Lines Matching +full:can +full:- +full:disable
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
37 If set to vendor, prefer vendor-specific driver
42 If set to none, disable the ACPI backlight interface.
51 Disable AML predefined validation mechanism
52 This mechanism can repair the evaluation result to make
69 Documentation/firmware-guide/acpi/debug.rst for more information about
90 can interfere with legacy drivers.
122 by unsupported hardware/firmware features can result in
125 This facility can be used to prevent such uncontrolled
127 Format: <byte> or <bitmap-list>
130 Disable auto-serialization of AML methods
133 auto-serialization feature.
137 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
141 Disable installation of static SSDTs at early boot time
151 Ignore the ACPI-based watchdog interface (WDAT) and let
172 acpi_osi=! # disable all built-in OS vendor
174 acpi_osi=!! # enable all built-in OS vendor
176 acpi_osi= # disable all strings
178 'acpi_osi=!' can be used in combination with single or
180 vendor string(s). Note that such command can only
191 can make '_OSI("Windows 2000")' TRUE.
195 exist in the ACPI namespace. NOTE that such command can
200 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
203 'acpi_osi=!*' can be used in combination with single or
205 string(s). Note that such command can affect the
215 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
217 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
236 For broken nForce2 BIOS resulting in XT-PIC timer.
245 as soon as the kernel's real-mode entry point is called.
278 off: disable AGP support
283 See Documentation/sound/alsa-configuration.rst
290 align_va_addr= [X86-64]
295 CPU-intensive style benchmark, and it can vary highly in
298 32: only for 32-bit processes
299 64: only for 64-bit processes
300 on: enable for both 32- and 64-bit processes
301 off: disable for both 32- and 64-bit processes
311 Allow execve() of 32-bit applications and setting of the
313 subset of the CPUs support 32-bit EL0. When this
314 parameter is present, the set of CPUs supporting 32-bit
316 and hot-unplug operations may be restricted.
318 See Documentation/arch/arm64/asymmetric-32bit.rst for more
321 amd_iommu= [HW,X86-64]
324 fullflush - Deprecated, equivalent to iommu.strict=1
325 off - do not initialize any AMD IOMMU found in
327 force_isolation - Force device isolation for all
332 force_enable - Force enable the IOMMU on platforms known
335 pgtbl_v1 - Use v1 page table for DMA-API (Default).
336 pgtbl_v2 - Use v2 page table for DMA-API.
337 irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
339 amd_iommu_dump= [HW,X86-64]
345 amd_iommu_intr= [HW,X86-64]
348 legacy - Use legacy interrupt remapping mode.
349 vapic - Use virtual APIC mode, which allows IOMMU
351 This mode requires kvm-amd.avic=1.
355 disable
388 Power management functions (SPARCstation-4/5 + deriv.)
390 Disable APC CPU standby support. SPARCstation-Fox does
391 not play well with APC CPU idle - disable it if you have
398 when initialising the APIC and IO-APIC components.
399 For X86-32, this can also be used to specify an APIC
419 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
422 0 -- disable.
423 1 -- enable.
426 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
429 arm64.nobti [ARM64] Unconditionally disable Branch Target
432 arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
435 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
438 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
441 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
444 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
468 audit= [KNL] Enable the audit sub-system
470 0 | off - kernel audit is disabled and can not be
472 unset - kernel audit is initialized but disabled and
474 1 | on - kernel audit is initialized and partially
485 behavior is to disable the BAU (i.e. bau=0).
487 0 - Disable the BAU.
488 1 - Enable the BAU.
489 unset - Disable the BAU.
509 Disable BERT OS support on buggy BIOSes.
512 Disable BGRT to avoid flickering OEM logo.
516 See Documentation/block/cmdline-partition.rst
526 Extended command line options can be added to an initrd
529 See Documentation/admin-guide/bootconfig.rst
534 bttv.pll= See Documentation/admin-guide/media/bttv.rst
543 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
562 inclusive. See arch/mips/include/asm/pgtable-bits.h
569 cgroup_disable= [KNL] Disable a particular controller or optional feature
570 Format: {name of the controller(s) or feature(s) to disable}
572 - foo isn't auto-mounted if you mount all cgroups in
574 - foo isn't visible as an individually mountable
576 - if foo is an optional feature then the feature is
580 cut the overhead, others just disable the usage. So
582 Specifying "pressure" disables per-cgroup pressure
585 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
594 cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
600 nosocket -- Disable socket memory accounting.
601 nokmem -- Disable kernel memory accounting.
602 nobpf -- Disable BPF memory accounting.
607 0 -- check protection applied by kernel (includes
609 1 -- check protection requested by application.
611 Value can be changed at runtime via
619 Disable CPUID feature X for the kernel. See
621 numbers X. Note the Linux-specific bits are not necessarily
622 stable over kernel options, but the vendor-specific
624 X can also be a string as appearing in the flags: line
633 Also note the kernel might malfunction if you disable
642 force such clocks to be always-on nor does it reserve
646 information, see Documentation/driver-api/clk.rst.
648 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
665 [X86-32] pit,hpet,tsc;
672 [X86-64] hpet,tsc
677 Enable/disable the eventstream feature of the ARM
678 architected timer so that code using WFE-based polling
679 loops can be debugged more effectively on production
698 clocksource-wdtest.holdoff= [KNL]
704 cma=nn[MG]@[start[MG][-end[MG]]]
715 Sets the size of kernel per-numa memory area for
717 per-numa CMA altogether. And If this option is not
719 With per-numa CMA enabled, DMA users on node nid will
746 com20020= [HW,NET] ARCnet - COM20020 chipset
750 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
754 ARCnet - COM90xx chipset (memory-mapped buffers)
783 See Documentation/admin-guide/serial-console.rst for more
793 Start an early, polled-mode console on the 8250/16550
796 MMIO inter-register address stride is either 8-bit
797 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
801 the h/w is not re-initialized.
807 Use to disable console output, i.e., to have kernel
828 syscall, or to executing "dmesg -S --raw" or to reading
843 Enable/disable the CPU sampling based debugging.
844 0: default value, disable debugging
852 disable the cpuidle sub-system
858 disable the cpufreq sub-system
866 [X86] Delay for N microsec between assert and de-assert
872 [SMP] Enable/disable parallel bringup of secondary CPUs
878 Run kdump after running panic-notifiers and dumping
882 because some panic notifiers can make the crashed
886 [KNL] Using kexec, Linux can switch to a 'crash kernel'
891 [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
894 See Documentation/admin-guide/kdump/kdump.rst for further details.
899 start-[end] where start and end are both
901 Documentation/admin-guide/kdump/kdump.rst for an example.
904 [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
912 [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
918 for 32-bit devices won't run out. Kernel would try to allocate
921 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
922 --> arm64: 128MiB
923 --> riscv: 128MiB
924 --> loongarch: 128MiB
927 0: to disable low allocation.
932 [KNL] Disable crypto self-tests
940 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
955 See also Documentation/input/devices/joystick-parport.rst
968 [KNL] verbose locking self-tests
971 self-tests.
973 (no extra messages), setting it to -1 (all bits set)
974 will print _a_lot_ more information - normally only
1009 Format: { on, no-mount, off }
1011 no-mount:
1012 Filesystem is not registered but kernel clients can
1013 access APIs and a crashkernel can be used to read
1016 get a -EPERM as result when trying to register files
1020 Default value is set in build-time with a kernel configuration.
1032 Documentation/admin-guide/mm/hugetlbpage.rst.
1046 delayacct [KNL] Enable per-task delay accounting
1090 can be useful when debugging issues that require an SLB
1093 disable= [IPV6]
1097 Disable RADIX MMU mode on POWER9
1100 Disable TLBIE instruction. Currently does not work
1108 disable BSP to wake up multiple CPUs without
1113 Disable Dynamic DMA Window support. Use this
1131 Disable PIN 1 of APIC timer
1132 Can be useful to work around chipset bugs.
1134 dis_ucode_ldr [X86] Disable the microcode loader.
1141 entries for DMA-API debugging code. One entry is
1142 required per DMA-API allocation. Use this if the
1143 DMA-API debugging code disables itself because the
1147 With this option the DMA-API debugging driver
1148 filter feature can be enabled at boot time. Just
1150 The filter can be disabled or changed to another
1165 Generic built-in EDID data sets are used, if one of
1170 available in Documentation/admin-guide/edid.rst. An EDID
1182 Control how the dt_cpu_ftrs device-tree binding is
1192 what data is available or for reverse-engineering.
1197 Documentation/admin-guide/dynamic-debug-howto.rst
1208 determined by stdout-path property in device tree's
1213 Start an early, polled-mode console on a Cadence
1224 Start an early, polled-mode console on the 8250/16550
1226 MMIO inter-register address stride is either 8-bit
1227 (mmio) or 32-bit (mmio32 or mmio32be).
1237 Start an early, polled-mode console on a pl011 serial
1241 the driver will use only 32-bit accessors to read/write
1250 Start an early, polled-mode console on a meson serial
1256 Start an early, polled-mode console on an msm serial
1262 Start an early, polled-mode console on an msm serial
1268 Start an early, polled-mode console on a serial port
1274 Start an early, polled-mode console on a serial port
1280 Use RISC-V SBI (Supervisor Binary Interface) for early
1298 Start an early, polled-mode console on a lantiq serial
1312 Start an early, polled-mode, output-only console on the
1317 Start an early, polled-mode console on the
1323 Start an early, polled-mode console on a Qualcomm
1331 coherent non-x86 systems that use system memory for
1357 Append ",keep" to not disable it when the real console
1360 Only one of vga, serial, or usb debug port can
1368 You can find the port for a given device in
1378 The xen option can only be used in Xen domains.
1380 The sclp output can only be used on s390.
1382 The bios output can only be used on SuperH.
1392 off: disable H/W event reporting through EDAC.
1404 disable_early_pci_dma: disable the busmaster bit on all
1406 nochunk: disable reading files in "chunks" in the EFI
1407 boot stub, as chunking can cause problems with some
1409 noruntime : disable EFI runtime services support
1413 claim. Specify efi=nosoftreserve to disable this
1421 Using this parameter you can use more than 50% of
1434 attribute is added to range 0x100000000-0x180000000 and
1435 0x10a0000000-0x1120000000.
1439 range 0x240000000-0x43fffffff.
1441 Using this parameter you can do debugging of EFI memmap
1442 related features. For example, you can do debugging of
1451 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1464 but can only be used if the backing tty is available
1468 elanfreq= [X86-32]
1476 See Documentation/admin-guide/kdump/kdump.rst for details.
1485 Can be useful to work around chipset bugs
1492 0 -- permissive (log only, no denials).
1493 1 -- enforcing (deny and log).
1495 Value can be changed at runtime via
1499 Disable Error Record Serialization Table (ERST)
1525 See also Documentation/fault-injection/.
1529 See Documentation/admin-guide/sysctl/net.rst for
1533 See Documentation/admin-guide/blockdev/floppy.rst.
1535 forcepae [X86-32]
1537 Many Pentium M systems disable PAE but may have a
1549 ftrace ring buffer that can be read at:
1555 Optionally, the snapshot can also be defined for a tracing
1571 ftrace_filter=[function-list]
1573 tracer at boot up. function-list is a comma-separated
1574 list of functions. This list can be changed at run
1578 ftrace_notrace=[function-list]
1580 function-list. This list can be changed at run time
1584 ftrace_graph_filter=[function-list]
1587 function-list is a comma-separated list of functions
1588 that can be changed at run time by the
1591 ftrace_graph_notrace=[function-list]
1593 function-list. This list is a comma-separated list of
1594 functions that can be changed at run time by the
1600 can be changed at run time by the max_graph_depth file
1613 off -- Don't create device links from firmware info.
1614 permissive -- Create device links from firmware info
1617 on -- Create device links from firmware info and use it
1619 rpm -- Like "on", but also use to order runtime PM.
1632 strict -- Default. Continue waiting on consumers to
1634 timeout -- Give up waiting on consumers and call
1644 See also Documentation/input/devices/joystick-parport.rst
1648 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1661 The mitigation may have a performance impact but can be
1665 force: Disable AVX to mitigate systems without
1670 off: Disable GDS mitigation.
1672 gcov_persist= [GCOV] When non-zero (default), profiling data for
1682 gpio-mockup.gpio_mockup_ranges
1685 gpio-mockup.gpio_mockup_named_lines
1717 against bounds-checking flaws in the kernel's
1720 off Disable hardened usercopy checks.
1723 [KNL] Should the hard-lockup detector generate
1729 for 64-bit NUMA, off otherwise.
1732 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1738 Disable Hardware Error Source Table (HEST) support;
1739 corresponding firmware-first mode error processing
1746 no Disable hibernation and resume.
1749 during restoration read-only).
1756 highres= [KNL] Enable/disable high resolution timer mode.
1775 hpet= [X86-32,HPET] option to control HPET usage
1776 Format: { enable (default) | disable | force |
1778 disable: disable HPET and use PIT instead
1792 number of pages to allocate per-node can be specified.
1793 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1801 hugepagesz=X hugepages=Y can be specified once for
1804 Documentation/admin-guide/mm/hugetlbpage.rst.
1809 of a CMA area per node can be specified.
1815 boot-time allocation of gigantic hugepages is skipped.
1826 off: disable HVO
1843 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1844 option. The value selected by this boot parameter can
1849 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1866 (disabled by default, and as a pre-condition
1868 i8042.direct [HW] Put keyboard port into non-translated mode
1869 i8042.dumbkbd [HW] Pretend that controller can only read data from
1874 i8042.noloop [HW] Disable the AUX Loopback command while probing
1882 suspend-to-ram transitions, only during s2r
1906 -1 -- never invert brightness
1907 0 -- machine default
1908 1 -- force brightness inversion
1910 ia32_emulation= [X86-64]
1912 When true, allows loading 32-bit programs and executing 32-bit
1922 Poll forces a polling idle loop that can slightly
1928 idle=nomwait: Disable mwait for CPU C-states
1956 legacy only accept legacy-NaN binaries, if supported
1958 2008 only accept 2008-NaN binaries, if supported
1967 'relaxed' straps the emulator for both legacy-NaN and
1968 2008-NaN, whereas 'strict' enables legacy-NaN only on
1977 Ignore loglevel setting - this will print /all/
1985 print warning at first misuse. Can be changed via
2044 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2045 "ima-sigv2" }
2046 Default: "ima-ng"
2058 different crypto accelerators. This option can be used
2066 different crypto accelerators. This option can be used
2078 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2079 initcall functions. Useful for debugging built-in
2089 but as a debugging aid, one can get the
2114 default (disallow access to all but pkey 0). Can
2124 0 -- basic integrity auditing messages. (Default)
2125 1 -- additional integrity auditing messages.
2131 Disable intel iommu driver.
2153 could harm performance of some high-throughput
2162 1 to 9 specify maximum depth of C-state.
2165 disable
2171 algorithms for p-state selection. There are two
2172 P-state selection algorithms provided by
2175 on whether or not the hardware managed P-states
2182 used along with the hardware-managed P-states (HWP)
2186 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2187 instead of acpi-cpufreq may disable platform features, such
2189 P-States information being indicated to OSPM and therefore
2192 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2205 Allow per-logical-CPU P-State performance control limits using
2208 intremap= [X86-64, Intel-IOMMU]
2210 off disable Interrupt Remapping
2211 nosid disable Source ID checking
2213 BIOS x2APIC opt-out request will be ignored
2214 nopost disable Interrupt Posting
2216 iomem= Disable strict checking of access to MMIO memory
2233 Disable IOMMU bypass, using IOMMU for PCI devices.
2237 0 - Try to allocate a 32-bit DMA address first, before
2239 1 - Allocate directly from the full usable range,
2241 greater than 32-bit addressing.
2245 0 - Lazy mode.
2251 1 - Strict mode.
2254 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2256 legacy driver-specific options takes precedence.
2261 0 - Use IOMMU translation for DMA.
2262 1 - Bypass the IOMMU for DMA.
2263 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2265 io7= [HW] IO7 for Marvel-based Alpha systems
2280 See Documentation/admin-guide/nfs/nfsroot.rst.
2304 Enables support for pseudo-NMIs in the kernel. This
2323 [Deprecated - use cpusets instead]
2324 Format: [flag-list,]<cpu-list>
2330 Disable the tick when a single task runs.
2347 advised to use cpusets instead to disable scheduler load
2349 It offers a much more flexible interface where CPUs can
2352 You can move a process onto or off an "isolated" CPU via
2355 "number of CPUs in system - 1".
2381 The format of <cpu-list> is described above.
2385 ivrs_ioapic [HW,X86-64]
2386 Provide an override to the IOAPIC-ID<->DEVICE-ID
2388 By default, PCI segment is 0, and can be omitted.
2390 For example, to map IOAPIC-ID decimal 10 to
2396 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2399 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2403 ivrs_hpet [HW,X86-64]
2404 Provide an override to the HPET-ID<->DEVICE-ID
2406 By default, PCI segment is 0, and can be omitted.
2408 For example, to map HPET-ID decimal 10 to
2414 * To map HPET-ID decimal 0 to PCI device 00:14.0
2417 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2421 ivrs_acpihid [HW,X86-64]
2422 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2424 By default, PCI segment is 0, and can be omitted.
2426 For example, to map UART-HID:UID AMD0020:0 to
2432 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2435 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2456 kernelcore= [KNL,X86,IA-64,PPC]
2459 the kernel for non-movable allocations. The requested
2469 subsystem. Note that allocations like PTEs-from-HighMem
2477 for non-movable allocations and remaining memory is used
2488 gdb or control-c on the dbgp connection. When
2489 not using this parameter you use sysrq-g to break into
2494 or a supported polling keyboard driver (non-usb).
2504 characters and can work in polling mode, you can use
2521 Configure the RouterBoard 532 series on-chip
2524 kmemleak= [KNL] Boot-time kmemleak enable/disable
2530 kprobe_event=[probe-list]
2532 The probe-list is a semicolon delimited list of probe
2551 default value can be overridden via
2562 execution by eliminating the write-protection faults
2607 back to huge pages. If the value is a non-zero N, KVM will
2612 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2615 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2616 a.k.a. Two-Dimensional Page Tables. Default is 1
2617 (enabled). Disable by KVM if hardware lacks support
2620 kvm-arm.mode=
2623 none: Forcefully disable KVM.
2625 nvhe: Standard nVHE-based mode, without support for
2628 protected: nVHE-based mode with support for guests whose
2631 nested: VHE-based mode with support for nested
2636 mode to "protected" will disable kexec and hibernation
2640 kvm-arm.vgic_v3_group0_trap=
2641 [KVM,ARM] Trap guest accesses to GICv3 group-0
2644 kvm-arm.vgic_v3_group1_trap=
2645 [KVM,ARM] Trap guest accesses to GICv3 group-1
2648 kvm-arm.vgic_v3_common_trap=
2652 kvm-arm.vgic_v4_enable=
2664 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2665 a.k.a. Two-Dimensional Page Tables. Default is 1
2666 (enabled). Disable by KVM if hardware lacks support
2669 kvm-intel.emulate_invalid_guest_state=
2671 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2677 kvm-intel.flexpriority=
2679 (TPR shadow). Default is 1 (enabled). Disable by KVM if
2682 kvm-intel.nested=
2686 kvm-intel.unrestricted_guest=
2689 is 1 (enabled). Disable by KVM if EPT is disabled or
2692 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2693 CVE-2018-3620.
2699 VMEXIT and VMENTER can leak host memory.
2704 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2706 (enabled). Disable by KVM if hardware lacks support
2713 internal buffers which can forward information to a
2717 forwarded data can be used in a cache side channel
2724 on - enable the interface for the mitigation
2789 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2795 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2799 value for LAPIC timer one-shot implementation. Default
2807 libata.dma=0 Disable all PATA and SATA DMA
2822 libata.force= [LIBATA] Force configurations. The format is a comma-
2834 first fan-out link behind PMP device. It does not
2841 The following configurations can be forced.
2848 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2855 * rstonce: only attempt one reset during hot-unplug
2858 * [no]dbdelay: Enable or disable the extra 200ms delay
2864 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2866 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2868 * [no]trim: Enable or disable (unqueued) TRIM.
2881 * [no]dmalog: Enable or disable the use of the
2884 * [no]iddevlog: Enable or disable access to the
2887 * [no]logdir: Enable or disable access to the general
2898 * [no]lpm: Enable or disable link power management.
2903 * [no]fua: Disable or enable FUA (Force Unit Access)
2908 * disable: Disable this device.
2950 Specify the number of self-propagating call_rcu()
2958 occasional long-duration lock hold time. Defaults
2959 to 100 milliseconds. Select 0 to disable.
2964 (MAX_NESTED_LOCKS). Specify zero to disable.
2969 Set the number of locking read-acquisition kthreads.
2974 Set the number of locking write-acquisition kthreads.
2977 Set time (s) after boot for CPU-hotplug testing.
2980 Set time (s) between CPU-hotplug operations, or
2981 zero to disable CPU-hotplug testing.
2984 Do periodic testing of real-time lock priority
2985 boosting. Select 0 to disable, 1 to boost
2989 non-real-time spinlocks, due to their disabling
2990 of preemption. Note that non-realtime mutexes
2991 disable boosting.
3003 Set task-shuffle interval (jiffies). Shuffling
3004 tasks allows some CPUs to go into dyntick-idle
3009 is useful for hands-off automated testing.
3028 Run the write-side locktorture kthreads at
3029 sched_set_fifo() real-time priority.
3035 console loglevel will be printed to the console. It can
3046 7 (KERN_DEBUG) debug-level messages
3056 logo.nologo [FB] Disables display of the built-in Linux logo.
3064 lp=auto printer driver. 'lp=reset' (which can be
3074 an IEEE 1284-compliant printer is attached; if
3080 time-consuming boot-time autodetection (up to 250 ms per
3101 machvec= [IA-64] Force the use of a particular machine-vector
3107 Example: machtype=lemote-yeeloong-2f-7inch
3109 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
3115 bootup you can bring up the other plugged cpu by executing
3122 (loop.max_loop) unconditionally pre-created at init time. The default
3125 devices can be requested on-demand with the
3126 /dev/loop-control interface.
3128 mce [X86-32] Machine Check Exception
3130 mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3133 See Documentation/admin-guide/md.rst.
3140 Control mitigation for the Micro-architectural Data
3144 internal buffers which can forward information to a
3148 forwarded data can be used in a cache side channel
3155 full - Enable MDS mitigation on vulnerable CPUs
3156 full,nosmt - Enable MDS mitigation and disable
3158 off - Unconditionally disable MDS mitigation
3160 On TAA-affected machines, mds=off can be prevented by
3162 mitigated with the same mechanism so in order to disable
3169 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3183 [ARC,MICROBLAZE] - the limit applies only to low memory,
3186 [ARM64] - only limits memory covered by the linear
3199 [ARM,MIPS] - override the memory layout reported by
3203 Multiple different regions can be specified with
3206 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3213 per-device physically contiguous DMA buffers.
3221 See Documentation/admin-guide/mm/memory-hotplug.rst.
3225 Such memmap=exactmap lines can be constructed based on
3234 Multiple different regions can be specified,
3246 Example: Exclude memory from 0x18690000-0x1869ffff
3260 memmap=<size>%<offset>-<oldtype>+<newtype>
3262 from <oldtype> to <newtype>. If "-<oldtype>" is left
3277 repeatable BIOS-originated corruption always
3278 affects the same memory, you can use memmap=
3306 The state of the flag can be read in
3313 default : 0 <disable>
3321 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3329 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3330 for details on when memory encryption can be activated.
3333 s2idle - Suspend-To-Idle
3334 shallow - Power-On Suspend or equivalent (if supported)
3335 deep - Suspend-To-RAM or equivalent (if supported)
3336 See Documentation/admin-guide/pm/sleep-states.rst.
3338 mfgpt_irq= [IA-32] Specify the IRQ to use for the
3339 Multi-Function General Purpose Timers on AMD Geode
3342 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3345 problem by letting the user disable the workaround.
3351 Enable or disable the microcode minimal revision
3354 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3361 0 - The attached screen is the 3.5" TFT
3362 1 - The attached screen is the 7" TFT
3363 2 - The VGA Shield is attached (1024x768)
3367 b - Enable backlight. The TFT backlight pin will be
3371 c - Enable the s3c camera interface.
3372 t - Reserved for enabling touchscreen support. The
3374 kernel as of 2.6.30, a preliminary port can be found
3376 https://repo.or.cz/w/linux-2.6/mini2440.git
3381 arch-independent options, each of which is an
3382 aggregation of existing arch-specific options.
3385 Disable all optional CPU mitigations. This
3405 ssbd=force-off [ARM64]
3418 have other ways of avoiding SMT-based attacks.
3453 full - Enable mitigation on vulnerable CPUs
3455 full,nosmt - Enable mitigation and disable SMT on
3458 off - Unconditionally disable mitigation
3461 mmio_stale_data=off can be prevented by an active
3464 disable this mitigation, you need to specify
3471 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3476 probe on this module. Otherwise, enable/disable
3482 by default. To enable/disable async probing for a
3501 module_blacklist= [KNL] Do not load a comma-separated list of
3515 movablecore= [KNL,X86,IA-64,PPC]
3526 movable_node [KNL] Boot-time switch to make hotplugable memory
3533 Format: <name>,<region-number>,<size>,<offset>
3536 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3544 See arch/arm/mach-s3c/mach-jive.c
3580 something different and driver-specific.
3591 0 to disable accounting
3620 [NFS] enable 64-bit inode numbers.
3621 If zero, the NFS client will fake up a 32-bit inode
3623 of returning the full 64-bit number.
3624 The default is to return 64-bit inode numbers.
3641 that the client can send to the NFSv4.1 server.
3651 disabling idmapping, which can make migration from
3659 [NFS4] Specify an additional fixed unique ident-
3660 ification string that NFSv4 clients can insert into
3690 driver. A non-zero value sets the minimum interval
3695 server-to-server copies for which this server is
3707 server-to-server copy, knfsd temporarily mounts
3714 See Documentation/admin-guide/nfs/nfsroot.rst.
3716 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3717 See Documentation/admin-guide/nfs/nfsroot.rst.
3720 See Documentation/admin-guide/nfs/nfsroot.rst.
3724 NMI stack-backtrace request.
3733 0 - turn hardlockup detector in nmi_watchdog off
3734 1 - turn hardlockup detector in nmi_watchdog on
3738 To disable both hard and soft lockup detectors,
3743 These settings can be accessed at runtime via
3746 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3750 no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces
3751 kernel to use 3-level paging instead.
3753 no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces
3754 kernel to use 4-level paging instead.
3757 caches in the slab allocator. Saves per-node memory,
3768 noautogroup Disable scheduler automatic task group creation.
3774 Disable suspending of consoles during suspend and
3776 messages can reach various consoles while the rest
3788 [KNL] Disable object debugging
3790 nodsp [SH] Disable hardware DSP at boot time.
3792 noefi Disable EFI runtime services support.
3794 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3796 noexec [IA-64]
3798 noexec32 [X86-64]
3799 This affects only 32-bit executables.
3800 noexec32=on: enable non-executable mappings (default)
3802 noexec32=off: disable non-executable mappings
3809 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3813 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3815 legacy floating-point registers on task switch.
3817 nohalt [IA-64] Tells the kernel not to use the power saving
3819 power-consumption. On the positive side, it reduces
3820 interrupt wake-up latency, which may improve performance
3822 real-time systems.
3831 difficult since unequal pointers can no longer be
3832 compared. However, if this command-line option is
3838 nohibernate [HIBERNATION] Disable hibernation and resume.
3849 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3851 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
3853 nohz= [KNL] Boottime enable/disable dynamic ticks
3873 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3875 [Deprecated - use intremap=off]
3877 nointroute [IA-64]
3879 noinvpcid [X86] Disable the INVPCID cpu feature.
3883 noirqdebug [X86-32] Disables the code which attempts to detect and
3884 disable unhandled interrupt sources.
3888 nojitter [IA-64] Disables jitter checking for ITC timers.
3895 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3898 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3900 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3902 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3904 nomca [IA-64] Disable machine check abort handling
3906 nomce [X86-32] Disable Machine Check Exception
3908 nomfgpt [X86-32] Disable Multi-Function General Purpose
3911 nomodeset Disable kernel modesetting. Most systems' firmware
3914 not load if they could possibly displace the pre-
3917 perform display-mode changes or accelerated rendering.
3921 nomodule Disable module load
3923 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3927 nopat [X86] Disable PAT (page attribute table extension of
3930 nopcid [X86-64] Disable the PCID cpu feature.
3932 nopku [X86] Disable Memory Protection Keys CPU feature found
3935 nopti [X86-64]
3951 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
3957 nosbagart [IA-64]
3959 no-scroll [VGA] Disables scrollback.
3960 This is required for the Braillex ib80-piezo Braille
3963 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
3966 Disable SMAP (Supervisor Mode Access Prevention)
3970 Disable SMEP (Supervisor Mode Execution Prevention)
3974 and disable the IO APIC. legacy for "maxcpus=0".
3976 nosmt [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
3979 [KNL,X86,PPC] Disable symmetric multithreading (SMT).
3980 nosmt=force: Force disable SMT, cannot be undone
3983 nosoftlockup [KNL] Disable the soft-lockup detector.
3986 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
3988 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
3992 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
3996 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
4001 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV] Disable
4011 [PPC] Don't flush the L1-D cache after accessing user data.
4014 Disable device dump. Device dump allows drivers to
4015 append dump data to vmcore so you can collect driver
4016 specified debug info. Drivers can append the data
4019 device dump can help save memory but the driver debug
4024 no-vmw-sched-clock
4025 [X86,PV_OPS] Disable paravirtualized VMware scheduler
4028 nowatchdog [KNL] Disable both lockup detectors, i.e.
4029 soft-lockup and NMI watchdog (hard-lockup).
4033 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4041 enabling legacy floating-point and sse state.
4060 cycles, each HW thread of the CTOP can run
4067 nptcg= [IA-64] Override max number of concurrent global TLB
4075 runtime you can physically add extra cpu until it reaches
4076 n. So during boot up some boot time memory for per-cpu
4077 variables need be pre-allocated for later physical cpu
4082 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4085 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4087 Allowed values are enable and disable
4090 'node', 'default' can be specified
4091 This can be set from sysctl after boot.
4092 See Documentation/admin-guide/sysctl/vm.rst for details.
4095 See Documentation/core-api/debugging-via-ohci1394.rst for more
4110 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4114 boundary - index of last SLC block on Flex-OneNAND.
4116 lock - Configure if Flex-OneNAND boundary should be locked.
4130 running on a platform with a direct-mapped memory-side
4131 cache, and this parameter can be used to
4132 override/disable that behavior. The state of the flag
4133 can be read from sysfs at:
4136 page_owner= [KNL] Boot-time page_owner enabling option.
4139 we can turn it on.
4142 page_poison= [KNL] Boot-time parameter changing the state of
4165 The optional switch "nousertaint" can be utilized to
4169 See Documentation/admin-guide/tainted-kernels.rst for
4170 extra details on the taint flags that users can pick
4177 User can chose combination of the following bits:
4202 possible conflicts). You can specify the base
4221 Set to non-zero to probe primary and secondary ISA
4227 Set to non-zero if a chip is present that snoops speed
4275 Set to non-zero to probe tertiary and further ISA
4284 of individual ports can be disabled by setting the
4291 Set to non-zero to probe QDI controllers. By default
4296 Set to non-zero to probe Winbond controllers. Use
4333 addresses can be specified after the base
4343 bios [X86-32] force use of PCI BIOS, don't access
4345 has a non-standard PCI host bridge.
4346 nobios [X86-32] disallow use of PCI BIOS, only direct
4352 data in IO port 0xCFC, both 32-bit).
4354 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4355 the function, IO port 0xCFA, also 8-bit, sets
4357 through ports 0xC000-0xCFFF).
4361 enabled, this kernel boot option can be used to
4362 disable the use of PCIE advanced error reporting.
4363 nodomains [PCI] Disable support for multiple PCI
4364 root domains (aka PCI segments, in ACPI-speak).
4365 nommconf [X86] Disable use of MMCONFIG for PCI
4371 enabled, this kernel boot option can be used to
4372 disable the use of MSI interrupts system-wide.
4373 noioapicquirk [APIC] Disable all boot interrupt quirks.
4377 primary IO-APIC for bridges that cannot disable
4380 noioapicreroute [APIC] Disable workaround that uses the
4384 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4402 assigned automatically to PCI devices. You can
4408 F0000h-100000h range.
4409 lastbus=N [X86] Scan all buses thru bus #N. Can be
4413 assign-busses [X86] Always assign all PCI bus
4434 <linux-pci@vger.kernel.org>.
4438 a bug to <linux-pci@vger.kernel.org>.
4443 skip_isa_align [X86] do not align io start addr, so can
4450 bfsort Sort PCI devices into breadth-first order.
4453 nobfsort Don't sort PCI devices into breadth-first order.
4454 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4455 tuning and use the BIOS-configured MPS defaults.
4462 or bus can support) for best performance.
4465 configuration allows peer-to-peer DMA between
4468 that hot-added devices will work.
4483 A PCI-PCI bridge can be specified if resource
4489 for 4096-byte alignment.
4490 ecrc= Enable/disable PCIe ECRC (transaction layer
4491 end-to-end CRC checking). Only effective if
4514 realloc= Enable/disable reallocating PCI bridge resources
4522 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4529 can resize a BAR to allow access to all VRAM.
4547 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4549 off Disable ASPM.
4558 dpc-native Use native PCIe service for DPC only. May
4560 compat Disable native PCIe services (PME, AER, DPC, PCIe
4564 off Disable power management of all PCIe ports
4575 Keep all power-domains already enabled by bootloader on,
4580 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4592 pirq= [SMP,APIC] Manual mp-table setup
4593 See Documentation/arch/x86/i386/IO-APIC.rst.
4597 See also Documentation/admin-guide/parport.rst.
4616 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4625 { on | off | curr | res | no-curr | no-res }
4661 Disable Hardware Transactional Memory
4665 none - Limited to cond_resched() calls
4666 voluntary - Limited to cond_resched() and might_sleep() calls
4667 full - Any section that isn't explicitly preempt disabled
4668 can be preempted anytime.
4670 print-fatal-signals=
4676 coredump - etc.
4679 you might want to try "ulimit -i unlimited".
4686 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4690 Disable console loglevel raise on oops, panic
4691 or lockdep-detected issues (only if lock debug is on).
4700 on - unlimited logging to /dev/kmsg from userspace
4701 off - logging to /dev/kmsg disabled
4702 ratelimit - ratelimit the logging
4706 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4709 Limit processor to maximum C-state
4713 Ignore the _CST method to determine C-states,
4720 Param: "schedule" - profile schedule points.
4721 Param: "sleep" - profile D-state sleeping (millisecs).
4723 Param: "kvm" - profile VM exits.
4724 Param: <number> - step/bucket size as a power of 2 for
4734 psi= [KNL] Enable or disable pressure stall information
4753 pti= [X86-64] Control Page Table Isolation of user and
4758 on - unconditionally enable
4759 off - unconditionally disable
4760 auto - kernel detects whether your CPU model is
4766 [KNL] Number of legacy pty's. Overwrites compiled-in
4769 quiet [KNL] Disable most log messages
4774 Disable RADIX GTSE feature and use hcall for TLB
4778 See Documentation/admin-guide/md.rst.
4781 See Documentation/admin-guide/blockdev/ramdisk.rst.
4786 [KNL] Disable trusting the use of the CPU's
4791 [KNL] Disable trusting the use of the a seed
4796 [KNL] Enable or disable kernel stack offset
4800 cross-syscall address exposures. This is only
4803 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4806 ras=option[,option,...] [KNL] RAS-specific options
4809 Disable the Correctable Errors Collector,
4812 rcu_nocbs[=cpu-list]
4817 enable the no-callback CPU mode, which prevents
4822 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4825 the offloaded CPUs, which can be useful for HPC
4826 and real-time workloads. It can also improve
4830 list of CPUs is set to no-callback mode from boot.
4834 no-callback mode from boot but the mode may be
4845 This improves the real-time response for the
4857 throttled so that userspace tests can safely
4859 If triggered before the RCU grace-period machinery
4869 RCU grace-period cleanup.
4873 RCU grace-period initialization.
4877 RCU grace-period pre-initialization, that is,
4878 the propagation of recent CPU-hotplug changes up
4882 Set delay from grace-period initialization to
4895 soliciting quiescent-state help from
4907 Set the SCHED_FIFO priority of the RCU per-CPU
4910 and for the RCU grace-period kthreads (rcu_bh,
4912 set, valid values are 1-99 and the default is 1
4913 (the least-favored priority). Otherwise, when
4914 RCU_BOOST is not set, valid values are 0-99 and
4915 the default is zero (non-realtime operation).
4920 On callback-offloaded (rcu_nocbs) CPUs,
4923 use of the ->nocb_bypass list. However, in the
4924 common non-flooded case, RCU queues directly to
4925 the main ->cblist in order to avoid the extra
4926 overhead of the ->nocb_bypass list and its lock.
4928 a single jiffy, RCU pre-queues the callbacks into
4929 the ->nocb_bypass queue. The definition of "too
4938 batch limiting is re-enabled.
4942 RCU's force-quiescent-state scan will aggressively
4947 disable more aggressive help enlistment.
4950 Set the page-cache refill delay (in milliseconds)
4951 in response to low-memory conditions. The range
4955 Set the shift-right count to use to compute
4956 the callback-invocation batch limit bl from
4963 Please note that this callback-invocation batch
4964 limit applies only to non-offloaded callback
4970 Disable autobalancing of the rcu_node combining
4973 cache-to-cache transfer latencies.
4979 and for NUMA systems with large remote-access
4995 the wakeup overhead on the global grace-period
4997 each group's NOCB grace-period kthread.
5000 Cause the grace-period kthread to get an extra
5002 it should at force-quiescent-state time.
5015 this specifies an rcu_read_unlock()-time delay
5019 of RCU-protected pointers after the relevant
5029 per-CPU rcuc kthreads. Defaults to a non-zero
5033 But note that CONFIG_PREEMPT_RT=y kernels disable
5039 grace-period primitives such as call_rcu().
5050 grace-period primitives.
5053 Set test-start holdoff period. The purpose of
5071 Test the double-argument variant of kfree_rcu().
5073 rcuscale.kfree_rcu_test_single, both the single-
5074 and double-argument variants are tested.
5077 Test the single-argument variant of kfree_rcu().
5079 rcuscale.kfree_rcu_test_double, both the single-
5080 and double-argument variants are tested.
5094 does not affect the data-collection interval,
5099 Set number of RCU readers. The value -1 selects
5101 "n" less than -1 selects N-n+1, where N is again
5102 the number of CPUs. For example, -2 selects N
5103 (the number of CPUs), -3 selects N+1, and so on.
5104 A value of "n" less than or equal to -N selects
5117 complete. This is useful for hands-off automated
5124 Write-side holdoff between grace periods,
5129 Additional write-side holdoff between grace
5147 for RCU grace-period forward-progress testing
5154 Specify the fraction of a CPU-stall-warning
5155 period to do tight-loop forward-progress testing.
5159 forward-progress tests.
5163 need_resched() during tight-loop forward-progress
5167 Use conditional/asynchronous update-side
5171 Use expedited update-side primitives, if available.
5174 Use normal (non-expedited) asynchronous
5175 update-side primitives, if available.
5178 Use normal (non-expedited) synchronous
5179 update-side primitives, if available. If all
5183 they are all non-zero.
5191 Leak an RCU-protected pointer out of the reader.
5192 This can of course result in splats, and is
5206 Set number of RCU callback-offload togglers.
5211 callback-offload toggling attempts.
5214 Set number of RCU readers. The value -1 selects
5215 N-1, where N is the number of CPUs. A value
5216 "n" less than -1 selects N-n-2, where N is again
5217 the number of CPUs. For example, -2 selects N
5218 (the number of CPUs), -3 selects N+1, and so on.
5221 Enable debug-object double-call_rcu() testing.
5224 Set time (s) after boot for CPU-hotplug testing.
5227 Set time (jiffies) between CPU-hotplug operations,
5228 or zero to disable CPU-hotplug testing.
5231 Set the number of read-then-exit kthreads used
5233 task-exit processing.
5236 The number of times in a given read-then-exit
5237 episode that a set of read-then-exit kthreads
5242 read-then-exit testing episodes.
5245 Set task-shuffle interval (s). Shuffling tasks
5246 allows some CPUs to go into dyntick-idle mode
5251 is useful for hands-off automated testing.
5255 warnings, zero to disable.
5260 any other stall-related activity. Note that
5266 in scheduling-while-atomic splats.
5275 Disable interrupts while stalling if set.
5279 grace-period kthread to test RCU CPU stall
5280 warnings, zero to disable. If both stall_cpu
5305 Test RCU's dyntick-idle handling. See also the
5360 Use expedited grace-period primitives, for
5363 but can increase CPU utilization, degrade
5364 real-time latency, and degrade energy efficiency.
5368 Use only normal grace-period primitives,
5371 real-time latency, CPU utilization, and
5372 energy efficiency, but can expose users to
5373 increased grace-period latency. This parameter
5380 only normal grace-period primitives. No effect
5386 post-boot attempt at an expedited RCU grace
5387 period to instead use normal non-expedited
5388 grace-period processing.
5396 set to the default value of -1.
5399 Set the minimum number of callback-queuing-time
5400 lock-contention events per jiffy required to
5401 cause the RCU Tasks flavors to switch to per-CPU
5404 the default value of -1.
5409 of -1 allows this to be automatically (and
5417 number avoids disturbing real-time workloads,
5422 cancel laziness on that CPU. Use -1 to disable
5432 only printed prior to the stall-warning message
5433 for a given grace period. Disable with a value
5451 warning messages. Disable with a value less
5460 of zero will disable batching. Batching is
5468 disable batching. Batching is always disabled
5476 disable batching. Batching is always disabled
5488 force - Override the decision by the kernel to hide the
5516 Set test-start holdoff period. The purpose of
5531 but the default has already reduced the per-pass
5536 Set number of readers. The default value of -1
5545 Set the read-side critical-section duration,
5549 Specify the read-protection implementation to test.
5575 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5583 reservetop= [X86-32]
5600 See Documentation/power/swsusp-and-swap-files.rst
5616 AMD-based UNRET and IBPB mitigations alone do not stop
5618 sibling threads. For that reason, STIBP is used on pro-
5622 off - no mitigation
5623 auto - automatically select a migitation
5624 auto,nosmt - automatically select a mitigation,
5628 ibpb - On AMD, mitigate short speculation
5633 ibpb,nosmt - Like "ibpb" above but will disable SMT
5637 unret - Force enable untrained return thunks,
5638 only effective on AMD f15h-f17h based
5640 unret,nosmt - Like unret, but will disable SMT when STIBP
5664 ring3mwait=disable
5665 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5675 ro [KNL] Mount root device read-only on boot
5678 on Mark read-only kernel memory as read-only (default).
5679 off Leave read-only kernel memory writable for debugging.
5680 full Mark read-only kernel memory and aliases as read-only
5686 debug-uart get routed to the D+ and D- pins of the usb
5692 block/early-lookup.c for details.
5693 Alternatively this can be "ram" for the legacy initial
5717 rw [KNL] Mount root device read-write on boot
5733 The default is 1 meaning that one can concurrently use
5736 once. With a value of 2 one can map all of memory twice
5746 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5747 Allowed values are enable and disable. This feature
5770 to 10 seconds for built-in smp_call_function()
5777 that requesting even small non-zero numbers of
5778 seconds can result in RCU CPU stall warnings,
5784 The default of -1 specifies a number of kthreads
5789 test before initiating CPU-hotplug operations.
5793 CPU-hotplug operations. Specifying zero (which
5794 is the default) disables CPU-hotplug operations.
5800 Non-zero values are useful for automated tests.
5813 preempt_disable() to disable CPU hotplug
5823 "wait" parameter. A value of -1 selects the
5824 default if all other weights are -1. However,
5826 value of -1 will instead select a weight of zero.
5831 non-zero "wait" parameter. See weight_single.
5838 this weighting can place serious IPI load
5844 non-zero "wait" parameter. See weight_single
5856 non-zero "wait" parameter. See weight_single
5863 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
5864 1 -- enable.
5872 selinux= [SELINUX] Disable or enable SELinux at boot time.
5875 0 -- disable.
5876 1 -- enable.
5879 serialnumber [BUGS=X86-32]
5881 sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
5889 to set it to "all" by meaning -- no limit here.
5895 simeth= [IA-64]
5905 Disable merging of slabs with similar size. May be
5909 layout control by attackers can usually be
5913 unchanged). Debug options disable merging on their
5926 slub_debug can create guard zones around objects and
5970 using the csdlock_debug- kernel parameter.
5975 system. By default, let CSD-lock acquisition
5977 for this value provides a 5-minute timeout.
5979 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
5980 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
5981 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
5982 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
5983 smsc-ircc2.ircc_irq= [HW] IRQ line
5984 smsc-ircc2.ircc_dma= [HW] DMA channel
5985 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
5995 Default: -1 (no limit)
5998 [KNL] Should the soft-lockup detector generate panics.
6001 A value of 1 instructs the soft-lockup detector
6002 to panic the machine when a soft-lockup occurs. It is
6005 respective build-time switch to that functionality.
6008 [KNL] Should the soft-lockup detector generate
6013 See Documentation/admin-guide/laptops/sonypi.rst
6020 on - unconditionally enable, implies
6022 off - unconditionally disable, implies
6024 auto - kernel detects whether your CPU model is
6036 Selecting 'off' will disable both the kernel and
6039 Specific mitigations can also be selected manually:
6041 retpoline - replace indirect branches
6042 retpoline,generic - Retpolines
6043 retpoline,lfence - LFENCE; indirect branch
6044 retpoline,amd - alias for retpoline,lfence
6045 eibrs - Enhanced/Auto IBRS
6046 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6047 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6048 ibrs - use IBRS to protect kernel
6058 on - Unconditionally enable mitigations. Is
6061 off - Unconditionally disable mitigations. Is
6064 prctl - Indirect branch speculation is enabled,
6065 but mitigation can be enabled via prctl
6070 - Like "prctl" above, but only STIBP is
6076 - Same as "prctl" above, but all seccomp
6081 - Like "seccomp" above, but only STIBP is
6086 auto - Kernel selects the mitigation depending on
6097 off - Disable mitigation
6098 microcode - Enable microcode mitigation only
6099 safe-ret - Enable sw-only safe RET mitigation (default)
6100 ibpb - Enable mitigation by issuing IBPB on
6102 ibpb-vmexit - Issue IBPB only on VMEXIT
6103 (cloud-specific mitigation)
6106 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6114 is that such stores are unlikely and that they can
6119 store can be used in a cache side channel attack, for
6128 on - Unconditionally disable Speculative Store Bypass
6129 off - Unconditionally enable Speculative Store Bypass
6130 auto - Kernel detects whether the CPU model contains an
6136 prctl - Control Speculative Store Bypass per thread
6140 seccomp - Same as "prctl" above, but all seccomp threads
6141 will disable SSB unless they explicitly opt out.
6148 on,auto - On Power8 and Power9 insert a store-forwarding
6152 off - No action.
6171 off - not enabled
6173 warn - the kernel will emit rate-limited warnings
6181 fatal - the kernel will send SIGBUS to applications
6186 ratelimit:N -
6206 Certain CPUs are vulnerable to an MDS-like
6207 exploit which can leak bits from the random
6211 microcode. However, the microcode fix can cause
6216 The microcode mitigation can be disabled with
6219 off: Disable mitigation and remove
6226 This kernel-boot parameter defaults to 128,
6227 but takes effect only when the low-order four
6244 instead of the compile-time CONFIG_NR_CPUS.
6248 grace-period sequence counter wrap for the
6249 srcu_data structure's ->srcu_gp_seq_needed field.
6260 expediting. Set to zero to disable automatic
6264 Specifies the number of no-delay instances
6271 Specifies the per-grace-period phase, number of
6272 non-sleeping polls of readers. Beyond this limit,
6278 Specifies number of microseconds of non-sleeping
6279 delay between each non-sleeping poll of readers.
6282 Specifies the number of update-side contention
6287 set for contention-based conversions to occur.
6290 Speculative Store Bypass Disable control
6297 force-on: Unconditionally enable mitigation for
6299 force-off: Unconditionally disable mitigation for
6315 disable the stack depot thereby saving the static memory
6322 stacktrace_filter=[function-list]
6324 will trace at boot up. function-list is a comma-separated
6325 list of functions. This list can be changed at run
6332 Set the STI (builtin display/keyboard on the HP-PARISC
6334 as the initial boot-console.
6346 Enable or disable strict sigaltstack size checks
6348 depends on the supported FPU features. This can
6394 to global on non-NUMA machines)
6400 RPC calls that can be sent from the client to a
6417 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6419 <int> -- Number of I/O TLB slabs
6420 <int> -- Second integer after comma. Number of swiotlb
6423 force -- force using of bounce buffers even if they
6425 noforce -- Never use bounce buffers (for debugging)
6440 Ignore sysrq setting - this boot parameter will
6448 cache size. See Documentation/networking/ip-sysctl.rst
6455 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6460 wakeup-capable RTC alarm.
6466 -1: disable all active trip points in all thermal zones
6470 -1: disable all critical trip points in all thermal zones
6474 1: disable ACPI thermal control
6477 -1: disable all passive trip points
6483 <deci-seconds>: poll all this frequency
6505 Prevent the CPU-hotplug component of torturing
6509 Dump the ftrace buffer at torture-test shutdown,
6510 even if there were no errors. This can be a
6513 with rotating-rust storage.
6518 disables verbose-printk() sleeping.
6521 Duration of each verbose-printk() sleep in jiffies.
6539 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
6553 The tp_printk_stop_on_boot (see below) can also be used
6560 frequency tracepoints such as irq or sched, can cause
6564 When tp_printk (above) is set, it can cause a lot of noise
6577 local - Use the per CPU time stamp counter
6581 global - Event time stamps are synchronize across
6584 counter - Simple counting of events (1, 2, ..)
6588 uptime - Use jiffies as the time stamp.
6589 perf - Use the same clock that perf uses.
6590 mono - Use ktime_get_mono_fast_ns() for time stamps.
6591 mono_raw - Use ktime_get_raw_fast_ns() for time
6593 boot - Use ktime_get_boot_fast_ns() for time stamps.
6597 trace_event=[event-list]
6599 to facilitate early boot debugging. The event-list is a
6600 comma-separated list of trace events to enable. See
6603 trace_instance=[instance-info]
6609 Events can be enabled at the time the instance is created
6623 trace_options=[option-list]
6624 [FTRACE] Enable or disable tracer options at boot.
6625 The option-list is a comma delimited list of options
6626 that can be enabled or disabled just as if you were
6639 trace_trigger=[trigger-list]
6659 [FTRACE] enable this option to disable tracing when a
6660 warning is hit. This turns off "tracing_on". Tracing can
6668 This option can also be set at run time via the sysctl
6674 Can be used to control the default behavior of the system
6676 See Documentation/admin-guide/mm/transhuge.rst
6684 - "tpm"
6685 - "tee"
6686 - "caam"
6695 Can be one of:
6696 - "kernel"
6697 - the same value as trusted.source: "tpm" or "tee"
6698 - "default"
6702 tsc= Disable clocksource stability checks for TSC.
6707 high-resolution timer mode on older hardware, and in
6710 Used to run time disable IRQ_TIME_ACCOUNTING on any
6712 can add overhead.
6716 [x86] nowatchdog: disable clocksource watchdog. Used
6728 can be overridden by a later tsc=nowatchdog. A console
6743 on - Enable TSX on the system. Although there are
6746 several previous speculation-related CVEs, and
6750 off - Disable TSX on the system. (Note that this
6758 auto - Disable TSX if X86_BUG_TAA is present,
6763 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6769 Similar to Micro-architectural Data Sampling (MDS)
6772 exploit against CPU internal buffers which can forward
6777 data can be used in a cache side channel attack, to
6784 full - Enable TAA mitigation on vulnerable CPUs
6787 full,nosmt - Enable TAA mitigation and disable SMT on
6790 vulnerable to cross-thread TAA attacks.
6791 off - Unconditionally disable TAA mitigation
6793 On MDS-affected machines, tsx_async_abort=off can be
6795 are mitigated with the same mechanism so in order to disable
6805 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6811 See also Documentation/input/devices/joystick-parport.rst
6813 udbg-immortal [PPC] When debugging early kernel crashes that
6819 Set number of hash buckets for UDP/UDP-Lite connections
6821 uhci-hcd.ignore_oc=
6823 Some badly-designed motherboards generate lots of
6832 unwind_debug [X86-64]
6833 Enable unwinder debug output. This can be
6840 (default -1 = authorized (same as 1),
6846 for newly-detected USB devices (default 2). This
6874 [USB] Specifies timeout for the initial 64-byte
6878 usbcore.nousb [USB] Disable the USB subsystem
6881 [USB] A list of quirk entries to augment the built-in
6884 VendorID:ProductID:Flags. The IDs are 4-digit hex
6886 will change the built-in quirk; setting it if it is
6891 a 255-byte read);
6892 b = USB_QUIRK_RESET_RESUME (device can't resume
6894 c = USB_QUIRK_NO_SET_INTF (device can't handle
6895 Set-Interface requests);
6896 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
6899 e = USB_QUIRK_RESET (device can't be reset
6903 bNumInterfaces count, and can't handle
6914 (bInterval-1).
6919 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
6925 k = USB_QUIRK_NO_LPM (device can't handle Link
6952 usb-storage.delay_use=
6956 usb-storage.quirks=
6958 override the built-in unusual_devs list. List
6961 and Product ID values (4-digit hex numbers) and
6963 to a common usb-storage quirk flag as follows:
7005 medium is write-protected).
7014 1 - undefined instruction events
7015 2 - system calls
7016 4 - invalid data aborts
7017 8 - SIGSEGV faults
7018 16 - SIGBUS faults
7032 vdso=0: disable VDSO mapping
7034 vdso32= [X86] Control the 32-bit vDSO
7035 vdso32=1: enable 32-bit VDSO
7036 vdso32=0 or vdso32=2: disable 32-bit VDSO
7046 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7048 vector= [IA-64,SMP]
7069 <size> := size (can use standard suffixes
7078 Can be used multiple times for multiple devices.
7080 vga= [BOOT,X86-32] Select a particular video mode
7082 Documentation/admin-guide/svga.rst.
7097 - Disable all of the above options
7100 size of <nn>. This can be used to increase the
7101 minimum size (128MB on x86). It can also be used to
7118 vsyscall= [X86-64]
7121 code). Most statically-linked binaries and older
7124 targets for exploits that can control RIP.
7145 see VGA-softcursor.txt. Default: 2 = underline.
7150 This is a 16-member array composed of values
7151 ranging from 0-255.
7156 This is a 16-member array composed of values
7157 ranging from 0-255.
7162 This is a 16-member array composed of values
7163 ranging from 0-255.
7168 Set system-wide default UTF-8 mode for all tty's.
7169 Default is 1, i.e. UTF-8 mode is enabled for all
7174 Format=<-1|0|1>
7175 Set system-wide default for whether a cursor
7176 is shown on new VTs. Default is -1,
7181 vt.italic= [VT] Default color for italic text; 0-15.
7184 vt.underline= [VT] Default color for underlined text; 0-15.
7188 see Documentation/watchdog/watchdog-parameters.rst
7189 or other driver-specific files in the
7203 Format: <cpu-list>
7208 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7213 it can be updated at runtime by writing to the
7217 Per-cpu work items which run for longer than this
7220 them from noticeably delaying other per-cpu work
7229 Per-cpu workqueues are generally preferred because
7231 locality; unfortunately, per-cpu workqueues tend to
7234 Enabling this makes the per-cpu workqueues which
7245 workqueues. Can be one of "cpu", "smt", "cache",
7248 Documentation/core-api/workqueue.rst.
7250 This can be changed after boot by writing to the
7261 forces round-robin CPU selection to flush out
7269 on - Enable writecombine, use WUC for ioremap_wc()
7270 off - Disable writecombine, use SUC for ioremap_wc()
7272 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7276 xen_512gb_limit [KNL,X86-64,XEN]
7286 ide-disks -- unplug primary master IDE devices
7287 aux-ide-disks -- unplug non-primary-master IDE devices
7288 nics -- unplug network devices
7289 all -- unplug all emulated devices (NICs and IDE disks)
7290 unnecessary -- unplugging emulated devices is
7293 never -- do not unplug even if version check succeeds
7301 Select whether to always use non-faulting (safe) MSR
7317 [KNL,X86,XEN] Disable the vector callback for Xen
7322 to Xen, for use by other domains. Can be also changed at runtime
7326 xen_timer_slop= [X86-64,XEN]
7349 Boolean parameter to disable using fifo event handling
7351 preferred over the 2-level event handling, as it is
7368 xive.store-eoi=off [PPC]
7374 xhci-hcd.quirks [USB,KNL]
7376 host controller quirks. Meaning of each bit can be
7392 can be written using xmon commands.
7394 memory, and other data can't be written using