/sys/kernel/tracing/snapshot.
1602			This is useful if you need tracing information from kernel
1603			boot up that is likely to be overridden by user space
1604			start up functionality.
1605
1606			Optionally, the snapshot can also be defined for a tracing
1607			instance that was created by the trace_instance= command
1608			line parameter.
1609
1610			trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1611
1612			The above will cause the "foo" tracing instance to trigger
1613			a snapshot at the end of boot up.
1614
1615	ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
1616			  ,<instance>=2(orig_cpu)]
1617			[FTRACE] will dump the trace buffers on oops.
1618			If no parameter is passed, ftrace will dump global
1619			buffers of all CPUs, if you pass 2 or orig_cpu, it
1620			will dump only the buffer of the CPU that triggered
1621			the oops, or the specific instance will be dumped if
1622			its name is passed. Multiple instance dump is also
1623			supported, and instances are separated by commas. Each
1624			instance supports only dump on CPU that triggered the
1625			oops by passing 2 or orig_cpu to it.
1626
1627			ftrace_dump_on_oops=foo=orig_cpu
1628
1629			The above will dump only the buffer of "foo" instance
1630			on CPU that triggered the oops.
1631
1632			ftrace_dump_on_oops,foo,bar=orig_cpu
1633
1634			The above will dump global buffer on all CPUs, the
1635			buffer of "foo" instance on all CPUs and the buffer
1636			of "bar" instance on CPU that triggered the oops.
1637
1638	ftrace_filter=[function-list]
1639			[FTRACE] Limit the functions traced by the function
1640			tracer at boot up. function-list is a comma-separated
1641			list of functions. This list can be changed at run
1642			time by the set_ftrace_filter file in the debugfs
1643			tracing directory.
1644
1645	ftrace_notrace=[function-list]
1646			[FTRACE] Do not trace the functions specified in
1647			function-list. This list can be changed at run time
1648			by the set_ftrace_notrace file in the debugfs
1649			tracing directory.
1650
1651	ftrace_graph_filter=[function-list]
1652			[FTRACE] Limit the top level callers functions traced
1653			by the function graph tracer at boot up.
1654			function-list is a comma-separated list of functions
1655			that can be changed at run time by the
1656			set_graph_function file in the debugfs tracing directory.
1657
1658	ftrace_graph_notrace=[function-list]
1659			[FTRACE] Do not trace from the functions specified in
1660			function-list.  This list is a comma-separated list of
1661			functions that can be changed at run time by the
1662			set_graph_notrace file in the debugfs tracing directory.
1663
1664	ftrace_graph_max_depth=<uint>
1665			[FTRACE] Used with the function graph tracer. This is
1666			the max depth it will trace into a function. This value
1667			can be changed at run time by the max_graph_depth file
1668			in the tracefs tracing directory. default: 0 (no limit)
1669
1670	fw_devlink=	[KNL,EARLY] Create device links between consumer and supplier
1671			devices by scanning the firmware to infer the
1672			consumer/supplier relationships. This feature is
1673			especially useful when drivers are loaded as modules as
1674			it ensures proper ordering of tasks like device probing
1675			(suppliers first, then consumers), supplier boot state
1676			clean up (only after all consumers have probed),
1677			suspend/resume & runtime PM (consumers first, then
1678			suppliers).
1679			Format: { off | permissive | on | rpm }
1680			off --	Don't create device links from firmware info.
1681			permissive -- Create device links from firmware info
1682				but use it only for ordering boot state clean
1683				up (sync_state() calls).
1684			on -- 	Create device links from firmware info and use it
1685				to enforce probe and suspend/resume ordering.
1686			rpm --	Like "on", but also use to order runtime PM.
1687
1688	fw_devlink.strict=<bool>
1689			[KNL,EARLY] Treat all inferred dependencies as mandatory
1690			dependencies. This only applies for fw_devlink=on|rpm.
1691			Format: <bool>
1692
1693	fw_devlink.sync_state =
1694			[KNL,EARLY] When all devices that could probe have finished
1695			probing, this parameter controls what to do with
1696			devices that haven't yet received their sync_state()
1697			calls.
1698			Format: { strict | timeout }
1699			strict -- Default. Continue waiting on consumers to
1700				probe successfully.
1701			timeout -- Give up waiting on consumers and call
1702				sync_state() on any devices that haven't yet
1703				received their sync_state() calls after
1704				deferred_probe_timeout has expired or by
1705				late_initcall() if !CONFIG_MODULES.
1706
1707	gamecon.map[2|3]=
1708			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1709			support via parallel port (up to 5 devices per port)
1710			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1711			See also Documentation/input/devices/joystick-parport.rst
1712
1713	gamma=		[HW,DRM]
1714
1715	gart_fix_e820=	[X86-64,EARLY] disable the fix e820 for K8 GART
1716			Format: off | on
1717			default: on
1718
1719	gather_data_sampling=
1720			[X86,INTEL,EARLY] Control the Gather Data Sampling (GDS)
1721			mitigation.
1722
1723			Gather Data Sampling is a hardware vulnerability which
1724			allows unprivileged speculative access to data which was
1725			previously stored in vector registers.
1726
1727			This issue is mitigated by default in updated microcode.
1728			The mitigation may have a performance impact but can be
1729			disabled. On systems without the microcode mitigation
1730			disabling AVX serves as a mitigation.
1731
1732			force:	Disable AVX to mitigate systems without
1733				microcode mitigation. No effect if the microcode
1734				mitigation is present. Known to cause crashes in
1735				userspace with buggy AVX enumeration.
1736
1737			off:	Disable GDS mitigation.
1738
1739	gbpages		[X86] Use GB pages for kernel direct mappings.
1740
1741	gcov_persist=	[GCOV] When non-zero (default), profiling data for
1742			kernel modules is saved and remains accessible via
1743			debugfs, even when the module is unloaded/reloaded.
1744			When zero, profiling data is discarded and associated
1745			debugfs files are removed at module unload time.
1746
1747	goldfish	[X86] Enable the goldfish android emulator platform.
1748			Don't use this when you are not running on the
1749			android emulator
1750
1751	gpio-mockup.gpio_mockup_ranges
1752			[HW] Sets the ranges of gpiochip of for this device.
1753			Format: <start1>,<end1>,<start2>,<end2>...
1754	gpio-mockup.gpio_mockup_named_lines
1755			[HW] Let the driver know GPIO lines should be named.
1756
1757	gpt		[EFI] Forces disk with valid GPT signature but
1758			invalid Protective MBR to be treated as GPT. If the
1759			primary GPT is corrupted, it enables the backup/alternate
1760			GPT to be used instead.
1761
1762	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1763			the "Enable 0" bit of the configuration register.
1764			Format: 0 | 1
1765			Default: 0
1766	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1767			the "Enable 0" bit of the configuration register.
1768			Format: 0 | 1
1769			Default: 0
1770	grcan.select=	[HW] Select which physical interface to use.
1771			Format: 0 | 1
1772			Default: 0
1773	grcan.txsize=	[HW] Sets the size of the tx buffer.
1774			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1775			Default: 1024
1776	grcan.rxsize=	[HW] Sets the size of the rx buffer.
1777			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1778			Default: 1024
1779
1780	hardened_usercopy=
1781			[KNL] Under CONFIG_HARDENED_USERCOPY, whether
1782			hardening is enabled for this boot. Hardened
1783			usercopy checking is used to protect the kernel
1784			from reading or writing beyond known memory
1785			allocation boundaries as a proactive defense
1786			against bounds-checking flaws in the kernel's
1787			copy_to_user()/copy_from_user() interface.
1788			The default is determined by
1789			CONFIG_HARDENED_USERCOPY_DEFAULT_ON.
1790		on	Perform hardened usercopy checks.
1791		off	Disable hardened usercopy checks.
1792
1793	hardlockup_all_cpu_backtrace=
1794			[KNL] Should the hard-lockup detector generate
1795			backtraces on all cpus.
1796			Format: 0 | 1
1797
1798	hashdist=	[KNL,NUMA] Large hashes allocated during boot
1799			are distributed across NUMA nodes.  Defaults on
1800			for 64-bit NUMA, off otherwise.
1801			Format: 0 | 1 (for off | on)
1802
1803	hd=		[EIDE] (E)IDE hard drive subsystem geometry
1804			Format: <cyl>,<head>,<sect>
1805
1806	hest_disable	[ACPI]
1807			Disable Hardware Error Source Table (HEST) support;
1808			corresponding firmware-first mode error processing
1809			logic will be disabled.
1810
1811	hibernate=	[HIBERNATION]
1812		noresume	Don't check if there's a hibernation image
1813				present during boot.
1814		nocompress	Don't compress/decompress hibernation images.
1815		no		Disable hibernation and resume.
1816		protect_image	Turn on image protection during restoration
1817				(that will set all pages holding image data
1818				during restoration read-only).
1819
1820	hibernate.compressor= 	[HIBERNATION] Compression algorithm to be
1821				used with hibernation.
1822				Format: { lzo | lz4 }
1823				Default: lzo
1824
1825				lzo: Select LZO compression algorithm to
1826				compress/decompress hibernation image.
1827
1828				lz4: Select LZ4 compression algorithm to
1829				compress/decompress hibernation image.
1830
1831	highmem=nn[KMG]	[KNL,BOOT,EARLY] forces the highmem zone to have an exact
1832			size of <nn>. This works even on boxes that have no
1833			highmem otherwise. This also works to reduce highmem
1834			size on bigger boxes.
1835
1836	highres=	[KNL] Enable/disable high resolution timer mode.
1837			Valid parameters: "on", "off"
1838			Default: "on"
1839
1840	hlt		[BUGS=ARM,SH]
1841
1842	hostname=	[KNL,EARLY] Set the hostname (aka UTS nodename).
1843			Format: <string>
1844			This allows setting the system's hostname during early
1845			startup. This sets the name returned by gethostname.
1846			Using this parameter to set the hostname makes it
1847			possible to ensure the hostname is correctly set before
1848			any userspace processes run, avoiding the possibility
1849			that a process may call gethostname before the hostname
1850			has been explicitly set, resulting in the calling
1851			process getting an incorrect result. The string must
1852			not exceed the maximum allowed hostname length (usually
1853			64 characters) and will be truncated otherwise.
1854
1855	hpet=		[X86-32,HPET] option to control HPET usage
1856			Format: { enable (default) | disable | force |
1857				verbose }
1858			disable: disable HPET and use PIT instead
1859			force: allow force enabled of undocumented chips (ICH4,
1860				VIA, nVidia)
1861			verbose: show contents of HPET registers during setup
1862
1863	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1864			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1865
1866	hugepages=	[HW,EARLY] Number of HugeTLB pages to allocate at boot.
1867			If this follows hugepagesz (below), it specifies
1868			the number of pages of hugepagesz to be allocated.
1869			If this is the first HugeTLB parameter on the command
1870			line, it specifies the number of pages to allocate for
1871			the default huge page size. If using node format, the
1872			number of pages to allocate per-node can be specified.
1873			See also Documentation/admin-guide/mm/hugetlbpage.rst.
1874			Format: <integer> or (node format)
1875				<node>:<integer>[,<node>:<integer>]
1876
1877	hugepagesz=
1878			[HW,EARLY] The size of the HugeTLB pages.  This is
1879			used in conjunction with hugepages (above) to
1880			allocate huge pages of a specific size at boot. The
1881			pair hugepagesz=X hugepages=Y can be specified once
1882			for each supported huge page size. Huge page sizes
1883			are architecture dependent. See also
1884			Documentation/admin-guide/mm/hugetlbpage.rst.
1885			Format: size[KMG]
1886
1887	hugepage_alloc_threads=
1888			[HW] The number of threads that should be used to
1889			allocate hugepages during boot. This option can be
1890			used to improve system bootup time when allocating
1891			a large amount of huge pages.
1892			The default value is 25% of the available hardware threads.
1893
1894			Note that this parameter only applies to non-gigantic huge pages.
1895
1896	hugetlb_cma=	[HW,CMA,EARLY] The size of a CMA area used for allocation
1897			of gigantic hugepages. Or using node format, the size
1898			of a CMA area per node can be specified.
1899			Format: nn[KMGTPE] or (node format)
1900				<node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1901
1902			Reserve a CMA area of given size and allocate gigantic
1903			hugepages using the CMA allocator. If enabled, the
1904			boot-time allocation of gigantic hugepages is skipped.
1905
1906	hugetlb_cma_only=
1907			[HW,CMA,EARLY] When allocating new HugeTLB pages, only
1908			try to allocate from the CMA areas.
1909
1910			This option does nothing if hugetlb_cma= is not also
1911			specified.
1912
1913	hugetlb_free_vmemmap=
1914			[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1915			enabled.
1916			Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1917			Allows heavy hugetlb users to free up some more
1918			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1919			Format: { on | off (default) }
1920
1921			on: enable HVO
1922			off: disable HVO
1923
1924			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1925			the default is on.
1926
1927			Note that the vmemmap pages may be allocated from the added
1928			memory block itself when memory_hotplug.memmap_on_memory is
1929			enabled, those vmemmap pages cannot be optimized even if this
1930			feature is enabled.  Other vmemmap pages not allocated from
1931			the added memory block itself do not be affected.
1932
1933	hung_task_panic=
1934			[KNL] Should the hung task detector generate panics.
1935			Format: 0 | 1
1936
1937			A value of 1 instructs the kernel to panic when a
1938			hung task is detected. The default value is controlled
1939			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1940			option. The value selected by this boot parameter can
1941			be changed later by the kernel.hung_task_panic sysctl.
1942
1943	hvc_iucv=	[S390]	Number of z/VM IUCV hypervisor console (HVC)
1944				terminal devices. Valid values: 0..8
1945	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
1946				If specified, z/VM IUCV HVC accepts connections
1947				from listed z/VM user IDs only.
1948
1949	hv_nopvspin	[X86,HYPER_V,EARLY]
1950			Disables the paravirt spinlock optimizations
1951			which allow the hypervisor to 'idle' the guest
1952			on lock contention.
1953
1954	hw_protection=	[HW]
1955			Format: reboot | shutdown
1956
1957			Hardware protection action taken on critical events like
1958			overtemperature or imminent voltage loss.
1959
1960	i2c_bus=	[HW]	Override the default board specific I2C bus speed
1961				or register an additional I2C bus that is not
1962				registered from board initialization code.
1963				Format:
1964				<bus_id>,<clkrate>
1965
1966	i2c_touchscreen_props= [HW,ACPI,X86]
1967			Set device-properties for ACPI-enumerated I2C-attached
1968			touchscreen, to e.g. fix coordinates of upside-down
1969			mounted touchscreens. If you need this option please
1970			submit a drivers/platform/x86/touchscreen_dmi.c patch
1971			adding a DMI quirk for this.
1972
1973			Format:
1974			<ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...]
1975			Where <val> is one of:
1976			Omit "=<val>" entirely	Set a boolean device-property
1977			Unsigned number		Set a u32 device-property
1978			Anything else		Set a string device-property
1979
1980			Examples (split over multiple lines):
1981			i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1982			touchscreen-inverted-y
1983
1984			i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
1985			touchscreen-size-y=1080:touchscreen-inverted-y:
1986			firmware-name=gsl1680-vendor-model.fw:silead,home-button
1987
1988	i8042.debug	[HW] Toggle i8042 debug mode
1989	i8042.unmask_kbd_data
1990			[HW] Enable printing of interrupt data from the KBD port
1991			     (disabled by default, and as a pre-condition
1992			     requires that i8042.debug=1 be enabled)
1993	i8042.direct	[HW] Put keyboard port into non-translated mode
1994	i8042.dumbkbd	[HW] Pretend that controller can only read data from
1995			     keyboard and cannot control its state
1996			     (Don't attempt to blink the leds)
1997	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1998	i8042.nokbd	[HW] Don't check/create keyboard port
1999	i8042.noloop	[HW] Disable the AUX Loopback command while probing
2000			     for the AUX port
2001	i8042.nomux	[HW] Don't check presence of an active multiplexing
2002			     controller
2003	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
2004			     controllers
2005	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
2006	i8042.reset	[HW] Reset the controller during init, cleanup and
2007			     suspend-to-ram transitions, only during s2r
2008			     transitions, or never reset
2009			Format: { 1 | Y | y | 0 | N | n }
2010			1, Y, y: always reset controller
2011			0, N, n: don't ever reset controller
2012			Default: only on s2r transitions on x86; most other
2013			architectures force reset to be always executed
2014	i8042.unlock	[HW] Unlock (ignore) the keylock
2015	i8042.kbdreset	[HW] Reset device connected to KBD port
2016	i8042.probe_defer
2017			[HW] Allow deferred probing upon i8042 probe errors
2018
2019	i810=		[HW,DRM]
2020
2021	i915.invert_brightness=
2022			[DRM] Invert the sense of the variable that is used to
2023			set the brightness of the panel backlight. Normally a
2024			brightness value of 0 indicates backlight switched off,
2025			and the maximum of the brightness value sets the backlight
2026			to maximum brightness. If this parameter is set to 0
2027			(default) and the machine requires it, or this parameter
2028			is set to 1, a brightness value of 0 sets the backlight
2029			to maximum brightness, and the maximum of the brightness
2030			value switches the backlight off.
2031			-1 -- never invert brightness
2032			 0 -- machine default
2033			 1 -- force brightness inversion
2034
2035	ia32_emulation=	[X86-64]
2036			Format: <bool>
2037			When true, allows loading 32-bit programs and executing 32-bit
2038			syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
2039			boot time. When false, unconditionally disables IA32 emulation.
2040
2041	icn=		[HW,ISDN]
2042			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
2043
2044
2045	idle=		[X86,EARLY]
2046			Format: idle=poll, idle=halt, idle=nomwait
2047
2048			idle=poll:  Don't do power saving in the idle loop
2049			using HLT, but poll for rescheduling event. This will
2050			make the CPUs eat a lot more power, but may be useful
2051			to get slightly better performance in multiprocessor
2052			benchmarks. It also makes some profiling using
2053			performance counters more accurate.  Please note that
2054			on systems with MONITOR/MWAIT support (like Intel
2055			EM64T CPUs) this option has no performance advantage
2056			over the normal idle loop.  It may also interact badly
2057			with hyperthreading.
2058
2059			idle=halt: Halt is forced to be used for CPU idle.
2060			In such case C2/C3 won't be used again.
2061
2062			idle=nomwait: Disable mwait for CPU C-states
2063
2064	idxd.sva=	[HW]
2065			Format: <bool>
2066			Allow force disabling of Shared Virtual Memory (SVA)
2067			support for the idxd driver. By default it is set to
2068			true (1).
2069
2070	idxd.tc_override= [HW]
2071			Format: <bool>
2072			Allow override of default traffic class configuration
2073			for the device. By default it is set to false (0).
2074
2075	ieee754=	[MIPS] Select IEEE Std 754 conformance mode
2076			Format: { strict | legacy | 2008 | relaxed | emulated }
2077			Default: strict
2078
2079			Choose which programs will be accepted for execution
2080			based on the IEEE 754 NaN encoding(s) supported by
2081			the FPU and the NaN encoding requested with the value
2082			of an ELF file header flag individually set by each
2083			binary.  Hardware implementations are permitted to
2084			support either or both of the legacy and the 2008 NaN
2085			encoding mode.
2086
2087			Available settings are as follows:
2088			strict	accept binaries that request a NaN encoding
2089				supported by the FPU
2090			legacy	only accept legacy-NaN binaries, if supported
2091				by the FPU
2092			2008	only accept 2008-NaN binaries, if supported
2093				by the FPU
2094			relaxed	accept any binaries regardless of whether
2095				supported by the FPU
2096			emulated accept any binaries but enable FPU emulator
2097				if binary mode is unsupported by the FPU.
2098
2099			The FPU emulator is always able to support both NaN
2100			encodings, so if no FPU hardware is present or it has
2101			been disabled with 'nofpu', then the settings of
2102			'legacy' and '2008' strap the emulator accordingly,
2103			'relaxed' straps the emulator for both legacy-NaN and
2104			2008-NaN, whereas 'strict' enables legacy-NaN only on
2105			legacy processors and both NaN encodings on MIPS32 or
2106			MIPS64 CPUs.
2107
2108			The setting for ABS.fmt/NEG.fmt instruction execution
2109			mode generally follows that for the NaN encoding,
2110			except where unsupported by hardware.
2111
2112	ignore_loglevel	[KNL,EARLY]
2113			Ignore loglevel setting - this will print /all/
2114			kernel messages to the console. Useful for debugging.
2115			We also add it as printk module parameter, so users
2116			could change it dynamically, usually by
2117			/sys/module/printk/parameters/ignore_loglevel.
2118
2119	ignore_rlimit_data
2120			Ignore RLIMIT_DATA setting for data mappings,
2121			print warning at first misuse.  Can be changed via
2122			/sys/module/kernel/parameters/ignore_rlimit_data.
2123
2124	ihash_entries=	[KNL]
2125			Set number of hash buckets for inode cache.
2126
2127	ima_appraise=	[IMA] appraise integrity measurements
2128			Format: { "off" | "enforce" | "fix" | "log" }
2129			default: "enforce"
2130
2131	ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
2132			The builtin appraise policy appraises all files
2133			owned by uid=0.
2134
2135	ima_canonical_fmt [IMA]
2136			Use the canonical format for the binary runtime
2137			measurements, instead of host native format.
2138
2139	ima_hash=	[IMA]
2140			Format: { md5 | sha1 | rmd160 | sha256 | sha384
2141				   | sha512 | ... }
2142			default: "sha1"
2143
2144			The list of supported hash algorithms is defined
2145			in crypto/hash_info.h.
2146
2147	ima_policy=	[IMA]
2148			The builtin policies to load during IMA setup.
2149			Format: "tcb | appraise_tcb | secure_boot |
2150				 fail_securely | critical_data"
2151
2152			The "tcb" policy measures all programs exec'd, files
2153			mmap'd for exec, and all files opened with the read
2154			mode bit set by either the effective uid (euid=0) or
2155			uid=0.
2156
2157			The "appraise_tcb" policy appraises the integrity of
2158			all files owned by root.
2159
2160			The "secure_boot" policy appraises the integrity
2161			of files (eg. kexec kernel image, kernel modules,
2162			firmware, policy, etc) based on file signatures.
2163
2164			The "fail_securely" policy forces file signature
2165			verification failure also on privileged mounted
2166			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2167			flag.
2168
2169			The "critical_data" policy measures kernel integrity
2170			critical data.
2171
2172	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
2173			Load a policy which meets the needs of the Trusted
2174			Computing Base.  This means IMA will measure all
2175			programs exec'd, files mmap'd for exec, and all files
2176			opened for read by uid=0.
2177
2178	ima_template=	[IMA]
2179			Select one of defined IMA measurements template formats.
2180			Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2181				   "ima-sigv2" }
2182			Default: "ima-ng"
2183
2184	ima_template_fmt=
2185			[IMA] Define a custom template format.
2186			Format: { "field1|...|fieldN" }
2187
2188	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2189			Format: <min_file_size>
2190			Set the minimal file size for using asynchronous hash.
2191			If left unspecified, ahash usage is disabled.
2192
2193			ahash performance varies for different data sizes on
2194			different crypto accelerators. This option can be used
2195			to achieve the best performance for a particular HW.
2196
2197	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2198			Format: <bufsize>
2199			Set hashing buffer size. Default: 4k.
2200
2201			ahash performance varies for different chunk sizes on
2202			different crypto accelerators. This option can be used
2203			to achieve best performance for particular HW.
2204
2205	indirect_target_selection= [X86,Intel] Mitigation control for Indirect
2206			Target Selection(ITS) bug in Intel CPUs. Updated
2207			microcode is also required for a fix in IBPB.
2208
2209			on:     Enable mitigation (default).
2210			off:    Disable mitigation.
2211			force:	Force the ITS bug and deploy default
2212				mitigation.
2213			vmexit: Only deploy mitigation if CPU is affected by
2214				guest/host isolation part of ITS.
2215			stuff:	Deploy RSB-fill mitigation when retpoline is
2216				also deployed. Otherwise, deploy the default
2217				mitigation.
2218
2219			For details see:
2220			Documentation/admin-guide/hw-vuln/indirect-target-selection.rst
2221
2222	init=		[KNL]
2223			Format: <full_path>
2224			Run specified binary instead of /sbin/init as init
2225			process.
2226
2227	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
2228			for working out where the kernel is dying during
2229			startup.
2230
2231	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
2232			initcall functions.  Useful for debugging built-in
2233			modules and initcalls.
2234
2235	initramfs_async= [KNL]
2236			Format: <bool>
2237			Default: 1
2238			This parameter controls whether the initramfs
2239			image is unpacked asynchronously, concurrently
2240			with devices being probed and
2241			initialized. This should normally just work,
2242			but as a debugging aid, one can get the
2243			historical behaviour of the initramfs
2244			unpacking being completed before device_ and
2245			late_ initcalls.
2246
2247	initrd=		[BOOT,EARLY] Specify the location of the initial ramdisk
2248
2249	initrdmem=	[KNL,EARLY] Specify a physical address and size from which to
2250			load the initrd. If an initrd is compiled in or
2251			specified in the bootparams, it takes priority over this
2252			setting.
2253			Format: ss[KMG],nn[KMG]
2254			Default is 0, 0
2255
2256	init_on_alloc=	[MM,EARLY] Fill newly allocated pages and heap objects with
2257			zeroes.
2258			Format: 0 | 1
2259			Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2260
2261	init_on_free=	[MM,EARLY] Fill freed pages and heap objects with zeroes.
2262			Format: 0 | 1
2263			Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2264
2265	init_pkru=	[X86] Specify the default memory protection keys rights
2266			register contents for all processes.  0x55555554 by
2267			default (disallow access to all but pkey 0).  Can
2268			override in debugfs after boot.
2269
2270	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
2271			Format: <irq>
2272
2273	int_pln_enable	[X86] Enable power limit notification interrupt
2274
2275	integrity_audit=[IMA]
2276			Format: { "0" | "1" }
2277			0 -- basic integrity auditing messages. (Default)
2278			1 -- additional integrity auditing messages.
2279
2280	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
2281		on
2282			Enable intel iommu driver.
2283		off
2284			Disable intel iommu driver.
2285		igfx_off [Default Off]
2286			By default, gfx is mapped as normal device. If a gfx
2287			device has a dedicated DMAR unit, the DMAR unit is
2288			bypassed by not enabling DMAR with this option. In
2289			this case, gfx device will use physical address for
2290			DMA.
2291		strict [Default Off]
2292			Deprecated, equivalent to iommu.strict=1.
2293		sp_off [Default Off]
2294			By default, super page will be supported if Intel IOMMU
2295			has the capability. With this option, super page will
2296			not be supported.
2297		sm_on
2298			Enable the Intel IOMMU scalable mode if the hardware
2299			advertises that it has support for the scalable mode
2300			translation.
2301		sm_off
2302			Disallow use of the Intel IOMMU scalable mode.
2303		tboot_noforce [Default Off]
2304			Do not force the Intel IOMMU enabled under tboot.
2305			By default, tboot will force Intel IOMMU on, which
2306			could harm performance of some high-throughput
2307			devices like 40GBit network cards, even if identity
2308			mapping is enabled.
2309			Note that using this option lowers the security
2310			provided by tboot because it makes the system
2311			vulnerable to DMA attacks.
2312
2313	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
2314			0	disables intel_idle and fall back on acpi_idle.
2315			1 to 9	specify maximum depth of C-state.
2316
2317	intel_pstate=	[X86,EARLY]
2318			disable
2319			  Do not enable intel_pstate as the default
2320			  scaling driver for the supported processors
2321                        active
2322                          Use intel_pstate driver to bypass the scaling
2323                          governors layer of cpufreq and provides it own
2324                          algorithms for p-state selection. There are two
2325                          P-state selection algorithms provided by
2326                          intel_pstate in the active mode: powersave and
2327                          performance.  The way they both operate depends
2328                          on whether or not the hardware managed P-states
2329                          (HWP) feature has been enabled in the processor
2330                          and possibly on the processor model.
2331			passive
2332			  Use intel_pstate as a scaling driver, but configure it
2333			  to work with generic cpufreq governors (instead of
2334			  enabling its internal governor).  This mode cannot be
2335			  used along with the hardware-managed P-states (HWP)
2336			  feature.
2337			force
2338			  Enable intel_pstate on systems that prohibit it by default
2339			  in favor of acpi-cpufreq. Forcing the intel_pstate driver
2340			  instead of acpi-cpufreq may disable platform features, such
2341			  as thermal controls and power capping, that rely on ACPI
2342			  P-States information being indicated to OSPM and therefore
2343			  should be used with caution. This option does not work with
2344			  processors that aren't supported by the intel_pstate driver
2345			  or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2346			no_hwp
2347			  Do not enable hardware P state control (HWP)
2348			  if available.
2349			hwp_only
2350			  Only load intel_pstate on systems which support
2351			  hardware P state control (HWP) if available.
2352			support_acpi_ppc
2353			  Enforce ACPI _PPC performance limits. If the Fixed ACPI
2354			  Description Table, specifies preferred power management
2355			  profile as "Enterprise Server" or "Performance Server",
2356			  then this feature is turned on by default.
2357			per_cpu_perf_limits
2358			  Allow per-logical-CPU P-State performance control limits using
2359			  cpufreq sysfs interface
2360			no_cas
2361			  Do not enable capacity-aware scheduling (CAS) on
2362			  hybrid systems
2363
2364	intremap=	[X86-64,Intel-IOMMU,EARLY]
2365			on	enable Interrupt Remapping (default)
2366			off	disable Interrupt Remapping
2367			nosid	disable Source ID checking
2368			no_x2apic_optout
2369				BIOS x2APIC opt-out request will be ignored
2370			nopost	disable Interrupt Posting
2371			posted_msi
2372				enable MSIs delivered as posted interrupts
2373
2374	iomem=		Disable strict checking of access to MMIO memory
2375		strict	regions from userspace.
2376		relaxed
2377
2378	iommu=		[X86,EARLY]
2379
2380		off
2381			Don't initialize and use any kind of IOMMU.
2382
2383		force
2384			Force the use of the hardware IOMMU even when
2385			it is not actually needed (e.g. because < 3 GB
2386			memory).
2387
2388		noforce
2389			Don't force hardware IOMMU usage when it is not
2390			needed. (default).
2391
2392		biomerge
2393		panic
2394		nopanic
2395		merge
2396		nomerge
2397
2398		soft
2399			Use software bounce buffering (SWIOTLB) (default for
2400			Intel machines). This can be used to prevent the usage
2401			of an available hardware IOMMU.
2402
2403			[X86]
2404		pt
2405			[X86]
2406		nopt
2407			[PPC/POWERNV]
2408		nobypass
2409			Disable IOMMU bypass, using IOMMU for PCI devices.
2410
2411		[X86]
2412		AMD Gart HW IOMMU-specific options:
2413
2414		<size>
2415			Set the size of the remapping area in bytes.
2416
2417		allowed
2418			Overwrite iommu off workarounds for specific chipsets
2419
2420		fullflush
2421			Flush IOMMU on each allocation (default).
2422
2423		nofullflush
2424			Don't use IOMMU fullflush.
2425
2426		memaper[=<order>]
2427			Allocate an own aperture over RAM with size
2428			32MB<<order.  (default: order=1, i.e. 64MB)
2429
2430		merge
2431			Do scatter-gather (SG) merging. Implies "force"
2432			(experimental).
2433
2434		nomerge
2435			Don't do scatter-gather (SG) merging.
2436
2437		noaperture
2438			Ask the IOMMU not to touch the aperture for AGP.
2439
2440		noagp
2441			Don't initialize the AGP driver and use full aperture.
2442
2443		panic
2444			Always panic when IOMMU overflows.
2445
2446	iommu.forcedac=	[ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
2447			Format: { "0" | "1" }
2448			0 - Try to allocate a 32-bit DMA address first, before
2449			  falling back to the full range if needed.
2450			1 - Allocate directly from the full usable range,
2451			  forcing Dual Address Cycle for PCI cards supporting
2452			  greater than 32-bit addressing.
2453
2454	iommu.strict=	[ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour
2455			Format: { "0" | "1" }
2456			0 - Lazy mode.
2457			  Request that DMA unmap operations use deferred
2458			  invalidation of hardware TLBs, for increased
2459			  throughput at the cost of reduced device isolation.
2460			  Will fall back to strict mode if not supported by
2461			  the relevant IOMMU driver.
2462			1 - Strict mode.
2463			  DMA unmap operations invalidate IOMMU hardware TLBs
2464			  synchronously.
2465			unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2466			Note: on x86, strict mode specified via one of the
2467			legacy driver-specific options takes precedence.
2468
2469	iommu.passthrough=
2470			[ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
2471			Format: { "0" | "1" }
2472			0 - Use IOMMU translation for DMA.
2473			1 - Bypass the IOMMU for DMA.
2474			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2475
2476	io7=		[HW] IO7 for Marvel-based Alpha systems
2477			See comment before marvel_specify_io7 in
2478			arch/alpha/kernel/core_marvel.c.
2479
2480	io_delay=	[X86,EARLY] I/O delay method
2481		0x80
2482			Standard port 0x80 based delay
2483		0xed
2484			Alternate port 0xed based delay (needed on some systems)
2485		udelay
2486			Simple two microseconds delay
2487		none
2488			No delay
2489
2490	ip=		[IP_PNP]
2491			See Documentation/admin-guide/nfs/nfsroot.rst.
2492
2493	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
2494			IPC identifiers from 32,768 to 16,777,216.
2495
2496	ipe.enforce=	[IPE]
2497			Format: <bool>
2498			Determine whether IPE starts in permissive (0) or
2499			enforce (1) mode. The default is enforce.
2500
2501	ipe.success_audit=
2502			[IPE]
2503			Format: <bool>
2504			Start IPE with success auditing enabled, emitting
2505			an audit event when a binary is allowed. The default
2506			is 0.
2507
2508	irqaffinity=	[SMP] Set the default irq affinity mask
2509			The argument is a cpu list, as described above.
2510
2511	irqchip.gicv2_force_probe=
2512			[ARM,ARM64,EARLY]
2513			Format: <bool>
2514			Force the kernel to look for the second 4kB page
2515			of a GICv2 controller even if the memory range
2516			exposed by the device tree is too small.
2517
2518	irqchip.gicv3_nolpi=
2519			[ARM,ARM64,EARLY]
2520			Force the kernel to ignore the availability of
2521			LPIs (and by consequence ITSs). Intended for system
2522			that use the kernel as a bootloader, and thus want
2523			to let secondary kernels in charge of setting up
2524			LPIs.
2525
2526	irqchip.gicv3_pseudo_nmi= [ARM64,EARLY]
2527			Enables support for pseudo-NMIs in the kernel. This
2528			requires the kernel to be built with
2529			CONFIG_ARM64_PSEUDO_NMI.
2530
2531	irqfixup	[HW]
2532			When an interrupt is not handled search all handlers
2533			for it. Intended to get systems with badly broken
2534			firmware running.
2535
2536	irqpoll		[HW]
2537			When an interrupt is not handled search all handlers
2538			for it. Also check all handlers each timer
2539			interrupt. Intended to get systems with badly broken
2540			firmware running.
2541
2542	isapnp=		[ISAPNP]
2543			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2544
2545	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2546			[Deprecated - use cpusets instead]
2547			Format: [flag-list,]<cpu-list>
2548
2549			Specify one or more CPUs to isolate from disturbances
2550			specified in the flag list (default: domain):
2551
2552			nohz
2553			  Disable the tick when a single task runs as well as
2554			  disabling other kernel noises like having RCU callbacks
2555			  offloaded. This is equivalent to the nohz_full parameter.
2556
2557			  A residual 1Hz tick is offloaded to workqueues, which you
2558			  need to affine to housekeeping through the global
2559			  workqueue's affinity configured via the
2560			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
2561			  by using the 'domain' flag described below.
2562
2563			  NOTE: by default the global workqueue runs on all CPUs,
2564			  so to protect individual CPUs the 'cpumask' file has to
2565			  be configured manually after bootup.
2566
2567			domain
2568			  Isolate from the general SMP balancing and scheduling
2569			  algorithms. Note that performing domain isolation this way
2570			  is irreversible: it's not possible to bring back a CPU to
2571			  the domains once isolated through isolcpus. It's strongly
2572			  advised to use cpusets instead to disable scheduler load
2573			  balancing through the "cpuset.sched_load_balance" file.
2574			  It offers a much more flexible interface where CPUs can
2575			  move in and out of an isolated set anytime.
2576
2577			  You can move a process onto or off an "isolated" CPU via
2578			  the CPU affinity syscalls or cpuset.
2579			  <cpu number> begins at 0 and the maximum value is
2580			  "number of CPUs in system - 1".
2581
2582			managed_irq
2583
2584			  Isolate from being targeted by managed interrupts
2585			  which have an interrupt mask containing isolated
2586			  CPUs. The affinity of managed interrupts is
2587			  handled by the kernel and cannot be changed via
2588			  the /proc/irq/* interfaces.
2589
2590			  This isolation is best effort and only effective
2591			  if the automatically assigned interrupt mask of a
2592			  device queue contains isolated and housekeeping
2593			  CPUs. If housekeeping CPUs are online then such
2594			  interrupts are directed to the housekeeping CPU
2595			  so that IO submitted on the housekeeping CPU
2596			  cannot disturb the isolated CPU.
2597
2598			  If a queue's affinity mask contains only isolated
2599			  CPUs then this parameter has no effect on the
2600			  interrupt routing decision, though interrupts are
2601			  only delivered when tasks running on those
2602			  isolated CPUs submit IO. IO submitted on
2603			  housekeeping CPUs has no influence on those
2604			  queues.
2605
2606			The format of <cpu-list> is described above.
2607
2608	iucv=		[HW,NET]
2609
2610	ivrs_ioapic	[HW,X86-64]
2611			Provide an override to the IOAPIC-ID<->DEVICE-ID
2612			mapping provided in the IVRS ACPI table.
2613			By default, PCI segment is 0, and can be omitted.
2614
2615			For example, to map IOAPIC-ID decimal 10 to
2616			PCI segment 0x1 and PCI device 00:14.0,
2617			write the parameter as:
2618				ivrs_ioapic=10@0001:00:14.0
2619
2620			Deprecated formats:
2621			* To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2622			  write the parameter as:
2623				ivrs_ioapic[10]=00:14.0
2624			* To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2625			  PCI device 00:14.0 write the parameter as:
2626				ivrs_ioapic[10]=0001:00:14.0
2627
2628	ivrs_hpet	[HW,X86-64]
2629			Provide an override to the HPET-ID<->DEVICE-ID
2630			mapping provided in the IVRS ACPI table.
2631			By default, PCI segment is 0, and can be omitted.
2632
2633			For example, to map HPET-ID decimal 10 to
2634			PCI segment 0x1 and PCI device 00:14.0,
2635			write the parameter as:
2636				ivrs_hpet=10@0001:00:14.0
2637
2638			Deprecated formats:
2639			* To map HPET-ID decimal 0 to PCI device 00:14.0
2640			  write the parameter as:
2641				ivrs_hpet[0]=00:14.0
2642			* To map HPET-ID decimal 10 to PCI segment 0x1 and
2643			  PCI device 00:14.0 write the parameter as:
2644				ivrs_ioapic[10]=0001:00:14.0
2645
2646	ivrs_acpihid	[HW,X86-64]
2647			Provide an override to the ACPI-HID:UID<->DEVICE-ID
2648			mapping provided in the IVRS ACPI table.
2649			By default, PCI segment is 0, and can be omitted.
2650
2651			For example, to map UART-HID:UID AMD0020:0 to
2652			PCI segment 0x1 and PCI device ID 00:14.5,
2653			write the parameter as:
2654				ivrs_acpihid=AMD0020:0@0001:00:14.5
2655
2656			Deprecated formats:
2657			* To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2658			  PCI device ID 00:14.5, write the parameter as:
2659				ivrs_acpihid[00:14.5]=AMD0020:0
2660			* To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2661			  PCI device ID 00:14.5, write the parameter as:
2662				ivrs_acpihid[0001:00:14.5]=AMD0020:0
2663
2664	js=		[HW,JOY] Analog joystick
2665			See Documentation/input/joydev/joystick.rst.
2666
2667	kasan_multi_shot
2668			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2669			report on every invalid memory access. Without this
2670			parameter KASAN will print report only for the first
2671			invalid access.
2672
2673	keep_bootcon	[KNL,EARLY]
2674			Do not unregister boot console at start. This is only
2675			useful for debugging when something happens in the window
2676			between unregistering the boot console and initializing
2677			the real console.
2678
2679	keepinitrd	[HW,ARM] See retain_initrd.
2680
2681	kernelcore=	[KNL,X86,PPC,EARLY]
2682			Format: nn[KMGTPE] | nn% | "mirror"
2683			This parameter specifies the amount of memory usable by
2684			the kernel for non-movable allocations.  The requested
2685			amount is spread evenly throughout all nodes in the
2686			system as ZONE_NORMAL.  The remaining memory is used for
2687			movable memory in its own zone, ZONE_MOVABLE.  In the
2688			event, a node is too small to have both ZONE_NORMAL and
2689			ZONE_MOVABLE, kernelcore memory will take priority and
2690			other nodes will have a larger ZONE_MOVABLE.
2691
2692			ZONE_MOVABLE is used for the allocation of pages that
2693			may be reclaimed or moved by the page migration
2694			subsystem.  Note that allocations like PTEs-from-HighMem
2695			still use the HighMem zone if it exists, and the Normal
2696			zone if it does not.
2697
2698			It is possible to specify the exact amount of memory in
2699			the form of "nn[KMGTPE]", a percentage of total system
2700			memory in the form of "nn%", or "mirror".  If "mirror"
2701			option is specified, mirrored (reliable) memory is used
2702			for non-movable allocations and remaining memory is used
2703			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
2704			are exclusive, so you cannot specify multiple forms.
2705
2706	kgdbdbgp=	[KGDB,HW,EARLY] kgdb over EHCI usb debug port.
2707			Format: <Controller#>[,poll interval]
2708			The controller # is the number of the ehci usb debug
2709			port as it is probed via PCI.  The poll interval is
2710			optional and is the number seconds in between
2711			each poll cycle to the debug port in case you need
2712			the functionality for interrupting the kernel with
2713			gdb or control-c on the dbgp connection.  When
2714			not using this parameter you use sysrq-g to break into
2715			the kernel debugger.
2716
2717	kgdboc=		[KGDB,HW] kgdb over consoles.
2718			Requires a tty driver that supports console polling,
2719			or a supported polling keyboard driver (non-usb).
2720			 Serial only format: <serial_device>[,baud]
2721			 keyboard only format: kbd
2722			 keyboard and serial format: kbd,<serial_device>[,baud]
2723			Optional Kernel mode setting:
2724			 kms, kbd format: kms,kbd
2725			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2726
2727	kgdboc_earlycon=	[KGDB,HW,EARLY]
2728			If the boot console provides the ability to read
2729			characters and can work in polling mode, you can use
2730			this parameter to tell kgdb to use it as a backend
2731			until the normal console is registered. Intended to
2732			be used together with the kgdboc parameter which
2733			specifies the normal console to transition to.
2734
2735			The name of the early console should be specified
2736			as the value of this parameter. Note that the name of
2737			the early console might be different than the tty
2738			name passed to kgdboc. It's OK to leave the value
2739			blank and the first boot console that implements
2740			read() will be picked.
2741
2742	kgdbwait	[KGDB,EARLY] Stop kernel execution and enter the
2743			kernel debugger at the earliest opportunity.
2744
2745	kmac=		[MIPS] Korina ethernet MAC address.
2746			Configure the RouterBoard 532 series on-chip
2747			Ethernet adapter MAC address.
2748
2749	kmemleak=	[KNL,EARLY] Boot-time kmemleak enable/disable
2750			Valid arguments: on, off
2751			Default: on
2752			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2753			the default is off.
2754
2755	kprobe_event=[probe-list]
2756			[FTRACE] Add kprobe events and enable at boot time.
2757			The probe-list is a semicolon delimited list of probe
2758			definitions. Each definition is same as kprobe_events
2759			interface, but the parameters are comma delimited.
2760			For example, to add a kprobe event on vfs_read with
2761			arg1 and arg2, add to the command line;
2762
2763			      kprobe_event=p,vfs_read,$arg1,$arg2
2764
2765			See also Documentation/trace/kprobetrace.rst "Kernel
2766			Boot Parameter" section.
2767
2768	kpti=		[ARM64,EARLY] Control page table isolation of
2769			user and kernel address spaces.
2770			Default: enabled on cores which need mitigation.
2771			0: force disabled
2772			1: force enabled
2773
2774	kunit.enable=	[KUNIT] Enable executing KUnit tests. Requires
2775			CONFIG_KUNIT to be set to be fully enabled. The
2776			default value can be overridden via
2777			KUNIT_DEFAULT_ENABLED.
2778			Default is 1 (enabled)
2779
2780	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2781			Default is 0 (don't ignore, but inject #GP)
2782
2783	kvm.eager_page_split=
2784			[KVM,X86] Controls whether or not KVM will try to
2785			proactively split all huge pages during dirty logging.
2786			Eager page splitting reduces interruptions to vCPU
2787			execution by eliminating the write-protection faults
2788			and MMU lock contention that would otherwise be
2789			required to split huge pages lazily.
2790
2791			VM workloads that rarely perform writes or that write
2792			only to a small region of VM memory may benefit from
2793			disabling eager page splitting to allow huge pages to
2794			still be used for reads.
2795
2796			The behavior of eager page splitting depends on whether
2797			KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2798			disabled, all huge pages in a memslot will be eagerly
2799			split when dirty logging is enabled on that memslot. If
2800			enabled, eager page splitting will be performed during
2801			the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2802			cleared.
2803
2804			Eager page splitting is only supported when kvm.tdp_mmu=Y.
2805
2806			Default is Y (on).
2807
2808	kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86]
2809			If enabled, KVM will enable virtualization in hardware
2810			when KVM is loaded, and disable virtualization when KVM
2811			is unloaded (if KVM is built as a module).
2812
2813			If disabled, KVM will dynamically enable and disable
2814			virtualization on-demand when creating and destroying
2815			VMs, i.e. on the 0=>1 and 1=>0 transitions of the
2816			number of VMs.
2817
2818			Enabling virtualization at module load avoids potential
2819			latency for creation of the 0=>1 VM, as KVM serializes
2820			virtualization enabling across all online CPUs.  The
2821			"cost" of enabling virtualization when KVM is loaded,
2822			is that doing so may interfere with using out-of-tree
2823			hypervisors that want to "own" virtualization hardware.
2824
2825	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2826				   Default is false (don't support).
2827
2828	kvm.nx_huge_pages=
2829			[KVM] Controls the software workaround for the
2830			X86_BUG_ITLB_MULTIHIT bug.
2831			force	: Always deploy workaround.
2832			off	: Never deploy workaround.
2833			auto    : Deploy workaround based on the presence of
2834				  X86_BUG_ITLB_MULTIHIT.
2835
2836			Default is 'auto'.
2837
2838			If the software workaround is enabled for the host,
2839			guests do need not to enable it for nested guests.
2840
2841	kvm.nx_huge_pages_recovery_ratio=
2842			[KVM] Controls how many 4KiB pages are periodically zapped
2843			back to huge pages.  0 disables the recovery, otherwise if
2844			the value is N KVM will zap 1/Nth of the 4KiB pages every
2845			period (see below).  The default is 60.
2846
2847	kvm.nx_huge_pages_recovery_period_ms=
2848			[KVM] Controls the time period at which KVM zaps 4KiB pages
2849			back to huge pages. If the value is a non-zero N, KVM will
2850			zap a portion (see ratio above) of the pages every N msecs.
2851			If the value is 0 (the default), KVM will pick a period based
2852			on the ratio, such that a page is zapped after 1 hour on average.
2853
2854	kvm-amd.nested=	[KVM,AMD] Control nested virtualization feature in
2855			KVM/SVM. Default is 1 (enabled).
2856
2857	kvm-amd.npt=	[KVM,AMD] Control KVM's use of Nested Page Tables,
2858			a.k.a. Two-Dimensional Page Tables. Default is 1
2859			(enabled). Disable by KVM if hardware lacks support
2860			for NPT.
2861
2862	kvm-arm.mode=
2863			[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
2864			operation.
2865
2866			none: Forcefully disable KVM.
2867
2868			nvhe: Standard nVHE-based mode, without support for
2869			      protected guests.
2870
2871			protected: Mode with support for guests whose state is
2872				   kept private from the host, using VHE or
2873				   nVHE depending on HW support.
2874
2875			nested: VHE-based mode with support for nested
2876				virtualization. Requires at least ARMv8.4
2877				hardware (with FEAT_NV2).
2878
2879			Defaults to VHE/nVHE based on hardware support. Setting
2880			mode to "protected" will disable kexec and hibernation
2881			for the host. To force nVHE on VHE hardware, add
2882			"arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" to the
2883			command-line.
2884			"nested" is experimental and should be used with
2885			extreme caution.
2886
2887	kvm-arm.vgic_v3_group0_trap=
2888			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2889			system registers
2890
2891	kvm-arm.vgic_v3_group1_trap=
2892			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2893			system registers
2894
2895	kvm-arm.vgic_v3_common_trap=
2896			[KVM,ARM,EARLY] Trap guest accesses to GICv3 common
2897			system registers
2898
2899	kvm-arm.vgic_v4_enable=
2900			[KVM,ARM,EARLY] Allow use of GICv4 for direct
2901			injection of LPIs.
2902
2903	kvm-arm.wfe_trap_policy=
2904			[KVM,ARM] Control when to set WFE instruction trap for
2905			KVM VMs. Traps are allowed but not guaranteed by the
2906			CPU architecture.
2907
2908			trap: set WFE instruction trap
2909
2910			notrap: clear WFE instruction trap
2911
2912	kvm-arm.wfi_trap_policy=
2913			[KVM,ARM] Control when to set WFI instruction trap for
2914			KVM VMs. Traps are allowed but not guaranteed by the
2915			CPU architecture.
2916
2917			trap: set WFI instruction trap
2918
2919			notrap: clear WFI instruction trap
2920
2921	kvm_cma_resv_ratio=n [PPC,EARLY]
2922			Reserves given percentage from system memory area for
2923			contiguous memory allocation for KVM hash pagetable
2924			allocation.
2925			By default it reserves 5% of total system memory.
2926			Format: <integer>
2927			Default: 5
2928
2929	kvm-intel.ept=	[KVM,Intel] Control KVM's use of Extended Page Tables,
2930			a.k.a. Two-Dimensional Page Tables.  Default is 1
2931			(enabled). Disable by KVM if hardware lacks support
2932			for EPT.
2933
2934	kvm-intel.emulate_invalid_guest_state=
2935			[KVM,Intel] Control whether to emulate invalid guest
2936			state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2937			as guest state is never invalid for unrestricted
2938			guests. This param doesn't apply to nested guests (L2),
2939			as KVM never emulates invalid L2 guest state.
2940			Default is 1 (enabled).
2941
2942	kvm-intel.flexpriority=
2943			[KVM,Intel] Control KVM's use of FlexPriority feature
2944			(TPR shadow). Default is 1 (enabled). Disable by KVM if
2945			hardware lacks support for it.
2946
2947	kvm-intel.nested=
2948			[KVM,Intel] Control nested virtualization feature in
2949			KVM/VMX. Default is 1 (enabled).
2950
2951	kvm-intel.unrestricted_guest=
2952			[KVM,Intel] Control KVM's use of unrestricted guest
2953			feature (virtualized real and unpaged mode). Default
2954			is 1 (enabled). Disable by KVM if EPT is disabled or
2955			hardware lacks support for it.
2956
2957	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2958			CVE-2018-3620.
2959
2960			Valid arguments: never, cond, always
2961
2962			always: L1D cache flush on every VMENTER.
2963			cond:	Flush L1D on VMENTER only when the code between
2964				VMEXIT and VMENTER can leak host memory.
2965			never:	Disables the mitigation
2966
2967			Default is cond (do L1 cache flush in specific instances)
2968
2969	kvm-intel.vpid=	[KVM,Intel] Control KVM's use of Virtual Processor
2970			Identification feature (tagged TLBs). Default is 1
2971			(enabled). Disable by KVM if hardware lacks support
2972			for it.
2973
2974	l1d_flush=	[X86,INTEL,EARLY]
2975			Control mitigation for L1D based snooping vulnerability.
2976
2977			Certain CPUs are vulnerable to an exploit against CPU
2978			internal buffers which can forward information to a
2979			disclosure gadget under certain conditions.
2980
2981			In vulnerable processors, the speculatively
2982			forwarded data can be used in a cache side channel
2983			attack, to access data to which the attacker does
2984			not have direct access.
2985
2986			This parameter controls the mitigation. The
2987			options are:
2988
2989			on         - enable the interface for the mitigation
2990
2991	l1tf=           [X86,EARLY] Control mitigation of the L1TF vulnerability on
2992			      affected CPUs
2993
2994			The kernel PTE inversion protection is unconditionally
2995			enabled and cannot be disabled.
2996
2997			full
2998				Provides all available mitigations for the
2999				L1TF vulnerability. Disables SMT and
3000				enables all mitigations in the
3001				hypervisors, i.e. unconditional L1D flush.
3002
3003				SMT control and L1D flush control via the
3004				sysfs interface is still possible after
3005				boot.  Hypervisors will issue a warning
3006				when the first VM is started in a
3007				potentially insecure configuration,
3008				i.e. SMT enabled or L1D flush disabled.
3009
3010			full,force
3011				Same as 'full', but disables SMT and L1D
3012				flush runtime control. Implies the
3013				'nosmt=force' command line option.
3014				(i.e. sysfs control of SMT is disabled.)
3015
3016			flush
3017				Leaves SMT enabled and enables the default
3018				hypervisor mitigation, i.e. conditional
3019				L1D flush.
3020
3021				SMT control and L1D flush control via the
3022				sysfs interface is still possible after
3023				boot.  Hypervisors will issue a warning
3024				when the first VM is started in a
3025				potentially insecure configuration,
3026				i.e. SMT enabled or L1D flush disabled.
3027
3028			flush,nosmt
3029
3030				Disables SMT and enables the default
3031				hypervisor mitigation.
3032
3033				SMT control and L1D flush control via the
3034				sysfs interface is still possible after
3035				boot.  Hypervisors will issue a warning
3036				when the first VM is started in a
3037				potentially insecure configuration,
3038				i.e. SMT enabled or L1D flush disabled.
3039
3040			flush,nowarn
3041				Same as 'flush', but hypervisors will not
3042				warn when a VM is started in a potentially
3043				insecure configuration.
3044
3045			off
3046				Disables hypervisor mitigations and doesn't
3047				emit any warnings.
3048				It also drops the swap size and available
3049				RAM limit restriction on both hypervisor and
3050				bare metal.
3051
3052			Default is 'flush'.
3053
3054			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3055
3056	l2cr=		[PPC]
3057
3058	l3cr=		[PPC]
3059
3060	lapic		[X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3061			disabled it.
3062
3063	lapic=		[X86,APIC] Do not use TSC deadline
3064			value for LAPIC timer one-shot implementation. Default
3065			back to the programmable timer unit in the LAPIC.
3066			Format: notscdeadline
3067
3068	lapic_timer_c2_ok	[X86,APIC,EARLY] trust the local apic timer
3069			in C2 power state.
3070
3071	libata.dma=	[LIBATA] DMA control
3072			libata.dma=0	  Disable all PATA and SATA DMA
3073			libata.dma=1	  PATA and SATA Disk DMA only
3074			libata.dma=2	  ATAPI (CDROM) DMA only
3075			libata.dma=4	  Compact Flash DMA only
3076			Combinations also work, so libata.dma=3 enables DMA
3077			for disks and CDROMs, but not CFs.
3078
3079	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
3080			libata.ignore_hpa=0	  keep BIOS limits (default)
3081			libata.ignore_hpa=1	  ignore limits, using full disk
3082
3083	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
3084			when set.
3085			Format: <int>
3086
3087	libata.force=	[LIBATA] Force configurations.  The format is a comma-
3088			separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
3089			PORT and DEVICE are decimal numbers matching port, link
3090			or device.  Basically, it matches the ATA ID string
3091			printed on console by libata.  If the whole ID part is
3092			omitted, the last PORT and DEVICE values are used.  If
3093			ID hasn't been specified yet, the configuration applies
3094			to all ports, links and devices.
3095
3096			If only DEVICE is omitted, the parameter applies to
3097			the port and all links and devices behind it.  DEVICE
3098			number of 0 either selects the first device or the
3099			first fan-out link behind PMP device.  It does not
3100			select the host link.  DEVICE number of 15 selects the
3101			host link and device attached to it.
3102
3103			The VAL specifies the configuration to force.  As long
3104			as there is no ambiguity, shortcut notation is allowed.
3105			For example, both 1.5 and 1.5G would work for 1.5Gbps.
3106			The following configurations can be forced.
3107
3108			* Cable type: 40c, 80c, short40c, unk, ign or sata.
3109			  Any ID with matching PORT is used.
3110
3111			* SATA link speed limit: 1.5Gbps or 3.0Gbps.
3112
3113			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3114			  udma[/][16,25,33,44,66,100,133] notation is also
3115			  allowed.
3116
3117			* nohrst, nosrst, norst: suppress hard, soft and both
3118			  resets.
3119
3120			* rstonce: only attempt one reset during hot-unplug
3121			  link recovery.
3122
3123			* [no]dbdelay: Enable or disable the extra 200ms delay
3124			  before debouncing a link PHY and device presence
3125			  detection.
3126
3127			* [no]ncq: Turn on or off NCQ.
3128
3129			* [no]ncqtrim: Enable or disable queued DSM TRIM.
3130
3131			* [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3132
3133			* [no]trim: Enable or disable (unqueued) TRIM.
3134
3135			* trim_zero: Indicate that TRIM command zeroes data.
3136
3137			* max_trim_128m: Set 128M maximum trim size limit.
3138
3139			* [no]dma: Turn on or off DMA transfers.
3140
3141			* atapi_dmadir: Enable ATAPI DMADIR bridge support.
3142
3143			* atapi_mod16_dma: Enable the use of ATAPI DMA for
3144			  commands that are not a multiple of 16 bytes.
3145
3146			* [no]dmalog: Enable or disable the use of the
3147			  READ LOG DMA EXT command to access logs.
3148
3149			* [no]iddevlog: Enable or disable access to the
3150			  identify device data log.
3151
3152			* [no]logdir: Enable or disable access to the general
3153			  purpose log directory.
3154
3155			* max_sec_128: Set transfer size limit to 128 sectors.
3156
3157			* max_sec_1024: Set or clear transfer size limit to
3158			  1024 sectors.
3159
3160			* max_sec_lba48: Set or clear transfer size limit to
3161			  65535 sectors.
3162
3163			* external: Mark port as external (hotplug-capable).
3164
3165			* [no]lpm: Enable or disable link power management.
3166
3167			* [no]setxfer: Indicate if transfer speed mode setting
3168			  should be skipped.
3169
3170			* [no]fua: Disable or enable FUA (Force Unit Access)
3171			  support for devices supporting this feature.
3172
3173			* dump_id: Dump IDENTIFY data.
3174
3175			* disable: Disable this device.
3176
3177			If there are multiple matching configurations changing
3178			the same attribute, the last one is used.
3179
3180	load_ramdisk=	[RAM] [Deprecated]
3181
3182	lockd.nlm_grace_period=P  [NFS] Assign grace period.
3183			Format: <integer>
3184
3185	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
3186			Format: <integer>
3187
3188	lockd.nlm_timeout=T	[NFS] Assign timeout value.
3189			Format: <integer>
3190
3191	lockd.nlm_udpport=M	[NFS] Assign UDP port.
3192			Format: <integer>
3193
3194	lockdown=	[SECURITY,EARLY]
3195			{ integrity | confidentiality }
3196			Enable the kernel lockdown feature. If set to
3197			integrity, kernel features that allow userland to
3198			modify the running kernel are disabled. If set to
3199			confidentiality, kernel features that allow userland
3200			to extract confidential information from the kernel
3201			are also disabled.
3202
3203	locktorture.acq_writer_lim= [KNL]
3204			Set the time limit in jiffies for a lock
3205			acquisition.  Acquisitions exceeding this limit
3206			will result in a splat once they do complete.
3207
3208	locktorture.bind_readers= [KNL]
3209			Specify the list of CPUs to which the readers are
3210			to be bound.
3211
3212	locktorture.bind_writers= [KNL]
3213			Specify the list of CPUs to which the writers are
3214			to be bound.
3215
3216	locktorture.call_rcu_chains= [KNL]
3217			Specify the number of self-propagating call_rcu()
3218			chains to set up.  These are used to ensure that
3219			there is a high probability of an RCU grace period
3220			in progress at any given time.	Defaults to 0,
3221			which disables these call_rcu() chains.
3222
3223	locktorture.long_hold= [KNL]
3224			Specify the duration in milliseconds for the
3225			occasional long-duration lock hold time.  Defaults
3226			to 100 milliseconds.  Select 0 to disable.
3227
3228	locktorture.nested_locks= [KNL]
3229			Specify the maximum lock nesting depth that
3230			locktorture is to exercise, up to a limit of 8
3231			(MAX_NESTED_LOCKS).  Specify zero to disable.
3232			Note that this parameter is ineffective on types
3233			of locks that do not support nested acquisition.
3234
3235	locktorture.nreaders_stress= [KNL]
3236			Set the number of locking read-acquisition kthreads.
3237			Defaults to being automatically set based on the
3238			number of online CPUs.
3239
3240	locktorture.nwriters_stress= [KNL]
3241			Set the number of locking write-acquisition kthreads.
3242
3243	locktorture.onoff_holdoff= [KNL]
3244			Set time (s) after boot for CPU-hotplug testing.
3245
3246	locktorture.onoff_interval= [KNL]
3247			Set time (s) between CPU-hotplug operations, or
3248			zero to disable CPU-hotplug testing.
3249
3250	locktorture.rt_boost= [KNL]
3251			Do periodic testing of real-time lock priority
3252			boosting.  Select 0 to disable, 1 to boost
3253			only rt_mutex, and 2 to boost unconditionally.
3254			Defaults to 2, which might seem to be an
3255			odd choice, but which should be harmless for
3256			non-real-time spinlocks, due to their disabling
3257			of preemption.	Note that non-realtime mutexes
3258			disable boosting.
3259
3260	locktorture.rt_boost_factor= [KNL]
3261			Number that determines how often and for how
3262			long priority boosting is exercised.  This is
3263			scaled down by the number of writers, so that the
3264			number of boosts per unit time remains roughly
3265			constant as the number of writers increases.
3266			On the other hand, the duration of each boost
3267			increases with the number of writers.
3268
3269	locktorture.shuffle_interval= [KNL]
3270			Set task-shuffle interval (jiffies).  Shuffling
3271			tasks allows some CPUs to go into dyntick-idle
3272			mode during the locktorture test.
3273
3274	locktorture.shutdown_secs= [KNL]
3275			Set time (s) after boot system shutdown.  This
3276			is useful for hands-off automated testing.
3277
3278	locktorture.stat_interval= [KNL]
3279			Time (s) between statistics printk()s.
3280
3281	locktorture.stutter= [KNL]
3282			Time (s) to stutter testing, for example,
3283			specifying five seconds causes the test to run for
3284			five seconds, wait for five seconds, and so on.
3285			This tests the locking primitive's ability to
3286			transition abruptly to and from idle.
3287
3288	locktorture.torture_type= [KNL]
3289			Specify the locking implementation to test.
3290
3291	locktorture.verbose= [KNL]
3292			Enable additional printk() statements.
3293
3294	locktorture.writer_fifo= [KNL]
3295			Run the write-side locktorture kthreads at
3296			sched_set_fifo() real-time priority.
3297
3298	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
3299			Format: <irq>
3300
3301	loglevel=	[KNL,EARLY]
3302			All Kernel Messages with a loglevel smaller than the
3303			console loglevel will be printed to the console. It can
3304			also be changed with klogd or other programs. The
3305			loglevels are defined as follows:
3306
3307			0 (KERN_EMERG)		system is unusable
3308			1 (KERN_ALERT)		action must be taken immediately
3309			2 (KERN_CRIT)		critical conditions
3310			3 (KERN_ERR)		error conditions
3311			4 (KERN_WARNING)	warning conditions
3312			5 (KERN_NOTICE)		normal but significant condition
3313			6 (KERN_INFO)		informational
3314			7 (KERN_DEBUG)		debug-level messages
3315
3316	log_buf_len=n[KMG] [KNL,EARLY]
3317			Sets the size of the printk ring buffer, in bytes.
3318			n must be a power of two and greater than the
3319			minimal size. The minimal size is defined by
3320			LOG_BUF_SHIFT kernel config parameter. There
3321			is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config
3322			parameter that allows to increase the default size
3323			depending on the number of CPUs. See init/Kconfig
3324			for more details.
3325
3326	logo.nologo	[FB] Disables display of the built-in Linux logo.
3327			This may be used to provide more screen space for
3328			kernel log messages and is useful when debugging
3329			kernel boot problems.
3330
3331	lp=0		[LP]	Specify parallel ports to use, e.g,
3332	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
3333	lp=reset		first parallel port). 'lp=0' disables the
3334	lp=auto			printer driver. 'lp=reset' (which can be
3335				specified in addition to the ports) causes
3336				attached printers to be reset. Using
3337				lp=port1,port2,... specifies the parallel ports
3338				to associate lp devices with, starting with
3339				lp0. A port specification may be 'none' to skip
3340				that lp device, or a parport name such as
3341				'parport0'. Specifying 'lp=auto' instead of a
3342				port specification list means that device IDs
3343				from each port should be examined, to see if
3344				an IEEE 1284-compliant printer is attached; if
3345				so, the driver will manage that printer.
3346				See also header of drivers/char/lp.c.
3347
3348	lpj=n		[KNL]
3349			Sets loops_per_jiffy to given constant, thus avoiding
3350			time-consuming boot-time autodetection (up to 250 ms per
3351			CPU). 0 enables autodetection (default). To determine
3352			the correct value for your kernel, boot with normal
3353			autodetection and see what value is printed. Note that
3354			on SMP systems the preset will be applied to all CPUs,
3355			which is likely to cause problems if your CPUs need
3356			significantly divergent settings. An incorrect value
3357			will cause delays in the kernel to be wrong, leading to
3358			unpredictable I/O errors and other breakage. Although
3359			unlikely, in the extreme case this might damage your
3360			hardware.
3361
3362	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
3363
3364	lsm=lsm1,...,lsmN
3365			[SECURITY] Choose order of LSM initialization. This
3366			overrides CONFIG_LSM, and the "security=" parameter.
3367
3368	machtype=	[Loongson] Share the same kernel image file between
3369			different yeeloong laptops.
3370			Example: machtype=lemote-yeeloong-2f-7inch
3371
3372	maxcpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
3373			will bring up during bootup.  maxcpus=n : n >= 0 limits
3374			the kernel to bring up 'n' processors. Surely after
3375			bootup you can bring up the other plugged cpu by executing
3376			"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3377			only takes effect during system bootup.
3378			While n=0 is a special case, it is equivalent to "nosmp",
3379			which also disables the IO APIC.
3380
3381	max_loop=	[LOOP] The number of loop block devices that get
3382	(loop.max_loop)	unconditionally pre-created at init time. The default
3383			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3384			of statically allocating a predefined number, loop
3385			devices can be requested on-demand with the
3386			/dev/loop-control interface.
3387
3388	mce=		[X86-{32,64}]
3389
3390			Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
3391
3392		off
3393			disable machine check
3394
3395		no_cmci
3396			disable CMCI(Corrected Machine Check Interrupt) that
3397			Intel processor supports.  Usually this disablement is
3398			not recommended, but it might be handy if your
3399			hardware is misbehaving.
3400
3401			Note that you'll get more problems without CMCI than
3402			with due to the shared banks, i.e. you might get
3403			duplicated error logs.
3404
3405		dont_log_ce
3406			don't make logs for corrected errors.  All events
3407			reported as corrected are silently cleared by OS. This
3408			option will be useful if you have no interest in any
3409			of corrected errors.
3410
3411		ignore_ce
3412			disable features for corrected errors, e.g.
3413			polling timer and CMCI.  All events reported as
3414			corrected are not cleared by OS and remained in its
3415			error banks.
3416
3417			Usually this disablement is not recommended, however
3418			if there is an agent checking/clearing corrected
3419			errors (e.g. BIOS or hardware monitoring
3420			applications), conflicting with OS's error handling,
3421			and you cannot deactivate the agent, then this option
3422			will be a help.
3423
3424		no_lmce
3425			do not opt-in to Local MCE delivery. Use legacy method
3426			to broadcast MCEs.
3427
3428		bootlog
3429			enable logging of machine checks left over from
3430			booting. Disabled by default on AMD Fam10h and older
3431			because some BIOS leave bogus ones.
3432
3433			If your BIOS doesn't do that it's a good idea to
3434			enable though to make sure you log even machine check
3435			events that result in a reboot. On Intel systems it is
3436			enabled by default.
3437
3438		nobootlog
3439			disable boot machine check logging.
3440
3441		monarchtimeout (number)
3442			sets the time in us to wait for other CPUs on machine
3443			checks. 0 to disable.
3444
3445		bios_cmci_threshold
3446			don't overwrite the bios-set CMCI threshold. This boot
3447			option prevents Linux from overwriting the CMCI
3448			threshold set by the bios.  Without this option, Linux
3449			always sets the CMCI threshold to 1. Enabling this may
3450			make memory predictive failure analysis less effective
3451			if the bios sets thresholds for memory errors since we
3452			will not see details for all errors.
3453
3454		recovery
3455			force-enable recoverable machine check code paths
3456
3457			Everything else is in sysfs now.
3458
3459
3460	md=		[HW] RAID subsystems devices and level
3461			See Documentation/admin-guide/md.rst.
3462
3463	mdacon=		[MDA]
3464			Format: <first>,<last>
3465			Specifies range of consoles to be captured by the MDA.
3466
3467	mds=		[X86,INTEL,EARLY]
3468			Control mitigation for the Micro-architectural Data
3469			Sampling (MDS) vulnerability.
3470
3471			Certain CPUs are vulnerable to an exploit against CPU
3472			internal buffers which can forward information to a
3473			disclosure gadget under certain conditions.
3474
3475			In vulnerable processors, the speculatively
3476			forwarded data can be used in a cache side channel
3477			attack, to access data to which the attacker does
3478			not have direct access.
3479
3480			This parameter controls the MDS mitigation. The
3481			options are:
3482
3483			full       - Enable MDS mitigation on vulnerable CPUs
3484			full,nosmt - Enable MDS mitigation and disable
3485				     SMT on vulnerable CPUs
3486			off        - Unconditionally disable MDS mitigation
3487
3488			On TAA-affected machines, mds=off can be prevented by
3489			an active TAA mitigation as both vulnerabilities are
3490			mitigated with the same mechanism so in order to disable
3491			this mitigation, you need to specify tsx_async_abort=off
3492			too.
3493
3494			Not specifying this option is equivalent to
3495			mds=full.
3496
3497			For details see: Documentation/admin-guide/hw-vuln/mds.rst
3498
3499	mem=nn[KMG]	[HEXAGON,EARLY] Set the memory size.
3500			Must be specified, otherwise memory size will be 0.
3501
3502	mem=nn[KMG]	[KNL,BOOT,EARLY] Force usage of a specific amount
3503			of memory Amount of memory to be used in cases
3504			as follows:
3505
3506			1 for test;
3507			2 when the kernel is not able to see the whole system memory;
3508			3 memory that lies after 'mem=' boundary is excluded from
3509			 the hypervisor, then assigned to KVM guests.
3510			4 to limit the memory available for kdump kernel.
3511
3512			[ARC,MICROBLAZE] - the limit applies only to low memory,
3513			high memory is not affected.
3514
3515			[ARM64] - only limits memory covered by the linear
3516			mapping. The NOMAP regions are not affected.
3517
3518			[X86] Work as limiting max address. Use together
3519			with memmap= to avoid physical address space collisions.
3520			Without memmap= PCI devices could be placed at addresses
3521			belonging to unused RAM.
3522
3523			Note that this only takes effects during boot time since
3524			in above case 3, memory may need be hot added after boot
3525			if system memory of hypervisor is not sufficient.
3526
3527	mem=nn[KMG]@ss[KMG]
3528			[ARM,MIPS,EARLY] - override the memory layout
3529			reported by firmware.
3530			Define a memory region of size nn[KMG] starting at
3531			ss[KMG].
3532			Multiple different regions can be specified with
3533			multiple mem= parameters on the command line.
3534
3535	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
3536			memory.
3537
3538	memblock=debug	[KNL,EARLY] Enable memblock debug messages.
3539
3540	memchunk=nn[KMG]
3541			[KNL,SH] Allow user to override the default size for
3542			per-device physically contiguous DMA buffers.
3543
3544	memhp_default_state=online/offline/online_kernel/online_movable
3545			[KNL] Set the initial state for the memory hotplug
3546			onlining policy. If not specified, the default value is
3547			set according to the
3548			CONFIG_MHP_DEFAULT_ONLINE_TYPE kernel config
3549			options.
3550			See Documentation/admin-guide/mm/memory-hotplug.rst.
3551
3552	memmap=exactmap	[KNL,X86,EARLY] Enable setting of an exact
3553			E820 memory map, as specified by the user.
3554			Such memmap=exactmap lines can be constructed based on
3555			BIOS output or other requirements. See the memmap=nn@ss
3556			option description.
3557
3558	memmap=nn[KMG]@ss[KMG]
3559			[KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory.
3560			Region of memory to be used is from ss to ss+nn.
3561			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3562			which limits max address to nn[KMG].
3563			Multiple different regions can be specified,
3564			comma delimited.
3565			Example:
3566				memmap=100M@2G,100M#3G,1G!1024G
3567
3568	memmap=nn[KMG]#ss[KMG]
3569			[KNL,ACPI,EARLY] Mark specific memory as ACPI data.
3570			Region of memory to be marked is from ss to ss+nn.
3571
3572	memmap=nn[KMG]$ss[KMG]
3573			[KNL,ACPI,EARLY] Mark specific memory as reserved.
3574			Region of memory to be reserved is from ss to ss+nn.
3575			Example: Exclude memory from 0x18690000-0x1869ffff
3576			         memmap=64K$0x18690000
3577			         or
3578			         memmap=0x10000$0x18690000
3579			Some bootloaders may need an escape character before '$',
3580			like Grub2, otherwise '$' and the following number
3581			will be eaten.
3582
3583	memmap=nn[KMG]!ss[KMG,EARLY]
3584			[KNL,X86] Mark specific memory as protected.
3585			Region of memory to be used, from ss to ss+nn.
3586			The memory region may be marked as e820 type 12 (0xc)
3587			and is NVDIMM or ADR memory.
3588
3589	memmap=<size>%<offset>-<oldtype>+<newtype>
3590			[KNL,ACPI,EARLY] Convert memory within the specified region
3591			from <oldtype> to <newtype>. If "-<oldtype>" is left
3592			out, the whole region will be marked as <newtype>,
3593			even if previously unavailable. If "+<newtype>" is left
3594			out, matching memory will be removed. Types are
3595			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3596			3 = ACPI, 12 = PRAM.
3597
3598	memory_corruption_check=0/1 [X86,EARLY]
3599			Some BIOSes seem to corrupt the first 64k of
3600			memory when doing things like suspend/resume.
3601			Setting this option will scan the memory
3602			looking for corruption.  Enabling this will
3603			both detect corruption and prevent the kernel
3604			from using the memory being corrupted.
3605			However, its intended as a diagnostic tool; if
3606			repeatable BIOS-originated corruption always
3607			affects the same memory, you can use memmap=
3608			to prevent the kernel from using that memory.
3609
3610	memory_corruption_check_size=size [X86,EARLY]
3611			By default it checks for corruption in the low
3612			64k, making this memory unavailable for normal
3613			use.  Use this parameter to scan for
3614			corruption in more or less memory.
3615
3616	memory_corruption_check_period=seconds [X86,EARLY]
3617			By default it checks for corruption every 60
3618			seconds.  Use this parameter to check at some
3619			other rate.  0 disables periodic checking.
3620
3621	memory_hotplug.memmap_on_memory
3622			[KNL,X86,ARM] Boolean flag to enable this feature.
3623			Format: {on | off (default)}
3624			When enabled, runtime hotplugged memory will
3625			allocate its internal metadata (struct pages,
3626			those vmemmap pages cannot be optimized even
3627			if hugetlb_free_vmemmap is enabled) from the
3628			hotadded memory which will allow to hotadd a
3629			lot of memory without requiring additional
3630			memory to do so.
3631			This feature is disabled by default because it
3632			has some implication on large (e.g. GB)
3633			allocations in some configurations (e.g. small
3634			memory blocks).
3635			The state of the flag can be read in
3636			/sys/module/memory_hotplug/parameters/memmap_on_memory.
3637			Note that even when enabled, there are a few cases where
3638			the feature is not effective.
3639
3640	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
3641			Format: <integer>
3642			default : 0 <disable>
3643			Specifies the number of memtest passes to be
3644			performed. Each pass selects another test
3645			pattern from a given set of patterns. Memtest
3646			fills the memory with this pattern, validates
3647			memory contents and reserves bad memory
3648			regions that are detected.
3649
3650	mem_encrypt=	[X86-64] AMD Secure Memory Encryption (SME) control
3651			Valid arguments: on, off
3652			Default: off
3653			mem_encrypt=on:		Activate SME
3654			mem_encrypt=off:	Do not activate SME
3655
3656			Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3657			for details on when memory encryption can be activated.
3658
3659	mem_sleep_default=	[SUSPEND] Default system suspend mode:
3660			s2idle  - Suspend-To-Idle
3661			shallow - Power-On Suspend or equivalent (if supported)
3662			deep    - Suspend-To-RAM or equivalent (if supported)
3663			See Documentation/admin-guide/pm/sleep-states.rst.
3664
3665	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
3666			the BIOS has incorrectly applied a workaround. TinyBIOS
3667			version 0.98 is known to be affected, 0.99 fixes the
3668			problem by letting the user disable the workaround.
3669
3670	mga=		[HW,DRM]
3671
3672	microcode.force_minrev=	[X86]
3673			Format: <bool>
3674			Enable or disable the microcode minimal revision
3675			enforcement for the runtime microcode loader.
3676
3677	mini2440=	[ARM,HW,KNL]
3678			Format:[0..2][b][c][t]
3679			Default: "0tb"
3680			MINI2440 configuration specification:
3681			0 - The attached screen is the 3.5" TFT
3682			1 - The attached screen is the 7" TFT
3683			2 - The VGA Shield is attached (1024x768)
3684			Leaving out the screen size parameter will not load
3685			the TFT driver, and the framebuffer will be left
3686			unconfigured.
3687			b - Enable backlight. The TFT backlight pin will be
3688			linked to the kernel VESA blanking code and a GPIO
3689			LED. This parameter is not necessary when using the
3690			VGA shield.
3691			c - Enable the s3c camera interface.
3692			t - Reserved for enabling touchscreen support. The
3693			touchscreen support is not enabled in the mainstream
3694			kernel as of 2.6.30, a preliminary port can be found
3695			in the "bleeding edge" mini2440 support kernel at
3696			https://repo.or.cz/w/linux-2.6/mini2440.git
3697
3698	mitigations=
3699			[X86,PPC,S390,ARM64,EARLY] Control optional mitigations for
3700			CPU vulnerabilities.  This is a set of curated,
3701			arch-independent options, each of which is an
3702			aggregation of existing arch-specific options.
3703
3704			Note, "mitigations" is supported if and only if the
3705			kernel was built with CPU_MITIGATIONS=y.
3706
3707			off
3708				Disable all optional CPU mitigations.  This
3709				improves system performance, but it may also
3710				expose users to several CPU vulnerabilities.
3711				Equivalent to: if nokaslr then kpti=0 [ARM64]
3712					       gather_data_sampling=off [X86]
3713					       indirect_target_selection=off [X86]
3714					       kvm.nx_huge_pages=off [X86]
3715					       l1tf=off [X86]
3716					       mds=off [X86]
3717					       mmio_stale_data=off [X86]
3718					       no_entry_flush [PPC]
3719					       no_uaccess_flush [PPC]
3720					       nobp=0 [S390]
3721					       nopti [X86,PPC]
3722					       nospectre_bhb [ARM64]
3723					       nospectre_v1 [X86,PPC]
3724					       nospectre_v2 [X86,PPC,S390,ARM64]
3725					       reg_file_data_sampling=off [X86]
3726					       retbleed=off [X86]
3727					       spec_rstack_overflow=off [X86]
3728					       spec_store_bypass_disable=off [X86,PPC]
3729					       spectre_bhi=off [X86]
3730					       spectre_v2_user=off [X86]
3731					       srbds=off [X86,INTEL]
3732					       ssbd=force-off [ARM64]
3733					       tsx_async_abort=off [X86]
3734
3735				Exceptions:
3736					       This does not have any effect on
3737					       kvm.nx_huge_pages when
3738					       kvm.nx_huge_pages=force.
3739
3740			auto (default)
3741				Mitigate all CPU vulnerabilities, but leave SMT
3742				enabled, even if it's vulnerable.  This is for
3743				users who don't want to be surprised by SMT
3744				getting disabled across kernel upgrades, or who
3745				have other ways of avoiding SMT-based attacks.
3746				Equivalent to: (default behavior)
3747
3748			auto,nosmt
3749				Mitigate all CPU vulnerabilities, disabling SMT
3750				if needed.  This is for users who always want to
3751				be fully mitigated, even if it means losing SMT.
3752				Equivalent to: l1tf=flush,nosmt [X86]
3753					       mds=full,nosmt [X86]
3754					       tsx_async_abort=full,nosmt [X86]
3755					       mmio_stale_data=full,nosmt [X86]
3756					       retbleed=auto,nosmt [X86]
3757
3758	mminit_loglevel=
3759			[KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this
3760			parameter allows control of the logging verbosity for
3761			the additional memory initialisation checks. A value
3762			of 0 disables mminit logging and a level of 4 will
3763			log everything. Information is printed at KERN_DEBUG
3764			so loglevel=8 may also need to be specified.
3765
3766	mmio_stale_data=
3767			[X86,INTEL,EARLY] Control mitigation for the Processor
3768			MMIO Stale Data vulnerabilities.
3769
3770			Processor MMIO Stale Data is a class of
3771			vulnerabilities that may expose data after an MMIO
3772			operation. Exposed data could originate or end in
3773			the same CPU buffers as affected by MDS and TAA.
3774			Therefore, similar to MDS and TAA, the mitigation
3775			is to clear the affected CPU buffers.
3776
3777			This parameter controls the mitigation. The
3778			options are:
3779
3780			full       - Enable mitigation on vulnerable CPUs
3781
3782			full,nosmt - Enable mitigation and disable SMT on
3783				     vulnerable CPUs.
3784
3785			off        - Unconditionally disable mitigation
3786
3787			On MDS or TAA affected machines,
3788			mmio_stale_data=off can be prevented by an active
3789			MDS or TAA mitigation as these vulnerabilities are
3790			mitigated with the same mechanism so in order to
3791			disable this mitigation, you need to specify
3792			mds=off and tsx_async_abort=off too.
3793
3794			Not specifying this option is equivalent to
3795			mmio_stale_data=full.
3796
3797			For details see:
3798			Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3799
3800	<module>.async_probe[=<bool>] [KNL]
3801			If no <bool> value is specified or if the value
3802			specified is not a valid <bool>, enable asynchronous
3803			probe on this module.  Otherwise, enable/disable
3804			asynchronous probe on this module as indicated by the
3805			<bool> value. See also: module.async_probe
3806
3807	module.async_probe=<bool>
3808			[KNL] When set to true, modules will use async probing
3809			by default. To enable/disable async probing for a
3810			specific module, use the module specific control that
3811			is documented under <module>.async_probe. When both
3812			module.async_probe and <module>.async_probe are
3813			specified, <module>.async_probe takes precedence for
3814			the specific module.
3815
3816	module.enable_dups_trace
3817			[KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3818			this means that duplicate request_module() calls will
3819			trigger a WARN_ON() instead of a pr_warn(). Note that
3820			if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3821			will always be issued and this option does nothing.
3822	module.sig_enforce
3823			[KNL] When CONFIG_MODULE_SIG is set, this means that
3824			modules without (valid) signatures will fail to load.
3825			Note that if CONFIG_MODULE_SIG_FORCE is set, that
3826			is always true, so this option does nothing.
3827
3828	module_blacklist=  [KNL] Do not load a comma-separated list of
3829			modules.  Useful for debugging problem modules.
3830
3831	mousedev.tap_time=
3832			[MOUSE] Maximum time between finger touching and
3833			leaving touchpad surface for touch to be considered
3834			a tap and be reported as a left button click (for
3835			touchpads working in absolute mode only).
3836			Format: <msecs>
3837	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
3838			reporting absolute coordinates, such as tablets
3839	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
3840			reporting absolute coordinates, such as tablets
3841
3842	movablecore=	[KNL,X86,PPC,EARLY]
3843			Format: nn[KMGTPE] | nn%
3844			This parameter is the complement to kernelcore=, it
3845			specifies the amount of memory used for migratable
3846			allocations.  If both kernelcore and movablecore is
3847			specified, then kernelcore will be at *least* the
3848			specified value but may be more.  If movablecore on its
3849			own is specified, the administrator must be careful
3850			that the amount of memory usable for all allocations
3851			is not too small.
3852
3853	movable_node	[KNL,EARLY] Boot-time switch to make hotplugable memory
3854			NUMA nodes to be movable. This means that the memory
3855			of such nodes will be usable only for movable
3856			allocations which rules out almost all kernel
3857			allocations. Use with caution!
3858
3859	MTD_Partition=	[MTD]
3860			Format: <name>,<region-number>,<size>,<offset>
3861
3862	MTD_Region=	[MTD] Format:
3863			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3864
3865	mtdparts=	[MTD]
3866			See drivers/mtd/parsers/cmdlinepart.c
3867
3868	mtouchusb.raw_coordinates=
3869			[HW] Make the MicroTouch USB driver use raw coordinates
3870			('y', default) or cooked coordinates ('n')
3871
3872	mtrr=debug	[X86,EARLY]
3873			Enable printing debug information related to MTRR
3874			registers at boot time.
3875
3876	mtrr_chunk_size=nn[KMG,X86,EARLY]
3877			used for mtrr cleanup. It is largest continuous chunk
3878			that could hold holes aka. UC entries.
3879
3880	mtrr_gran_size=nn[KMG,X86,EARLY]
3881			Used for mtrr cleanup. It is granularity of mtrr block.
3882			Default is 1.
3883			Large value could prevent small alignment from
3884			using up MTRRs.
3885
3886	mtrr_spare_reg_nr=n [X86,EARLY]
3887			Format: <integer>
3888			Range: 0,7 : spare reg number
3889			Default : 1
3890			Used for mtrr cleanup. It is spare mtrr entries number.
3891			Set to 2 or more if your graphical card needs more.
3892
3893	multitce=off	[PPC]  This parameter disables the use of the pSeries
3894			firmware feature for updating multiple TCE entries
3895			at a time.
3896
3897	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
3898
3899	netdev=		[NET] Network devices parameters
3900			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3901			Note that mem_start is often overloaded to mean
3902			something different and driver-specific.
3903			This usage is only documented in each driver source
3904			file if at all.
3905
3906	netpoll.carrier_timeout=
3907			[NET] Specifies amount of time (in seconds) that
3908			netpoll should wait for a carrier. By default netpoll
3909			waits 4 seconds.
3910
3911	nf_conntrack.acct=
3912			[NETFILTER] Enable connection tracking flow accounting
3913			0 to disable accounting
3914			1 to enable accounting
3915			Default value is 0.
3916
3917	nfs.cache_getent=
3918			[NFS] sets the pathname to the program which is used
3919			to update the NFS client cache entries.
3920
3921	nfs.cache_getent_timeout=
3922			[NFS] sets the timeout after which an attempt to
3923			update a cache entry is deemed to have failed.
3924
3925	nfs.callback_nr_threads=
3926			[NFSv4] set the total number of threads that the
3927			NFS client will assign to service NFSv4 callback
3928			requests.
3929
3930	nfs.callback_tcpport=
3931			[NFS] set the TCP port on which the NFSv4 callback
3932			channel should listen.
3933
3934	nfs.delay_retrans=
3935			[NFS] specifies the number of times the NFSv4 client
3936			retries the request before returning an EAGAIN error,
3937			after a reply of NFS4ERR_DELAY from the server.
3938			Only applies if the softerr mount option is enabled,
3939			and the specified value is >= 0.
3940
3941	nfs.enable_ino64=
3942			[NFS] enable 64-bit inode numbers.
3943			If zero, the NFS client will fake up a 32-bit inode
3944			number for the readdir() and stat() syscalls instead
3945			of returning the full 64-bit number.
3946			The default is to return 64-bit inode numbers.
3947
3948	nfs.idmap_cache_timeout=
3949			[NFS] set the maximum lifetime for idmapper cache
3950			entries.
3951
3952	nfs.max_session_cb_slots=
3953			[NFSv4.1] Sets the maximum number of session
3954			slots the client will assign to the callback
3955			channel. This determines the maximum number of
3956			callbacks the client will process in parallel for
3957			a particular server.
3958
3959	nfs.max_session_slots=
3960			[NFSv4.1] Sets the maximum number of session slots
3961			the client will attempt to negotiate with the server.
3962			This limits the number of simultaneous RPC requests
3963			that the client can send to the NFSv4.1 server.
3964			Note that there is little point in setting this
3965			value higher than the max_tcp_slot_table_limit.
3966
3967	nfs.nfs4_disable_idmapping=
3968			[NFSv4] When set to the default of '1', this option
3969			ensures that both the RPC level authentication
3970			scheme and the NFS level operations agree to use
3971			numeric uids/gids if the mount is using the
3972			'sec=sys' security flavour. In effect it is
3973			disabling idmapping, which can make migration from
3974			legacy NFSv2/v3 systems to NFSv4 easier.
3975			Servers that do not support this mode of operation
3976			will be autodetected by the client, and it will fall
3977			back to using the idmapper.
3978			To turn off this behaviour, set the value to '0'.
3979
3980	nfs.nfs4_unique_id=
3981			[NFS4] Specify an additional fixed unique ident-
3982			ification string that NFSv4 clients can insert into
3983			their nfs_client_id4 string.  This is typically a
3984			UUID that is generated at system install time.
3985
3986	nfs.recover_lost_locks=
3987			[NFSv4] Attempt to recover locks that were lost due
3988			to a lease timeout on the server. Please note that
3989			doing this risks data corruption, since there are
3990			no guarantees that the file will remain unchanged
3991			after the locks are lost.
3992			If you want to enable the kernel legacy behaviour of
3993			attempting to recover these locks, then set this
3994			parameter to '1'.
3995			The default parameter value of '0' causes the kernel
3996			not to attempt recovery of lost locks.
3997
3998	nfs.send_implementation_id=
3999			[NFSv4.1] Send client implementation identification
4000			information in exchange_id requests.
4001			If zero, no implementation identification information
4002			will be sent.
4003			The default is to send the implementation identification
4004			information.
4005
4006	nfs4.layoutstats_timer=
4007			[NFSv4.2] Change the rate at which the kernel sends
4008			layoutstats to the pNFS metadata server.
4009
4010			Setting this to value to 0 causes the kernel to use
4011			whatever value is the default set by the layout
4012			driver. A non-zero value sets the minimum interval
4013			in seconds between layoutstats transmissions.
4014
4015	nfsd.inter_copy_offload_enable=
4016			[NFSv4.2] When set to 1, the server will support
4017			server-to-server copies for which this server is
4018			the destination of the copy.
4019
4020	nfsd.nfs4_disable_idmapping=
4021			[NFSv4] When set to the default of '1', the NFSv4
4022			server will return only numeric uids and gids to
4023			clients using auth_sys, and will accept numeric uids
4024			and gids from such clients.  This is intended to ease
4025			migration from NFSv2/v3.
4026
4027	nfsd.nfsd4_ssc_umount_timeout=
4028			[NFSv4.2] When used as the destination of a
4029			server-to-server copy, knfsd temporarily mounts
4030			the source server.  It caches the mount in case
4031			it will be needed again, and discards it if not
4032			used for the number of milliseconds specified by
4033			this parameter.
4034
4035	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
4036			See Documentation/admin-guide/nfs/nfsroot.rst.
4037
4038	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
4039			See Documentation/admin-guide/nfs/nfsroot.rst.
4040
4041	nfsrootdebug	[NFS] enable nfsroot debugging messages.
4042			See Documentation/admin-guide/nfs/nfsroot.rst.
4043
4044	nmi_backtrace.backtrace_idle [KNL]
4045			Dump stacks even of idle CPUs in response to an
4046			NMI stack-backtrace request.
4047
4048	nmi_debug=	[KNL,SH] Specify one or more actions to take
4049			when a NMI is triggered.
4050			Format: [state][,regs][,debounce][,die]
4051
4052	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
4053			Format: [panic,][nopanic,][rNNN,][num]
4054			Valid num: 0 or 1
4055			0 - turn hardlockup detector in nmi_watchdog off
4056			1 - turn hardlockup detector in nmi_watchdog on
4057			rNNN - configure the watchdog with raw perf event 0xNNN
4058
4059			When panic is specified, panic when an NMI watchdog
4060			timeout occurs (or 'nopanic' to not panic on an NMI
4061			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
4062			To disable both hard and soft lockup detectors,
4063			please see 'nowatchdog'.
4064			This is useful when you use a panic=... timeout and
4065			need the box quickly up again.
4066
4067			These settings can be accessed at runtime via
4068			the nmi_watchdog and hardlockup_panic sysctls.
4069
4070	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
4071			emulation library even if a 387 maths coprocessor
4072			is present.
4073
4074	no4lvl		[RISCV,EARLY] Disable 4-level and 5-level paging modes.
4075			Forces kernel to use 3-level paging instead.
4076
4077	no5lvl		[X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4078			kernel to use 4-level paging instead.
4079
4080	noalign		[KNL,ARM]
4081
4082	noapic		[SMP,APIC,EARLY] Tells the kernel to not make use of any
4083			IOAPICs that may be present in the system.
4084
4085	noapictimer	[APIC,X86] Don't set up the APIC timer
4086
4087	noautogroup	Disable scheduler automatic task group creation.
4088
4089	nocache		[ARM,EARLY]
4090
4091	no_console_suspend
4092			[HW] Never suspend the console
4093			Disable suspending of consoles during suspend and
4094			hibernate operations.  Once disabled, debugging
4095			messages can reach various consoles while the rest
4096			of the system is being put to sleep (ie, while
4097			debugging driver suspend/resume hooks).  This may
4098			not work reliably with all consoles, but is known
4099			to work with serial and VGA consoles.
4100			To facilitate more flexible debugging, we also add
4101			console_suspend, a printk module parameter to control
4102			it. Users could use console_suspend (usually
4103			/sys/module/printk/parameters/console_suspend) to
4104			turn on/off it dynamically.
4105
4106	no_debug_objects
4107			[KNL,EARLY] Disable object debugging
4108
4109	nodsp		[SH] Disable hardware DSP at boot time.
4110
4111	noefi		[EFI,EARLY] Disable EFI runtime services support.
4112
4113	no_entry_flush  [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4114
4115	noexec32	[X86-64]
4116			This affects only 32-bit executables.
4117			noexec32=on: enable non-executable mappings (default)
4118				read doesn't imply executable mappings
4119			noexec32=off: disable non-executable mappings
4120				read implies executable mappings
4121
4122	no_file_caps	Tells the kernel not to honor file capabilities.  The
4123			only way then for a file to be executed with privilege
4124			is to be setuid root or executed by root.
4125
4126	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
4127
4128	nofsgsbase	[X86] Disables FSGSBASE instructions.
4129
4130	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
4131			register save and restore. The kernel will only save
4132			legacy floating-point registers on task switch.
4133
4134	nogbpages	[X86] Do not use GB pages for kernel direct mappings.
4135
4136	no_hash_pointers
4137			[KNL,EARLY]
4138			Force pointers printed to the console or buffers to be
4139			unhashed.  By default, when a pointer is printed via %p
4140			format string, that pointer is "hashed", i.e. obscured
4141			by hashing the pointer value.  This is a security feature
4142			that hides actual kernel addresses from unprivileged
4143			users, but it also makes debugging the kernel more
4144			difficult since unequal pointers can no longer be
4145			compared.  However, if this command-line option is
4146			specified, then all normal pointers will have their true
4147			value printed. This option should only be specified when
4148			debugging the kernel.  Please do not use on production
4149			kernels.
4150
4151	nohibernate	[HIBERNATION] Disable hibernation and resume.
4152
4153	nohlt		[ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
4154			busy wait in do_idle() and not use the arch_cpu_idle()
4155			implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
4156			to be effective. This is useful on platforms where the
4157			sleep(SH) or wfi(ARM,ARM64) instructions do not work
4158			correctly or when doing power measurements to evaluate
4159			the impact of the sleep instructions. This is also
4160			useful when using JTAG debugger.
4161
4162	nohpet		[X86] Don't use the HPET timer.
4163
4164	nohugeiomap	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
4165
4166	nohugevmalloc	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
4167
4168	nohz=		[KNL] Boottime enable/disable dynamic ticks
4169			Valid arguments: on, off
4170			Default: on
4171
4172	nohz_full=	[KNL,BOOT,SMP,ISOL]
4173			The argument is a cpu list, as described above.
4174			In kernels built with CONFIG_NO_HZ_FULL=y, set
4175			the specified list of CPUs whose tick will be stopped
4176			whenever possible. The boot CPU will be forced outside
4177			the range to maintain the timekeeping.  Any CPUs
4178			in this list will have their RCU callbacks offloaded,
4179			just as if they had also been called out in the
4180			rcu_nocbs= boot parameter.
4181
4182			Note that this argument takes precedence over
4183			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4184
4185	noinitrd	[RAM] Tells the kernel not to load any configured
4186			initial RAM disk.
4187
4188	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4189			remapping.
4190			[Deprecated - use intremap=off]
4191
4192	noinvpcid	[X86,EARLY] Disable the INVPCID cpu feature.
4193
4194	noiotrap	[SH] Disables trapped I/O port accesses.
4195
4196	noirqdebug	[X86-32] Disables the code which attempts to detect and
4197			disable unhandled interrupt sources.
4198
4199	noisapnp	[ISAPNP] Disables ISA PnP code.
4200
4201	nokaslr		[KNL,EARLY]
4202			When CONFIG_RANDOMIZE_BASE is set, this disables
4203			kernel and module base offset ASLR (Address Space
4204			Layout Randomization).
4205
4206	no-kvmapf	[X86,KVM,EARLY] Disable paravirtualized asynchronous page
4207			fault handling.
4208
4209	no-kvmclock	[X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4210
4211	nolapic		[X86-32,APIC,EARLY] Do not enable or use the local APIC.
4212
4213	nolapic_timer	[X86-32,APIC,EARLY] Do not use the local APIC timer.
4214
4215	nomce		[X86-32] Disable Machine Check Exception
4216
4217	nomfgpt		[X86-32] Disable Multi-Function General Purpose
4218			Timer usage (for AMD Geode machines).
4219
4220	nomodeset	Disable kernel modesetting. Most systems' firmware
4221			sets up a display mode and provides framebuffer memory
4222			for output. With nomodeset, DRM and fbdev drivers will
4223			not load if they could possibly displace the pre-
4224			initialized output. Only the system framebuffer will
4225			be available for use. The respective drivers will not
4226			perform display-mode changes or accelerated rendering.
4227
4228			Useful as error fallback, or for testing and debugging.
4229
4230	nomodule	Disable module load
4231
4232	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
4233			shutdown the other cpus.  Instead use the REBOOT_VECTOR
4234			irq.
4235
4236	nopat		[X86,EARLY] Disable PAT (page attribute table extension of
4237			pagetables) support.
4238
4239	nopcid		[X86-64,EARLY] Disable the PCID cpu feature.
4240
4241	nopku		[X86] Disable Memory Protection Keys CPU feature found
4242			in some Intel CPUs.
4243
4244	nopti		[X86-64,EARLY]
4245			Equivalent to pti=off
4246
4247	nopv=		[X86,XEN,KVM,HYPER_V,VMWARE,EARLY]
4248			Disables the PV optimizations forcing the guest to run
4249			as generic guest with no PV drivers. Currently support
4250			XEN HVM, KVM, HYPER_V and VMWARE guest.
4251
4252	nopvspin	[X86,XEN,KVM,EARLY]
4253			Disables the qspinlock slow path using PV optimizations
4254			which allow the hypervisor to 'idle' the guest on lock
4255			contention.
4256
4257	norandmaps	Don't use address space randomization.  Equivalent to
4258			echo 0 > /proc/sys/kernel/randomize_va_space
4259
4260	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
4261			with UP alternatives
4262
4263	noresume	[SWSUSP] Disables resume and restores original swap
4264			space.
4265
4266	no-scroll	[VGA] Disables scrollback.
4267			This is required for the Braillex ib80-piezo Braille
4268			reader made by F.H. Papenmeier (Germany).
4269
4270	nosgx		[X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4271
4272	nosmap		[PPC,EARLY]
4273			Disable SMAP (Supervisor Mode Access Prevention)
4274			even if it is supported by processor.
4275
4276	nosmep		[PPC64s,EARLY]
4277			Disable SMEP (Supervisor Mode Execution Prevention)
4278			even if it is supported by processor.
4279
4280	nosmp		[SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
4281			and disable the IO APIC.  legacy for "maxcpus=0".
4282
4283	nosmt		[KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT).
4284			Equivalent to smt=1.
4285
4286			[KNL,X86,PPC,S390] Disable symmetric multithreading (SMT).
4287			nosmt=force: Force disable SMT, cannot be undone
4288				     via the sysfs control file.
4289
4290	nosoftlockup	[KNL] Disable the soft-lockup detector.
4291
4292	nospec_store_bypass_disable
4293			[HW,EARLY] Disable all mitigations for the Speculative
4294			Store Bypass vulnerability
4295
4296	nospectre_bhb	[ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4297			history injection) vulnerability. System may allow data leaks
4298			with this option.
4299
4300	nospectre_v1	[X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4301			(bounds check bypass). With this option data leaks are
4302			possible in the system.
4303
4304	nospectre_v2	[X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4305			for the Spectre variant 2 (indirect branch
4306			prediction) vulnerability. System may allow data
4307			leaks with this option.
4308
4309	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4310			Disable paravirtualized steal time accounting. steal time
4311			is computed, but won't influence scheduler behaviour
4312
4313	nosync		[HW,M68K] Disables sync negotiation for all devices.
4314
4315	no_timer_check	[X86,APIC] Disables the code which tests for broken
4316			timer IRQ sources, i.e., the IO-APIC timer. This can
4317			work around problems with incorrect timer
4318			initialization on some boards.
4319
4320	no_uaccess_flush
4321	                [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4322
4323	novmcoredd	[KNL,KDUMP]
4324			Disable device dump. Device dump allows drivers to
4325			append dump data to vmcore so you can collect driver
4326			specified debug info.  Drivers can append the data
4327			without any limit and this data is stored in memory,
4328			so this may cause significant memory stress.  Disabling
4329			device dump can help save memory but the driver debug
4330			data will be no longer available.  This parameter
4331			is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4332			is set.
4333
4334	no-vmw-sched-clock
4335			[X86,PV_OPS,EARLY] Disable paravirtualized VMware
4336			scheduler clock and use the default one.
4337
4338	nowatchdog	[KNL] Disable both lockup detectors, i.e.
4339			soft-lockup and NMI watchdog (hard-lockup).
4340
4341	nowb		[ARM,EARLY]
4342
4343	nox2apic	[X86-64,APIC,EARLY] Do not enable x2APIC mode.
4344
4345			NOTE: this parameter will be ignored on systems with the
4346			LEGACY_XAPIC_DISABLED bit set in the
4347			IA32_XAPIC_DISABLE_STATUS MSR.
4348
4349	noxsave		[BUGS=X86] Disables x86 extended register state save
4350			and restore using xsave. The kernel will fallback to
4351			enabling legacy floating-point and sse state.
4352
4353	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
4354			register states. The kernel will fall back to use
4355			xsave to save the states. By using this parameter,
4356			performance of saving the states is degraded because
4357			xsave doesn't support modified optimization while
4358			xsaveopt supports it on xsaveopt enabled systems.
4359
4360	noxsaves	[X86] Disables xsaves and xrstors used in saving and
4361			restoring x86 extended register state in compacted
4362			form of xsave area. The kernel will fall back to use
4363			xsaveopt and xrstor to save and restore the states
4364			in standard form of xsave area. By using this
4365			parameter, xsave area per process might occupy more
4366			memory on xsaves enabled systems.
4367
4368	nr_cpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
4369			could support.  nr_cpus=n : n >= 1 limits the kernel to
4370			support 'n' processors. It could be larger than the
4371			number of already plugged CPU during bootup, later in
4372			runtime you can physically add extra cpu until it reaches
4373			n. So during boot up some boot time memory for per-cpu
4374			variables need be pre-allocated for later physical cpu
4375			hot plugging.
4376
4377	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
4378
4379	numa=off 	[KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY]
4380			Disable NUMA, Only set up a single NUMA node
4381			spanning all memory.
4382
4383	numa=fake=<size>[MG]
4384			[KNL, ARM64, RISCV, X86, EARLY]
4385			If given as a memory unit, fills all system RAM with
4386			nodes of size interleaved over physical nodes.
4387
4388	numa=fake=<N>
4389			[KNL, ARM64, RISCV, X86, EARLY]
4390			If given as an integer, fills all system RAM with N
4391			fake nodes interleaved over physical nodes.
4392
4393	numa=fake=<N>U
4394			[KNL, ARM64, RISCV, X86, EARLY]
4395			If given as an integer followed by 'U', it will
4396			divide each physical node into N emulated nodes.
4397
4398	numa=noacpi	[X86] Don't parse the SRAT table for NUMA setup
4399
4400	numa=nohmat	[X86] Don't parse the HMAT table for NUMA setup, or
4401			soft-reserved memory partitioning.
4402
4403	numa_balancing=	[KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4404			NUMA balancing.
4405			Allowed values are enable and disable
4406
4407	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4408			'node', 'default' can be specified
4409			This can be set from sysctl after boot.
4410			See Documentation/admin-guide/sysctl/vm.rst for details.
4411
4412	ohci1394_dma=early	[HW,EARLY] enable debugging via the ohci1394 driver.
4413			See Documentation/core-api/debugging-via-ohci1394.rst for more
4414			info.
4415
4416	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4417			Rather than timing out after 20 ms if an EC
4418			command is not properly ACKed, override the length
4419			of the timeout.  We have interrupts disabled while
4420			waiting for the ACK, so if this is set too high
4421			interrupts *may* be lost!
4422
4423	omap_mux=	[OMAP] Override bootloader pin multiplexing.
4424			Format: <mux_mode0.mode_name=value>...
4425			For example, to override I2C bus2:
4426			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4427
4428	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
4429
4430			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4431
4432			boundary - index of last SLC block on Flex-OneNAND.
4433				   The remaining blocks are configured as MLC blocks.
4434			lock	 - Configure if Flex-OneNAND boundary should be locked.
4435				   Once locked, the boundary cannot be changed.
4436				   1 indicates lock status, 0 indicates unlock status.
4437
4438	oops=panic	[KNL,EARLY]
4439			Always panic on oopses. Default is to just kill the
4440			process, but there is a small probability of
4441			deadlocking the machine.
4442			This will also cause panics on machine check exceptions.
4443			Useful together with panic=30 to trigger a reboot.
4444
4445	page_alloc.shuffle=
4446			[KNL] Boolean flag to control whether the page allocator
4447			should randomize its free lists. This parameter can be
4448			used to enable/disable page randomization. The state of
4449			the flag can be read from sysfs at:
4450			/sys/module/page_alloc/parameters/shuffle.
4451			This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
4452
4453	page_owner=	[KNL,EARLY] Boot-time page_owner enabling option.
4454			Storage of the information about who allocated
4455			each page is disabled in default. With this switch,
4456			we can turn it on.
4457			on: enable the feature
4458
4459	page_poison=	[KNL,EARLY] Boot-time parameter changing the state of
4460			poisoning on the buddy allocator, available with
4461			CONFIG_PAGE_POISONING=y.
4462			off: turn off poisoning (default)
4463			on: turn on poisoning
4464
4465	page_reporting.page_reporting_order=
4466			[KNL] Minimal page reporting order
4467			Format: <integer>
4468			Adjust the minimal page reporting order. The page
4469			reporting is disabled when it exceeds MAX_PAGE_ORDER.
4470
4471	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
4472			timeout > 0: seconds before rebooting
4473			timeout = 0: wait forever
4474			timeout < 0: reboot immediately
4475			Format: <timeout>
4476
4477	panic_on_taint=	[KNL,EARLY]
4478			Bitmask for conditionally calling panic() in add_taint()
4479			Format: <hex>[,nousertaint]
4480			Hexadecimal bitmask representing the set of TAINT flags
4481			that will cause the kernel to panic when add_taint() is
4482			called with any of the flags in this set.
4483			The optional switch "nousertaint" can be utilized to
4484			prevent userspace forced crashes by writing to sysctl
4485			/proc/sys/kernel/tainted any flagset matching with the
4486			bitmask set on panic_on_taint.
4487			See Documentation/admin-guide/tainted-kernels.rst for
4488			extra details on the taint flags that users can pick
4489			to compose the bitmask to assign to panic_on_taint.
4490
4491	panic_on_warn=1	panic() instead of WARN().  Useful to cause kdump
4492			on a WARN().
4493
4494	panic_print=	Bitmask for printing system info when panic happens.
4495			User can chose combination of the following bits:
4496			bit 0: print all tasks info
4497			bit 1: print system memory info
4498			bit 2: print timer info
4499			bit 3: print locks info if CONFIG_LOCKDEP is on
4500			bit 4: print ftrace buffer
4501			bit 5: print all printk messages in buffer
4502			bit 6: print all CPUs backtrace (if available in the arch)
4503			bit 7: print only tasks in uninterruptible (blocked) state
4504			*Be aware* that this option may print a _lot_ of lines,
4505			so there are risks of losing older messages in the log.
4506			Use this option carefully, maybe worth to setup a
4507			bigger log buffer with "log_buf_len" along with this.
4508
4509	parkbd.port=	[HW] Parallel port number the keyboard adapter is
4510			connected to, default is 0.
4511			Format: <parport#>
4512	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
4513			0 for XT, 1 for AT (default is AT).
4514			Format: <mode>
4515
4516	parport=	[HW,PPT] Specify parallel ports. 0 disables.
4517			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4518			Use 'auto' to force the driver to use any
4519			IRQ/DMA settings detected (the default is to
4520			ignore detected IRQ/DMA settings because of
4521			possible conflicts). You can specify the base
4522			address, IRQ, and DMA settings; IRQ and DMA
4523			should be numbers, or 'auto' (for using detected
4524			settings on that particular port), or 'nofifo'
4525			(to avoid using a FIFO even if it is detected).
4526			Parallel ports are assigned in the order they
4527			are specified on the command line, starting
4528			with parport0.
4529
4530	parport_init_mode=	[HW,PPT]
4531			Configure VIA parallel port to operate in
4532			a specific mode. This is necessary on Pegasos
4533			computer where firmware has no options for setting
4534			up parallel port mode and sets it to spp.
4535			Currently this function knows 686a and 8231 chips.
4536			Format: [spp|ps2|epp|ecp|ecpepp]
4537
4538	pata_legacy.all=	[HW,LIBATA]
4539			Format: <int>
4540			Set to non-zero to probe primary and secondary ISA
4541			port ranges on PCI systems where no PCI PATA device
4542			has been found at either range.  Disabled by default.
4543
4544	pata_legacy.autospeed=	[HW,LIBATA]
4545			Format: <int>
4546			Set to non-zero if a chip is present that snoops speed
4547			changes.  Disabled by default.
4548
4549	pata_legacy.ht6560a=	[HW,LIBATA]
4550			Format: <int>
4551			Set to 1, 2, or 3 for HT 6560A on the primary channel,
4552			the secondary channel, or both channels respectively.
4553			Disabled by default.
4554
4555	pata_legacy.ht6560b=	[HW,LIBATA]
4556			Format: <int>
4557			Set to 1, 2, or 3 for HT 6560B on the primary channel,
4558			the secondary channel, or both channels respectively.
4559			Disabled by default.
4560
4561	pata_legacy.iordy_mask=	[HW,LIBATA]
4562			Format: <int>
4563			IORDY enable mask.  Set individual bits to allow IORDY
4564			for the respective channel.  Bit 0 is for the first
4565			legacy channel handled by this driver, bit 1 is for
4566			the second channel, and so on.  The sequence will often
4567			correspond to the primary legacy channel, the secondary
4568			legacy channel, and so on, but the handling of a PCI
4569			bus and the use of other driver options may interfere
4570			with the sequence.  By default IORDY is allowed across
4571			all channels.
4572
4573	pata_legacy.opti82c46x=	[HW,LIBATA]
4574			Format: <int>
4575			Set to 1, 2, or 3 for Opti 82c611A on the primary
4576			channel, the secondary channel, or both channels
4577			respectively.  Disabled by default.
4578
4579	pata_legacy.opti82c611a=	[HW,LIBATA]
4580			Format: <int>
4581			Set to 1, 2, or 3 for Opti 82c465MV on the primary
4582			channel, the secondary channel, or both channels
4583			respectively.  Disabled by default.
4584
4585	pata_legacy.pio_mask=	[HW,LIBATA]
4586			Format: <int>
4587			PIO mode mask for autospeed devices.  Set individual
4588			bits to allow the use of the respective PIO modes.
4589			Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4590			All modes allowed by default.
4591
4592	pata_legacy.probe_all=	[HW,LIBATA]
4593			Format: <int>
4594			Set to non-zero to probe tertiary and further ISA
4595			port ranges on PCI systems.  Disabled by default.
4596
4597	pata_legacy.probe_mask=	[HW,LIBATA]
4598			Format: <int>
4599			Probe mask for legacy ISA PATA ports.  Depending on
4600			platform configuration and the use of other driver
4601			options up to 6 legacy ports are supported: 0x1f0,
4602			0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4603			of individual ports can be disabled by setting the
4604			corresponding bits in the mask to 1.  Bit 0 is for
4605			the first port in the list above (0x1f0), and so on.
4606			By default all supported ports are probed.
4607
4608	pata_legacy.qdi=	[HW,LIBATA]
4609			Format: <int>
4610			Set to non-zero to probe QDI controllers.  By default
4611			set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4612
4613	pata_legacy.winbond=	[HW,LIBATA]
4614			Format: <int>
4615			Set to non-zero to probe Winbond controllers.  Use
4616			the standard I/O port (0x130) if 1, otherwise the
4617			value given is the I/O port to use (typically 0x1b0).
4618			By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4619			0 otherwise.
4620
4621	pata_platform.pio_mask=	[HW,LIBATA]
4622			Format: <int>
4623			Supported PIO mode mask.  Set individual bits to allow
4624			the use of the respective PIO modes.  Bit 0 is for
4625			mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
4626			allowed by default.
4627
4628	pause_on_oops=<int>
4629			Halt all CPUs after the first oops has been printed for
4630			the specified number of seconds.  This is to be used if
4631			your oopses keep scrolling off the screen.
4632
4633	pcbit=		[HW,ISDN]
4634
4635	pci=option[,option...]	[PCI,EARLY] various PCI subsystem options.
4636
4637				Some options herein operate on a specific device
4638				or a set of devices (<pci_dev>). These are
4639				specified in one of the following formats:
4640
4641				[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4642				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4643
4644				Note: the first format specifies a PCI
4645				bus/device/function address which may change
4646				if new hardware is inserted, if motherboard
4647				firmware changes, or due to changes caused
4648				by other kernel parameters. If the
4649				domain is left unspecified, it is
4650				taken to be zero. Optionally, a path
4651				to a device through multiple device/function
4652				addresses can be specified after the base
4653				address (this is more robust against
4654				renumbering issues).  The second format
4655				selects devices using IDs from the
4656				configuration space which may match multiple
4657				devices in the system.
4658
4659		earlydump	dump PCI config space before the kernel
4660				changes anything
4661		off		[X86] don't probe for the PCI bus
4662		bios		[X86-32] force use of PCI BIOS, don't access
4663				the hardware directly. Use this if your machine
4664				has a non-standard PCI host bridge.
4665		nobios		[X86-32] disallow use of PCI BIOS, only direct
4666				hardware access methods are allowed. Use this
4667				if you experience crashes upon bootup and you
4668				suspect they are caused by the BIOS.
4669		conf1		[X86] Force use of PCI Configuration Access
4670				Mechanism 1 (config address in IO port 0xCF8,
4671				data in IO port 0xCFC, both 32-bit).
4672		conf2		[X86] Force use of PCI Configuration Access
4673				Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4674				the function, IO port 0xCFA, also 8-bit, sets
4675				bus number. The config space is then accessed
4676				through ports 0xC000-0xCFFF).
4677				See http://wiki.osdev.org/PCI for more info
4678				on the configuration access mechanisms.
4679		noaer		[PCIE] If the PCIEAER kernel config parameter is
4680				enabled, this kernel boot option can be used to
4681				disable the use of PCIE advanced error reporting.
4682		nodomains	[PCI] Disable support for multiple PCI
4683				root domains (aka PCI segments, in ACPI-speak).
4684		nommconf	[X86] Disable use of MMCONFIG for PCI
4685				Configuration
4686		check_enable_amd_mmconf [X86] check for and enable
4687				properly configured MMIO access to PCI
4688				config space on AMD family 10h CPU
4689		nomsi		[MSI] If the PCI_MSI kernel config parameter is
4690				enabled, this kernel boot option can be used to
4691				disable the use of MSI interrupts system-wide.
4692		noioapicquirk	[APIC] Disable all boot interrupt quirks.
4693				Safety option to keep boot IRQs enabled. This
4694				should never be necessary.
4695		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
4696				primary IO-APIC for bridges that cannot disable
4697				boot IRQs. This fixes a source of spurious IRQs
4698				when the system masks IRQs.
4699		noioapicreroute	[APIC] Disable workaround that uses the
4700				boot IRQ equivalent of an IRQ that connects to
4701				a chipset where boot IRQs cannot be disabled.
4702				The opposite of ioapicreroute.
4703		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
4704				routing table. These calls are known to be buggy
4705				on several machines and they hang the machine
4706				when used, but on other computers it's the only
4707				way to get the interrupt routing table. Try
4708				this option if the kernel is unable to allocate
4709				IRQs or discover secondary PCI buses on your
4710				motherboard.
4711		rom		[X86] Assign address space to expansion ROMs.
4712				Use with caution as certain devices share
4713				address decoders between ROMs and other
4714				resources.
4715		norom		[X86] Do not assign address space to
4716				expansion ROMs that do not already have
4717				BIOS assigned address ranges.
4718		nobar		[X86] Do not assign address space to the
4719				BARs that weren't assigned by the BIOS.
4720		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
4721				assigned automatically to PCI devices. You can
4722				make the kernel exclude IRQs of your ISA cards
4723				this way.
4724		pirqaddr=0xAAAAA	[X86] Specify the physical address
4725				of the PIRQ table (normally generated
4726				by the BIOS) if it is outside the
4727				F0000h-100000h range.
4728		lastbus=N	[X86] Scan all buses thru bus #N. Can be
4729				useful if the kernel is unable to find your
4730				secondary buses and you want to tell it
4731				explicitly which ones they are.
4732		assign-busses	[X86] Always assign all PCI bus
4733				numbers ourselves, overriding
4734				whatever the firmware may have done.
4735		usepirqmask	[X86] Honor the possible IRQ mask stored
4736				in the BIOS $PIR table. This is needed on
4737				some systems with broken BIOSes, notably
4738				some HP Pavilion N5400 and Omnibook XE3
4739				notebooks. This will have no effect if ACPI
4740				IRQ routing is enabled.
4741		noacpi		[X86] Do not use ACPI for IRQ routing
4742				or for PCI scanning.
4743		use_crs		[X86] Use PCI host bridge window information
4744				from ACPI.  On BIOSes from 2008 or later, this
4745				is enabled by default.  If you need to use this,
4746				please report a bug.
4747		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
4748				If you need to use this, please report a bug.
4749		use_e820	[X86] Use E820 reservations to exclude parts of
4750				PCI host bridge windows. This is a workaround
4751				for BIOS defects in host bridge _CRS methods.
4752				If you need to use this, please report a bug to
4753				<linux-pci@vger.kernel.org>.
4754		no_e820		[X86] Ignore E820 reservations for PCI host
4755				bridge windows. This is the default on modern
4756				hardware. If you need to use this, please report
4757				a bug to <linux-pci@vger.kernel.org>.
4758		routeirq	Do IRQ routing for all PCI devices.
4759				This is normally done in pci_enable_device(),
4760				so this option is a temporary workaround
4761				for broken drivers that don't call it.
4762		skip_isa_align	[X86] do not align io start addr, so can
4763				handle more pci cards
4764		noearly		[X86] Don't do any early type 1 scanning.
4765				This might help on some broken boards which
4766				machine check when some devices' config space
4767				is read. But various workarounds are disabled
4768				and some IOMMU drivers will not work.
4769		bfsort		Sort PCI devices into breadth-first order.
4770				This sorting is done to get a device
4771				order compatible with older (<= 2.4) kernels.
4772		nobfsort	Don't sort PCI devices into breadth-first order.
4773		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
4774				tuning and use the BIOS-configured MPS defaults.
4775		pcie_bus_safe	Set every device's MPS to the largest value
4776				supported by all devices below the root complex.
4777		pcie_bus_perf	Set device MPS to the largest allowable MPS
4778				based on its parent bus. Also set MRRS (Max
4779				Read Request Size) to the largest supported
4780				value (no larger than the MPS that the device
4781				or bus can support) for best performance.
4782		pcie_bus_peer2peer	Set every device's MPS to 128B, which
4783				every device is guaranteed to support. This
4784				configuration allows peer-to-peer DMA between
4785				any pair of devices, possibly at the cost of
4786				reduced performance.  This also guarantees
4787				that hot-added devices will work.
4788		cbiosize=nn[KMG]	The fixed amount of bus space which is
4789				reserved for the CardBus bridge's IO window.
4790				The default value is 256 bytes.
4791		cbmemsize=nn[KMG]	The fixed amount of bus space which is
4792				reserved for the CardBus bridge's memory
4793				window. The default value is 64 megabytes.
4794		resource_alignment=
4795				Format:
4796				[<order of align>@]<pci_dev>[; ...]
4797				Specifies alignment and device to reassign
4798				aligned memory resources. How to
4799				specify the device is described above.
4800				If <order of align> is not specified,
4801				PAGE_SIZE is used as alignment.
4802				A PCI-PCI bridge can be specified if resource
4803				windows need to be expanded.
4804				To specify the alignment for several
4805				instances of a device, the PCI vendor,
4806				device, subvendor, and subdevice may be
4807				specified, e.g., 12@pci:8086:9c22:103c:198f
4808				for 4096-byte alignment.
4809		ecrc=		Enable/disable PCIe ECRC (transaction layer
4810				end-to-end CRC checking). Only effective if
4811				OS has native AER control (either granted by
4812				ACPI _OSC or forced via "pcie_ports=native")
4813				bios: Use BIOS/firmware settings. This is the
4814				the default.
4815				off: Turn ECRC off
4816				on: Turn ECRC on.
4817		hpiosize=nn[KMG]	The fixed amount of bus space which is
4818				reserved for hotplug bridge's IO window.
4819				Default size is 256 bytes.
4820		hpmmiosize=nn[KMG]	The fixed amount of bus space which is
4821				reserved for hotplug bridge's MMIO window.
4822				Default size is 2 megabytes.
4823		hpmmioprefsize=nn[KMG]	The fixed amount of bus space which is
4824				reserved for hotplug bridge's MMIO_PREF window.
4825				Default size is 2 megabytes.
4826		hpmemsize=nn[KMG]	The fixed amount of bus space which is
4827				reserved for hotplug bridge's MMIO and
4828				MMIO_PREF window.
4829				Default size is 2 megabytes.
4830		hpbussize=nn	The minimum amount of additional bus numbers
4831				reserved for buses below a hotplug bridge.
4832				Default is 1.
4833		realloc=	Enable/disable reallocating PCI bridge resources
4834				if allocations done by BIOS are too small to
4835				accommodate resources required by all child
4836				devices.
4837				off: Turn realloc off
4838				on: Turn realloc on
4839		realloc		same as realloc=on
4840		noari		do not use PCIe ARI.
4841		noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
4842				do not use PCIe ATS (and IOMMU device IOTLB).
4843		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
4844				only look for one device below a PCIe downstream
4845				port.
4846		big_root_window	Try to add a big 64bit memory window to the PCIe
4847				root complex on AMD CPUs. Some GFX hardware
4848				can resize a BAR to allow access to all VRAM.
4849				Adding the window is slightly risky (it may
4850				conflict with unreported devices), so this
4851				taints the kernel.
4852		disable_acs_redir=<pci_dev>[; ...]
4853				Specify one or more PCI devices (in the format
4854				specified above) separated by semicolons.
4855				Each device specified will have the PCI ACS
4856				redirect capabilities forced off which will
4857				allow P2P traffic between devices through
4858				bridges without forcing it upstream. Note:
4859				this removes isolation between devices and
4860				may put more devices in an IOMMU group.
4861		config_acs=
4862				Format:
4863				<ACS flags>@<pci_dev>[; ...]
4864				Specify one or more PCI devices (in the format
4865				specified above) optionally prepended with flags
4866				and separated by semicolons. The respective
4867				capabilities will be enabled, disabled or
4868				unchanged based on what is specified in
4869				flags.
4870
4871				ACS Flags is defined as follows:
4872				  bit-0 : ACS Source Validation
4873				  bit-1 : ACS Translation Blocking
4874				  bit-2 : ACS P2P Request Redirect
4875				  bit-3 : ACS P2P Completion Redirect
4876				  bit-4 : ACS Upstream Forwarding
4877				  bit-5 : ACS P2P Egress Control
4878				  bit-6 : ACS Direct Translated P2P
4879				Each bit can be marked as:
4880				  '0' – force disabled
4881				  '1' – force enabled
4882				  'x' – unchanged
4883				For example,
4884				  pci=config_acs=10x@pci:0:0
4885				would configure all devices that support
4886				ACS to enable P2P Request Redirect, disable
4887				Translation Blocking, and leave Source
4888				Validation unchanged from whatever power-up
4889				or firmware set it to.
4890
4891				Note: this may remove isolation between devices
4892				and may put more devices in an IOMMU group.
4893		force_floating	[S390] Force usage of floating interrupts.
4894		nomio		[S390] Do not use MIO instructions.
4895		norid		[S390] ignore the RID field and force use of
4896				one PCI domain per PCI function
4897		notph		[PCIE] If the PCIE_TPH kernel config parameter
4898				is enabled, this kernel boot option can be used
4899				to disable PCIe TLP Processing Hints support
4900				system-wide.
4901
4902	pcie_aspm=	[PCIE] Forcibly enable or ignore PCIe Active State Power
4903			Management.
4904		off	Don't touch ASPM configuration at all.  Leave any
4905			configuration done by firmware unchanged.
4906		force	Enable ASPM even on devices that claim not to support it.
4907			WARNING: Forcing ASPM on may cause system lockups.
4908
4909	pcie_ports=	[PCIE] PCIe port services handling:
4910		native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4911			even if the platform doesn't give the OS permission to
4912			use them.  This may cause conflicts if the platform
4913			also tries to use these services.
4914		dpc-native	Use native PCIe service for DPC only.  May
4915				cause conflicts if firmware uses AER or DPC.
4916		compat	Disable native PCIe services (PME, AER, DPC, PCIe
4917			hotplug).
4918
4919	pcie_port_pm=	[PCIE] PCIe port power management handling:
4920		off	Disable power management of all PCIe ports
4921		force	Forcibly enable power management of all PCIe ports
4922
4923	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
4924		nomsi	Do not use MSI for native PCIe PME signaling (this makes
4925			all PCIe root ports use INTx for all services).
4926
4927	pcmv=		[HW,PCMCIA] BadgePAD 4
4928
4929	pd_ignore_unused
4930			[PM]
4931			Keep all power-domains already enabled by bootloader on,
4932			even if no driver has claimed them. This is useful
4933			for debug and development, but should not be
4934			needed on a platform with proper driver support.
4935
4936	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
4937			boot time.
4938			Format: { 0 | 1 }
4939			See arch/parisc/kernel/pdc_chassis.c
4940
4941	percpu_alloc=	[MM,EARLY]
4942			Select which percpu first chunk allocator to use.
4943			Currently supported values are "embed" and "page".
4944			Archs may support subset or none of the	selections.
4945			See comments in mm/percpu.c for details on each
4946			allocator.  This parameter is primarily	for debugging
4947			and performance comparison.
4948
4949	pirq=		[SMP,APIC] Manual mp-table setup
4950			See Documentation/arch/x86/i386/IO-APIC.rst.
4951
4952	plip=		[PPT,NET] Parallel port network link
4953			Format: { parport<nr> | timid | 0 }
4954			See also Documentation/admin-guide/parport.rst.
4955
4956	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
4957			Override pmtimer IOPort with a hex value.
4958			e.g. pmtmr=0x508
4959
4960	pmu_override=	[PPC] Override the PMU.
4961			This option takes over the PMU facility, so it is no
4962			longer usable by perf. Setting this option starts the
4963			PMU counters by setting MMCR0 to 0 (the FC bit is
4964			cleared). If a number is given, then MMCR1 is set to
4965			that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4966			remains 0.
4967
4968	pm_debug_messages	[SUSPEND,KNL]
4969			Enable suspend/resume debug messages during boot up.
4970
4971	pnp.debug=1	[PNP]
4972			Enable PNP debug messages (depends on the
4973			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
4974			via /sys/module/pnp/parameters/debug.  We always show
4975			current resource usage; turning this on also shows
4976			possible settings and some assignment information.
4977
4978	pnpacpi=	[ACPI]
4979			{ off }
4980
4981	pnpbios=	[ISAPNP]
4982			{ on | off | curr | res | no-curr | no-res }
4983
4984	pnp_reserve_irq=
4985			[ISAPNP] Exclude IRQs for the autoconfiguration
4986
4987	pnp_reserve_dma=
4988			[ISAPNP] Exclude DMAs for the autoconfiguration
4989
4990	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
4991			Ranges are in pairs (I/O port base and size).
4992
4993	pnp_reserve_mem=
4994			[ISAPNP] Exclude memory regions for the
4995			autoconfiguration.
4996			Ranges are in pairs (memory base and size).
4997
4998	ports=		[IP_VS_FTP] IPVS ftp helper module
4999			Default is 21.
5000			Up to 8 (IP_VS_APP_MAX_PORTS) ports
5001			may be specified.
5002			Format: <port>,<port>....
5003
5004	possible_cpus=  [SMP,S390,X86]
5005			Format: <unsigned int>
5006			Set the number of possible CPUs, overriding the
5007			regular discovery mechanisms (such as ACPI/FW, etc).
5008
5009	powersave=off	[PPC] This option disables power saving features.
5010			It specifically disables cpuidle and sets the
5011			platform machine description specific power_save
5012			function to NULL. On Idle the CPU just reduces
5013			execution priority.
5014
5015	ppc_strict_facility_enable
5016			[PPC,ENABLE] This option catches any kernel floating point,
5017			Altivec, VSX and SPE outside of regions specifically
5018			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
5019			There is some performance impact when enabling this.
5020
5021	ppc_tm=		[PPC,EARLY]
5022			Format: {"off"}
5023			Disable Hardware Transactional Memory
5024
5025	preempt=	[KNL]
5026			Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
5027			none - Limited to cond_resched() calls
5028			voluntary - Limited to cond_resched() and might_sleep() calls
5029			full - Any section that isn't explicitly preempt disabled
5030			       can be preempted anytime.  Tasks will also yield
5031			       contended spinlocks (if the critical section isn't
5032			       explicitly preempt disabled beyond the lock itself).
5033			lazy - Scheduler controlled. Similar to full but instead
5034			       of preempting the task immediately, the task gets
5035			       one HZ tick time to yield itself before the
5036			       preemption will be forced. One preemption is when the
5037			       task returns to user space.
5038
5039	print-fatal-signals=
5040			[KNL] debug: print fatal signals
5041
5042			If enabled, warn about various signal handling
5043			related application anomalies: too many signals,
5044			too many POSIX.1 timers, fatal signals causing a
5045			coredump - etc.
5046
5047			If you hit the warning due to signal overflow,
5048			you might want to try "ulimit -i unlimited".
5049
5050			default: off.
5051
5052	printk.always_kmsg_dump=
5053			Trigger kmsg_dump for cases other than kernel oops or
5054			panics
5055			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5056			default: disabled
5057
5058	printk.console_no_auto_verbose=
5059			Disable console loglevel raise on oops, panic
5060			or lockdep-detected issues (only if lock debug is on).
5061			With an exception to setups with low baudrate on
5062			serial console, keeping this 0 is a good choice
5063			in order to provide more debug information.
5064			Format: <bool>
5065			default: 0 (auto_verbose is enabled)
5066
5067	printk.debug_non_panic_cpus=
5068			Allows storing messages from non-panic CPUs into
5069			the printk log buffer during panic(). They are
5070			flushed to consoles by the panic-CPU on
5071			a best-effort basis.
5072			Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5073			Default: disabled
5074
5075	printk.devkmsg={on,off,ratelimit}
5076			Control writing to /dev/kmsg.
5077			on - unlimited logging to /dev/kmsg from userspace
5078			off - logging to /dev/kmsg disabled
5079			ratelimit - ratelimit the logging
5080			Default: ratelimit
5081
5082	printk.time=	Show timing data prefixed to each printk message line
5083			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5084
5085	proc_mem.force_override= [KNL]
5086			Format: {always | ptrace | never}
5087			Traditionally /proc/pid/mem allows memory permissions to be
5088			overridden without restrictions. This option may be set to
5089			restrict that. Can be one of:
5090			- 'always': traditional behavior always allows mem overrides.
5091			- 'ptrace': only allow mem overrides for active ptracers.
5092			- 'never':  never allow mem overrides.
5093			If not specified, default is the CONFIG_PROC_MEM_* choice.
5094
5095	processor.max_cstate=	[HW,ACPI]
5096			Limit processor to maximum C-state
5097			max_cstate=9 overrides any DMI blacklist limit.
5098
5099	processor.nocst	[HW,ACPI]
5100			Ignore the _CST method to determine C-states,
5101			instead using the legacy FADT method
5102
5103	profile=	[KNL] Enable kernel profiling via /proc/profile
5104			Format: [<profiletype>,]<number>
5105			Param: <profiletype>: "schedule" or "kvm"
5106				[defaults to kernel profiling]
5107			Param: "schedule" - profile schedule points.
5108			Param: "kvm" - profile VM exits.
5109			Param: <number> - step/bucket size as a power of 2 for
5110				statistical time based profiling.
5111
5112	prompt_ramdisk=	[RAM] [Deprecated]
5113
5114	prot_virt=	[S390] enable hosting protected virtual machines
5115			isolated from the hypervisor (if hardware supports
5116			that). If enabled, the default kernel base address
5117			might be overridden even when Kernel Address Space
5118			Layout Randomization is disabled.
5119			Format: <bool>
5120
5121	psi=		[KNL] Enable or disable pressure stall information
5122			tracking.
5123			Format: <bool>
5124
5125	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
5126			probe for; one of (bare|imps|exps|lifebook|any).
5127	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
5128			per second.
5129	psmouse.resetafter=	[HW,MOUSE]
5130			Try to reset the device after so many bad packets
5131			(0 = never).
5132	psmouse.resolution=
5133			[HW,MOUSE] Set desired mouse resolution, in dpi.
5134	psmouse.smartscroll=
5135			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
5136			0 = disabled, 1 = enabled (default).
5137
5138	pstore.backend=	Specify the name of the pstore backend to use
5139
5140	pti=		[X86-64] Control Page Table Isolation of user and
5141			kernel address spaces.  Disabling this feature
5142			removes hardening, but improves performance of
5143			system calls and interrupts.
5144
5145			on   - unconditionally enable
5146			off  - unconditionally disable
5147			auto - kernel detects whether your CPU model is
5148			       vulnerable to issues that PTI mitigates
5149
5150			Not specifying this option is equivalent to pti=auto.
5151
5152	pty.legacy_count=
5153			[KNL] Number of legacy pty's. Overwrites compiled-in
5154			default number.
5155
5156	quiet		[KNL,EARLY] Disable most log messages
5157
5158	r128=		[HW,DRM]
5159
5160	radix_hcall_invalidate=on  [PPC/PSERIES]
5161			Disable RADIX GTSE feature and use hcall for TLB
5162			invalidate.
5163
5164	raid=		[HW,RAID]
5165			See Documentation/admin-guide/md.rst.
5166
5167	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
5168			See Documentation/admin-guide/blockdev/ramdisk.rst.
5169
5170	ramdisk_start=	[RAM] RAM disk image start address
5171
5172	random.trust_cpu=off
5173			[KNL,EARLY] Disable trusting the use of the CPU's
5174			random number generator (if available) to
5175			initialize the kernel's RNG.
5176
5177	random.trust_bootloader=off
5178			[KNL,EARLY] Disable trusting the use of the a seed
5179			passed by the bootloader (if available) to
5180			initialize the kernel's RNG.
5181
5182	randomize_kstack_offset=
5183			[KNL,EARLY] Enable or disable kernel stack offset
5184			randomization, which provides roughly 5 bits of
5185			entropy, frustrating memory corruption attacks
5186			that depend on stack address determinism or
5187			cross-syscall address exposures. This is only
5188			available on architectures that have defined
5189			CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
5190			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5191			Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
5192
5193	ras=option[,option,...]	[KNL] RAS-specific options
5194
5195		cec_disable	[X86]
5196				Disable the Correctable Errors Collector,
5197				see CONFIG_RAS_CEC help text.
5198
5199	rcu_nocbs[=cpu-list]
5200			[KNL] The optional argument is a cpu list,
5201			as described above.
5202
5203			In kernels built with CONFIG_RCU_NOCB_CPU=y,
5204			enable the no-callback CPU mode, which prevents
5205			such CPUs' callbacks from being invoked in
5206			softirq context.  Invocation of such CPUs' RCU
5207			callbacks will instead be offloaded to "rcuox/N"
5208			kthreads created for that purpose, where "x" is
5209			"p" for RCU-preempt, "s" for RCU-sched, and "g"
5210			for the kthreads that mediate grace periods; and
5211			"N" is the CPU number. This reduces OS jitter on
5212			the offloaded CPUs, which can be useful for HPC
5213			and real-time workloads.  It can also improve
5214			energy efficiency for asymmetric multiprocessors.
5215
5216			If a cpulist is passed as an argument, the specified
5217			list of	CPUs is set to no-callback mode from boot.
5218
5219			Otherwise, if the '=' sign and the cpulist
5220			arguments are omitted, no CPU will be set to
5221			no-callback mode from boot but the mode may be
5222			toggled at runtime via cpusets.
5223
5224			Note that this argument takes precedence over
5225			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
5226
5227	rcu_nocb_poll	[KNL]
5228			Rather than requiring that offloaded CPUs
5229			(specified by rcu_nocbs= above) explicitly
5230			awaken the corresponding "rcuoN" kthreads,
5231			make these kthreads poll for callbacks.
5232			This improves the real-time response for the
5233			offloaded CPUs by relieving them of the need to
5234			wake up the corresponding kthread, but degrades
5235			energy efficiency by requiring that the kthreads
5236			periodically wake up to do the polling.
5237
5238	rcutree.blimit=	[KNL]
5239			Set maximum number of finished RCU callbacks to
5240			process in one batch.
5241
5242	rcutree.csd_lock_suppress_rcu_stall=	[KNL]
5243			Do only a one-line RCU CPU stall warning when
5244			there is an ongoing too-long CSD-lock wait.
5245
5246	rcutree.do_rcu_barrier=	[KNL]
5247			Request a call to rcu_barrier().  This is
5248			throttled so that userspace tests can safely
5249			hammer on the sysfs variable if they so choose.
5250			If triggered before the RCU grace-period machinery
5251			is fully active, this will error out with EAGAIN.
5252
5253	rcutree.dump_tree=	[KNL]
5254			Dump the structure of the rcu_node combining tree
5255			out at early boot.  This is used for diagnostic
5256			purposes, to verify correct tree setup.
5257
5258	rcutree.gp_cleanup_delay=	[KNL]
5259			Set the number of jiffies to delay each step of
5260			RCU grace-period cleanup.
5261
5262	rcutree.gp_init_delay=	[KNL]
5263			Set the number of jiffies to delay each step of
5264			RCU grace-period initialization.
5265
5266	rcutree.gp_preinit_delay=	[KNL]
5267			Set the number of jiffies to delay each step of
5268			RCU grace-period pre-initialization, that is,
5269			the propagation of recent CPU-hotplug changes up
5270			the rcu_node combining tree.
5271
5272	rcutree.jiffies_till_first_fqs= [KNL]
5273			Set delay from grace-period initialization to
5274			first attempt to force quiescent states.
5275			Units are jiffies, minimum value is zero,
5276			and maximum value is HZ.
5277
5278	rcutree.jiffies_till_next_fqs= [KNL]
5279			Set delay between subsequent attempts to force
5280			quiescent states.  Units are jiffies, minimum
5281			value is one, and maximum value is HZ.
5282
5283	rcutree.jiffies_till_sched_qs= [KNL]
5284			Set required age in jiffies for a
5285			given grace period before RCU starts
5286			soliciting quiescent-state help from
5287			rcu_note_context_switch() and cond_resched().
5288			If not specified, the kernel will calculate
5289			a value based on the most recent settings
5290			of rcutree.jiffies_till_first_fqs
5291			and rcutree.jiffies_till_next_fqs.
5292			This calculated value may be viewed in
5293			rcutree.jiffies_to_sched_qs.  Any attempt to set
5294			rcutree.jiffies_to_sched_qs will be cheerfully
5295			overwritten.
5296
5297	rcutree.kthread_prio= 	 [KNL,BOOT]
5298			Set the SCHED_FIFO priority of the RCU per-CPU
5299			kthreads (rcuc/N). This value is also used for
5300			the priority of the RCU boost threads (rcub/N)
5301			and for the RCU grace-period kthreads (rcu_bh,
5302			rcu_preempt, and rcu_sched). If RCU_BOOST is
5303			set, valid values are 1-99 and the default is 1
5304			(the least-favored priority).  Otherwise, when
5305			RCU_BOOST is not set, valid values are 0-99 and
5306			the default is zero (non-realtime operation).
5307			When RCU_NOCB_CPU is set, also adjust the
5308			priority of NOCB callback kthreads.
5309
5310	rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5311			On callback-offloaded (rcu_nocbs) CPUs,
5312			RCU reduces the lock contention that would
5313			otherwise be caused by callback floods through
5314			use of the ->nocb_bypass list.	However, in the
5315			common non-flooded case, RCU queues directly to
5316			the main ->cblist in order to avoid the extra
5317			overhead of the ->nocb_bypass list and its lock.
5318			But if there are too many callbacks queued during
5319			a single jiffy, RCU pre-queues the callbacks into
5320			the ->nocb_bypass queue.  The definition of "too
5321			many" is supplied by this kernel boot parameter.
5322
5323	rcutree.nohz_full_patience_delay= [KNL]
5324			On callback-offloaded (rcu_nocbs) CPUs, avoid
5325			disturbing RCU unless the grace period has
5326			reached the specified age in milliseconds.
5327			Defaults to zero.  Large values will be capped
5328			at five seconds.  All values will be rounded down
5329			to the nearest value representable by jiffies.
5330
5331	rcutree.qhimark= [KNL]
5332			Set threshold of queued RCU callbacks beyond which
5333			batch limiting is disabled.
5334
5335	rcutree.qlowmark= [KNL]
5336			Set threshold of queued RCU callbacks below which
5337			batch limiting is re-enabled.
5338
5339	rcutree.qovld= [KNL]
5340			Set threshold of queued RCU callbacks beyond which
5341			RCU's force-quiescent-state scan will aggressively
5342			enlist help from cond_resched() and sched IPIs to
5343			help CPUs more quickly reach quiescent states.
5344			Set to less than zero to make this be set based
5345			on rcutree.qhimark at boot time and to zero to
5346			disable more aggressive help enlistment.
5347
5348	rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5349			Set the page-cache refill delay (in milliseconds)
5350			in response to low-memory conditions.  The range
5351			of permitted values is in the range 0:100000.
5352
5353	rcutree.rcu_divisor= [KNL]
5354			Set the shift-right count to use to compute
5355			the callback-invocation batch limit bl from
5356			the number of callbacks queued on this CPU.
5357			The result will be bounded below by the value of
5358			the rcutree.blimit kernel parameter.  Every bl
5359			callbacks, the softirq handler will exit in
5360			order to allow the CPU to do other work.
5361
5362			Please note that this callback-invocation batch
5363			limit applies only to non-offloaded callback
5364			invocation.  Offloaded callbacks are instead
5365			invoked in the context of an rcuoc kthread, which
5366			scheduler will preempt as it does any other task.
5367
5368	rcutree.rcu_fanout_exact= [KNL]
5369			Disable autobalancing of the rcu_node combining
5370			tree.  This is used by rcutorture, and might
5371			possibly be useful for architectures having high
5372			cache-to-cache transfer latencies.
5373
5374	rcutree.rcu_fanout_leaf= [KNL]
5375			Change the number of CPUs assigned to each
5376			leaf rcu_node structure.  Useful for very
5377			large systems, which will choose the value 64,
5378			and for NUMA systems with large remote-access
5379			latencies, which will choose a value aligned
5380			with the appropriate hardware boundaries.
5381
5382	rcutree.rcu_min_cached_objs= [KNL]
5383			Minimum number of objects which are cached and
5384			maintained per one CPU. Object size is equal
5385			to PAGE_SIZE. The cache allows to reduce the
5386			pressure to page allocator, also it makes the
5387			whole algorithm to behave better in low memory
5388			condition.
5389
5390	rcutree.rcu_nocb_gp_stride= [KNL]
5391			Set the number of NOCB callback kthreads in
5392			each group, which defaults to the square root
5393			of the number of CPUs.	Larger numbers reduce
5394			the wakeup overhead on the global grace-period
5395			kthread, but increases that same overhead on
5396			each group's NOCB grace-period kthread.
5397
5398	rcutree.rcu_kick_kthreads= [KNL]
5399			Cause the grace-period kthread to get an extra
5400			wake_up() if it sleeps three times longer than
5401			it should at force-quiescent-state time.
5402			This wake_up() will be accompanied by a
5403			WARN_ONCE() splat and an ftrace_dump().
5404
5405	rcutree.rcu_resched_ns= [KNL]
5406			Limit the time spend invoking a batch of RCU
5407			callbacks to the specified number of nanoseconds.
5408			By default, this limit is checked only once
5409			every 32 callbacks in order to limit the pain
5410			inflicted by local_clock() overhead.
5411
5412	rcutree.rcu_unlock_delay= [KNL]
5413			In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5414			this specifies an rcu_read_unlock()-time delay
5415			in microseconds.  This defaults to zero.
5416			Larger delays increase the probability of
5417			catching RCU pointer leaks, that is, buggy use
5418			of RCU-protected pointers after the relevant
5419			rcu_read_unlock() has completed.
5420
5421	rcutree.sysrq_rcu= [KNL]
5422			Commandeer a sysrq key to dump out Tree RCU's
5423			rcu_node tree with an eye towards determining
5424			why a new grace period has not yet started.
5425
5426	rcutree.use_softirq=	[KNL]
5427			If set to zero, move all RCU_SOFTIRQ processing to
5428			per-CPU rcuc kthreads.  Defaults to a non-zero
5429			value, meaning that RCU_SOFTIRQ is used by default.
5430			Specify rcutree.use_softirq=0 to use rcuc kthreads.
5431
5432			But note that CONFIG_PREEMPT_RT=y kernels disable
5433			this kernel boot parameter, forcibly setting it
5434			to zero.
5435
5436	rcutree.enable_rcu_lazy= [KNL]
5437			To save power, batch RCU callbacks and flush after
5438			delay, memory pressure or callback list growing too
5439			big.
5440
5441	rcutree.rcu_normal_wake_from_gp= [KNL]
5442			Reduces a latency of synchronize_rcu() call. This approach
5443			maintains its own track of synchronize_rcu() callers, so it
5444			does not interact with regular callbacks because it does not
5445			use a call_rcu[_hurry]() path. Please note, this is for a
5446			normal grace period.
5447
5448			How to enable it:
5449
5450			echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp
5451			or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1"
5452
5453			Default is 0.
5454
5455	rcuscale.gp_async= [KNL]
5456			Measure performance of asynchronous
5457			grace-period primitives such as call_rcu().
5458
5459	rcuscale.gp_async_max= [KNL]
5460			Specify the maximum number of outstanding
5461			callbacks per writer thread.  When a writer
5462			thread exceeds this limit, it invokes the
5463			corresponding flavor of rcu_barrier() to allow
5464			previously posted callbacks to drain.
5465
5466	rcuscale.gp_exp= [KNL]
5467			Measure performance of expedited synchronous
5468			grace-period primitives.
5469
5470	rcuscale.holdoff= [KNL]
5471			Set test-start holdoff period.  The purpose of
5472			this parameter is to delay the start of the
5473			test until boot completes in order to avoid
5474			interference.
5475
5476	rcuscale.kfree_by_call_rcu= [KNL]
5477			In kernels built with CONFIG_RCU_LAZY=y, test
5478			call_rcu() instead of kfree_rcu().
5479
5480	rcuscale.kfree_mult= [KNL]
5481			Instead of allocating an object of size kfree_obj,
5482			allocate one of kfree_mult * sizeof(kfree_obj).
5483			Defaults to 1.
5484
5485	rcuscale.kfree_rcu_test= [KNL]
5486			Set to measure performance of kfree_rcu() flooding.
5487
5488	rcuscale.kfree_rcu_test_double= [KNL]
5489			Test the double-argument variant of kfree_rcu().
5490			If this parameter has the same value as
5491			rcuscale.kfree_rcu_test_single, both the single-
5492			and double-argument variants are tested.
5493
5494	rcuscale.kfree_rcu_test_single= [KNL]
5495			Test the single-argument variant of kfree_rcu().
5496			If this parameter has the same value as
5497			rcuscale.kfree_rcu_test_double, both the single-
5498			and double-argument variants are tested.
5499
5500	rcuscale.kfree_nthreads= [KNL]
5501			The number of threads running loops of kfree_rcu().
5502
5503	rcuscale.kfree_alloc_num= [KNL]
5504			Number of allocations and frees done in an iteration.
5505
5506	rcuscale.kfree_loops= [KNL]
5507			Number of loops doing rcuscale.kfree_alloc_num number
5508			of allocations and frees.
5509
5510	rcuscale.minruntime= [KNL]
5511			Set the minimum test run time in seconds.  This
5512			does not affect the data-collection interval,
5513			but instead allows better measurement of things
5514			like CPU consumption.
5515
5516	rcuscale.nreaders= [KNL]
5517			Set number of RCU readers.  The value -1 selects
5518			N, where N is the number of CPUs.  A value
5519			"n" less than -1 selects N-n+1, where N is again
5520			the number of CPUs.  For example, -2 selects N
5521			(the number of CPUs), -3 selects N+1, and so on.
5522			A value of "n" less than or equal to -N selects
5523			a single reader.
5524
5525	rcuscale.nwriters= [KNL]
5526			Set number of RCU writers.  The values operate
5527			the same as for rcuscale.nreaders.
5528			N, where N is the number of CPUs
5529
5530	rcuscale.scale_type= [KNL]
5531			Specify the RCU implementation to test.
5532
5533	rcuscale.shutdown= [KNL]
5534			Shut the system down after performance tests
5535			complete.  This is useful for hands-off automated
5536			testing.
5537
5538	rcuscale.verbose= [KNL]
5539			Enable additional printk() statements.
5540
5541	rcuscale.writer_holdoff= [KNL]
5542			Write-side holdoff between grace periods,
5543			in microseconds.  The default of zero says
5544			no holdoff.
5545
5546	rcuscale.writer_holdoff_jiffies= [KNL]
5547			Additional write-side holdoff between grace
5548			periods, but in jiffies.  The default of zero
5549			says no holdoff.
5550
5551	rcutorture.fqs_duration= [KNL]
5552			Set duration of force_quiescent_state bursts
5553			in microseconds.
5554
5555	rcutorture.fqs_holdoff= [KNL]
5556			Set holdoff time within force_quiescent_state bursts
5557			in microseconds.
5558
5559	rcutorture.fqs_stutter= [KNL]
5560			Set wait time between force_quiescent_state bursts
5561			in seconds.
5562
5563	rcutorture.fwd_progress= [KNL]
5564			Specifies the number of kthreads to be used
5565			for  RCU grace-period forward-progress testing
5566			for the types of RCU supporting this notion.
5567			Defaults to 1 kthread, values less than zero or
5568			greater than the number of CPUs cause the number
5569			of CPUs to be used.
5570
5571	rcutorture.fwd_progress_div= [KNL]
5572			Specify the fraction of a CPU-stall-warning
5573			period to do tight-loop forward-progress testing.
5574
5575	rcutorture.fwd_progress_holdoff= [KNL]
5576			Number of seconds to wait between successive
5577			forward-progress tests.
5578
5579	rcutorture.fwd_progress_need_resched= [KNL]
5580			Enclose cond_resched() calls within checks for
5581			need_resched() during tight-loop forward-progress
5582			testing.
5583
5584	rcutorture.gp_cond= [KNL]
5585			Use conditional/asynchronous update-side
5586			normal-grace-period primitives, if available.
5587
5588	rcutorture.gp_cond_exp= [KNL]
5589			Use conditional/asynchronous update-side
5590			expedited-grace-period primitives, if available.
5591
5592	rcutorture.gp_cond_full= [KNL]
5593			Use conditional/asynchronous update-side
5594			normal-grace-period primitives that also take
5595			concurrent expedited grace periods into account,
5596			if available.
5597
5598	rcutorture.gp_cond_exp_full= [KNL]
5599			Use conditional/asynchronous update-side
5600			expedited-grace-period primitives that also take
5601			concurrent normal grace periods into account,
5602			if available.
5603
5604	rcutorture.gp_cond_wi= [KNL]
5605			Nominal wait interval for normal conditional
5606			grace periods (specified by rcutorture's
5607			gp_cond and gp_cond_full module parameters),
5608			in microseconds.  The actual wait interval will
5609			be randomly selected to nanosecond granularity up
5610			to this wait interval.	Defaults to 16 jiffies,
5611			for example, 16,000 microseconds on a system
5612			with HZ=1000.
5613
5614	rcutorture.gp_cond_wi_exp= [KNL]
5615			Nominal wait interval for expedited conditional
5616			grace periods (specified by rcutorture's
5617			gp_cond_exp and gp_cond_exp_full module
5618			parameters), in microseconds.  The actual wait
5619			interval will be randomly selected to nanosecond
5620			granularity up to this wait interval.  Defaults to
5621			128 microseconds.
5622
5623	rcutorture.gp_exp= [KNL]
5624			Use expedited update-side primitives, if available.
5625
5626	rcutorture.gp_normal= [KNL]
5627			Use normal (non-expedited) asynchronous
5628			update-side primitives, if available.
5629
5630	rcutorture.gp_poll= [KNL]
5631			Use polled update-side normal-grace-period
5632			primitives, if available.
5633
5634	rcutorture.gp_poll_exp= [KNL]
5635			Use polled update-side expedited-grace-period
5636			primitives, if available.
5637
5638	rcutorture.gp_poll_full= [KNL]
5639			Use polled update-side normal-grace-period
5640			primitives that also take concurrent expedited
5641			grace periods into account, if available.
5642
5643	rcutorture.gp_poll_exp_full= [KNL]
5644			Use polled update-side expedited-grace-period
5645			primitives that also take concurrent normal
5646			grace periods into account, if available.
5647
5648	rcutorture.gp_poll_wi= [KNL]
5649			Nominal wait interval for normal conditional
5650			grace periods (specified by rcutorture's
5651			gp_poll and gp_poll_full module parameters),
5652			in microseconds.  The actual wait interval will
5653			be randomly selected to nanosecond granularity up
5654			to this wait interval.	Defaults to 16 jiffies,
5655			for example, 16,000 microseconds on a system
5656			with HZ=1000.
5657
5658	rcutorture.gp_poll_wi_exp= [KNL]
5659			Nominal wait interval for expedited conditional
5660			grace periods (specified by rcutorture's
5661			gp_poll_exp and gp_poll_exp_full module
5662			parameters), in microseconds.  The actual wait
5663			interval will be randomly selected to nanosecond
5664			granularity up to this wait interval.  Defaults to
5665			128 microseconds.
5666
5667	rcutorture.gp_sync= [KNL]
5668			Use normal (non-expedited) synchronous
5669			update-side primitives, if available.  If all
5670			of rcutorture.gp_cond=, rcutorture.gp_exp=,
5671			rcutorture.gp_normal=, and rcutorture.gp_sync=
5672			are zero, rcutorture acts as if is interpreted
5673			they are all non-zero.
5674
5675	rcutorture.irqreader= [KNL]
5676			Run RCU readers from irq handlers, or, more
5677			accurately, from a timer handler.  Not all RCU
5678			flavors take kindly to this sort of thing.
5679
5680	rcutorture.leakpointer= [KNL]
5681			Leak an RCU-protected pointer out of the reader.
5682			This can of course result in splats, and is
5683			intended to test the ability of things like
5684			CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5685			such leaks.
5686
5687	rcutorture.n_barrier_cbs= [KNL]
5688			Set callbacks/threads for rcu_barrier() testing.
5689
5690	rcutorture.nfakewriters= [KNL]
5691			Set number of concurrent RCU writers.  These just
5692			stress RCU, they don't participate in the actual
5693			test, hence the "fake".
5694
5695	rcutorture.nocbs_nthreads= [KNL]
5696			Set number of RCU callback-offload togglers.
5697			Zero (the default) disables toggling.
5698
5699	rcutorture.nocbs_toggle= [KNL]
5700			Set the delay in milliseconds between successive
5701			callback-offload toggling attempts.
5702
5703	rcutorture.nreaders= [KNL]
5704			Set number of RCU readers.  The value -1 selects
5705			N-1, where N is the number of CPUs.  A value
5706			"n" less than -1 selects N-n-2, where N is again
5707			the number of CPUs.  For example, -2 selects N
5708			(the number of CPUs), -3 selects N+1, and so on.
5709
5710	rcutorture.object_debug= [KNL]
5711			Enable debug-object double-call_rcu() testing.
5712
5713	rcutorture.onoff_holdoff= [KNL]
5714			Set time (s) after boot for CPU-hotplug testing.
5715
5716	rcutorture.onoff_interval= [KNL]
5717			Set time (jiffies) between CPU-hotplug operations,
5718			or zero to disable CPU-hotplug testing.
5719
5720	rcutorture.preempt_duration= [KNL]
5721			Set duration (in milliseconds) of preemptions
5722			by a high-priority FIFO real-time task.  Set to
5723			zero (the default) to disable.	The CPUs to
5724			preempt are selected randomly from the set that
5725			are online at a given point in time.  Races with
5726			CPUs going offline are ignored, with that attempt
5727			at preemption skipped.
5728
5729	rcutorture.preempt_interval= [KNL]
5730			Set interval (in milliseconds, defaulting to one
5731			second) between preemptions by a high-priority
5732			FIFO real-time task.  This delay is mediated
5733			by an hrtimer and is further fuzzed to avoid
5734			inadvertent synchronizations.
5735
5736	rcutorture.read_exit_burst= [KNL]
5737			The number of times in a given read-then-exit
5738			episode that a set of read-then-exit kthreads
5739			is spawned.
5740
5741	rcutorture.read_exit_delay= [KNL]
5742			The delay, in seconds, between successive
5743			read-then-exit testing episodes.
5744
5745	rcutorture.reader_flavor= [KNL]
5746			A bit mask indicating which readers to use.
5747			If there is more than one bit set, the readers
5748			are entered from low-order bit up, and are
5749			exited in the opposite order.  For SRCU, the
5750			0x1 bit is normal readers, 0x2 NMI-safe readers,
5751			and 0x4 light-weight readers.
5752
5753	rcutorture.shuffle_interval= [KNL]
5754			Set task-shuffle interval (s).  Shuffling tasks
5755			allows some CPUs to go into dyntick-idle mode
5756			during the rcutorture test.
5757
5758	rcutorture.shutdown_secs= [KNL]
5759			Set time (s) after boot system shutdown.  This
5760			is useful for hands-off automated testing.
5761
5762	rcutorture.stall_cpu= [KNL]
5763			Duration of CPU stall (s) to test RCU CPU stall
5764			warnings, zero to disable.
5765
5766	rcutorture.stall_cpu_block= [KNL]
5767			Sleep while stalling if set.  This will result
5768			in warnings from preemptible RCU in addition to
5769			any other stall-related activity.  Note that
5770			in kernels built with CONFIG_PREEMPTION=n and
5771			CONFIG_PREEMPT_COUNT=y, this parameter will
5772			cause the CPU to pass through a quiescent state.
5773			Given CONFIG_PREEMPTION=n, this will suppress
5774			RCU CPU stall warnings, but will instead result
5775			in scheduling-while-atomic splats.
5776
5777			Use of this module parameter results in splats.
5778
5779
5780	rcutorture.stall_cpu_holdoff= [KNL]
5781			Time to wait (s) after boot before inducing stall.
5782
5783	rcutorture.stall_cpu_irqsoff= [KNL]
5784			Disable interrupts while stalling if set, but only
5785			on the first stall in the set.
5786
5787	rcutorture.stall_cpu_repeat= [KNL]
5788			Number of times to repeat the stall sequence,
5789			so that rcutorture.stall_cpu_repeat=3 will result
5790			in four stall sequences.
5791
5792	rcutorture.stall_gp_kthread= [KNL]
5793			Duration (s) of forced sleep within RCU
5794			grace-period kthread to test RCU CPU stall
5795			warnings, zero to disable.  If both stall_cpu
5796			and stall_gp_kthread are specified, the
5797			kthread is starved first, then the CPU.
5798
5799	rcutorture.stat_interval= [KNL]
5800			Time (s) between statistics printk()s.
5801
5802	rcutorture.stutter= [KNL]
5803			Time (s) to stutter testing, for example, specifying
5804			five seconds causes the test to run for five seconds,
5805			wait for five seconds, and so on.  This tests RCU's
5806			ability to transition abruptly to and from idle.
5807
5808	rcutorture.test_boost= [KNL]
5809			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
5810			"Maybe" means test if the RCU implementation
5811			under test support RCU priority boosting.
5812
5813	rcutorture.test_boost_duration= [KNL]
5814			Duration (s) of each individual boost test.
5815
5816	rcutorture.test_boost_holdoff= [KNL]
5817			Holdoff time (s) from start of test to the start
5818			of RCU priority-boost testing.	Defaults to zero,
5819			that is, no holdoff.
5820
5821	rcutorture.test_boost_interval= [KNL]
5822			Interval (s) between each boost test.
5823
5824	rcutorture.test_no_idle_hz= [KNL]
5825			Test RCU's dyntick-idle handling.  See also the
5826			rcutorture.shuffle_interval parameter.
5827
5828	rcutorture.torture_type= [KNL]
5829			Specify the RCU implementation to test.
5830
5831	rcutorture.verbose= [KNL]
5832			Enable additional printk() statements.
5833
5834	rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5835			Dump ftrace buffer after reporting RCU CPU
5836			stall warning.
5837
5838	rcupdate.rcu_cpu_stall_notifiers= [KNL]
5839			Provide RCU CPU stall notifiers, but see the
5840			warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
5841			option's help text.  TL;DR:  You almost certainly
5842			do not want rcupdate.rcu_cpu_stall_notifiers.
5843
5844	rcupdate.rcu_cpu_stall_suppress= [KNL]
5845			Suppress RCU CPU stall warning messages.
5846
5847	rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5848			Suppress RCU CPU stall warning messages and
5849			rcutorture writer stall warnings that occur
5850			during early boot, that is, during the time
5851			before the init task is spawned.
5852
5853	rcupdate.rcu_cpu_stall_timeout= [KNL]
5854			Set timeout for RCU CPU stall warning messages.
5855			The value is in seconds and the maximum allowed
5856			value is 300 seconds.
5857
5858	rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5859			Set timeout for expedited RCU CPU stall warning
5860			messages.  The value is in milliseconds
5861			and the maximum allowed value is 21000
5862			milliseconds. Please note that this value is
5863			adjusted to an arch timer tick resolution.
5864			Setting this to zero causes the value from
5865			rcupdate.rcu_cpu_stall_timeout to be used (after
5866			conversion from seconds to milliseconds).
5867
5868	rcupdate.rcu_cpu_stall_cputime= [KNL]
5869			Provide statistics on the cputime and count of
5870			interrupts and tasks during the sampling period. For
5871			multiple continuous RCU stalls, all sampling periods
5872			begin at half of the first RCU stall timeout.
5873
5874	rcupdate.rcu_exp_stall_task_details= [KNL]
5875			Print stack dumps of any tasks blocking the
5876			current expedited RCU grace period during an
5877			expedited RCU CPU stall warning.
5878
5879	rcupdate.rcu_expedited= [KNL]
5880			Use expedited grace-period primitives, for
5881			example, synchronize_rcu_expedited() instead
5882			of synchronize_rcu().  This reduces latency,
5883			but can increase CPU utilization, degrade
5884			real-time latency, and degrade energy efficiency.
5885			No effect on CONFIG_TINY_RCU kernels.
5886
5887	rcupdate.rcu_normal= [KNL]
5888			Use only normal grace-period primitives,
5889			for example, synchronize_rcu() instead of
5890			synchronize_rcu_expedited().  This improves
5891			real-time latency, CPU utilization, and
5892			energy efficiency, but can expose users to
5893			increased grace-period latency.  This parameter
5894			overrides rcupdate.rcu_expedited.  No effect on
5895			CONFIG_TINY_RCU kernels.
5896
5897	rcupdate.rcu_normal_after_boot= [KNL]
5898			Once boot has completed (that is, after
5899			rcu_end_inkernel_boot() has been invoked), use
5900			only normal grace-period primitives.  No effect
5901			on CONFIG_TINY_RCU kernels.
5902
5903			But note that CONFIG_PREEMPT_RT=y kernels enables
5904			this kernel boot parameter, forcibly setting
5905			it to the value one, that is, converting any
5906			post-boot attempt at an expedited RCU grace
5907			period to instead use normal non-expedited
5908			grace-period processing.
5909
5910	rcupdate.rcu_task_collapse_lim= [KNL]
5911			Set the maximum number of callbacks present
5912			at the beginning of a grace period that allows
5913			the RCU Tasks flavors to collapse back to using
5914			a single callback queue.  This switching only
5915			occurs when rcupdate.rcu_task_enqueue_lim is
5916			set to the default value of -1.
5917
5918	rcupdate.rcu_task_contend_lim= [KNL]
5919			Set the minimum number of callback-queuing-time
5920			lock-contention events per jiffy required to
5921			cause the RCU Tasks flavors to switch to per-CPU
5922			callback queuing.  This switching only occurs
5923			when rcupdate.rcu_task_enqueue_lim is set to
5924			the default value of -1.
5925
5926	rcupdate.rcu_task_enqueue_lim= [KNL]
5927			Set the number of callback queues to use for the
5928			RCU Tasks family of RCU flavors.  The default
5929			of -1 allows this to be automatically (and
5930			dynamically) adjusted.	This parameter is intended
5931			for use in testing.
5932
5933	rcupdate.rcu_task_ipi_delay= [KNL]
5934			Set time in jiffies during which RCU tasks will
5935			avoid sending IPIs, starting with the beginning
5936			of a given grace period.  Setting a large
5937			number avoids disturbing real-time workloads,
5938			but lengthens grace periods.
5939
5940	rcupdate.rcu_task_lazy_lim= [KNL]
5941			Number of callbacks on a given CPU that will
5942			cancel laziness on that CPU.  Use -1 to disable
5943			cancellation of laziness, but be advised that
5944			doing so increases the danger of OOM due to
5945			callback flooding.
5946
5947	rcupdate.rcu_task_stall_info= [KNL]
5948			Set initial timeout in jiffies for RCU task stall
5949			informational messages, which give some indication
5950			of the problem for those not patient enough to
5951			wait for ten minutes.  Informational messages are
5952			only printed prior to the stall-warning message
5953			for a given grace period. Disable with a value
5954			less than or equal to zero.  Defaults to ten
5955			seconds.  A change in value does not take effect
5956			until the beginning of the next grace period.
5957
5958	rcupdate.rcu_task_stall_info_mult= [KNL]
5959			Multiplier for time interval between successive
5960			RCU task stall informational messages for a given
5961			RCU tasks grace period.  This value is clamped
5962			to one through ten, inclusive.	It defaults to
5963			the value three, so that the first informational
5964			message is printed 10 seconds into the grace
5965			period, the second at 40 seconds, the third at
5966			160 seconds, and then the stall warning at 600
5967			seconds would prevent a fourth at 640 seconds.
5968
5969	rcupdate.rcu_task_stall_timeout= [KNL]
5970			Set timeout in jiffies for RCU task stall
5971			warning messages.  Disable with a value less
5972			than or equal to zero.	Defaults to ten minutes.
5973			A change in value does not take effect until
5974			the beginning of the next grace period.
5975
5976	rcupdate.rcu_tasks_lazy_ms= [KNL]
5977			Set timeout in milliseconds RCU Tasks asynchronous
5978			callback batching for call_rcu_tasks().
5979			A negative value will take the default.  A value
5980			of zero will disable batching.	Batching is
5981			always disabled for synchronize_rcu_tasks().
5982
5983	rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
5984			Set timeout in milliseconds RCU Tasks
5985			Trace asynchronous callback batching for
5986			call_rcu_tasks_trace().  A negative value
5987			will take the default.	A value of zero will
5988			disable batching.  Batching is always disabled
5989			for synchronize_rcu_tasks_trace().
5990
5991	rcupdate.rcu_self_test= [KNL]
5992			Run the RCU early boot self tests
5993
5994	rdinit=		[KNL]
5995			Format: <full_path>
5996			Run specified binary instead of /init from the ramdisk,
5997			used for early userspace startup. See initrd.
5998
5999	rdrand=		[X86,EARLY]
6000			force - Override the decision by the kernel to hide the
6001				advertisement of RDRAND support (this affects
6002				certain AMD processors because of buggy BIOS
6003				support, specifically around the suspend/resume
6004				path).
6005
6006	rdt=		[HW,X86,RDT]
6007			Turn on/off individual RDT features. List is:
6008			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
6009			mba, smba, bmec.
6010			E.g. to turn on cmt and turn off mba use:
6011				rdt=cmt,!mba
6012
6013	reboot=		[KNL]
6014			Format (x86 or x86_64):
6015				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
6016				[[,]s[mp]#### \
6017				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
6018				[[,]f[orce]
6019			Where reboot_mode is one of warm (soft) or cold (hard) or gpio
6020					(prefix with 'panic_' to set mode for panic
6021					reboot only),
6022			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
6023			      reboot_force is either force or not specified,
6024			      reboot_cpu is s[mp]#### with #### being the processor
6025					to be used for rebooting.
6026
6027		acpi
6028			Use the ACPI RESET_REG in the FADT. If ACPI is not
6029			configured or the ACPI reset does not work, the reboot
6030			path attempts the reset using the keyboard controller.
6031
6032		bios
6033			Use the CPU reboot vector for warm reset
6034
6035		cold
6036			Set the cold reboot flag
6037
6038		default
6039			There are some built-in platform specific "quirks"
6040			- you may see: "reboot: <name> series board detected.
6041			Selecting <type> for reboots." In the case where you
6042			think the quirk is in error (e.g. you have newer BIOS,
6043			or newer board) using this option will ignore the
6044			built-in quirk table, and use the generic default
6045			reboot actions.
6046
6047		efi
6048			Use efi reset_system runtime service. If EFI is not
6049			configured or the EFI reset does not work, the reboot
6050			path attempts the reset using the keyboard controller.
6051
6052		force
6053			Don't stop other CPUs on reboot. This can make reboot
6054			more reliable in some cases.
6055
6056		kbd
6057			Use the keyboard controller. cold reset (default)
6058
6059		pci
6060			Use a write to the PCI config space register 0xcf9 to
6061			trigger reboot.
6062
6063		triple
6064			Force a triple fault (init)
6065
6066		warm
6067			Don't set the cold reboot flag
6068
6069			Using warm reset will be much faster especially on big
6070			memory systems because the BIOS will not go through
6071			the memory check.  Disadvantage is that not all
6072			hardware will be completely reinitialized on reboot so
6073			there may be boot problems on some systems.
6074
6075
6076	refscale.holdoff= [KNL]
6077			Set test-start holdoff period.  The purpose of
6078			this parameter is to delay the start of the
6079			test until boot completes in order to avoid
6080			interference.
6081
6082	refscale.lookup_instances= [KNL]
6083			Number of data elements to use for the forms of
6084			SLAB_TYPESAFE_BY_RCU testing.  A negative number
6085			is negated and multiplied by nr_cpu_ids, while
6086			zero specifies nr_cpu_ids.
6087
6088	refscale.loops= [KNL]
6089			Set the number of loops over the synchronization
6090			primitive under test.  Increasing this number
6091			reduces noise due to loop start/end overhead,
6092			but the default has already reduced the per-pass
6093			noise to a handful of picoseconds on ca. 2020
6094			x86 laptops.
6095
6096	refscale.nreaders= [KNL]
6097			Set number of readers.  The default value of -1
6098			selects N, where N is roughly 75% of the number
6099			of CPUs.  A value of zero is an interesting choice.
6100
6101	refscale.nruns= [KNL]
6102			Set number of runs, each of which is dumped onto
6103			the console log.
6104
6105	refscale.readdelay= [KNL]
6106			Set the read-side critical-section duration,
6107			measured in microseconds.
6108
6109	refscale.scale_type= [KNL]
6110			Specify the read-protection implementation to test.
6111
6112	refscale.shutdown= [KNL]
6113			Shut down the system at the end of the performance
6114			test.  This defaults to 1 (shut it down) when
6115			refscale is built into the kernel and to 0 (leave
6116			it running) when refscale is built as a module.
6117
6118	refscale.verbose= [KNL]
6119			Enable additional printk() statements.
6120
6121	refscale.verbose_batched= [KNL]
6122			Batch the additional printk() statements.  If zero
6123			(the default) or negative, print everything.  Otherwise,
6124			print every Nth verbose statement, where N is the value
6125			specified.
6126
6127	regulator_ignore_unused
6128			[REGULATOR]
6129			Prevents regulator framework from disabling regulators
6130			that are unused, due no driver claiming them. This may
6131			be useful for debug and development, but should not be
6132			needed on a platform with proper driver support.
6133
6134	relax_domain_level=
6135			[KNL, SMP] Set scheduler's default relax_domain_level.
6136			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6137
6138	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
6139			Format: <base1>,<size1>[,<base2>,<size2>,...]
6140			Reserve I/O ports or memory so the kernel won't use
6141			them.  If <base> is less than 0x10000, the region
6142			is assumed to be I/O ports; otherwise it is memory.
6143
6144	reserve_mem=	[RAM]
6145			Format: nn[KMG]:<align>:<label>
6146			Reserve physical memory and label it with a name that
6147			other subsystems can use to access it. This is typically
6148			used for systems that do not wipe the RAM, and this command
6149			line will try to reserve the same physical memory on
6150			soft reboots. Note, it is not guaranteed to be the same
6151			location. For example, if anything about the system changes
6152			or if booting a different kernel. It can also fail if KASLR
6153			places the kernel at the location of where the RAM reservation
6154			was from a previous boot, the new reservation will be at a
6155			different location.
6156			Any subsystem using this feature must add a way to verify
6157			that the contents of the physical memory is from a previous
6158			boot, as there may be cases where the memory will not be
6159			located at the same location.
6160
6161			The format is size:align:label for example, to request
6162			12 megabytes of 4096 alignment for ramoops:
6163
6164			reserve_mem=12M:4096:oops ramoops.mem_name=oops
6165
6166	reservetop=	[X86-32,EARLY]
6167			Format: nn[KMG]
6168			Reserves a hole at the top of the kernel virtual
6169			address space.
6170
6171	reset_devices	[KNL] Force drivers to reset the underlying device
6172			during initialization.
6173
6174	resume=		[SWSUSP]
6175			Specify the partition device for software suspend
6176			Format:
6177			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
6178
6179	resume_offset=	[SWSUSP]
6180			Specify the offset from the beginning of the partition
6181			given by "resume=" at which the swap header is located,
6182			in <PAGE_SIZE> units (needed only for swap files).
6183			See  Documentation/power/swsusp-and-swap-files.rst
6184
6185	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
6186			read the resume files
6187
6188	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
6189			Useful for devices that are detected asynchronously
6190			(e.g. USB and MMC devices).
6191
6192	retain_initrd	[RAM] Keep initrd memory after extraction. After boot, it will
6193			be accessible via /sys/firmware/initrd.
6194
6195	retbleed=	[X86] Control mitigation of RETBleed (Arbitrary
6196			Speculative Code Execution with Return Instructions)
6197			vulnerability.
6198
6199			AMD-based UNRET and IBPB mitigations alone do not stop
6200			sibling threads from influencing the predictions of other
6201			sibling threads. For that reason, STIBP is used on pro-
6202			cessors that support it, and mitigate SMT on processors
6203			that don't.
6204
6205			off          - no mitigation
6206			auto         - automatically select a migitation
6207			auto,nosmt   - automatically select a mitigation,
6208				       disabling SMT if necessary for
6209				       the full mitigation (only on Zen1
6210				       and older without STIBP).
6211			ibpb         - On AMD, mitigate short speculation
6212				       windows on basic block boundaries too.
6213				       Safe, highest perf impact. It also
6214				       enables STIBP if present. Not suitable
6215				       on Intel.
6216			ibpb,nosmt   - Like "ibpb" above but will disable SMT
6217				       when STIBP is not available. This is
6218				       the alternative for systems which do not
6219				       have STIBP.
6220			unret        - Force enable untrained return thunks,
6221				       only effective on AMD f15h-f17h based
6222				       systems.
6223			unret,nosmt  - Like unret, but will disable SMT when STIBP
6224				       is not available. This is the alternative for
6225				       systems which do not have STIBP.
6226
6227			Selecting 'auto' will choose a mitigation method at run
6228			time according to the CPU.
6229
6230			Not specifying this option is equivalent to retbleed=auto.
6231
6232	rfkill.default_state=
6233		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
6234			etc. communication is blocked by default.
6235		1	Unblocked.
6236
6237	rfkill.master_switch_mode=
6238		0	The "airplane mode" button does nothing.
6239		1	The "airplane mode" button toggles between everything
6240			blocked and the previous configuration.
6241		2	The "airplane mode" button toggles between everything
6242			blocked and everything unblocked.
6243
6244	ring3mwait=disable
6245			[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
6246			CPUs.
6247
6248	riscv_isa_fallback [RISCV,EARLY]
6249			When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
6250			falling back to detecting extension support by parsing
6251			"riscv,isa" property on devicetree systems when the
6252			replacement properties are not found. See the Kconfig
6253			entry for RISCV_ISA_FALLBACK.
6254
6255	ro		[KNL] Mount root device read-only on boot
6256
6257	rodata=		[KNL,EARLY]
6258		on	Mark read-only kernel memory as read-only (default).
6259		off	Leave read-only kernel memory writable for debugging.
6260		full	Mark read-only kernel memory and aliases as read-only
6261		        [arm64]
6262
6263	rockchip.usb_uart
6264			[EARLY]
6265			Enable the uart passthrough on the designated usb port
6266			on Rockchip SoCs. When active, the signals of the
6267			debug-uart get routed to the D+ and D- pins of the usb
6268			port and the regular usb controller gets disabled.
6269
6270	root=		[KNL] Root filesystem
6271			Usually this a a block device specifier of some kind,
6272			see the early_lookup_bdev comment in
6273			block/early-lookup.c for details.
6274			Alternatively this can be "ram" for the legacy initial
6275			ramdisk, "nfs" and "cifs" for root on a network file
6276			system, or "mtd" and "ubi" for mounting from raw flash.
6277
6278	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
6279			mount the root filesystem
6280
6281	rootflags=	[KNL] Set root filesystem mount option string
6282
6283	rootfstype=	[KNL] Set root filesystem type
6284
6285	rootwait	[KNL] Wait (indefinitely) for root device to show up.
6286			Useful for devices that are detected asynchronously
6287			(e.g. USB and MMC devices).
6288
6289	rootwait=	[KNL] Maximum time (in seconds) to wait for root device
6290			to show up before attempting to mount the root
6291			filesystem.
6292
6293	rproc_mem=nn[KMG][@address]
6294			[KNL,ARM,CMA] Remoteproc physical memory block.
6295			Memory area to be used by remote processor image,
6296			managed by CMA.
6297
6298	rw		[KNL] Mount root device read-write on boot
6299
6300	S		[KNL] Run init in single mode
6301
6302	s390_iommu=	[HW,S390]
6303			Set s390 IOTLB flushing mode
6304		strict
6305			With strict flushing every unmap operation will result
6306			in an IOTLB flush. Default is lazy flushing before
6307			reuse, which is faster. Deprecated, equivalent to
6308			iommu.strict=1.
6309
6310	s390_iommu_aperture=	[KNL,S390]
6311			Specifies the size of the per device DMA address space
6312			accessible through the DMA and IOMMU APIs as a decimal
6313			factor of the size of main memory.
6314			The default is 1 meaning that one can concurrently use
6315			as many DMA addresses as physical memory is installed,
6316			if supported by hardware, and thus map all of memory
6317			once. With a value of 2 one can map all of memory twice
6318			and so on. As a special case a factor of 0 imposes no
6319			restrictions other than those given by hardware at the
6320			cost of significant additional memory use for tables.
6321
6322	sa1100ir	[NET]
6323			See drivers/net/irda/sa1100_ir.c.
6324
6325	sched_verbose	[KNL,EARLY] Enables verbose scheduler debug messages.
6326
6327	schedstats=	[KNL,X86] Enable or disable scheduled statistics.
6328			Allowed values are enable and disable. This feature
6329			incurs a small amount of overhead in the scheduler
6330			but is useful for debugging and performance tuning.
6331
6332	sched_thermal_decay_shift=
6333			[Deprecated]
6334			[KNL, SMP] Set a decay shift for scheduler thermal
6335			pressure signal. Thermal pressure signal follows the
6336			default decay period of other scheduler pelt
6337			signals(usually 32 ms but configurable). Setting
6338			sched_thermal_decay_shift will left shift the decay
6339			period for the thermal pressure signal by the shift
6340			value.
6341			i.e. with the default pelt decay period of 32 ms
6342			sched_thermal_decay_shift   thermal pressure decay pr
6343				1			64 ms
6344				2			128 ms
6345			and so on.
6346			Format: integer between 0 and 10
6347			Default is 0.
6348
6349	scftorture.holdoff= [KNL]
6350			Number of seconds to hold off before starting
6351			test.  Defaults to zero for module insertion and
6352			to 10 seconds for built-in smp_call_function()
6353			tests.
6354
6355	scftorture.longwait= [KNL]
6356			Request ridiculously long waits randomly selected
6357			up to the chosen limit in seconds.  Zero (the
6358			default) disables this feature.  Please note
6359			that requesting even small non-zero numbers of
6360			seconds can result in RCU CPU stall warnings,
6361			softlockup complaints, and so on.
6362
6363	scftorture.nthreads= [KNL]
6364			Number of kthreads to spawn to invoke the
6365			smp_call_function() family of functions.
6366			The default of -1 specifies a number of kthreads
6367			equal to the number of CPUs.
6368
6369	scftorture.onoff_holdoff= [KNL]
6370			Number seconds to wait after the start of the
6371			test before initiating CPU-hotplug operations.
6372
6373	scftorture.onoff_interval= [KNL]
6374			Number seconds to wait between successive
6375			CPU-hotplug operations.  Specifying zero (which
6376			is the default) disables CPU-hotplug operations.
6377
6378	scftorture.shutdown_secs= [KNL]
6379			The number of seconds following the start of the
6380			test after which to shut down the system.  The
6381			default of zero avoids shutting down the system.
6382			Non-zero values are useful for automated tests.
6383
6384	scftorture.stat_interval= [KNL]
6385			The number of seconds between outputting the
6386			current test statistics to the console.  A value
6387			of zero disables statistics output.
6388
6389	scftorture.stutter_cpus= [KNL]
6390			The number of jiffies to wait between each change
6391			to the set of CPUs under test.
6392
6393	scftorture.use_cpus_read_lock= [KNL]
6394			Use use_cpus_read_lock() instead of the default
6395			preempt_disable() to disable CPU hotplug
6396			while invoking one of the smp_call_function*()
6397			functions.
6398
6399	scftorture.verbose= [KNL]
6400			Enable additional printk() statements.
6401
6402	scftorture.weight_single= [KNL]
6403			The probability weighting to use for the
6404			smp_call_function_single() function with a zero
6405			"wait" parameter.  A value of -1 selects the
6406			default if all other weights are -1.  However,
6407			if at least one weight has some other value, a
6408			value of -1 will instead select a weight of zero.
6409
6410	scftorture.weight_single_wait= [KNL]
6411			The probability weighting to use for the
6412			smp_call_function_single() function with a
6413			non-zero "wait" parameter.  See weight_single.
6414
6415	scftorture.weight_many= [KNL]
6416			The probability weighting to use for the
6417			smp_call_function_many() function with a zero
6418			"wait" parameter.  See weight_single.
6419			Note well that setting a high probability for
6420			this weighting can place serious IPI load
6421			on the system.
6422
6423	scftorture.weight_many_wait= [KNL]
6424			The probability weighting to use for the
6425			smp_call_function_many() function with a
6426			non-zero "wait" parameter.  See weight_single
6427			and weight_many.
6428
6429	scftorture.weight_all= [KNL]
6430			The probability weighting to use for the
6431			smp_call_function_all() function with a zero
6432			"wait" parameter.  See weight_single and
6433			weight_many.
6434
6435	scftorture.weight_all_wait= [KNL]
6436			The probability weighting to use for the
6437			smp_call_function_all() function with a
6438			non-zero "wait" parameter.  See weight_single
6439			and weight_many.
6440
6441	sdw_mclk_divider=[SDW]
6442			Specify the MCLK divider for Intel SoundWire buses in
6443			case the BIOS does not provide the clock rate properly.
6444
6445	skew_tick=	[KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
6446			xtime_lock contention on larger systems, and/or RCU lock
6447			contention on all systems with CONFIG_MAXSMP set.
6448			Format: { "0" | "1" }
6449			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6450			1 -- enable.
6451			Note: increases power consumption, thus should only be
6452			enabled if running jitter sensitive (HPC/RT) workloads.
6453
6454	security=	[SECURITY] Choose a legacy "major" security module to
6455			enable at boot. This has been deprecated by the
6456			"lsm=" parameter.
6457
6458	selinux=	[SELINUX] Disable or enable SELinux at boot time.
6459			Format: { "0" | "1" }
6460			See security/selinux/Kconfig help text.
6461			0 -- disable.
6462			1 -- enable.
6463			Default value is 1.
6464
6465	serialnumber	[BUGS=X86-32]
6466
6467	sev=option[,option...] [X86-64]
6468
6469		debug
6470			Enable debug messages.
6471
6472		nosnp
6473			Do not enable SEV-SNP (applies to host/hypervisor
6474			only). Setting 'nosnp' avoids the RMP check overhead
6475			in memory accesses when users do not want to run
6476			SEV-SNP guests.
6477
6478	shapers=	[NET]
6479			Maximal number of shapers.
6480
6481	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
6482			Limit apic dumping. The parameter defines the maximal
6483			number of local apics being dumped. Also it is possible
6484			to set it to "all" by meaning -- no limit here.
6485			Format: { 1 (default) | 2 | ... | all }.
6486			The parameter valid if only apic=debug or
6487			apic=verbose is specified.
6488			Example: apic=debug show_lapic=all
6489
6490	slab_debug[=options[,slabs][;[options[,slabs]]...]	[MM]
6491			Enabling slab_debug allows one to determine the
6492			culprit if slab objects become corrupted. Enabling
6493			slab_debug can create guard zones around objects and
6494			may poison objects when not in use. Also tracks the
6495			last alloc / free. For more information see
6496			Documentation/mm/slub.rst.
6497			(slub_debug legacy name also accepted for now)
6498
6499	slab_max_order= [MM]
6500			Determines the maximum allowed order for slabs.
6501			A high setting may cause OOMs due to memory
6502			fragmentation. For more information see
6503			Documentation/mm/slub.rst.
6504			(slub_max_order legacy name also accepted for now)
6505
6506	slab_merge	[MM]
6507			Enable merging of slabs with similar size when the
6508			kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6509			(slub_merge legacy name also accepted for now)
6510
6511	slab_min_objects=	[MM]
6512			The minimum number of objects per slab. SLUB will
6513			increase the slab order up to slab_max_order to
6514			generate a sufficiently large slab able to contain
6515			the number of objects indicated. The higher the number
6516			of objects the smaller the overhead of tracking slabs
6517			and the less frequently locks need to be acquired.
6518			For more information see Documentation/mm/slub.rst.
6519			(slub_min_objects legacy name also accepted for now)
6520
6521	slab_min_order=	[MM]
6522			Determines the minimum page order for slabs. Must be
6523			lower or equal to slab_max_order. For more information see
6524			Documentation/mm/slub.rst.
6525			(slub_min_order legacy name also accepted for now)
6526
6527	slab_nomerge	[MM]
6528			Disable merging of slabs with similar size. May be
6529			necessary if there is some reason to distinguish
6530			allocs to different slabs, especially in hardened
6531			environments where the risk of heap overflows and
6532			layout control by attackers can usually be
6533			frustrated by disabling merging. This will reduce
6534			most of the exposure of a heap attack to a single
6535			cache (risks via metadata attacks are mostly
6536			unchanged). Debug options disable merging on their
6537			own.
6538			For more information see Documentation/mm/slub.rst.
6539			(slub_nomerge legacy name also accepted for now)
6540
6541	slab_strict_numa	[MM]
6542			Support memory policies on a per object level
6543			in the slab allocator. The default is for memory
6544			policies to be applied at the folio level when
6545			a new folio is needed or a partial folio is
6546			retrieved from the lists. Increases overhead
6547			in the slab fastpaths but gains more accurate
6548			NUMA kernel object placement which helps with slow
6549			interconnects in NUMA systems.
6550
6551	slram=		[HW,MTD]
6552
6553	smart2=		[HW]
6554			Format: <io1>[,<io2>[,...,<io8>]]
6555
6556	smp.csd_lock_timeout= [KNL]
6557			Specify the period of time in milliseconds
6558			that smp_call_function() and friends will wait
6559			for a CPU to release the CSD lock.  This is
6560			useful when diagnosing bugs involving CPUs
6561			disabling interrupts for extended periods
6562			of time.  Defaults to 5,000 milliseconds, and
6563			setting a value of zero disables this feature.
6564			This feature may be more efficiently disabled
6565			using the csdlock_debug- kernel parameter.
6566
6567	smp.panic_on_ipistall= [KNL]
6568			If a csd_lock_timeout extends for more than
6569			the specified number of milliseconds, panic the
6570			system.  By default, let CSD-lock acquisition
6571			take as long as they take.  Specifying 300,000
6572			for this value provides a 5-minute timeout.
6573
6574	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
6575	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
6576	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
6577	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
6578	smsc-ircc2.ircc_irq=	[HW] IRQ line
6579	smsc-ircc2.ircc_dma=	[HW] DMA channel
6580	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6581				0: Toshiba Satellite 1800 (GP data pin select)
6582				1: Fast pin select (default)
6583				2: ATC IRMode
6584
6585	smt=		[KNL,MIPS,S390,EARLY] Set the maximum number of threads
6586			(logical CPUs) to use per physical CPU on systems
6587			capable of symmetric multithreading (SMT). Will
6588			be capped to the actual hardware limit.
6589			Format: <integer>
6590			Default: -1 (no limit)
6591
6592	softlockup_panic=
6593			[KNL] Should the soft-lockup detector generate panics.
6594			Format: 0 | 1
6595
6596			A value of 1 instructs the soft-lockup detector
6597			to panic the machine when a soft-lockup occurs. It is
6598			also controlled by the kernel.softlockup_panic sysctl
6599			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6600			respective build-time switch to that functionality.
6601
6602	softlockup_all_cpu_backtrace=
6603			[KNL] Should the soft-lockup detector generate
6604			backtraces on all cpus.
6605			Format: 0 | 1
6606
6607	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
6608			See Documentation/admin-guide/laptops/sonypi.rst
6609
6610	spectre_bhi=	[X86] Control mitigation of Branch History Injection
6611			(BHI) vulnerability.  This setting affects the
6612			deployment of the HW BHI control and the SW BHB
6613			clearing sequence.
6614
6615			on     - (default) Enable the HW or SW mitigation as
6616				 needed.  This protects the kernel from
6617				 both syscalls and VMs.
6618			vmexit - On systems which don't have the HW mitigation
6619				 available, enable the SW mitigation on vmexit
6620				 ONLY.  On such systems, the host kernel is
6621				 protected from VM-originated BHI attacks, but
6622				 may still be vulnerable to syscall attacks.
6623			off    - Disable the mitigation.
6624
6625	spectre_v2=	[X86,EARLY] Control mitigation of Spectre variant 2
6626			(indirect branch speculation) vulnerability.
6627			The default operation protects the kernel from
6628			user space attacks.
6629
6630			on   - unconditionally enable, implies
6631			       spectre_v2_user=on
6632			off  - unconditionally disable, implies
6633			       spectre_v2_user=off
6634			auto - kernel detects whether your CPU model is
6635			       vulnerable
6636
6637			Selecting 'on' will, and 'auto' may, choose a
6638			mitigation method at run time according to the
6639			CPU, the available microcode, the setting of the
6640			CONFIG_MITIGATION_RETPOLINE configuration option,
6641			and the compiler with which the kernel was built.
6642
6643			Selecting 'on' will also enable the mitigation
6644			against user space to user space task attacks.
6645			Selecting specific mitigation does not force enable
6646			user mitigations.
6647
6648			Selecting 'off' will disable both the kernel and
6649			the user space protections.
6650
6651			Specific mitigations can also be selected manually:
6652
6653			retpoline	  - replace indirect branches
6654			retpoline,generic - Retpolines
6655			retpoline,lfence  - LFENCE; indirect branch
6656			retpoline,amd     - alias for retpoline,lfence
6657			eibrs		  - Enhanced/Auto IBRS
6658			eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
6659			eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
6660			ibrs		  - use IBRS to protect kernel
6661
6662			Not specifying this option is equivalent to
6663			spectre_v2=auto.
6664
6665	spectre_v2_user=
6666			[X86] Control mitigation of Spectre variant 2
6667		        (indirect branch speculation) vulnerability between
6668		        user space tasks
6669
6670			on	- Unconditionally enable mitigations. Is
6671				  enforced by spectre_v2=on
6672
6673			off     - Unconditionally disable mitigations. Is
6674				  enforced by spectre_v2=off
6675
6676			prctl   - Indirect branch speculation is enabled,
6677				  but mitigation can be enabled via prctl
6678				  per thread.  The mitigation control state
6679				  is inherited on fork.
6680
6681			prctl,ibpb
6682				- Like "prctl" above, but only STIBP is
6683				  controlled per thread. IBPB is issued
6684				  always when switching between different user
6685				  space processes.
6686
6687			seccomp
6688				- Same as "prctl" above, but all seccomp
6689				  threads will enable the mitigation unless
6690				  they explicitly opt out.
6691
6692			seccomp,ibpb
6693				- Like "seccomp" above, but only STIBP is
6694				  controlled per thread. IBPB is issued
6695				  always when switching between different
6696				  user space processes.
6697
6698			auto    - Kernel selects the mitigation depending on
6699				  the available CPU features and vulnerability.
6700
6701			Default mitigation: "prctl"
6702
6703			Not specifying this option is equivalent to
6704			spectre_v2_user=auto.
6705
6706	spec_rstack_overflow=
6707			[X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs
6708
6709			off		- Disable mitigation
6710			microcode	- Enable microcode mitigation only
6711			safe-ret	- Enable sw-only safe RET mitigation (default)
6712			ibpb		- Enable mitigation by issuing IBPB on
6713					  kernel entry
6714			ibpb-vmexit	- Issue IBPB only on VMEXIT
6715					  (cloud-specific mitigation)
6716
6717	spec_store_bypass_disable=
6718			[HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6719			(Speculative Store Bypass vulnerability)
6720
6721			Certain CPUs are vulnerable to an exploit against a
6722			a common industry wide performance optimization known
6723			as "Speculative Store Bypass" in which recent stores
6724			to the same memory location may not be observed by
6725			later loads during speculative execution. The idea
6726			is that such stores are unlikely and that they can
6727			be detected prior to instruction retirement at the
6728			end of a particular speculation execution window.
6729
6730			In vulnerable processors, the speculatively forwarded
6731			store can be used in a cache side channel attack, for
6732			example to read memory to which the attacker does not
6733			directly have access (e.g. inside sandboxed code).
6734
6735			This parameter controls whether the Speculative Store
6736			Bypass optimization is used.
6737
6738			On x86 the options are:
6739
6740			on      - Unconditionally disable Speculative Store Bypass
6741			off     - Unconditionally enable Speculative Store Bypass
6742			auto    - Kernel detects whether the CPU model contains an
6743				  implementation of Speculative Store Bypass and
6744				  picks the most appropriate mitigation. If the
6745				  CPU is not vulnerable, "off" is selected. If the
6746				  CPU is vulnerable the default mitigation is
6747				  architecture and Kconfig dependent. See below.
6748			prctl   - Control Speculative Store Bypass per thread
6749				  via prctl. Speculative Store Bypass is enabled
6750				  for a process by default. The state of the control
6751				  is inherited on fork.
6752			seccomp - Same as "prctl" above, but all seccomp threads
6753				  will disable SSB unless they explicitly opt out.
6754
6755			Default mitigations:
6756			X86:	"prctl"
6757
6758			On powerpc the options are:
6759
6760			on,auto - On Power8 and Power9 insert a store-forwarding
6761				  barrier on kernel entry and exit. On Power7
6762				  perform a software flush on kernel entry and
6763				  exit.
6764			off	- No action.
6765
6766			Not specifying this option is equivalent to
6767			spec_store_bypass_disable=auto.
6768
6769	split_lock_detect=
6770			[X86] Enable split lock detection or bus lock detection
6771
6772			When enabled (and if hardware support is present), atomic
6773			instructions that access data across cache line
6774			boundaries will result in an alignment check exception
6775			for split lock detection or a debug exception for
6776			bus lock detection.
6777
6778			off	- not enabled
6779
6780			warn	- the kernel will emit rate-limited warnings
6781				  about applications triggering the #AC
6782				  exception or the #DB exception. This mode is
6783				  the default on CPUs that support split lock
6784				  detection or bus lock detection. Default
6785				  behavior is by #AC if both features are
6786				  enabled in hardware.
6787
6788			fatal	- the kernel will send SIGBUS to applications
6789				  that trigger the #AC exception or the #DB
6790				  exception. Default behavior is by #AC if
6791				  both features are enabled in hardware.
6792
6793			ratelimit:N -
6794				  Set system wide rate limit to N bus locks
6795				  per second for bus lock detection.
6796				  0 < N <= 1000.
6797
6798				  N/A for split lock detection.
6799
6800
6801			If an #AC exception is hit in the kernel or in
6802			firmware (i.e. not while executing in user mode)
6803			the kernel will oops in either "warn" or "fatal"
6804			mode.
6805
6806			#DB exception for bus lock is triggered only when
6807			CPL > 0.
6808
6809	srbds=		[X86,INTEL,EARLY]
6810			Control the Special Register Buffer Data Sampling
6811			(SRBDS) mitigation.
6812
6813			Certain CPUs are vulnerable to an MDS-like
6814			exploit which can leak bits from the random
6815			number generator.
6816
6817			By default, this issue is mitigated by
6818			microcode.  However, the microcode fix can cause
6819			the RDRAND and RDSEED instructions to become
6820			much slower.  Among other effects, this will
6821			result in reduced throughput from /dev/urandom.
6822
6823			The microcode mitigation can be disabled with
6824			the following option:
6825
6826			off:    Disable mitigation and remove
6827				performance impact to RDRAND and RDSEED
6828
6829	srcutree.big_cpu_lim [KNL]
6830			Specifies the number of CPUs constituting a
6831			large system, such that srcu_struct structures
6832			should immediately allocate an srcu_node array.
6833			This kernel-boot parameter defaults to 128,
6834			but takes effect only when the low-order four
6835			bits of srcutree.convert_to_big is equal to 3
6836			(decide at boot).
6837
6838	srcutree.convert_to_big [KNL]
6839			Specifies under what conditions an SRCU tree
6840			srcu_struct structure will be converted to big
6841			form, that is, with an rcu_node tree:
6842
6843				   0:  Never.
6844				   1:  At init_srcu_struct() time.
6845				   2:  When rcutorture decides to.
6846				   3:  Decide at boot time (default).
6847				0x1X:  Above plus if high contention.
6848
6849			Either way, the srcu_node tree will be sized based
6850			on the actual runtime number of CPUs (nr_cpu_ids)
6851			instead of the compile-time CONFIG_NR_CPUS.
6852
6853	srcutree.counter_wrap_check [KNL]
6854			Specifies how frequently to check for
6855			grace-period sequence counter wrap for the
6856			srcu_data structure's ->srcu_gp_seq_needed field.
6857			The greater the number of bits set in this kernel
6858			parameter, the less frequently counter wrap will
6859			be checked for.  Note that the bottom two bits
6860			are ignored.
6861
6862	srcutree.exp_holdoff [KNL]
6863			Specifies how many nanoseconds must elapse
6864			since the end of the last SRCU grace period for
6865			a given srcu_struct until the next normal SRCU
6866			grace period will be considered for automatic
6867			expediting.  Set to zero to disable automatic
6868			expediting.
6869
6870	srcutree.srcu_max_nodelay [KNL]
6871			Specifies the number of no-delay instances
6872			per jiffy for which the SRCU grace period
6873			worker thread will be rescheduled with zero
6874			delay. Beyond this limit, worker thread will
6875			be rescheduled with a sleep delay of one jiffy.
6876
6877	srcutree.srcu_max_nodelay_phase [KNL]
6878			Specifies the per-grace-period phase, number of
6879			non-sleeping polls of readers. Beyond this limit,
6880			grace period worker thread will be rescheduled
6881			with a sleep delay of one jiffy, between each
6882			rescan of the readers, for a grace period phase.
6883
6884	srcutree.srcu_retry_check_delay [KNL]
6885			Specifies number of microseconds of non-sleeping
6886			delay between each non-sleeping poll of readers.
6887
6888	srcutree.small_contention_lim [KNL]
6889			Specifies the number of update-side contention
6890			events per jiffy will be tolerated before
6891			initiating a conversion of an srcu_struct
6892			structure to big form.	Note that the value of
6893			srcutree.convert_to_big must have the 0x10 bit
6894			set for contention-based conversions to occur.
6895
6896	ssbd=		[ARM64,HW,EARLY]
6897			Speculative Store Bypass Disable control
6898
6899			On CPUs that are vulnerable to the Speculative
6900			Store Bypass vulnerability and offer a
6901			firmware based mitigation, this parameter
6902			indicates how the mitigation should be used:
6903
6904			force-on:  Unconditionally enable mitigation for
6905				   for both kernel and userspace
6906			force-off: Unconditionally disable mitigation for
6907				   for both kernel and userspace
6908			kernel:    Always enable mitigation in the
6909				   kernel, and offer a prctl interface
6910				   to allow userspace to register its
6911				   interest in being mitigated too.
6912
6913	stack_guard_gap=	[MM]
6914			override the default stack gap protection. The value
6915			is in page units and it defines how many pages prior
6916			to (for stacks growing down) resp. after (for stacks
6917			growing up) the main stack are reserved for no other
6918			mapping. Default value is 256 pages.
6919
6920	stack_depot_disable= [KNL,EARLY]
6921			Setting this to true through kernel command line will
6922			disable the stack depot thereby saving the static memory
6923			consumed by the stack hash table. By default this is set
6924			to false.
6925
6926	stacktrace	[FTRACE]
6927			Enabled the stack tracer on boot up.
6928
6929	stacktrace_filter=[function-list]
6930			[FTRACE] Limit the functions that the stack tracer
6931			will trace at boot up. function-list is a comma-separated
6932			list of functions. This list can be changed at run
6933			time by the stack_trace_filter file in the debugfs
6934			tracing directory. Note, this enables stack tracing
6935			and the stacktrace above is not needed.
6936
6937	sti=		[PARISC,HW]
6938			Format: <num>
6939			Set the STI (builtin display/keyboard on the HP-PARISC
6940			machines) console (graphic card) which should be used
6941			as the initial boot-console.
6942			See also comment in drivers/video/console/sticore.c.
6943
6944	sti_font=	[HW]
6945			See comment in drivers/video/console/sticore.c.
6946
6947	stifb=		[HW]
6948			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6949
6950        strict_sas_size=
6951			[X86]
6952			Format: <bool>
6953			Enable or disable strict sigaltstack size checks
6954			against the required signal frame size which
6955			depends on the supported FPU features. This can
6956			be used to filter out binaries which have
6957			not yet been made aware of AT_MINSIGSTKSZ.
6958
6959	stress_hpt	[PPC,EARLY]
6960			Limits the number of kernel HPT entries in the hash
6961			page table to increase the rate of hash page table
6962			faults on kernel addresses.
6963
6964	stress_slb	[PPC,EARLY]
6965			Limits the number of kernel SLB entries, and flushes
6966			them frequently to increase the rate of SLB faults
6967			on kernel addresses.
6968
6969	sunrpc.min_resvport=
6970	sunrpc.max_resvport=
6971			[NFS,SUNRPC]
6972			SunRPC servers often require that client requests
6973			originate from a privileged port (i.e. a port in the
6974			range 0 < portnr < 1024).
6975			An administrator who wishes to reserve some of these
6976			ports for other uses may adjust the range that the
6977			kernel's sunrpc client considers to be privileged
6978			using these two parameters to set the minimum and
6979			maximum port values.
6980
6981	sunrpc.svc_rpc_per_connection_limit=
6982			[NFS,SUNRPC]
6983			Limit the number of requests that the server will
6984			process in parallel from a single connection.
6985			The default value is 0 (no limit).
6986
6987	sunrpc.pool_mode=
6988			[NFS]
6989			Control how the NFS server code allocates CPUs to
6990			service thread pools.  Depending on how many NICs
6991			you have and where their interrupts are bound, this
6992			option will affect which CPUs will do NFS serving.
6993			Note: this parameter cannot be changed while the
6994			NFS server is running.
6995
6996			auto	    the server chooses an appropriate mode
6997				    automatically using heuristics
6998			global	    a single global pool contains all CPUs
6999			percpu	    one pool for each CPU
7000			pernode	    one pool for each NUMA node (equivalent
7001				    to global on non-NUMA machines)
7002
7003	sunrpc.tcp_slot_table_entries=
7004	sunrpc.udp_slot_table_entries=
7005			[NFS,SUNRPC]
7006			Sets the upper limit on the number of simultaneous
7007			RPC calls that can be sent from the client to a
7008			server. Increasing these values may allow you to
7009			improve throughput, but will also increase the
7010			amount of memory reserved for use by the client.
7011
7012	suspend.pm_test_delay=
7013			[SUSPEND]
7014			Sets the number of seconds to remain in a suspend test
7015			mode before resuming the system (see
7016			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
7017			is set. Default value is 5.
7018
7019	svm=		[PPC]
7020			Format: { on | off | y | n | 1 | 0 }
7021			This parameter controls use of the Protected
7022			Execution Facility on pSeries.
7023
7024	swiotlb=	[ARM,PPC,MIPS,X86,S390,EARLY]
7025			Format: { <int> [,<int>] | force | noforce }
7026			<int> -- Number of I/O TLB slabs
7027			<int> -- Second integer after comma. Number of swiotlb
7028				 areas with their own lock. Will be rounded up
7029				 to a power of 2.
7030			force -- force using of bounce buffers even if they
7031			         wouldn't be automatically used by the kernel
7032			noforce -- Never use bounce buffers (for debugging)
7033
7034	switches=	[HW,M68k,EARLY]
7035
7036	sysctl.*=	[KNL]
7037			Set a sysctl parameter, right before loading the init
7038			process, as if the value was written to the respective
7039			/proc/sys/... file. Both '.' and '/' are recognized as
7040			separators. Unrecognized parameters and invalid values
7041			are reported in the kernel log. Sysctls registered
7042			later by a loaded module cannot be set this way.
7043			Example: sysctl.vm.swappiness=40
7044
7045	sysrq_always_enabled
7046			[KNL]
7047			Ignore sysrq setting - this boot parameter will
7048			neutralize any effect of /proc/sys/kernel/sysrq.
7049			Useful for debugging.
7050
7051	tcpmhash_entries= [KNL,NET]
7052			Set the number of tcp_metrics_hash slots.
7053			Default value is 8192 or 16384 depending on total
7054			ram pages. This is used to specify the TCP metrics
7055			cache size. See Documentation/networking/ip-sysctl.rst
7056			"tcp_no_metrics_save" section for more details.
7057
7058	tdfx=		[HW,DRM]
7059
7060	test_suspend=	[SUSPEND]
7061			Format: { "mem" | "standby" | "freeze" }[,N]
7062			Specify "mem" (for Suspend-to-RAM) or "standby" (for
7063			standby suspend) or "freeze" (for suspend type freeze)
7064			as the system sleep state during system startup with
7065			the optional capability to repeat N number of times.
7066			The system is woken from this state using a
7067			wakeup-capable RTC alarm.
7068
7069	thash_entries=	[KNL,NET]
7070			Set number of hash buckets for TCP connection
7071
7072	thermal.act=	[HW,ACPI]
7073			-1: disable all active trip points in all thermal zones
7074			<degrees C>: override all lowest active trip points
7075
7076	thermal.crt=	[HW,ACPI]
7077			-1: disable all critical trip points in all thermal zones
7078			<degrees C>: override all critical trip points
7079
7080	thermal.off=	[HW,ACPI]
7081			1: disable ACPI thermal control
7082
7083	thermal.psv=	[HW,ACPI]
7084			-1: disable all passive trip points
7085			<degrees C>: override all passive trip points to this
7086			value
7087
7088	thermal.tzp=	[HW,ACPI]
7089			Specify global default ACPI thermal zone polling rate
7090			<deci-seconds>: poll all this frequency
7091			0: no polling (default)
7092
7093	thp_anon=	[KNL]
7094			Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7095			state is one of "always", "madvise", "never" or "inherit".
7096			Control the default behavior of the system with respect
7097			to anonymous transparent hugepages.
7098			Can be used multiple times for multiple anon THP sizes.
7099			See Documentation/admin-guide/mm/transhuge.rst for more
7100			details.
7101
7102	threadirqs	[KNL,EARLY]
7103			Force threading of all interrupt handlers except those
7104			marked explicitly IRQF_NO_THREAD.
7105
7106	thp_shmem=	[KNL]
7107			Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7108			Control the default policy of each hugepage size for the
7109			internal shmem mount. <policy> is one of policies available
7110			for the shmem mount ("always", "inherit", "never", "within_size",
7111			and "advise").
7112			It can be used multiple times for multiple shmem THP sizes.
7113			See Documentation/admin-guide/mm/transhuge.rst for more
7114			details.
7115
7116	topology=	[S390,EARLY]
7117			Format: {off | on}
7118			Specify if the kernel should make use of the cpu
7119			topology information if the hardware supports this.
7120			The scheduler will make use of this information and
7121			e.g. base its process migration decisions on it.
7122			Default is on.
7123
7124	torture.disable_onoff_at_boot= [KNL]
7125			Prevent the CPU-hotplug component of torturing
7126			until after init has spawned.
7127
7128	torture.ftrace_dump_at_shutdown= [KNL]
7129			Dump the ftrace buffer at torture-test shutdown,
7130			even if there were no errors.  This can be a
7131			very costly operation when many torture tests
7132			are running concurrently, especially on systems
7133			with rotating-rust storage.
7134
7135	torture.verbose_sleep_frequency= [KNL]
7136			Specifies how many verbose printk()s should be
7137			emitted between each sleep.  The default of zero
7138			disables verbose-printk() sleeping.
7139
7140	torture.verbose_sleep_duration= [KNL]
7141			Duration of each verbose-printk() sleep in jiffies.
7142
7143	tpm.disable_pcr_integrity= [HW,TPM]
7144			Do not protect PCR registers from unintended physical
7145			access, or interposers in the bus by the means of
7146			having an integrity protected session wrapped around
7147			TPM2_PCR_Extend command. Consider this in a situation
7148			where TPM is heavily utilized by IMA, thus protection
7149			causing a major performance hit, and the space where
7150			machines are deployed is by other means guarded.
7151
7152	tpm_suspend_pcr=[HW,TPM]
7153			Format: integer pcr id
7154			Specify that at suspend time, the tpm driver
7155			should extend the specified pcr with zeros,
7156			as a workaround for some chips which fail to
7157			flush the last written pcr on TPM_SaveState.
7158			This will guarantee that all the other pcrs
7159			are saved.
7160
7161	tpm_tis.interrupts= [HW,TPM]
7162			Enable interrupts for the MMIO based physical layer
7163			for the FIFO interface. By default it is set to false
7164			(0). For more information about TPM hardware interfaces
7165			defined by Trusted Computing Group (TCG) see
7166			https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7167
7168	tp_printk	[FTRACE]
7169			Have the tracepoints sent to printk as well as the
7170			tracing ring buffer. This is useful for early boot up
7171			where the system hangs or reboots and does not give the
7172			option for reading the tracing buffer or performing a
7173			ftrace_dump_on_oops.
7174
7175			To turn off having tracepoints sent to printk,
7176			 echo 0 > /proc/sys/kernel/tracepoint_printk
7177			Note, echoing 1 into this file without the
7178			tp_printk kernel cmdline option has no effect.
7179
7180			The tp_printk_stop_on_boot (see below) can also be used
7181			to stop the printing of events to console at
7182			late_initcall_sync.
7183
7184			** CAUTION **
7185
7186			Having tracepoints sent to printk() and activating high
7187			frequency tracepoints such as irq or sched, can cause
7188			the system to live lock.
7189
7190	tp_printk_stop_on_boot [FTRACE]
7191			When tp_printk (above) is set, it can cause a lot of noise
7192			on the console. It may be useful to only include the
7193			printing of events during boot up, as user space may
7194			make the system inoperable.
7195
7196			This command line option will stop the printing of events
7197			to console at the late_initcall_sync() time frame.
7198
7199	trace_buf_size=nn[KMG]
7200			[FTRACE] will set tracing buffer size on each cpu.
7201
7202	trace_clock=	[FTRACE] Set the clock used for tracing events
7203			at boot up.
7204			local - Use the per CPU time stamp counter
7205				(converted into nanoseconds). Fast, but
7206				depending on the architecture, may not be
7207				in sync between CPUs.
7208			global - Event time stamps are synchronize across
7209				CPUs. May be slower than the local clock,
7210				but better for some race conditions.
7211			counter - Simple counting of events (1, 2, ..)
7212				note, some counts may be skipped due to the
7213				infrastructure grabbing the clock more than
7214				once per event.
7215			uptime - Use jiffies as the time stamp.
7216			perf - Use the same clock that perf uses.
7217			mono - Use ktime_get_mono_fast_ns() for time stamps.
7218			mono_raw - Use ktime_get_raw_fast_ns() for time
7219				stamps.
7220			boot - Use ktime_get_boot_fast_ns() for time stamps.
7221			Architectures may add more clocks. See
7222			Documentation/trace/ftrace.rst for more details.
7223
7224	trace_event=[event-list]
7225			[FTRACE] Set and start specified trace events in order
7226			to facilitate early boot debugging. The event-list is a
7227			comma-separated list of trace events to enable. See
7228			also Documentation/trace/events.rst
7229
7230			To enable modules, use :mod: keyword:
7231
7232			trace_event=:mod:<module>
7233
7234			The value before :mod: will only enable specific events
7235			that are part of the module. See the above mentioned
7236			document for more information.
7237
7238	trace_instance=[instance-info]
7239			[FTRACE] Create a ring buffer instance early in boot up.
7240			This will be listed in:
7241
7242				/sys/kernel/tracing/instances
7243
7244			Events can be enabled at the time the instance is created
7245			via:
7246
7247				trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
7248
7249			Note, the "<system*>:" portion is optional if the event is
7250			unique.
7251
7252				trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
7253
7254			will enable the "sched_switch" event (note, the "sched:" is optional, and
7255			the same thing would happen if it was left off). The irq_handler_entry
7256			event, and all events under the "initcall" system.
7257
7258			Flags can be added to the instance to modify its behavior when it is
7259			created. The flags are separated by '^'.
7260
7261			The available flags are:
7262
7263			    traceoff	- Have the tracing instance tracing disabled after it is created.
7264			    traceprintk	- Have trace_printk() write into this trace instance
7265					  (note, "printk" and "trace_printk" can also be used)
7266
7267				trace_instance=foo^traceoff^traceprintk,sched,irq
7268
7269			The flags must come before the defined events.
7270
7271			If memory has been reserved (see memmap for x86), the instance
7272			can use that memory:
7273
7274				memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M
7275
7276			The above will create a "boot_map" instance that uses the physical
7277			memory at 0x284500000 that is 12Megs. The per CPU buffers of that
7278			instance will be split up accordingly.
7279
7280			Alternatively, the memory can be reserved by the reserve_mem option:
7281
7282				reserve_mem=12M:4096:trace trace_instance=boot_map@trace
7283
7284			This will reserve 12 megabytes at boot up with a 4096 byte alignment
7285			and place the ring buffer in this memory. Note that due to KASLR, the
7286			memory may not be the same location each time, which will not preserve
7287			the buffer content.
7288
7289			Also note that the layout of the ring buffer data may change between
7290			kernel versions where the validator will fail and reset the ring buffer
7291			if the layout is not the same as the previous kernel.
7292
7293			If the ring buffer is used for persistent bootups and has events enabled,
7294			it is recommend to disable tracing so that events from a previous boot do not
7295			mix with events of the current boot (unless you are debugging a random crash
7296			at boot up).
7297
7298				reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
7299
7300			Note, saving the trace buffer across reboots does require that the system
7301			is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION
7302			can force a memory reset on boot which will clear any trace that was stored.
7303			This is just one of many ways that can clear memory. Make sure your system
7304			keeps the content of memory across reboots before relying on this option.
7305
7306			NB: Both the mapped address and size must be page aligned for the architecture.
7307
7308			See also Documentation/trace/debugging.rst
7309
7310
7311	trace_options=[option-list]
7312			[FTRACE] Enable or disable tracer options at boot.
7313			The option-list is a comma delimited list of options
7314			that can be enabled or disabled just as if you were
7315			to echo the option name into
7316
7317			    /sys/kernel/tracing/trace_options
7318
7319			For example, to enable stacktrace option (to dump the
7320			stack trace of each event), add to the command line:
7321
7322			      trace_options=stacktrace
7323
7324			See also Documentation/trace/ftrace.rst "trace options"
7325			section.
7326
7327	trace_trigger=[trigger-list]
7328			[FTRACE] Add a event trigger on specific events.
7329			Set a trigger on top of a specific event, with an optional
7330			filter.
7331
7332			The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
7333			Where more than one trigger may be specified that are comma deliminated.
7334
7335			For example:
7336
7337			  trace_trigger="sched_switch.stacktrace if prev_state == 2"
7338
7339			The above will enable the "stacktrace" trigger on the "sched_switch"
7340			event but only trigger it if the "prev_state" of the "sched_switch"
7341			event is "2" (TASK_UNINTERUPTIBLE).
7342
7343			See also "Event triggers" in Documentation/trace/events.rst
7344
7345
7346	traceoff_after_boot
7347			[FTRACE] Sometimes tracing is used to debug issues
7348			during the boot process. Since the trace buffer has a
7349			limited amount of storage, it may be prudent to
7350			disable tracing after the boot is finished, otherwise
7351			the critical information may be overwritten.  With this
7352			option, the main tracing buffer will be turned off at
7353			the end of the boot process.
7354
7355	traceoff_on_warning
7356			[FTRACE] enable this option to disable tracing when a
7357			warning is hit. This turns off "tracing_on". Tracing can
7358			be enabled again by echoing '1' into the "tracing_on"
7359			file located in /sys/kernel/tracing/
7360
7361			This option is useful, as it disables the trace before
7362			the WARNING dump is called, which prevents the trace to
7363			be filled with content caused by the warning output.
7364
7365			This option can also be set at run time via the sysctl
7366			option:  kernel/traceoff_on_warning
7367
7368	transparent_hugepage=
7369			[KNL]
7370			Format: [always|madvise|never]
7371			Can be used to control the default behavior of the system
7372			with respect to transparent hugepages.
7373			See Documentation/admin-guide/mm/transhuge.rst
7374			for more details.
7375
7376	transparent_hugepage_shmem= [KNL]
7377			Format: [always|within_size|advise|never|deny|force]
7378			Can be used to control the hugepage allocation policy for
7379			the internal shmem mount.
7380			See Documentation/admin-guide/mm/transhuge.rst
7381			for more details.
7382
7383	transparent_hugepage_tmpfs= [KNL]
7384			Format: [always|within_size|advise|never]
7385			Can be used to control the default hugepage allocation policy
7386			for the tmpfs mount.
7387			See Documentation/admin-guide/mm/transhuge.rst
7388			for more details.
7389
7390	trusted.source=	[KEYS]
7391			Format: <string>
7392			This parameter identifies the trust source as a backend
7393			for trusted keys implementation. Supported trust
7394			sources:
7395			- "tpm"
7396			- "tee"
7397			- "caam"
7398			- "dcp"
7399			If not specified then it defaults to iterating through
7400			the trust source list starting with TPM and assigns the
7401			first trust source as a backend which is initialized
7402			successfully during iteration.
7403
7404	trusted.rng=	[KEYS]
7405			Format: <string>
7406			The RNG used to generate key material for trusted keys.
7407			Can be one of:
7408			- "kernel"
7409			- the same value as trusted.source: "tpm" or "tee"
7410			- "default"
7411			If not specified, "default" is used. In this case,
7412			the RNG's choice is left to each individual trust source.
7413
7414	trusted.dcp_use_otp_key
7415			This is intended to be used in combination with
7416			trusted.source=dcp and will select the DCP OTP key
7417			instead of the DCP UNIQUE key blob encryption.
7418
7419	trusted.dcp_skip_zk_test
7420			This is intended to be used in combination with
7421			trusted.source=dcp and will disable the check if the
7422			blob key is all zeros. This is helpful for situations where
7423			having this key zero'ed is acceptable. E.g. in testing
7424			scenarios.
7425
7426	tsc=		Disable clocksource stability checks for TSC.
7427			Format: <string>
7428			[x86] reliable: mark tsc clocksource as reliable, this
7429			disables clocksource verification at runtime, as well
7430			as the stability checks done at bootup.	Used to enable
7431			high-resolution timer mode on older hardware, and in
7432			virtualized environment.
7433			[x86] noirqtime: Do not use TSC to do irq accounting.
7434			Used to run time disable IRQ_TIME_ACCOUNTING on any
7435			platforms where RDTSC is slow and this accounting
7436			can add overhead.
7437			[x86] unstable: mark the TSC clocksource as unstable, this
7438			marks the TSC unconditionally unstable at bootup and
7439			avoids any further wobbles once the TSC watchdog notices.
7440			[x86] nowatchdog: disable clocksource watchdog. Used
7441			in situations with strict latency requirements (where
7442			interruptions from clocksource watchdog are not
7443			acceptable).
7444			[x86] recalibrate: force recalibration against a HW timer
7445			(HPET or PM timer) on systems whose TSC frequency was
7446			obtained from HW or FW using either an MSR or CPUID(0x15).
7447			Warn if the difference is more than 500 ppm.
7448			[x86] watchdog: Use TSC as the watchdog clocksource with
7449			which to check other HW timers (HPET or PM timer), but
7450			only on systems where TSC has been deemed trustworthy.
7451			This will be suppressed by an earlier tsc=nowatchdog and
7452			can be overridden by a later tsc=nowatchdog.  A console
7453			message will flag any such suppression or overriding.
7454
7455	tsc_early_khz=  [X86,EARLY] Skip early TSC calibration and use the given
7456			value instead. Useful when the early TSC frequency discovery
7457			procedure is not reliable, such as on overclocked systems
7458			with CPUID.16h support and partial CPUID.15h support.
7459			Format: <unsigned int>
7460
7461	tsx=		[X86] Control Transactional Synchronization
7462			Extensions (TSX) feature in Intel processors that
7463			support TSX control.
7464
7465			This parameter controls the TSX feature. The options are:
7466
7467			on	- Enable TSX on the system. Although there are
7468				mitigations for all known security vulnerabilities,
7469				TSX has been known to be an accelerator for
7470				several previous speculation-related CVEs, and
7471				so there may be unknown	security risks associated
7472				with leaving it enabled.
7473
7474			off	- Disable TSX on the system. (Note that this
7475				option takes effect only on newer CPUs which are
7476				not vulnerable to MDS, i.e., have
7477				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
7478				the new IA32_TSX_CTRL MSR through a microcode
7479				update. This new MSR allows for the reliable
7480				deactivation of the TSX functionality.)
7481
7482			auto	- Disable TSX if X86_BUG_TAA is present,
7483				  otherwise enable TSX on the system.
7484
7485			Not specifying this option is equivalent to tsx=off.
7486
7487			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7488			for more details.
7489
7490	tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
7491			Abort (TAA) vulnerability.
7492
7493			Similar to Micro-architectural Data Sampling (MDS)
7494			certain CPUs that support Transactional
7495			Synchronization Extensions (TSX) are vulnerable to an
7496			exploit against CPU internal buffers which can forward
7497			information to a disclosure gadget under certain
7498			conditions.
7499
7500			In vulnerable processors, the speculatively forwarded
7501			data can be used in a cache side channel attack, to
7502			access data to which the attacker does not have direct
7503			access.
7504
7505			This parameter controls the TAA mitigation.  The
7506			options are:
7507
7508			full       - Enable TAA mitigation on vulnerable CPUs
7509				     if TSX is enabled.
7510
7511			full,nosmt - Enable TAA mitigation and disable SMT on
7512				     vulnerable CPUs. If TSX is disabled, SMT
7513				     is not disabled because CPU is not
7514				     vulnerable to cross-thread TAA attacks.
7515			off        - Unconditionally disable TAA mitigation
7516
7517			On MDS-affected machines, tsx_async_abort=off can be
7518			prevented by an active MDS mitigation as both vulnerabilities
7519			are mitigated with the same mechanism so in order to disable
7520			this mitigation, you need to specify mds=off too.
7521
7522			Not specifying this option is equivalent to
7523			tsx_async_abort=full.  On CPUs which are MDS affected
7524			and deploy MDS mitigation, TAA mitigation is not
7525			required and doesn't provide any additional
7526			mitigation.
7527
7528			For details see:
7529			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7530
7531	turbografx.map[2|3]=	[HW,JOY]
7532			TurboGraFX parallel port interface
7533			Format:
7534			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
7535			See also Documentation/input/devices/joystick-parport.rst
7536
7537	udbg-immortal	[PPC] When debugging early kernel crashes that
7538			happen after console_init() and before a proper
7539			console driver takes over, this boot options might
7540			help "seeing" what's going on.
7541
7542	uhash_entries=	[KNL,NET]
7543			Set number of hash buckets for UDP/UDP-Lite connections
7544
7545	uhci-hcd.ignore_oc=
7546			[USB] Ignore overcurrent events (default N).
7547			Some badly-designed motherboards generate lots of
7548			bogus events, for ports that aren't wired to
7549			anything.  Set this parameter to avoid log spamming.
7550			Note that genuine overcurrent events won't be
7551			reported either.
7552
7553	unaligned_scalar_speed=
7554			[RISCV]
7555			Format: {slow | fast | unsupported}
7556			Allow skipping scalar unaligned access speed tests. This
7557			is useful for testing alternative code paths and to skip
7558			the tests in environments where they run too slowly. All
7559			CPUs must have the same scalar unaligned access speed.
7560
7561	unaligned_vector_speed=
7562			[RISCV]
7563			Format: {slow | fast | unsupported}
7564			Allow skipping vector unaligned access speed tests. This
7565			is useful for testing alternative code paths and to skip
7566			the tests in environments where they run too slowly. All
7567			CPUs must have the same vector unaligned access speed.
7568
7569	unknown_nmi_panic
7570			[X86] Cause panic on unknown NMI.
7571
7572	unwind_debug	[X86-64,EARLY]
7573			Enable unwinder debug output.  This can be
7574			useful for debugging certain unwinder error
7575			conditions, including corrupt stacks and
7576			bad/missing unwinder metadata.
7577
7578	usbcore.authorized_default=
7579			[USB] Default USB device authorization:
7580			(default -1 = authorized (same as 1),
7581			0 = not authorized, 1 = authorized, 2 = authorized
7582			if device connected to internal port)
7583
7584	usbcore.autosuspend=
7585			[USB] The autosuspend time delay (in seconds) used
7586			for newly-detected USB devices (default 2).  This
7587			is the time required before an idle device will be
7588			autosuspended.  Devices for which the delay is set
7589			to a negative value won't be autosuspended at all.
7590
7591	usbcore.usbfs_snoop=
7592			[USB] Set to log all usbfs traffic (default 0 = off).
7593
7594	usbcore.usbfs_snoop_max=
7595			[USB] Maximum number of bytes to snoop in each URB
7596			(default = 65536).
7597
7598	usbcore.blinkenlights=
7599			[USB] Set to cycle leds on hubs (default 0 = off).
7600
7601	usbcore.old_scheme_first=
7602			[USB] Start with the old device initialization
7603			scheme (default 0 = off).
7604
7605	usbcore.usbfs_memory_mb=
7606			[USB] Memory limit (in MB) for buffers allocated by
7607			usbfs (default = 16, 0 = max = 2047).
7608
7609	usbcore.use_both_schemes=
7610			[USB] Try the other device initialization scheme
7611			if the first one fails (default 1 = enabled).
7612
7613	usbcore.initial_descriptor_timeout=
7614			[USB] Specifies timeout for the initial 64-byte
7615			USB_REQ_GET_DESCRIPTOR request in milliseconds
7616			(default 5000 = 5.0 seconds).
7617
7618	usbcore.nousb	[USB] Disable the USB subsystem
7619
7620	usbcore.quirks=
7621			[USB] A list of quirk entries to augment the built-in
7622			usb core quirk list. List entries are separated by
7623			commas. Each entry has the form
7624			VendorID:ProductID:Flags. The IDs are 4-digit hex
7625			numbers and Flags is a set of letters. Each letter
7626			will change the built-in quirk; setting it if it is
7627			clear and clearing it if it is set. The letters have
7628			the following meanings:
7629				a = USB_QUIRK_STRING_FETCH_255 (string
7630					descriptors must not be fetched using
7631					a 255-byte read);
7632				b = USB_QUIRK_RESET_RESUME (device can't resume
7633					correctly so reset it instead);
7634				c = USB_QUIRK_NO_SET_INTF (device can't handle
7635					Set-Interface requests);
7636				d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7637					handle its Configuration or Interface
7638					strings);
7639				e = USB_QUIRK_RESET (device can't be reset
7640					(e.g morph devices), don't use reset);
7641				f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7642					more interface descriptions than the
7643					bNumInterfaces count, and can't handle
7644					talking to these interfaces);
7645				g = USB_QUIRK_DELAY_INIT (device needs a pause
7646					during initialization, after we read
7647					the device descriptor);
7648				h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7649					high speed and super speed interrupt
7650					endpoints, the USB 2.0 and USB 3.0 spec
7651					require the interval in microframes (1
7652					microframe = 125 microseconds) to be
7653					calculated as interval = 2 ^
7654					(bInterval-1).
7655					Devices with this quirk report their
7656					bInterval as the result of this
7657					calculation instead of the exponent
7658					variable used in the calculation);
7659				i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7660					handle device_qualifier descriptor
7661					requests);
7662				j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7663					generates spurious wakeup, ignore
7664					remote wakeup capability);
7665				k = USB_QUIRK_NO_LPM (device can't handle Link
7666					Power Management);
7667				l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7668					(Device reports its bInterval as linear
7669					frames instead of the USB 2.0
7670					calculation);
7671				m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7672					to be disconnected before suspend to
7673					prevent spurious wakeup);
7674				n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7675					pause after every control message);
7676				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7677					delay after resetting its port);
7678				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
7679					(Reduce timeout of the SET_ADDRESS
7680					request from 5000 ms to 500 ms);
7681			Example: quirks=0781:5580:bk,0a5c:5834:gij
7682
7683	usbhid.mousepoll=
7684			[USBHID] The interval which mice are to be polled at.
7685
7686	usbhid.jspoll=
7687			[USBHID] The interval which joysticks are to be polled at.
7688
7689	usbhid.kbpoll=
7690			[USBHID] The interval which keyboards are to be polled at.
7691
7692	usb-storage.delay_use=
7693			[UMS] The delay in seconds before a new device is
7694			scanned for Logical Units (default 1).
7695			Optionally the delay in milliseconds if the value has
7696			suffix with "ms".
7697			Example: delay_use=2567ms
7698
7699	usb-storage.quirks=
7700			[UMS] A list of quirks entries to supplement or
7701			override the built-in unusual_devs list.  List
7702			entries are separated by commas.  Each entry has
7703			the form VID:PID:Flags where VID and PID are Vendor
7704			and Product ID values (4-digit hex numbers) and
7705			Flags is a set of characters, each corresponding
7706			to a common usb-storage quirk flag as follows:
7707				a = SANE_SENSE (collect more than 18 bytes
7708					of sense data, not on uas);
7709				b = BAD_SENSE (don't collect more than 18
7710					bytes of sense data, not on uas);
7711				c = FIX_CAPACITY (decrease the reported
7712					device capacity by one sector);
7713				d = NO_READ_DISC_INFO (don't use
7714					READ_DISC_INFO command, not on uas);
7715				e = NO_READ_CAPACITY_16 (don't use
7716					READ_CAPACITY_16 command);
7717				f = NO_REPORT_OPCODES (don't use report opcodes
7718					command, uas only);
7719				g = MAX_SECTORS_240 (don't transfer more than
7720					240 sectors at a time, uas only);
7721				h = CAPACITY_HEURISTICS (decrease the
7722					reported device capacity by one
7723					sector if the number is odd);
7724				i = IGNORE_DEVICE (don't bind to this
7725					device);
7726				j = NO_REPORT_LUNS (don't use report luns
7727					command, uas only);
7728				k = NO_SAME (do not use WRITE_SAME, uas only)
7729				l = NOT_LOCKABLE (don't try to lock and
7730					unlock ejectable media, not on uas);
7731				m = MAX_SECTORS_64 (don't transfer more
7732					than 64 sectors = 32 KB at a time,
7733					not on uas);
7734				n = INITIAL_READ10 (force a retry of the
7735					initial READ(10) command, not on uas);
7736				o = CAPACITY_OK (accept the capacity
7737					reported by the device, not on uas);
7738				p = WRITE_CACHE (the device cache is ON
7739					by default, not on uas);
7740				r = IGNORE_RESIDUE (the device reports
7741					bogus residue values, not on uas);
7742				s = SINGLE_LUN (the device has only one
7743					Logical Unit);
7744				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7745					commands, uas only);
7746				u = IGNORE_UAS (don't bind to the uas driver);
7747				w = NO_WP_DETECT (don't test whether the
7748					medium is write-protected).
7749				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7750					even if the device claims no cache,
7751					not on uas)
7752			Example: quirks=0419:aaf5:rl,0421:0433:rc
7753
7754	user_debug=	[KNL,ARM]
7755			Format: <int>
7756			See arch/arm/Kconfig.debug help text.
7757				 1 - undefined instruction events
7758				 2 - system calls
7759				 4 - invalid data aborts
7760				 8 - SIGSEGV faults
7761				16 - SIGBUS faults
7762			Example: user_debug=31
7763
7764	vdso=		[X86,SH,SPARC]
7765			On X86_32, this is an alias for vdso32=.  Otherwise:
7766
7767			vdso=1: enable VDSO (the default)
7768			vdso=0: disable VDSO mapping
7769
7770	vdso32=		[X86] Control the 32-bit vDSO
7771			vdso32=1: enable 32-bit VDSO
7772			vdso32=0 or vdso32=2: disable 32-bit VDSO
7773
7774			See the help text for CONFIG_COMPAT_VDSO for more
7775			details.  If CONFIG_COMPAT_VDSO is set, the default is
7776			vdso32=0; otherwise, the default is vdso32=1.
7777
7778			For compatibility with older kernels, vdso32=2 is an
7779			alias for vdso32=0.
7780
7781			Try vdso32=0 if you encounter an error that says:
7782			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7783
7784	video=		[FB,EARLY] Frame buffer configuration
7785			See Documentation/fb/modedb.rst.
7786
7787	video.brightness_switch_enabled= [ACPI]
7788			Format: [0|1]
7789			If set to 1, on receiving an ACPI notify event
7790			generated by hotkey, video driver will adjust brightness
7791			level and then send out the event to user space through
7792			the allocated input device. If set to 0, video driver
7793			will only send out the event without touching backlight
7794			brightness level.
7795			default: 1
7796
7797	virtio_mmio.device=
7798			[VMMIO] Memory mapped virtio (platform) device.
7799
7800				<size>@<baseaddr>:<irq>[:<id>]
7801			where:
7802				<size>     := size (can use standard suffixes
7803						like K, M and G)
7804				<baseaddr> := physical base address
7805				<irq>      := interrupt number (as passed to
7806						request_irq())
7807				<id>       := (optional) platform device id
7808			example:
7809				virtio_mmio.device=1K@0x100b0000:48:7
7810
7811			Can be used multiple times for multiple devices.
7812
7813	vga=		[BOOT,X86-32] Select a particular video mode
7814			See Documentation/arch/x86/boot.rst and
7815			Documentation/admin-guide/svga.rst.
7816			Use vga=ask for menu.
7817			This is actually a boot loader parameter; the value is
7818			passed to the kernel using a special protocol.
7819
7820	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
7821			May slow down system boot speed, especially when
7822			enabled on systems with a large amount of memory.
7823			All options are enabled by default, and this
7824			interface is meant to allow for selectively
7825			enabling or disabling specific virtual memory
7826			debugging features.
7827
7828			Available options are:
7829			  P	Enable page structure init time poisoning
7830			  -	Disable all of the above options
7831
7832	vmalloc=nn[KMG]	[KNL,BOOT,EARLY] Forces the vmalloc area to have an
7833			exact size of <nn>. This can be used to increase
7834			the minimum size (128MB on x86, arm32 platforms).
7835			It can also be used to decrease the size and leave more room
7836			for directly mapped kernel RAM. Note that this parameter does
7837			not exist on many other platforms (including arm64, alpha,
7838			loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc,
7839			parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc).
7840
7841	vmcp_cma=nn[MG]	[KNL,S390,EARLY]
7842			Sets the memory size reserved for contiguous memory
7843			allocations for the vmcp device driver.
7844
7845	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
7846			Format: <command>
7847
7848	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
7849			Format: <command>
7850
7851	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
7852			Format: <command>
7853
7854	vsyscall=	[X86-64,EARLY]
7855			Controls the behavior of vsyscalls (i.e. calls to
7856			fixed addresses of 0xffffffffff600x00 from legacy
7857			code).  Most statically-linked binaries and older
7858			versions of glibc use these calls.  Because these
7859			functions are at fixed addresses, they make nice
7860			targets for exploits that can control RIP.
7861
7862			emulate     Vsyscalls turn into traps and are emulated
7863			            reasonably safely.  The vsyscall page is
7864				    readable.
7865
7866			xonly       [default] Vsyscalls turn into traps and are
7867			            emulated reasonably safely.  The vsyscall
7868				    page is not readable.
7869
7870			none        Vsyscalls don't work at all.  This makes
7871			            them quite hard to use for exploits but
7872			            might break your system.
7873
7874	vt.color=	[VT] Default text color.
7875			Format: 0xYX, X = foreground, Y = background.
7876			Default: 0x07 = light gray on black.
7877
7878	vt.cur_default=	[VT] Default cursor shape.
7879			Format: 0xCCBBAA, where AA, BB, and CC are the same as
7880			the parameters of the <Esc>[?A;B;Cc escape sequence;
7881			see vga-softcursor.rst. Default: 2 = underline.
7882
7883	vt.default_blu=	[VT]
7884			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7885			Change the default blue palette of the console.
7886			This is a 16-member array composed of values
7887			ranging from 0-255.
7888
7889	vt.default_grn=	[VT]
7890			Format: <green0>,<green1>,<green2>,...,<green15>
7891			Change the default green palette of the console.
7892			This is a 16-member array composed of values
7893			ranging from 0-255.
7894
7895	vt.default_red=	[VT]
7896			Format: <red0>,<red1>,<red2>,...,<red15>
7897			Change the default red palette of the console.
7898			This is a 16-member array composed of values
7899			ranging from 0-255.
7900
7901	vt.default_utf8=
7902			[VT]
7903			Format=<0|1>
7904			Set system-wide default UTF-8 mode for all tty's.
7905			Default is 1, i.e. UTF-8 mode is enabled for all
7906			newly opened terminals.
7907
7908	vt.global_cursor_default=
7909			[VT]
7910			Format=<-1|0|1>
7911			Set system-wide default for whether a cursor
7912			is shown on new VTs. Default is -1,
7913			i.e. cursors will be created by default unless
7914			overridden by individual drivers. 0 will hide
7915			cursors, 1 will display them.
7916
7917	vt.italic=	[VT] Default color for italic text; 0-15.
7918			Default: 2 = green.
7919
7920	vt.underline=	[VT] Default color for underlined text; 0-15.
7921			Default: 3 = cyan.
7922
7923	watchdog timers	[HW,WDT] For information on watchdog timers,
7924			see Documentation/watchdog/watchdog-parameters.rst
7925			or other driver-specific files in the
7926			Documentation/watchdog/ directory.
7927
7928	watchdog_thresh=
7929			[KNL]
7930			Set the hard lockup detector stall duration
7931			threshold in seconds. The soft lockup detector
7932			threshold is set to twice the value. A value of 0
7933			disables both lockup detectors. Default is 10
7934			seconds.
7935
7936	workqueue.unbound_cpus=
7937			[KNL,SMP] Specify to constrain one or some CPUs
7938			to use in unbound workqueues.
7939			Format: <cpu-list>
7940			By default, all online CPUs are available for
7941			unbound workqueues.
7942
7943	workqueue.watchdog_thresh=
7944			If CONFIG_WQ_WATCHDOG is configured, workqueue can
7945			warn stall conditions and dump internal state to
7946			help debugging.  0 disables workqueue stall
7947			detection; otherwise, it's the stall threshold
7948			duration in seconds.  The default value is 30 and
7949			it can be updated at runtime by writing to the
7950			corresponding sysfs file.
7951
7952	workqueue.panic_on_stall=<uint>
7953			Panic when workqueue stall is detected by
7954			CONFIG_WQ_WATCHDOG. It sets the number times of the
7955			stall to trigger panic.
7956
7957			The default is 0, which disables the panic on stall.
7958
7959	workqueue.cpu_intensive_thresh_us=
7960			Per-cpu work items which run for longer than this
7961			threshold are automatically considered CPU intensive
7962			and excluded from concurrency management to prevent
7963			them from noticeably delaying other per-cpu work
7964			items. Default is 10000 (10ms).
7965
7966			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7967			will report the work functions which violate this
7968			threshold repeatedly. They are likely good
7969			candidates for using WQ_UNBOUND workqueues instead.
7970
7971	workqueue.cpu_intensive_warning_thresh=<uint>
7972			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7973			will report the work functions which violate the
7974			intensive_threshold_us repeatedly. In order to prevent
7975			spurious warnings, start printing only after a work
7976			function has violated this threshold number of times.
7977
7978			The default is 4 times. 0 disables the warning.
7979
7980	workqueue.power_efficient
7981			Per-cpu workqueues are generally preferred because
7982			they show better performance thanks to cache
7983			locality; unfortunately, per-cpu workqueues tend to
7984			be more power hungry than unbound workqueues.
7985
7986			Enabling this makes the per-cpu workqueues which
7987			were observed to contribute significantly to power
7988			consumption unbound, leading to measurably lower
7989			power usage at the cost of small performance
7990			overhead.
7991
7992			The default value of this parameter is determined by
7993			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7994
7995        workqueue.default_affinity_scope=
7996			Select the default affinity scope to use for unbound
7997			workqueues. Can be one of "cpu", "smt", "cache",
7998			"numa" and "system". Default is "cache". For more
7999			information, see the Affinity Scopes section in
8000			Documentation/core-api/workqueue.rst.
8001
8002			This can be changed after boot by writing to the
8003			matching /sys/module/workqueue/parameters file. All
8004			workqueues with the "default" affinity scope will be
8005			updated accordingly.
8006
8007	workqueue.debug_force_rr_cpu
8008			Workqueue used to implicitly guarantee that work
8009			items queued without explicit CPU specified are put
8010			on the local CPU.  This guarantee is no longer true
8011			and while local CPU is still preferred work items
8012			may be put on foreign CPUs.  This debug option
8013			forces round-robin CPU selection to flush out
8014			usages which depend on the now broken guarantee.
8015			When enabled, memory and cache locality will be
8016			impacted.
8017
8018	writecombine=	[LOONGARCH,EARLY] Control the MAT (Memory Access
8019			Type) of ioremap_wc().
8020
8021			on   - Enable writecombine, use WUC for ioremap_wc()
8022			off  - Disable writecombine, use SUC for ioremap_wc()
8023
8024	x2apic_phys	[X86-64,APIC,EARLY] Use x2apic physical mode instead of
8025			default x2apic cluster mode on platforms
8026			supporting x2apic.
8027
8028	xen_512gb_limit		[KNL,X86-64,XEN]
8029			Restricts the kernel running paravirtualized under Xen
8030			to use only up to 512 GB of RAM. The reason to do so is
8031			crash analysis tools and Xen tools for doing domain
8032			save/restore/migration must be enabled to handle larger
8033			domains.
8034
8035	xen_emul_unplug=		[HW,X86,XEN,EARLY]
8036			Unplug Xen emulated devices
8037			Format: [unplug0,][unplug1]
8038			ide-disks -- unplug primary master IDE devices
8039			aux-ide-disks -- unplug non-primary-master IDE devices
8040			nics -- unplug network devices
8041			all -- unplug all emulated devices (NICs and IDE disks)
8042			unnecessary -- unplugging emulated devices is
8043				unnecessary even if the host did not respond to
8044				the unplug protocol
8045			never -- do not unplug even if version check succeeds
8046
8047	xen_legacy_crash	[X86,XEN,EARLY]
8048			Crash from Xen panic notifier, without executing late
8049			panic() code such as dumping handler.
8050
8051	xen_mc_debug	[X86,XEN,EARLY]
8052			Enable multicall debugging when running as a Xen PV guest.
8053			Enabling this feature will reduce performance a little
8054			bit, so it should only be enabled for obtaining extended
8055			debug data in case of multicall errors.
8056
8057	xen_msr_safe=	[X86,XEN,EARLY]
8058			Format: <bool>
8059			Select whether to always use non-faulting (safe) MSR
8060			access functions when running as Xen PV guest. The
8061			default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
8062
8063	xen_nopv	[X86]
8064			Disables the PV optimizations forcing the HVM guest to
8065			run as generic HVM guest with no PV drivers.
8066			This option is obsoleted by the "nopv" option, which
8067			has equivalent effect for XEN platform.
8068
8069	xen_no_vector_callback
8070			[KNL,X86,XEN,EARLY] Disable the vector callback for Xen
8071			event channel interrupts.
8072
8073	xen_scrub_pages=	[XEN]
8074			Boolean option to control scrubbing pages before giving them back
8075			to Xen, for use by other domains. Can be also changed at runtime
8076			with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
8077			Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
8078
8079	xen_timer_slop=	[X86-64,XEN,EARLY]
8080			Set the timer slop (in nanoseconds) for the virtual Xen
8081			timers (default is 100000). This adjusts the minimum
8082			delta of virtualized Xen timers, where lower values
8083			improve timer resolution at the expense of processing
8084			more timer interrupts.
8085
8086	xen.balloon_boot_timeout= [XEN]
8087			The time (in seconds) to wait before giving up to boot
8088			in case initial ballooning fails to free enough memory.
8089			Applies only when running as HVM or PVH guest and
8090			started with less memory configured than allowed at
8091			max. Default is 180.
8092
8093	xen.event_eoi_delay=	[XEN]
8094			How long to delay EOI handling in case of event
8095			storms (jiffies). Default is 10.
8096
8097	xen.event_loop_timeout=	[XEN]
8098			After which time (jiffies) the event handling loop
8099			should start to delay EOI handling. Default is 2.
8100
8101	xen.fifo_events=	[XEN]
8102			Boolean parameter to disable using fifo event handling
8103			even if available. Normally fifo event handling is
8104			preferred over the 2-level event handling, as it is
8105			fairer and the number of possible event channels is
8106			much higher. Default is on (use fifo events).
8107
8108	xirc2ps_cs=	[NET,PCMCIA]
8109			Format:
8110			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
8111
8112	xive=		[PPC]
8113			By default on POWER9 and above, the kernel will
8114			natively use the XIVE interrupt controller. This option
8115			allows the fallback firmware mode to be used:
8116
8117			off       Fallback to firmware control of XIVE interrupt
8118				  controller on both pseries and powernv
8119				  platforms. Only useful on POWER9 and above.
8120
8121	xive.store-eoi=off	[PPC]
8122			By default on POWER10 and above, the kernel will use
8123			stores for EOI handling when the XIVE interrupt mode
8124			is active. This option allows the XIVE driver to use
8125			loads instead, as on POWER9.
8126
8127	xhci-hcd.quirks		[USB,KNL]
8128			A hex value specifying bitmask with supplemental xhci
8129			host controller quirks. Meaning of each bit can be
8130			consulted in header drivers/usb/host/xhci.h.
8131
8132	xmon		[PPC,EARLY]
8133			Format: { early | on | rw | ro | off }
8134			Controls if xmon debugger is enabled. Default is off.
8135			Passing only "xmon" is equivalent to "xmon=early".
8136			early	Call xmon as early as possible on boot; xmon
8137				debugger is called from setup_arch().
8138			on	xmon debugger hooks will be installed so xmon
8139				is only called on a kernel crash. Default mode,
8140				i.e. either "ro" or "rw" mode, is controlled
8141				with CONFIG_XMON_DEFAULT_RO_MODE.
8142			rw	xmon debugger hooks will be installed so xmon
8143				is called only on a kernel crash, mode is write,
8144				meaning SPR registers, memory and, other data
8145				can be written using xmon commands.
8146			ro 	same as "rw" option above but SPR registers,
8147				memory, and other data can't be written using
8148				xmon commands.
8149			off	xmon is disabled.
8150