Lines Matching +full:fan +full:- +full:stop +full:- +full:to +full:- +full:start +full:- +full:us
4 By default, unaccepted memory is accepted lazily to
9 accept_memory=eager can be used to accept all memory
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
22 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT to memory
24 nocmcff -- Disable firmware first mode for corrected
26 source to check if firmware has set the FF flag. This
28 nospcr -- disable console in ACPI SPCR table as
45 If set to vendor, prefer vendor-specific 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.
53 force FADT to use 32 bit addresses rather than the
60 This mechanism can repair the evaluation result to make
62 This option is useful for developers to identify the
64 has something to do with the repair mechanism.
69 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
70 debug output. Bits in debug_layer correspond to a
73 Bits in debug_level correspond to a level in
76 The debug_level mask defaults to "info". See
77 Documentation/firmware-guide/acpi/debug.rst for more information about
82 Enable AML "Debug" output, i.e., stores to the Debug
85 Enable all messages related to ACPI hardware:
90 if you need to capture more output.
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
110 By default, this is disabled due to x86 early mapping
129 Due to the existence of _Lxx/_Exx, some GPEs triggered
133 This facility can be used to prevent such uncontrolled
135 Format: <byte> or <bitmap-list>
138 Disable auto-serialization of AML methods
139 AML control methods that contain the opcodes to create
141 auto-serialization feature.
143 This option allows to turn off the feature.
156 tables to /sys/firmware/acpi/tables/dynamic.
159 Ignore the ACPI-based watchdog interface (WDAT) and let
163 Pass the RSDP address to the kernel, mostly used
164 on machines running EFI runtime service to boot the
168 Format: To spoof as Windows 98: ="Microsoft Windows"
170 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
173 be necessary to carry out a cold reboot _twice_ in a
174 row to make it take effect on the platform firmware).
180 acpi_osi=! # disable all built-in OS vendor
182 acpi_osi=!! # enable all built-in OS vendor
187 multiple 'acpi_osi="string1"' to support specific OS
198 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
212 multiple 'acpi_osi="string1"' to support specific
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
228 equivalent to
236 to assume that this machine's pmtimer latches its value
244 For broken nForce2 BIOS resulting in XT-PIC timer.
253 as soon as the kernel's real-mode entry point is called.
254 s4_hwsig causes the kernel to check the ACPI hardware
256 refuse to resume if it has changed. This complies with
259 on docking. So the default behaviour is to allow resume
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
270 sci_force_enable causes the kernel to set SCI_EN directly
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).
287 try_unsupported: try to drive unsupported chipsets
291 See Documentation/sound/alsa-configuration.rst
295 behaviour to be specified. Bit 0 enables warnings,
298 align_va_addr= [X86-64]
301 gives you up to 3% performance improvement on AMD F15h
303 CPU-intensive style benchmark, and it can vary highly in
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
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.
319 Allow execve() of 32-bit applications and setting of the
321 subset of the CPUs support 32-bit EL0. When this
322 parameter is present, the set of CPUs supporting 32-bit
324 and hot-unplug operations may be restricted.
326 See Documentation/arch/arm64/asymmetric-32bit.rst for more
329 amd_iommu= [HW,X86-64]
330 Pass parameters to the AMD IOMMU driver in the system.
332 fullflush - Deprecated, equivalent to iommu.strict=1
333 off - do not initialize any AMD IOMMU found in
335 force_isolation - Force device isolation for all
337 allowed anymore to lift isolation
340 force_enable - Force enable the IOMMU on platforms known
341 to be buggy with IOMMU enabled. Use this
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.
352 amd_iommu_dump= [HW,X86-64]
353 Enable AMD IOMMU driver option to dump the ACPI table
358 amd_iommu_intr= [HW,X86-64]
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.
375 tries to match the same performance level if it is
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
388 to the current workload.
393 Disable amd-pstate preferred core.
396 Map of devices attached to JOY0DAT and JOY1DAT
402 connected to one of 16 gameports
406 Power management functions (SPARCstation-4/5 + deriv.)
408 Disable APC CPU standby support. SPARCstation-Fox does
409 not play well with APC CPU idle - disable it if you have
412 apic [APIC,X86-64] Use IO-APIC. Default.
418 when initialising the APIC and IO-APIC components.
422 bsp: External NMI is delivered only to CPU 0
423 all: External NMIs are broadcast to all CPUs as a
442 0 -- disable.
443 1 -- enable.
446 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
494 audit= [KNL] Enable the audit sub-system
496 0 | off - kernel audit is disabled and can not be
498 unset - kernel audit is initialized but disabled and
500 1 | on - kernel audit is initialized and partially
511 behavior is to disable the BAU (i.e. bau=0).
513 0 - Disable the BAU.
514 1 - Enable the BAU.
515 unset - Disable the BAU.
536 Control the ability to open a mounted block device
538 the FS. This was implemented as a means to prevent
550 Disable BGRT to avoid flickering OEM logo.
554 See Documentation/block/cmdline-partition.rst
557 Milliseconds to delay each printk during boot.
559 and you may also have to specify "lpj=". Boot_delay
565 Extended command line options can be added to an initrd
566 and this will cause the kernel to look for it.
568 See Documentation/admin-guide/bootconfig.rst
573 bttv.pll= See Documentation/admin-guide/media/bttv.rst
582 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
585 to fix known problems, but for some CPUs it is not
586 possible to determine what the correct size should be.
595 the system trusted keyring to be used for certificate
600 algorithm. Accepted values range from 0 to 7
601 inclusive. See arch/mips/include/asm/pgtable-bits.h
609 Format: {name of the controller(s) or feature(s) to disable}
611 - foo isn't auto-mounted if you mount all cgroups in
613 - foo isn't visible as an individually mountable
615 - if foo is an optional feature then the feature is
621 Specifying "pressure" disables per-cgroup pressure
627 Like cgroup_disable, but only applies to cgroup v1;
635 Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
637 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
639 nosocket -- Disable socket memory accounting.
640 nokmem -- Disable kernel memory accounting.
641 nobpf -- Disable BPF memory accounting.
646 0 -- check protection applied by kernel (includes
648 1 -- check protection requested by application.
652 Setting checkreqprot to 1 is deprecated.
660 numbers X. Note the Linux-specific bits are not necessarily
661 stable over kernel options, but the vendor-specific
681 force such clocks to be always-on nor does it reserve
685 information, see Documentation/driver-api/clk.rst.
687 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
689 Forces specified clocksource (if available) to be used
691 clocksource is not available, it defaults to PIT.
698 Some clocksource names to choose from, depending on
704 [X86-32] pit,hpet,tsc;
711 [X86-64] hpet,tsc
717 architected timer so that code using WFE-based polling
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.
731 clocksource-wdtest.holdoff= [KNL]
734 Defaults to zero when built as a module and to
737 cma=nn[MG]@[start[MG][-end[MG]]]
748 Sets the size of kernel per-numa memory area for
750 per-numa CMA altogether. And If this option is not
752 With per-numa CMA enabled, DMA users on node nid will
753 first try to allocate buffer from the pernuma area
755 they will fallback to the global default memory area.
764 first try to allocate buffer from the numa area
766 they will fallback to the global default memory area.
771 to determine OS memory pressure for page stealing by
777 allocations, by default set to 256K.
779 com20020= [HW,NET] ARCnet - COM20020 chipset
783 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
787 ARCnet - COM90xx chipset (memory-mapped buffers)
795 When set to true, drop data on the 3215 console when
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
816 See Documentation/admin-guide/serial-console.rst for more
828 The mapping of the serial ports to the tty instances
831 $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
832 /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
837 is ready. The use of an earlycon parameter in addition to
845 Start an early, polled-mode console on the 8250/16550
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).
851 to be equivalent to 'mmio'. 'options' are specified in
853 the h/w is not re-initialized.
859 Use to disable console output, i.e., to have kernel
864 If the device connected to the port is not a TTY but a braille
877 Switch to syslog format: "<%u>[time stamp] text\n"
879 prefix. The format is similar to one used by syslog()
880 syscall, or to executing "dmesg -S --raw" or to reading
885 Defaults to 0.
904 disable the cpuidle sub-system
907 [CPU_IDLE] Name of the cpuidle governor to use.
910 disable the cpufreq sub-system
914 policy to use. This governor must be registered in the
918 [X86,EARLY] Delay for N microsec between assert and de-assert
919 of APIC INIT to start processors. This delay occurs
930 Only jump to kdump kernel after running the panic
939 like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
942 [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
947 [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
948 under 4G first, and fall back to reserve region above
950 See Documentation/admin-guide/kdump/kdump.rst for further details.
955 start-[end] where start and end are both
957 Documentation/admin-guide/kdump/kdump.rst for an example.
960 [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
962 Allow kernel to allocate physical memory region from top,
968 [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
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
977 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
978 --> arm64: 128MiB
979 --> riscv: 128MiB
980 --> loongarch: 128MiB
983 0: to disable low allocation.
988 [KNL] Disable crypto self-tests
996 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
998 additional debug data is printed to the console
1000 CPU is pinged again in order to try to resolve
1011 See also Documentation/input/devices/joystick-parport.rst
1018 of siphash to hash pointers. Use this option if you are
1019 seeing instances of '(___ptrval___)') and need to see a
1024 [KNL] verbose locking self-tests
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.
1043 parameter to 1 or 2 should be enough to identify most
1045 kernel or driver code when a CPU writes to (or reads
1059 Note: to get most of debug_pagealloc error reports, it's
1060 useful to also enable the page_owner functionality.
1063 debugfs= [KNL,EARLY] This parameter enables what is exposed to
1065 Format: { on, no-mount, off }
1067 no-mount:
1069 access APIs and a crashkernel can be used to read
1070 its content. There is nothing to mount.
1072 get a -EPERM as result when trying to register files
1076 Default value is set in build-time with a kernel configuration.
1085 filesystems. If not specified, defaults to the
1088 Documentation/admin-guide/mm/hugetlbpage.rst.
1092 [KNL] Debugging option to set a timeout in seconds for
1093 deferred probe to give up waiting on dependencies to
1102 delayacct [KNL] Enable per-task delay accounting
1123 [HW] Factor to multiply fan speed with.
1126 [HW] Maximum configurable fan speed.
1145 causes the kernel to fall back to 256MB segments which
1147 miss to occur.
1161 to workaround buggy firmware.
1167 The kernel tries to adjust MTRR layout from continuous
1168 to discrete, to make X server driver able to add WB
1175 possibly causing your machine to run very slowly.
1179 Can be useful to work around chipset bugs.
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
1194 With this option the DMA-API debugging driver
1196 pass the driver to filter for as the parameter.
1197 The filter can be disabled or changed to another
1203 vulnerability which may allow userspace to infer
1214 are enabled. In order to disable RFDS mitigation all
1215 VERW based mitigations need to be disabled.
1218 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1221 List of driver names to be probed asynchronously. *
1230 This parameter allows to specify an EDID data sets
1233 connector, if its name and a colon are prepended to
1243 Control how the dt_cpu_ftrs device-tree binding is
1246 off: Do not use it, fall back to legacy cpu table.
1247 known: Do not pass through unknown features to guests
1252 x86 Macs. Useful for driver authors to determine
1253 what data is available or for reverse-engineering.
1258 Documentation/admin-guide/dynamic-debug-howto.rst
1269 determined by stdout-path property in device tree's
1274 Start an early, polled-mode console on a Cadence
1285 Start an early, polled-mode console on the 8250/16550
1287 MMIO inter-register address stride is either 8-bit
1288 (mmio) or 32-bit (mmio32 or mmio32be).
1290 to be equivalent to 'mmio'. 'options' are specified
1294 to 'BASE_BAUD' * 16.
1298 Start an early, polled-mode console on a pl011 serial
1302 the driver will use only 32-bit accessors to read/write
1306 Start an early console on a litex serial port at the
1311 Start an early, polled-mode console on a meson serial
1317 Start an early, polled-mode console on an msm serial
1323 Start an early, polled-mode console on an msm serial
1329 Start an early, polled-mode console on a serial port
1335 Start an early, polled-mode console on a serial port
1341 Use RISC-V SBI (Supervisor Binary Interface) for early
1359 Start an early, polled-mode console on a lantiq serial
1373 Start an early, polled-mode, output-only console on the
1378 Start an early, polled-mode console on the
1384 Start an early, polled-mode console on a Qualcomm
1390 Start an early, unaccelerated console on the EFI
1392 coherent non-x86 systems that use system memory for
1419 Use "nocfg" to skip UART configuration, assume
1422 Append ",keep" to not disable it when the real console
1449 The optional "force" to "pciserial" enables use of a
1453 edac_report= [HW,EDAC] Control how to report EDAC event
1455 on: enable EDAC to report H/W event. May be overridden
1458 force: enforce the use of EDAC to report H/W event.
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
1492 that is to be dynamically loaded by Linux. If there are
1495 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1504 This is designed to be used in conjunction with
1512 elanfreq= [X86-32]
1517 Specifies physical address of start of kernel core
1519 kexec loader will pass this option to capture kernel.
1520 See Documentation/admin-guide/kdump/kdump.rst for details.
1523 The kernel tries to adjust MTRR layout from continuous
1524 to discrete, to make X server driver able to add WB
1529 Can be useful to work around chipset bugs
1531 The kernel tries to set a reasonable default.
1536 0 -- permissive (log only, no denials).
1537 1 -- enforcing (deny and log).
1552 Permit 'security.evm' to be updated regardless of
1555 early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
1558 might be disabled to achieve that (e.g. parallelized
1570 See also Documentation/fault-injection/.
1574 See Documentation/admin-guide/sysctl/net.rst for
1578 See Documentation/admin-guide/blockdev/floppy.rst.
1580 forcepae [X86-32]
1587 fred= [X86-64]
1594 [FTRACE] will set and start the specified tracer
1595 as early as possible in order to facilitate early
1603 boot up that is likely to be overridden by user space
1604 start up functionality.
1612 The above will cause the "foo" tracing instance to trigger
1625 oops by passing 2 or orig_cpu to it.
1638 ftrace_filter=[function-list]
1640 tracer at boot up. function-list is a comma-separated
1645 ftrace_notrace=[function-list]
1647 function-list. This list can be changed at run time
1651 ftrace_graph_filter=[function-list]
1654 function-list is a comma-separated list of functions
1658 ftrace_graph_notrace=[function-list]
1660 function-list. This list is a comma-separated list of
1671 devices by scanning the firmware to infer the
1680 off -- Don't create device links from firmware info.
1681 permissive -- Create device links from firmware info
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.
1695 probing, this parameter controls what to do with
1699 strict -- Default. Continue waiting on consumers to
1701 timeout -- Give up waiting on consumers and call
1709 support via parallel port (up to 5 devices per port)
1711 See also Documentation/input/devices/joystick-parport.rst
1715 gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART
1724 allows unprivileged speculative access to data which was
1732 force: Disable AVX to mitigate systems without
1734 mitigation is present. Known to cause crashes in
1741 gcov_persist= [GCOV] When non-zero (default), profiling data for
1751 gpio-mockup.gpio_mockup_ranges
1754 gpio-mockup.gpio_mockup_named_lines
1758 invalid Protective MBR to be treated as GPT. If the
1760 GPT to be used instead.
1770 grcan.select= [HW] Select which physical interface to use.
1783 usercopy checking is used to protect the kernel
1786 against bounds-checking flaws in the kernel's
1794 [KNL] Should the hard-lockup detector generate
1800 for 64-bit NUMA, off otherwise.
1808 corresponding firmware-first mode error processing
1818 during restoration read-only).
1820 hibernate.compressor= [HIBERNATION] Compression algorithm to be
1825 lzo: Select LZO compression algorithm to
1828 lz4: Select LZ4 compression algorithm to
1831 highmem=nn[KMG] [KNL,BOOT,EARLY] forces the highmem zone to have an exact
1833 highmem otherwise. This also works to reduce highmem
1846 Using this parameter to set the hostname makes it
1847 possible to ensure the hostname is correctly set before
1855 hpet= [X86-32,HPET] option to control HPET usage
1863 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1866 hugepages= [HW,EARLY] Number of HugeTLB pages to allocate at boot.
1868 the number of pages of hugepagesz to be allocated.
1870 line, it specifies the number of pages to allocate for
1872 number of pages to allocate per-node can be specified.
1873 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1879 used in conjunction with hugepages (above) to
1884 Documentation/admin-guide/mm/hugetlbpage.rst.
1888 [HW] The number of threads that should be used to
1890 used to improve system bootup time when allocating
1894 Note that this parameter only applies to non-gigantic huge pages.
1904 boot-time allocation of gigantic hugepages is skipped.
1908 try to allocate from the CMA areas.
1917 Allows heavy hugetlb users to free up some more
1937 A value of 1 instructs the kernel to panic when a
1939 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1945 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1951 which allow the hypervisor to 'idle' the guest
1967 Set device-properties for ACPI-enumerated I2C-attached
1968 touchscreen, to e.g. fix coordinates of upside-down
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
1981 i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1982 touchscreen-inverted-y
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
1991 (disabled by default, and as a pre-condition
1993 i8042.direct [HW] Put keyboard port into non-translated mode
1996 (Don't attempt to blink the leds)
2003 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
2007 suspend-to-ram transitions, only during s2r
2013 architectures force reset to be always executed
2015 i8042.kbdreset [HW] Reset device connected to KBD port
2022 [DRM] Invert the sense of the variable that is used to
2026 to maximum brightness. If this parameter is set to 0
2028 is set to 1, a brightness value of 0 sets the backlight
2029 to maximum brightness, and the maximum of the brightness
2031 -1 -- never invert brightness
2032 0 -- machine default
2033 1 -- force brightness inversion
2035 ia32_emulation= [X86-64]
2037 When true, allows loading 32-bit programs and executing 32-bit
2051 to get slightly better performance in multiprocessor
2059 idle=halt: Halt is forced to be used for CPU idle.
2062 idle=nomwait: Disable mwait for CPU C-states
2067 support for the idxd driver. By default it is set to
2073 for the device. By default it is set to false (0).
2083 binary. Hardware implementations are permitted to
2090 legacy only accept legacy-NaN binaries, if supported
2092 2008 only accept 2008-NaN binaries, if supported
2099 The FPU emulator is always able to support both NaN
2103 'relaxed' straps the emulator for both legacy-NaN and
2104 2008-NaN, whereas 'strict' enables legacy-NaN only on
2113 Ignore loglevel setting - this will print /all/
2114 kernel messages to the console. Useful for debugging.
2148 The builtin policies to load during IMA setup.
2180 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2181 "ima-sigv2" }
2182 Default: "ima-ng"
2195 to achieve the best performance for a particular HW.
2203 to achieve best performance for particular HW.
2215 stuff: Deploy RSB-fill mitigation when retpoline is
2220 Documentation/admin-guide/hw-vuln/indirect-target-selection.rst
2231 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2232 initcall functions. Useful for debugging built-in
2249 initrdmem= [KNL,EARLY] Specify a physical address and size from which to
2267 default (disallow access to all but pkey 0). Can
2277 0 -- basic integrity auditing messages. (Default)
2278 1 -- additional integrity auditing messages.
2292 Deprecated, equivalent to iommu.strict=1.
2306 could harm performance of some high-throughput
2311 vulnerable to DMA attacks.
2315 1 to 9 specify maximum depth of C-state.
2322 Use intel_pstate driver to bypass the scaling
2324 algorithms for p-state selection. There are two
2325 P-state selection algorithms provided by
2328 on whether or not the hardware managed P-states
2333 to work with generic cpufreq governors (instead of
2335 used along with the hardware-managed P-states (HWP)
2339 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2340 instead of acpi-cpufreq may disable platform features, such
2342 P-States information being indicated to OSPM and therefore
2345 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2358 Allow per-logical-CPU P-State performance control limits using
2361 Do not enable capacity-aware scheduling (CAS) on
2364 intremap= [X86-64,Intel-IOMMU,EARLY]
2369 BIOS x2APIC opt-out request will be ignored
2374 iomem= Disable strict checking of access to MMIO memory
2400 Intel machines). This can be used to prevent the usage
2412 AMD Gart HW IOMMU-specific options:
2431 Do scatter-gather (SG) merging. Implies "force"
2435 Don't do scatter-gather (SG) merging.
2438 Ask the IOMMU not to touch the aperture for AGP.
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,
2452 greater than 32-bit addressing.
2456 0 - Lazy mode.
2460 Will fall back to strict mode if not supported by
2462 1 - Strict mode.
2465 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2467 legacy driver-specific options takes precedence.
2470 [ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
2472 0 - Use IOMMU translation for DMA.
2473 1 - Bypass the IOMMU for DMA.
2474 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2476 io7= [HW] IO7 for Marvel-based Alpha systems
2491 See Documentation/admin-guide/nfs/nfsroot.rst.
2494 IPC identifiers from 32,768 to 16,777,216.
2504 Start IPE with success auditing enabled, emitting
2514 Force the kernel to look for the second 4kB page
2520 Force the kernel to ignore the availability of
2523 to let secondary kernels in charge of setting up
2527 Enables support for pseudo-NMIs in the kernel. This
2528 requires the kernel to be built with
2533 for it. Intended to get systems with badly broken
2539 interrupt. Intended to get systems with badly broken
2546 [Deprecated - use cpusets instead]
2547 Format: [flag-list,]<cpu-list>
2549 Specify one or more CPUs to isolate from disturbances
2555 offloaded. This is equivalent to the nohz_full parameter.
2557 A residual 1Hz tick is offloaded to workqueues, which you
2558 need to affine to housekeeping through the global
2564 so to protect individual CPUs the 'cpumask' file has to
2570 is irreversible: it's not possible to bring back a CPU to
2572 advised to use cpusets instead to disable scheduler load
2580 "number of CPUs in system - 1".
2594 interrupts are directed to the housekeeping CPU
2606 The format of <cpu-list> is described above.
2610 ivrs_ioapic [HW,X86-64]
2611 Provide an override to the IOAPIC-ID<->DEVICE-ID
2615 For example, to map IOAPIC-ID decimal 10 to
2621 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2624 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2628 ivrs_hpet [HW,X86-64]
2629 Provide an override to the HPET-ID<->DEVICE-ID
2633 For example, to map HPET-ID decimal 10 to
2639 * To map HPET-ID decimal 0 to PCI device 00:14.0
2642 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2646 ivrs_acpihid [HW,X86-64]
2647 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2651 For example, to map UART-HID:UID AMD0020:0 to
2657 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2660 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2668 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2674 Do not unregister boot console at start. This is only
2684 the kernel for non-movable allocations. The requested
2688 event, a node is too small to have both ZONE_NORMAL and
2694 subsystem. Note that allocations like PTEs-from-HighMem
2698 It is possible to specify the exact amount of memory in
2702 for non-movable allocations and remaining memory is used
2711 each poll cycle to the debug port in case you need
2713 gdb or control-c on the dbgp connection. When
2714 not using this parameter you use sysrq-g to break into
2719 or a supported polling keyboard driver (non-usb).
2728 If the boot console provides the ability to read
2730 this parameter to tell kgdb to use it as a backend
2731 until the normal console is registered. Intended to
2733 specifies the normal console to transition to.
2738 name passed to kgdboc. It's OK to leave the value
2742 kgdbwait [KGDB,EARLY] Stop kernel execution and enter the
2746 Configure the RouterBoard 532 series on-chip
2749 kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable
2755 kprobe_event=[probe-list]
2757 The probe-list is a semicolon delimited list of probe
2760 For example, to add a kprobe event on vfs_read with
2761 arg1 and arg2, add to the command line;
2775 CONFIG_KUNIT to be set to be fully enabled. The
2780 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2784 [KVM,X86] Controls whether or not KVM will try to
2786 Eager page splitting reduces interruptions to vCPU
2787 execution by eliminating the write-protection faults
2789 required to split huge pages lazily.
2792 only to a small region of VM memory may benefit from
2793 disabling eager page splitting to allow huge pages to
2814 virtualization on-demand when creating and destroying
2822 is that doing so may interfere with using out-of-tree
2823 hypervisors that want to "own" virtualization hardware.
2839 guests do need not to enable it for nested guests.
2843 back to huge pages. 0 disables the recovery, otherwise if
2849 back to huge pages. If the value is a non-zero N, KVM will
2854 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
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
2862 kvm-arm.mode=
2868 nvhe: Standard nVHE-based mode, without support for
2875 nested: VHE-based mode with support for nested
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.
2887 kvm-arm.vgic_v3_group0_trap=
2888 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2891 kvm-arm.vgic_v3_group1_trap=
2892 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2895 kvm-arm.vgic_v3_common_trap=
2896 [KVM,ARM,EARLY] Trap guest accesses to GICv3 common
2899 kvm-arm.vgic_v4_enable=
2903 kvm-arm.wfe_trap_policy=
2904 [KVM,ARM] Control when to set WFE instruction trap for
2912 kvm-arm.wfi_trap_policy=
2913 [KVM,ARM] Control when to set WFI instruction trap for
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
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,
2938 guests. This param doesn't apply to nested guests (L2),
2942 kvm-intel.flexpriority=
2947 kvm-intel.nested=
2951 kvm-intel.unrestricted_guest=
2957 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2958 CVE-2018-3620.
2969 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2977 Certain CPUs are vulnerable to an exploit against CPU
2978 internal buffers which can forward information to a
2983 attack, to access data to which the attacker does
2989 on - enable the interface for the mitigation
3054 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3060 lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3064 value for LAPIC timer one-shot implementation. Default
3065 back to the programmable timer unit in the LAPIC.
3087 libata.force= [LIBATA] Force configurations. The format is a comma-
3094 to all ports, links and devices.
3096 If only DEVICE is omitted, the parameter applies to
3099 first fan-out link behind PMP device. It does not
3101 host link and device attached to it.
3103 The VAL specifies the configuration to force. As long
3113 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3120 * rstonce: only attempt one reset during hot-unplug
3147 READ LOG DMA EXT command to access logs.
3149 * [no]iddevlog: Enable or disable access to the
3152 * [no]logdir: Enable or disable access to the general
3155 * max_sec_128: Set transfer size limit to 128 sectors.
3157 * max_sec_1024: Set or clear transfer size limit to
3160 * max_sec_lba48: Set or clear transfer size limit to
3163 * external: Mark port as external (hotplug-capable).
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
3200 to extract confidential information from the kernel
3209 Specify the list of CPUs to which the readers are
3210 to be bound.
3213 Specify the list of CPUs to which the writers are
3214 to be bound.
3217 Specify the number of self-propagating call_rcu()
3218 chains to set up. These are used to ensure that
3220 in progress at any given time. Defaults to 0,
3225 occasional long-duration lock hold time. Defaults
3226 to 100 milliseconds. Select 0 to disable.
3230 locktorture is to exercise, up to a limit of 8
3231 (MAX_NESTED_LOCKS). Specify zero to disable.
3236 Set the number of locking read-acquisition kthreads.
3237 Defaults to being automatically set based on the
3241 Set the number of locking write-acquisition kthreads.
3244 Set time (s) after boot for CPU-hotplug testing.
3247 Set time (s) between CPU-hotplug operations, or
3248 zero to disable CPU-hotplug testing.
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
3256 non-real-time spinlocks, due to their disabling
3257 of preemption. Note that non-realtime mutexes
3270 Set task-shuffle interval (jiffies). Shuffling
3271 tasks allows some CPUs to go into dyntick-idle
3276 is useful for hands-off automated testing.
3282 Time (s) to stutter testing, for example,
3283 specifying five seconds causes the test to run for
3285 This tests the locking primitive's ability to
3286 transition abruptly to and from idle.
3289 Specify the locking implementation to test.
3295 Run the write-side locktorture kthreads at
3296 sched_set_fifo() real-time priority.
3303 console loglevel will be printed to the console. It can
3314 7 (KERN_DEBUG) debug-level messages
3322 parameter that allows to increase the default size
3326 logo.nologo [FB] Disables display of the built-in Linux logo.
3327 This may be used to provide more screen space for
3331 lp=0 [LP] Specify parallel ports to use, e.g,
3335 specified in addition to the ports) causes
3336 attached printers to be reset. Using
3338 to associate lp devices with, starting with
3339 lp0. A port specification may be 'none' to skip
3343 from each port should be examined, to see if
3344 an IEEE 1284-compliant printer is attached; if
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
3354 on SMP systems the preset will be applied to all CPUs,
3355 which is likely to cause problems if your CPUs need
3357 will cause delays in the kernel to be wrong, leading to
3370 Example: machtype=lemote-yeeloong-2f-7inch
3374 the kernel to bring up 'n' processors. Surely after
3378 While n=0 is a special case, it is equivalent to "nosmp",
3382 (loop.max_loop) unconditionally pre-created at init time. The default
3385 devices can be requested on-demand with the
3386 /dev/loop-control interface.
3388 mce= [X86-{32,64}]
3402 with due to the shared banks, i.e. you might get
3425 do not opt-in to Local MCE delivery. Use legacy method
3426 to broadcast MCEs.
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
3442 sets the time in us to wait for other CPUs on machine
3443 checks. 0 to disable.
3446 don't overwrite the bios-set CMCI threshold. This boot
3449 always sets the CMCI threshold to 1. Enabling this may
3455 force-enable recoverable machine check code paths
3461 See Documentation/admin-guide/md.rst.
3465 Specifies range of consoles to be captured by the MDA.
3468 Control mitigation for the Micro-architectural Data
3471 Certain CPUs are vulnerable to an exploit against CPU
3472 internal buffers which can forward information to a
3477 attack, to access data to which the attacker does
3483 full - Enable MDS mitigation on vulnerable CPUs
3484 full,nosmt - Enable MDS mitigation and disable
3486 off - Unconditionally disable MDS mitigation
3488 On TAA-affected machines, mds=off can be prevented by
3490 mitigated with the same mechanism so in order to disable
3491 this mitigation, you need to specify tsx_async_abort=off
3494 Not specifying this option is equivalent to
3497 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3503 of memory Amount of memory to be used in cases
3507 2 when the kernel is not able to see the whole system memory;
3509 the hypervisor, then assigned to KVM guests.
3510 4 to limit the memory available for kdump kernel.
3512 [ARC,MICROBLAZE] - the limit applies only to low memory,
3515 [ARM64] - only limits memory covered by the linear
3519 with memmap= to avoid physical address space collisions.
3521 belonging to unused RAM.
3528 [ARM,MIPS,EARLY] - override the memory layout
3535 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3541 [KNL,SH] Allow user to override the default size for
3542 per-device physically contiguous DMA buffers.
3547 set according to the
3550 See Documentation/admin-guide/mm/memory-hotplug.rst.
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].
3570 Region of memory to be marked is from ss to ss+nn.
3574 Region of memory to be reserved is from ss to ss+nn.
3575 Example: Exclude memory from 0x18690000-0x1869ffff
3585 Region of memory to be used, from ss to ss+nn.
3589 memmap=<size>%<offset>-<oldtype>+<newtype>
3591 from <oldtype> to <newtype>. If "-<oldtype>" is left
3599 Some BIOSes seem to corrupt the first 64k of
3606 repeatable BIOS-originated corruption always
3608 to prevent the kernel from using that memory.
3613 use. Use this parameter to scan for
3618 seconds. Use this parameter to check at some
3622 [KNL,X86,ARM] Boolean flag to enable this feature.
3628 hotadded memory which will allow to hotadd a
3630 memory to do so.
3643 Specifies the number of memtest passes to be
3650 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3656 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
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.
3665 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3667 version 0.98 is known to be affected, 0.99 fixes the
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)
3687 b - Enable backlight. The TFT backlight pin will be
3688 linked to the kernel VESA blanking code and a GPIO
3691 c - Enable the s3c camera interface.
3692 t - Reserved for enabling touchscreen support. The
3696 https://repo.or.cz/w/linux-2.6/mini2440.git
3701 arch-independent options, each of which is an
3702 aggregation of existing arch-specific options.
3710 expose users to several CPU vulnerabilities.
3711 Equivalent to: if nokaslr then kpti=0 [ARM64]
3732 ssbd=force-off [ARM64]
3743 users who don't want to be surprised by SMT
3745 have other ways of avoiding SMT-based attacks.
3746 Equivalent to: (default behavior)
3750 if needed. This is for users who always want to
3752 Equivalent to: l1tf=flush,nosmt [X86]
3764 so loglevel=8 may also need to be specified.
3774 Therefore, similar to MDS and TAA, the mitigation
3775 is to clear the affected CPU buffers.
3780 full - Enable mitigation on vulnerable CPUs
3782 full,nosmt - Enable mitigation and disable SMT on
3785 off - Unconditionally disable mitigation
3790 mitigated with the same mechanism so in order to
3791 disable this mitigation, you need to specify
3794 Not specifying this option is equivalent to
3798 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3808 [KNL] When set to true, modules will use async probing
3809 by default. To enable/disable async probing for a
3824 modules without (valid) signatures will fail to load.
3828 module_blacklist= [KNL] Do not load a comma-separated list of
3833 leaving touchpad surface for touch to be considered
3844 This parameter is the complement to kernelcore=, it
3853 movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory
3854 NUMA nodes to be movable. This means that the memory
3860 Format: <name>,<region-number>,<size>,<offset>
3863 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3873 Enable printing debug information related to MTRR
3891 Set to 2 or more if your graphical card needs more.
3901 Note that mem_start is often overloaded to mean
3902 something different and driver-specific.
3913 0 to disable accounting
3914 1 to enable accounting
3918 [NFS] sets the pathname to the program which is used
3919 to update the NFS client cache entries.
3922 [NFS] sets the timeout after which an attempt to
3923 update a cache entry is deemed to have failed.
3927 NFS client will assign to service NFSv4 callback
3942 [NFS] enable 64-bit inode numbers.
3943 If zero, the NFS client will fake up a 32-bit inode
3945 of returning the full 64-bit number.
3946 The default is to return 64-bit inode numbers.
3954 slots the client will assign to the callback
3961 the client will attempt to negotiate with the server.
3963 that the client can send to the NFSv4.1 server.
3968 [NFSv4] When set to the default of '1', this option
3970 scheme and the NFS level operations agree to use
3974 legacy NFSv2/v3 systems to NFSv4 easier.
3977 back to using the idmapper.
3978 To turn off this behaviour, set the value to '0'.
3981 [NFS4] Specify an additional fixed unique ident-
3987 [NFSv4] Attempt to recover locks that were lost due
3988 to a lease timeout on the server. Please note that
3992 If you want to enable the kernel legacy behaviour of
3993 attempting to recover these locks, then set this
3994 parameter to '1'.
3996 not to attempt recovery of lost locks.
4003 The default is to send the implementation identification
4008 layoutstats to the pNFS metadata server.
4010 Setting this to value to 0 causes the kernel to use
4012 driver. A non-zero value sets the minimum interval
4016 [NFSv4.2] When set to 1, the server will support
4017 server-to-server copies for which this server is
4021 [NFSv4] When set to the default of '1', the NFSv4
4022 server will return only numeric uids and gids to
4024 and gids from such clients. This is intended to ease
4029 server-to-server copy, knfsd temporarily mounts
4036 See Documentation/admin-guide/nfs/nfsroot.rst.
4038 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
4039 See Documentation/admin-guide/nfs/nfsroot.rst.
4042 See Documentation/admin-guide/nfs/nfsroot.rst.
4045 Dump stacks even of idle CPUs in response to an
4046 NMI stack-backtrace request.
4048 nmi_debug= [KNL,SH] Specify one or more actions to take
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
4060 timeout occurs (or 'nopanic' to not panic on an NMI
4062 To disable both hard and soft lockup detectors,
4070 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
4074 no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes.
4075 Forces kernel to use 3-level paging instead.
4077 no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4078 kernel to use 4-level paging instead.
4082 noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any
4096 of the system is being put to sleep (ie, while
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
4103 /sys/module/printk/parameters/console_suspend) to
4113 no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4115 noexec32 [X86-64]
4116 This affects only 32-bit executables.
4117 noexec32=on: enable non-executable mappings (default)
4119 noexec32=off: disable non-executable mappings
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.
4130 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4132 legacy floating-point registers on task switch.
4138 Force pointers printed to the console or buffers to be
4145 compared. However, if this command-line option is
4153 nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
4156 to be effective. This is useful on platforms where the
4158 correctly or when doing power measurements to evaluate
4177 the range to maintain the timekeeping. Any CPUs
4185 noinitrd [RAM] Tells the kernel not to load any configured
4188 nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4190 [Deprecated - use intremap=off]
4196 noirqdebug [X86-32] Disables the code which attempts to detect and
4206 no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page
4209 no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4211 nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC.
4213 nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer.
4215 nomce [X86-32] Disable Machine Check Exception
4217 nomfgpt [X86-32] Disable Multi-Function General Purpose
4223 not load if they could possibly displace the pre-
4226 perform display-mode changes or accelerated rendering.
4232 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
4239 nopcid [X86-64,EARLY] Disable the PCID cpu feature.
4244 nopti [X86-64,EARLY]
4245 Equivalent to pti=off
4248 Disables the PV optimizations forcing the guest to run
4254 which allow the hypervisor to 'idle' the guest on lock
4257 norandmaps Don't use address space randomization. Equivalent to
4260 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4266 no-scroll [VGA] Disables scrollback.
4267 This is required for the Braillex ib80-piezo Braille
4270 nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4280 nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
4284 Equivalent to smt=1.
4290 nosoftlockup [KNL] Disable the soft-lockup detector.
4296 nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4309 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4316 timer IRQ sources, i.e., the IO-APIC timer. This can
4321 [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4324 Disable device dump. Device dump allows drivers to
4325 append dump data to vmcore so you can collect driver
4334 no-vmw-sched-clock
4339 soft-lockup and NMI watchdog (hard-lockup).
4343 nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode.
4350 and restore using xsave. The kernel will fallback to
4351 enabling legacy floating-point and sse state.
4354 register states. The kernel will fall back to use
4355 xsave to save the states. By using this parameter,
4362 form of xsave area. The kernel will fall back to use
4363 xsaveopt and xrstor to save and restore the states
4369 could support. nr_cpus=n : n >= 1 limits the kernel to
4373 n. So during boot up some boot time memory for per-cpu
4374 variables need be pre-allocated for later physical cpu
4377 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4401 soft-reserved memory partitioning.
4410 See Documentation/admin-guide/sysctl/vm.rst for details.
4413 See Documentation/core-api/debugging-via-ohci1394.rst for more
4425 For example, to override I2C bus2:
4428 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4432 boundary - index of last SLC block on Flex-OneNAND.
4434 lock - Configure if Flex-OneNAND boundary should be locked.
4439 Always panic on oopses. Default is to just kill the
4443 Useful together with panic=30 to trigger a reboot.
4446 [KNL] Boolean flag to control whether the page allocator
4448 used to enable/disable page randomization. The state of
4453 page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
4459 page_poison= [KNL,EARLY] Boot-time parameter changing the state of
4481 that will cause the kernel to panic when add_taint() is
4483 The optional switch "nousertaint" can be utilized to
4484 prevent userspace forced crashes by writing to sysctl
4487 See Documentation/admin-guide/tainted-kernels.rst for
4489 to compose the bitmask to assign to panic_on_taint.
4491 panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump
4506 Use this option carefully, maybe worth to setup a
4510 connected to, default is 0.
4518 Use 'auto' to force the driver to use any
4519 IRQ/DMA settings detected (the default is to
4525 (to avoid using a FIFO even if it is detected).
4531 Configure VIA parallel port to operate in
4534 up parallel port mode and sets it to spp.
4540 Set to non-zero to probe primary and secondary ISA
4546 Set to non-zero if a chip is present that snoops speed
4551 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4557 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4563 IORDY enable mask. Set individual bits to allow IORDY
4567 correspond to the primary legacy channel, the secondary
4575 Set to 1, 2, or 3 for Opti 82c611A on the primary
4581 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4588 bits to allow the use of the respective PIO modes.
4594 Set to non-zero to probe tertiary and further ISA
4601 options up to 6 legacy ports are supported: 0x1f0,
4604 corresponding bits in the mask to 1. Bit 0 is for
4610 Set to non-zero to probe QDI controllers. By default
4611 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4615 Set to non-zero to probe Winbond controllers. Use
4617 value given is the I/O port to use (typically 0x1b0).
4618 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4623 Supported PIO mode mask. Set individual bits to allow
4630 the specified number of seconds. This is to be used if
4647 firmware changes, or due to changes caused
4650 taken to be zero. Optionally, a path
4651 to a device through multiple device/function
4662 bios [X86-32] force use of PCI BIOS, don't access
4664 has a non-standard PCI host bridge.
4665 nobios [X86-32] disallow use of PCI BIOS, only direct
4671 data in IO port 0xCFC, both 32-bit).
4673 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4674 the function, IO port 0xCFA, also 8-bit, sets
4676 through ports 0xC000-0xCFFF).
4680 enabled, this kernel boot option can be used to
4683 root domains (aka PCI segments, in ACPI-speak).
4687 properly configured MMIO access to PCI
4690 enabled, this kernel boot option can be used to
4691 disable the use of MSI interrupts system-wide.
4693 Safety option to keep boot IRQs enabled. This
4695 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4696 primary IO-APIC for bridges that cannot disable
4700 boot IRQ equivalent of an IRQ that connects to
4703 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4704 routing table. These calls are known to be buggy
4707 way to get the interrupt routing table. Try
4708 this option if the kernel is unable to allocate
4711 rom [X86] Assign address space to expansion ROMs.
4715 norom [X86] Do not assign address space to
4718 nobar [X86] Do not assign address space to the
4720 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4721 assigned automatically to PCI devices. You can
4727 F0000h-100000h range.
4729 useful if the kernel is unable to find your
4730 secondary buses and you want to tell it
4732 assign-busses [X86] Always assign all PCI bus
4745 is enabled by default. If you need to use this,
4748 If you need to use this, please report a bug.
4749 use_e820 [X86] Use E820 reservations to exclude parts of
4752 If you need to use this, please report a bug to
4753 <linux-pci@vger.kernel.org>.
4756 hardware. If you need to use this, please report
4757 a bug to <linux-pci@vger.kernel.org>.
4762 skip_isa_align [X86] do not align io start addr, so can
4769 bfsort Sort PCI devices into breadth-first order.
4770 This sorting is done to get a device
4772 nobfsort Don't sort PCI devices into breadth-first order.
4774 tuning and use the BIOS-configured MPS defaults.
4775 pcie_bus_safe Set every device's MPS to the largest value
4777 pcie_bus_perf Set device MPS to the largest allowable MPS
4779 Read Request Size) to the largest supported
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
4787 that hot-added devices will work.
4797 Specifies alignment and device to reassign
4798 aligned memory resources. How to
4802 A PCI-PCI bridge can be specified if resource
4803 windows need to be expanded.
4804 To specify the alignment for several
4808 for 4096-byte alignment.
4810 end-to-end CRC checking). Only effective if
4834 if allocations done by BIOS are too small to
4841 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4846 big_root_window Try to add a big 64bit memory window to the PCIe
4848 can resize a BAR to allow access to all VRAM.
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
4886 ACS to enable P2P Request Redirect, disable
4888 Validation unchanged from whatever power-up
4889 or firmware set it to.
4899 to disable PCIe TLP Processing Hints support
4900 system-wide.
4906 force Enable ASPM even on devices that claim not to support it.
4911 even if the platform doesn't give the OS permission to
4913 also tries to use these services.
4914 dpc-native Use native PCIe service for DPC only. May
4931 Keep all power-domains already enabled by bootloader on,
4942 Select which percpu first chunk allocator to use.
4949 pirq= [SMP,APIC] Manual mp-table setup
4950 See Documentation/arch/x86/i386/IO-APIC.rst.
4954 See also Documentation/admin-guide/parport.rst.
4963 PMU counters by setting MMCR0 to 0 (the FC bit is
4964 cleared). If a number is given, then MMCR1 is set to
4973 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4982 { on | off | curr | res | no-curr | no-res }
5000 Up to 8 (IP_VS_APP_MAX_PORTS) ports
5012 function to NULL. On Idle the CPU just reduces
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
5033 lazy - Scheduler controlled. Similar to full but instead
5035 one HZ tick time to yield itself before the
5037 task returns to user space.
5039 print-fatal-signals=
5045 coredump - etc.
5047 If you hit the warning due to signal overflow,
5048 you might want to try "ulimit -i unlimited".
5060 or lockdep-detected issues (only if lock debug is on).
5061 With an exception to setups with low baudrate on
5063 in order to provide more debug information.
5068 Allows storing messages from non-panic CPUs into
5070 flushed to consoles by the panic-CPU on
5071 a best-effort basis.
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
5082 printk.time= Show timing data prefixed to each printk message line
5087 Traditionally /proc/pid/mem allows memory permissions to be
5088 overridden without restrictions. This option may be set to
5090 - 'always': traditional behavior always allows mem overrides.
5091 - 'ptrace': only allow mem overrides for active ptracers.
5092 - 'never': never allow mem overrides.
5096 Limit processor to maximum C-state
5100 Ignore the _CST method to determine C-states,
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
5125 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
5130 Try to reset the device after so many bad packets
5138 pstore.backend= Specify the name of the pstore backend to use
5140 pti= [X86-64] Control Page Table Isolation of user and
5145 on - unconditionally enable
5146 off - unconditionally disable
5147 auto - kernel detects whether your CPU model is
5148 vulnerable to issues that PTI mitigates
5150 Not specifying this option is equivalent to pti=auto.
5153 [KNL] Number of legacy pty's. Overwrites compiled-in
5165 See Documentation/admin-guide/md.rst.
5168 See Documentation/admin-guide/blockdev/ramdisk.rst.
5170 ramdisk_start= [RAM] RAM disk image start address
5174 random number generator (if available) to
5179 passed by the bootloader (if available) to
5187 cross-syscall address exposures. This is only
5193 ras=option[,option,...] [KNL] RAS-specific options
5199 rcu_nocbs[=cpu-list]
5204 enable the no-callback CPU mode, which prevents
5207 callbacks will instead be offloaded to "rcuox/N"
5209 "p" for RCU-preempt, "s" for RCU-sched, and "g"
5213 and real-time workloads. It can also improve
5217 list of CPUs is set to no-callback mode from boot.
5220 arguments are omitted, no CPU will be set to
5221 no-callback mode from boot but the mode may be
5232 This improves the real-time response for the
5233 offloaded CPUs by relieving them of the need to
5236 periodically wake up to do the polling.
5239 Set maximum number of finished RCU callbacks to
5243 Do only a one-line RCU CPU stall warning when
5244 there is an ongoing too-long CSD-lock wait.
5247 Request a call to rcu_barrier(). This is
5250 If triggered before the RCU grace-period machinery
5256 purposes, to verify correct tree setup.
5259 Set the number of jiffies to delay each step of
5260 RCU grace-period cleanup.
5263 Set the number of jiffies to delay each step of
5264 RCU grace-period initialization.
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
5273 Set delay from grace-period initialization to
5274 first attempt to force quiescent states.
5279 Set delay between subsequent attempts to force
5286 soliciting quiescent-state help from
5293 rcutree.jiffies_to_sched_qs. Any attempt to set
5298 Set the SCHED_FIFO priority of the RCU per-CPU
5301 and for the RCU grace-period kthreads (rcu_bh,
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).
5311 On callback-offloaded (rcu_nocbs) CPUs,
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.
5319 a single jiffy, RCU pre-queues the callbacks into
5320 the ->nocb_bypass queue. The definition of "too
5324 On callback-offloaded (rcu_nocbs) CPUs, avoid
5327 Defaults to zero. Large values will be capped
5329 to the nearest value representable by jiffies.
5337 batch limiting is re-enabled.
5341 RCU's force-quiescent-state scan will aggressively
5342 enlist help from cond_resched() and sched IPIs to
5344 Set to less than zero to make this be set based
5345 on rcutree.qhimark at boot time and to zero to
5349 Set the page-cache refill delay (in milliseconds)
5350 in response to low-memory conditions. The range
5354 Set the shift-right count to use to compute
5355 the callback-invocation batch limit bl from
5360 order to allow the CPU to do other work.
5362 Please note that this callback-invocation batch
5363 limit applies only to non-offloaded callback
5372 cache-to-cache transfer latencies.
5375 Change the number of CPUs assigned to each
5378 and for NUMA systems with large remote-access
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
5392 each group, which defaults to the square root
5394 the wakeup overhead on the global grace-period
5396 each group's NOCB grace-period kthread.
5399 Cause the grace-period kthread to get an extra
5401 it should at force-quiescent-state time.
5407 callbacks to the specified number of nanoseconds.
5409 every 32 callbacks in order to limit the pain
5414 this specifies an rcu_read_unlock()-time delay
5415 in microseconds. This defaults to zero.
5418 of RCU-protected pointers after the relevant
5422 Commandeer a sysrq key to dump out Tree RCU's
5427 If set to zero, move all RCU_SOFTIRQ processing to
5428 per-CPU rcuc kthreads. Defaults to a non-zero
5430 Specify rcutree.use_softirq=0 to use rcuc kthreads.
5434 to zero.
5437 To save power, batch RCU callbacks and flush after
5448 How to enable it:
5457 grace-period primitives such as call_rcu().
5463 corresponding flavor of rcu_barrier() to allow
5464 previously posted callbacks to drain.
5468 grace-period primitives.
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
5483 Defaults to 1.
5486 Set to measure performance of kfree_rcu() flooding.
5489 Test the double-argument variant of kfree_rcu().
5491 rcuscale.kfree_rcu_test_single, both the single-
5492 and double-argument variants are tested.
5495 Test the single-argument variant of kfree_rcu().
5497 rcuscale.kfree_rcu_test_double, both the single-
5498 and double-argument variants are tested.
5512 does not affect the data-collection interval,
5517 Set number of RCU readers. The value -1 selects
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
5531 Specify the RCU implementation to test.
5535 complete. This is useful for hands-off automated
5542 Write-side holdoff between grace periods,
5547 Additional write-side holdoff between grace
5564 Specifies the number of kthreads to be used
5565 for RCU grace-period forward-progress testing
5567 Defaults to 1 kthread, values less than zero or
5569 of CPUs to be used.
5572 Specify the fraction of a CPU-stall-warning
5573 period to do tight-loop forward-progress testing.
5576 Number of seconds to wait between successive
5577 forward-progress tests.
5581 need_resched() during tight-loop forward-progress
5585 Use conditional/asynchronous update-side
5586 normal-grace-period primitives, if available.
5589 Use conditional/asynchronous update-side
5590 expedited-grace-period primitives, if available.
5593 Use conditional/asynchronous update-side
5594 normal-grace-period primitives that also take
5599 Use conditional/asynchronous update-side
5600 expedited-grace-period primitives that also take
5609 be randomly selected to nanosecond granularity up
5610 to this wait interval. Defaults to 16 jiffies,
5619 interval will be randomly selected to nanosecond
5620 granularity up to this wait interval. Defaults to
5624 Use expedited update-side primitives, if available.
5627 Use normal (non-expedited) asynchronous
5628 update-side primitives, if available.
5631 Use polled update-side normal-grace-period
5635 Use polled update-side expedited-grace-period
5639 Use polled update-side normal-grace-period
5644 Use polled update-side expedited-grace-period
5653 be randomly selected to nanosecond granularity up
5654 to this wait interval. Defaults to 16 jiffies,
5663 interval will be randomly selected to nanosecond
5664 granularity up to this wait interval. Defaults to
5668 Use normal (non-expedited) synchronous
5669 update-side primitives, if available. If all
5673 they are all non-zero.
5678 flavors take kindly to this sort of thing.
5681 Leak an RCU-protected pointer out of the reader.
5683 intended to test the ability of things like
5684 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5696 Set number of RCU callback-offload togglers.
5701 callback-offload toggling attempts.
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.
5711 Enable debug-object double-call_rcu() testing.
5714 Set time (s) after boot for CPU-hotplug testing.
5717 Set time (jiffies) between CPU-hotplug operations,
5718 or zero to disable CPU-hotplug testing.
5722 by a high-priority FIFO real-time task. Set to
5723 zero (the default) to disable. The CPUs to
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
5737 The number of times in a given read-then-exit
5738 episode that a set of read-then-exit kthreads
5743 read-then-exit testing episodes.
5746 A bit mask indicating which readers to use.
5748 are entered from low-order bit up, and are
5750 0x1 bit is normal readers, 0x2 NMI-safe readers,
5751 and 0x4 light-weight readers.
5754 Set task-shuffle interval (s). Shuffling tasks
5755 allows some CPUs to go into dyntick-idle mode
5760 is useful for hands-off automated testing.
5763 Duration of CPU stall (s) to test RCU CPU stall
5764 warnings, zero to disable.
5768 in warnings from preemptible RCU in addition to
5769 any other stall-related activity. Note that
5772 cause the CPU to pass through a quiescent state.
5775 in scheduling-while-atomic splats.
5781 Time to wait (s) after boot before inducing stall.
5788 Number of times to repeat the stall sequence,
5794 grace-period kthread to test RCU CPU stall
5795 warnings, zero to disable. If both stall_cpu
5803 Time (s) to stutter testing, for example, specifying
5804 five seconds causes the test to run for five seconds,
5806 ability to transition abruptly to and from idle.
5817 Holdoff time (s) from start of test to the start
5818 of RCU priority-boost testing. Defaults to zero,
5825 Test RCU's dyntick-idle handling. See also the
5829 Specify the RCU implementation to test.
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).
5880 Use expedited grace-period primitives, for
5884 real-time latency, and degrade energy efficiency.
5888 Use only normal grace-period primitives,
5891 real-time latency, CPU utilization, and
5892 energy efficiency, but can expose users to
5893 increased grace-period latency. This parameter
5900 only normal grace-period primitives. No effect
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.
5913 the RCU Tasks flavors to collapse back to using
5916 set to the default value of -1.
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
5923 when rcupdate.rcu_task_enqueue_lim is set to
5924 the default value of -1.
5927 Set the number of callback queues to use for the
5929 of -1 allows this to be automatically (and
5937 number avoids disturbing real-time workloads,
5942 cancel laziness on that CPU. Use -1 to disable
5944 doing so increases the danger of OOM due to
5950 of the problem for those not patient enough to
5952 only printed prior to the stall-warning message
5954 less than or equal to zero. Defaults to ten
5962 to one through ten, inclusive. It defaults to
5972 than or equal to zero. Defaults to ten minutes.
6000 force - Override the decision by the kernel to hide the
6010 E.g. to turn on cmt and turn off mba use:
6020 (prefix with 'panic_' to set mode for panic
6025 to be used for rebooting.
6039 There are some built-in platform specific "quirks"
6040 - you may see: "reboot: <name> series board detected.
6044 built-in quirk table, and use the generic default
6053 Don't stop other CPUs on reboot. This can make reboot
6060 Use a write to the PCI config space register 0xcf9 to
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
6083 Number of data elements to use for the forms of
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
6097 Set number of readers. The default value of -1
6106 Set the read-side critical-section duration,
6110 Specify the read-protection implementation to test.
6114 test. This defaults to 1 (shut it down) when
6115 refscale is built into the kernel and to 0 (leave
6136 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6138 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
6142 is assumed to be I/O ports; otherwise it is memory.
6147 other subsystems can use to access it. This is typically
6149 line will try to reserve the same physical memory on
6150 soft reboots. Note, it is not guaranteed to be the same
6156 Any subsystem using this feature must add a way to verify
6161 The format is size:align:label for example, to request
6166 reservetop= [X86-32,EARLY]
6171 reset_devices [KNL] Force drivers to reset the underlying device
6183 See Documentation/power/swsusp-and-swap-files.rst
6185 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
6188 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
6199 AMD-based UNRET and IBPB mitigations alone do not stop
6201 sibling threads. For that reason, STIBP is used on pro-
6205 off - no mitigation
6206 auto - automatically select a migitation
6207 auto,nosmt - automatically select a mitigation,
6211 ibpb - On AMD, mitigate short speculation
6216 ibpb,nosmt - Like "ibpb" above but will disable SMT
6220 unret - Force enable untrained return thunks,
6221 only effective on AMD f15h-f17h based
6223 unret,nosmt - Like unret, but will disable SMT when STIBP
6228 time according to the CPU.
6230 Not specifying this option is equivalent to retbleed=auto.
6250 falling back to detecting extension support by parsing
6255 ro [KNL] Mount root device read-only on boot
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
6267 debug-uart get routed to the D+ and D- pins of the usb
6273 block/early-lookup.c for details.
6278 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
6285 rootwait [KNL] Wait (indefinitely) for root device to show up.
6289 rootwait= [KNL] Maximum time (in seconds) to wait for root device
6290 to show up before attempting to mount the root
6295 Memory area to be used by remote processor image,
6298 rw [KNL] Mount root device read-write on boot
6307 reuse, which is faster. Deprecated, equivalent to
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()
6357 up to the chosen limit in seconds. Zero (the
6359 that requesting even small non-zero numbers of
6364 Number of kthreads to spawn to invoke the
6366 The default of -1 specifies a number of kthreads
6367 equal to the number of CPUs.
6370 Number seconds to wait after the start of the
6371 test before initiating CPU-hotplug operations.
6374 Number seconds to wait between successive
6375 CPU-hotplug operations. Specifying zero (which
6376 is the default) disables CPU-hotplug operations.
6379 The number of seconds following the start of the
6380 test after which to shut down the system. The
6382 Non-zero values are useful for automated tests.
6386 current test statistics to the console. A value
6390 The number of jiffies to wait between each change
6391 to the set of CPUs under test.
6395 preempt_disable() to disable CPU hotplug
6403 The probability weighting to use for the
6405 "wait" parameter. A value of -1 selects the
6406 default if all other weights are -1. However,
6408 value of -1 will instead select a weight of zero.
6411 The probability weighting to use for the
6413 non-zero "wait" parameter. See weight_single.
6416 The probability weighting to use for the
6424 The probability weighting to use for the
6426 non-zero "wait" parameter. See weight_single
6430 The probability weighting to use for the
6436 The probability weighting to use for the
6438 non-zero "wait" parameter. See weight_single
6445 skew_tick= [KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
6449 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6450 1 -- enable.
6454 security= [SECURITY] Choose a legacy "major" security module to
6461 0 -- disable.
6462 1 -- enable.
6465 serialnumber [BUGS=X86-32]
6467 sev=option[,option...] [X86-64]
6473 Do not enable SEV-SNP (applies to host/hypervisor
6475 in memory accesses when users do not want to run
6476 SEV-SNP guests.
6484 to set it to "all" by meaning -- no limit here.
6491 Enabling slab_debug allows one to determine the
6501 A high setting may cause OOMs due to memory
6513 increase the slab order up to slab_max_order to
6514 generate a sufficiently large slab able to contain
6517 and the less frequently locks need to be acquired.
6523 lower or equal to slab_max_order. For more information see
6529 necessary if there is some reason to distinguish
6530 allocs to different slabs, especially in hardened
6534 most of the exposure of a heap attack to a single
6544 policies to be applied at the folio level when
6559 for a CPU to release the CSD lock. This is
6562 of time. Defaults to 5,000 milliseconds, and
6565 using the csdlock_debug- kernel parameter.
6570 system. By default, let CSD-lock acquisition
6572 for this value provides a 5-minute timeout.
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:
6586 (logical CPUs) to use per physical CPU on systems
6588 be capped to the actual hardware limit.
6590 Default: -1 (no limit)
6593 [KNL] Should the soft-lockup detector generate panics.
6596 A value of 1 instructs the soft-lockup detector
6597 to panic the machine when a soft-lockup occurs. It is
6600 respective build-time switch to that functionality.
6603 [KNL] Should the soft-lockup detector generate
6608 See Documentation/admin-guide/laptops/sonypi.rst
6615 on - (default) Enable the HW or SW mitigation as
6618 vmexit - On systems which don't have the HW mitigation
6621 protected from VM-originated BHI attacks, but
6622 may still be vulnerable to syscall attacks.
6623 off - Disable the mitigation.
6630 on - unconditionally enable, implies
6632 off - unconditionally disable, implies
6634 auto - kernel detects whether your CPU model is
6638 mitigation method at run time according to the
6644 against user space to user space task attacks.
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
6662 Not specifying this option is equivalent to
6670 on - Unconditionally enable mitigations. Is
6673 off - Unconditionally disable mitigations. Is
6676 prctl - Indirect branch speculation is enabled,
6682 - Like "prctl" above, but only STIBP is
6688 - Same as "prctl" above, but all seccomp
6693 - Like "seccomp" above, but only STIBP is
6698 auto - Kernel selects the mitigation depending on
6703 Not specifying this option is equivalent to
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
6714 ibpb-vmexit - Issue IBPB only on VMEXIT
6715 (cloud-specific mitigation)
6721 Certain CPUs are vulnerable to an exploit against a
6724 to the same memory location may not be observed by
6727 be detected prior to instruction retirement at the
6732 example to read memory to which the attacker does not
6740 on - Unconditionally disable Speculative Store Bypass
6741 off - Unconditionally enable Speculative Store Bypass
6742 auto - Kernel detects whether the CPU model contains an
6748 prctl - Control Speculative Store Bypass per thread
6752 seccomp - Same as "prctl" above, but all seccomp threads
6760 on,auto - On Power8 and Power9 insert a store-forwarding
6764 off - No action.
6766 Not specifying this option is equivalent to
6778 off - not enabled
6780 warn - the kernel will emit rate-limited warnings
6788 fatal - the kernel will send SIGBUS to applications
6793 ratelimit:N -
6794 Set system wide rate limit to N bus locks
6813 Certain CPUs are vulnerable to an MDS-like
6819 the RDRAND and RDSEED instructions to become
6827 performance impact to RDRAND and RDSEED
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
6840 srcu_struct structure will be converted to big
6845 2: When rcutorture decides to.
6851 instead of the compile-time CONFIG_NR_CPUS.
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.
6867 expediting. Set to zero to disable automatic
6871 Specifies the number of no-delay instances
6878 Specifies the per-grace-period phase, number of
6879 non-sleeping polls of readers. Beyond this limit,
6885 Specifies number of microseconds of non-sleeping
6886 delay between each non-sleeping poll of readers.
6889 Specifies the number of update-side contention
6892 structure to big form. Note that the value of
6894 set for contention-based conversions to occur.
6899 On CPUs that are vulnerable to the Speculative
6904 force-on: Unconditionally enable mitigation for
6906 force-off: Unconditionally disable mitigation for
6910 to allow userspace to register its
6916 to (for stacks growing down) resp. after (for stacks
6921 Setting this to true through kernel command line will
6924 to false.
6929 stacktrace_filter=[function-list]
6931 will trace at boot up. function-list is a comma-separated
6939 Set the STI (builtin display/keyboard on the HP-PARISC
6941 as the initial boot-console.
6956 be used to filter out binaries which have
6961 page table to increase the rate of hash page table
6966 them frequently to increase the rate of SLB faults
6975 An administrator who wishes to reserve some of these
6977 kernel's sunrpc client considers to be privileged
6978 using these two parameters to set the minimum and
6989 Control how the NFS server code allocates CPUs to
7001 to global on non-NUMA machines)
7007 RPC calls that can be sent from the client to a
7008 server. Increasing these values may allow you to
7014 Sets the number of seconds to remain in a suspend test
7026 <int> -- Number of I/O TLB slabs
7027 <int> -- Second integer after comma. Number of swiotlb
7029 to a power of 2.
7030 force -- force using of bounce buffers even if they
7032 noforce -- Never use bounce buffers (for debugging)
7038 process, as if the value was written to the respective
7047 Ignore sysrq setting - this boot parameter will
7054 ram pages. This is used to specify the TCP metrics
7055 cache size. See Documentation/networking/ip-sysctl.rst
7062 Specify "mem" (for Suspend-to-RAM) or "standby" (for
7065 the optional capability to repeat N number of times.
7067 wakeup-capable RTC alarm.
7073 -1: disable all active trip points in all thermal zones
7077 -1: disable all critical trip points in all thermal zones
7084 -1: disable all passive trip points
7085 <degrees C>: override all passive trip points to this
7090 <deci-seconds>: poll all this frequency
7094 Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7097 to anonymous transparent hugepages.
7099 See Documentation/admin-guide/mm/transhuge.rst for more
7107 Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7113 See Documentation/admin-guide/mm/transhuge.rst for more
7125 Prevent the CPU-hotplug component of torturing
7129 Dump the ftrace buffer at torture-test shutdown,
7133 with rotating-rust storage.
7138 disables verbose-printk() sleeping.
7141 Duration of each verbose-printk() sleep in jiffies.
7156 as a workaround for some chips which fail to
7163 for the FIFO interface. By default it is set to false
7166 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7169 Have the tracepoints sent to printk as well as the
7175 To turn off having tracepoints sent to printk,
7181 to stop the printing of events to console at
7186 Having tracepoints sent to printk() and activating high
7188 the system to live lock.
7192 on the console. It may be useful to only include the
7196 This command line option will stop the printing of events
7197 to console at the late_initcall_sync() time frame.
7204 local - Use the per CPU time stamp counter
7208 global - Event time stamps are synchronize across
7211 counter - Simple counting of events (1, 2, ..)
7212 note, some counts may be skipped due to the
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
7220 boot - Use ktime_get_boot_fast_ns() for time stamps.
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
7230 To enable modules, use :mod: keyword:
7238 trace_instance=[instance-info]
7258 Flags can be added to the instance to modify its behavior when it is
7263 traceoff - Have the tracing instance tracing disabled after it is created.
7264 traceprintk - Have trace_printk() write into this trace instance
7285 and place the ring buffer in this memory. Note that due to KASLR, the
7294 it is recommend to disable tracing so that events from a previous boot do not
7301 is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION
7311 trace_options=[option-list]
7313 The option-list is a comma delimited list of options
7315 to echo the option name into
7319 For example, to enable stacktrace option (to dump the
7320 stack trace of each event), add to the command line:
7327 trace_trigger=[trigger-list]
7347 [FTRACE] Sometimes tracing is used to debug issues
7349 limited amount of storage, it may be prudent to
7356 [FTRACE] enable this option to disable tracing when a
7362 the WARNING dump is called, which prevents the trace to
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
7378 Can be used to control the hugepage allocation policy for
7380 See Documentation/admin-guide/mm/transhuge.rst
7385 Can be used to control the default hugepage allocation policy
7387 See Documentation/admin-guide/mm/transhuge.rst
7395 - "tpm"
7396 - "tee"
7397 - "caam"
7398 - "dcp"
7399 If not specified then it defaults to iterating through
7406 The RNG used to generate key material for trusted keys.
7408 - "kernel"
7409 - the same value as trusted.source: "tpm" or "tee"
7410 - "default"
7412 the RNG's choice is left to each individual trust source.
7415 This is intended to be used in combination with
7420 This is intended to be used in combination with
7430 as the stability checks done at bootup. Used to enable
7431 high-resolution timer mode on older hardware, and in
7433 [x86] noirqtime: Do not use TSC to do irq accounting.
7434 Used to run time disable IRQ_TIME_ACCOUNTING on any
7449 which to check other HW timers (HPET or PM timer), but
7467 on - Enable TSX on the system. Although there are
7469 TSX has been known to be an accelerator for
7470 several previous speculation-related CVEs, and
7474 off - Disable TSX on the system. (Note that this
7476 not vulnerable to MDS, i.e., have
7482 auto - Disable TSX if X86_BUG_TAA is present,
7485 Not specifying this option is equivalent to tsx=off.
7487 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7493 Similar to Micro-architectural Data Sampling (MDS)
7495 Synchronization Extensions (TSX) are vulnerable to an
7497 information to a disclosure gadget under certain
7501 data can be used in a cache side channel attack, to
7502 access data to which the attacker does not have direct
7508 full - Enable TAA mitigation on vulnerable CPUs
7511 full,nosmt - Enable TAA mitigation and disable SMT on
7514 vulnerable to cross-thread TAA attacks.
7515 off - Unconditionally disable TAA mitigation
7517 On MDS-affected machines, tsx_async_abort=off can be
7519 are mitigated with the same mechanism so in order to disable
7520 this mitigation, you need to specify mds=off too.
7522 Not specifying this option is equivalent to
7529 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7535 See also Documentation/input/devices/joystick-parport.rst
7537 udbg-immortal [PPC] When debugging early kernel crashes that
7543 Set number of hash buckets for UDP/UDP-Lite connections
7545 uhci-hcd.ignore_oc=
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.
7557 is useful for testing alternative code paths and to skip
7565 is useful for testing alternative code paths and to skip
7572 unwind_debug [X86-64,EARLY]
7580 (default -1 = authorized (same as 1),
7582 if device connected to internal port)
7586 for newly-detected USB devices (default 2). This
7589 to a negative value won't be autosuspended at all.
7592 [USB] Set to log all usbfs traffic (default 0 = off).
7595 [USB] Maximum number of bytes to snoop in each URB
7599 [USB] Set to cycle leds on hubs (default 0 = off).
7602 [USB] Start with the old device initialization
7614 [USB] Specifies timeout for the initial 64-byte
7621 [USB] A list of quirk entries to augment the built-in
7624 VendorID:ProductID:Flags. The IDs are 4-digit hex
7626 will change the built-in quirk; setting it if it is
7631 a 255-byte read);
7635 Set-Interface requests);
7644 talking to these interfaces);
7652 microframe = 125 microseconds) to be
7654 (bInterval-1).
7672 to be disconnected before suspend to
7680 request from 5000 ms to 500 ms);
7684 [USBHID] The interval which mice are to be polled at.
7687 [USBHID] The interval which joysticks are to be polled at.
7690 [USBHID] The interval which keyboards are to be polled at.
7692 usb-storage.delay_use=
7699 usb-storage.quirks=
7700 [UMS] A list of quirks entries to supplement or
7701 override the built-in unusual_devs list. List
7704 and Product ID values (4-digit hex numbers) and
7706 to a common usb-storage quirk flag as follows:
7724 i = IGNORE_DEVICE (don't bind to this
7729 l = NOT_LOCKABLE (don't try to lock and
7746 u = IGNORE_UAS (don't bind to the uas driver);
7748 medium is write-protected).
7757 1 - undefined instruction events
7758 2 - system calls
7759 4 - invalid data aborts
7760 8 - SIGSEGV faults
7761 16 - SIGBUS faults
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
7782 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7789 If set to 1, on receiving an ACPI notify event
7791 level and then send out the event to user space through
7792 the allocated input device. If set to 0, video driver
7805 <irq> := interrupt number (as passed to
7813 vga= [BOOT,X86-32] Select a particular video mode
7815 Documentation/admin-guide/svga.rst.
7818 passed to the kernel using a special protocol.
7824 interface is meant to allow for selectively
7830 - Disable all of the above options
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
7835 It can also be used to decrease the size and leave more room
7854 vsyscall= [X86-64,EARLY]
7855 Controls the behavior of vsyscalls (i.e. calls to
7857 code). Most statically-linked binaries and older
7871 them quite hard to use for exploits but
7881 see vga-softcursor.rst. Default: 2 = underline.
7886 This is a 16-member array composed of values
7887 ranging from 0-255.
7892 This is a 16-member array composed of values
7893 ranging from 0-255.
7898 This is a 16-member array composed of values
7899 ranging from 0-255.
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
7910 Format=<-1|0|1>
7911 Set system-wide default for whether a cursor
7912 is shown on new VTs. Default is -1,
7917 vt.italic= [VT] Default color for italic text; 0-15.
7920 vt.underline= [VT] Default color for underlined text; 0-15.
7924 see Documentation/watchdog/watchdog-parameters.rst
7925 or other driver-specific files in the
7932 threshold is set to twice the value. A value of 0
7937 [KNL,SMP] Specify to constrain one or some CPUs
7938 to use in unbound workqueues.
7939 Format: <cpu-list>
7945 warn stall conditions and dump internal state to
7949 it can be updated at runtime by writing to the
7955 stall to trigger panic.
7960 Per-cpu work items which run for longer than this
7962 and excluded from concurrency management to prevent
7963 them from noticeably delaying other per-cpu work
7974 intensive_threshold_us repeatedly. In order to prevent
7975 spurious warnings, start printing only after a work
7981 Per-cpu workqueues are generally preferred because
7982 they show better performance thanks to cache
7983 locality; unfortunately, per-cpu workqueues tend to
7986 Enabling this makes the per-cpu workqueues which
7987 were observed to contribute significantly to power
7988 consumption unbound, leading to measurably lower
7996 Select the default affinity scope to use for unbound
8000 Documentation/core-api/workqueue.rst.
8002 This can be changed after boot by writing to the
8008 Workqueue used to implicitly guarantee that work
8013 forces round-robin CPU selection to flush out
8021 on - Enable writecombine, use WUC for ioremap_wc()
8022 off - Disable writecombine, use SUC for ioremap_wc()
8024 x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of
8028 xen_512gb_limit [KNL,X86-64,XEN]
8030 to use only up to 512 GB of RAM. The reason to do so is
8032 save/restore/migration must be enabled to handle larger
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
8045 never -- do not unplug even if version check succeeds
8059 Select whether to always use non-faulting (safe) MSR
8064 Disables the PV optimizations forcing the HVM guest to
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
8079 xen_timer_slop= [X86-64,XEN,EARLY]
8087 The time (in seconds) to wait before giving up to boot
8088 in case initial ballooning fails to free enough memory.
8094 How long to delay EOI handling in case of event
8099 should start to delay EOI handling. Default is 2.
8102 Boolean parameter to disable using fifo event handling
8104 preferred over the 2-level event handling, as it is
8115 allows the fallback firmware mode to be used:
8117 off Fallback to firmware control of XIVE interrupt
8121 xive.store-eoi=off [PPC]
8124 is active. This option allows the XIVE driver to use
8127 xhci-hcd.quirks [USB,KNL]
8135 Passing only "xmon" is equivalent to "xmon=early".