Lines Matching +full:bit +full:- +full:set +full:- +full:to +full:- +full:disable
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
26 If set to vendor, prefer vendor-specific driver
29 If set to video, use the ACPI video.ko driver.
30 If set to native, use the device's native backlight mode.
31 If set to none, disable the ACPI backlight interface.
34 force FADT to use 32 bit addresses rather than the
35 64 bit X_* addresses. Some firmware have broken 64
36 bit addresses for force ACPI ignore these and use
37 the older legacy 32 bit addresses.
40 Disable AML predefined validation mechanism
41 This mechanism can repair the evaluation result to make
43 This option is useful for developers to identify the
45 has something to do with the repair mechanism.
50 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
51 debug output. Bits in debug_layer correspond to a
54 Bits in debug_level correspond to a level in
57 The debug_level mask defaults to "info". See
58 Documentation/firmware-guide/acpi/debug.rst for more information about
65 Enable AML "Debug" output, i.e., stores to the Debug
68 Enable all messages related to ACPI hardware:
73 if you need to capture more output.
82 strict (default): access to resources claimed by ACPI
83 is denied; legacy drivers trying to access reserved
84 resources will fail to bind to device using them.
85 lax: access to resources claimed by ACPI is allowed;
86 legacy drivers trying to access reserved resources
93 By default, this is disabled due to x86 early mapping
112 Due to the existence of _Lxx/_Exx, some GPEs triggered
116 This facility can be used to prevent such uncontrolled
121 Disable auto-serialization of AML methods
122 AML control methods that contain the opcodes to create
124 auto-serialization feature.
126 This option allows to turn off the feature.
128 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
132 Disable installation of static SSDTs at early boot time
139 tables to /sys/firmware/acpi/tables/dynamic.
142 Ignore the ACPI-based watchdog interface (WDAT) and let
146 Pass the RSDP address to the kernel, mostly used
147 on machines running EFI runtime service to boot the
151 Format: To spoof as Windows 98: ="Microsoft Windows"
153 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
156 be necessary to carry out a cold reboot _twice_ in a
157 row to make it take effect on the platform firmware).
163 acpi_osi=! # disable all built-in OS vendor
165 acpi_osi=!! # enable all built-in OS vendor
167 acpi_osi= # disable all strings
170 multiple 'acpi_osi="string1"' to support specific OS
181 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 multiple 'acpi_osi="string1"' to support specific
200 still not able to affect the final state of a string if
201 there are quirks related to this string. This command
202 is useful when one want to control the state of the
203 feature group strings to debug BIOS issues related to
211 equivalent to
219 to assume that this machine's pmtimer latches its value
227 For broken nForce2 BIOS resulting in XT-PIC timer.
235 as soon as the kernel's real-mode entry point is called.
239 control method, with respect to putting devices into
240 low power states, to be enforced (the ACPI 2.0 ordering
244 sci_force_enable causes the kernel to set SCI_EN directly
247 nobl causes the internal blacklist of systems known to
248 behave incorrectly in some ways with respect to system
249 suspend and resume to be ignored (use wisely).
260 off: disable AGP support
261 try_unsupported: try to drive unsupported chipsets
265 See Documentation/sound/alsa-configuration.rst
269 behaviour to be specified. Bit 0 enables warnings,
270 bit 1 enables fixups, and bit 2 sends a segfault.
272 align_va_addr= [X86-64]
275 gives you up to 3% performance improvement on AMD F15h
277 CPU-intensive style benchmark, and it can vary highly in
280 32: only for 32-bit processes
281 64: only for 64-bit processes
282 on: enable for both 32- and 64-bit processes
283 off: disable for both 32- and 64-bit processes
288 and you need to use tracing_snapshot() on boot up, and
289 do not want to use tracing_snapshot_alloc() as it needs
290 to be done where GFP_KERNEL allocations are allowed.
299 Allow execve() of 32-bit applications and setting of the
301 subset of the CPUs support 32-bit EL0. When this
302 parameter is present, the set of CPUs supporting 32-bit
304 and hot-unplug operations may be restricted.
306 amd_iommu= [HW,X86-64]
307 Pass parameters to the AMD IOMMU driver in the system.
309 fullflush - enable flushing of IO/TLB entries when
313 off - do not initialize any AMD IOMMU found in
315 force_isolation - Force device isolation for all
317 allowed anymore to lift isolation
321 amd_iommu_dump= [HW,X86-64]
322 Enable AMD IOMMU driver option to dump the ACPI table
327 amd_iommu_intr= [HW,X86-64]
330 legacy - Use legacy interrupt remapping mode.
331 vapic - Use virtual APIC mode, which allows IOMMU
332 to inject interrupts directly into guest.
333 This mode requires kvm-amd.avic=1.
337 Map of devices attached to JOY0DAT and JOY1DAT
343 connected to one of 16 gameports
347 Power management functions (SPARCstation-4/5 + deriv.)
349 Disable APC CPU standby support. SPARCstation-Fox does
350 not play well with APC CPU idle - disable it if you have
357 when initialising the APIC and IO-APIC components.
358 For X86-32, this can also be used to specify an APIC
365 bsp: External NMI is delivered only to CPU 0
366 all: External NMIs are broadcast to all CPUs as a
378 to set it to "all" by meaning -- no limit here.
387 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
390 arm64.nobti [ARM64] Unconditionally disable Branch Target
393 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
396 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
408 atkbd.set= [HW] Select keyboard code set
420 audit= [KNL] Enable the audit sub-system
422 0 | off - kernel audit is disabled and can not be
424 unset - kernel audit is initialized but disabled and
426 1 | on - kernel audit is initialized and partially
432 audit_backlog_limit= [KNL] Set the audit queue size limit.
437 behavior is to disable the BAU (i.e. bau=0).
439 0 - Disable the BAU.
440 1 - Enable the BAU.
441 unset - Disable the BAU.
462 See Documentation/block/cmdline-partition.rst
464 boot_delay= Milliseconds to delay each printk during boot.
465 Values larger than 10 seconds (10000) are changed to
470 Extended command line options can be added to an initrd
471 and this will cause the kernel to look for it.
473 See Documentation/admin-guide/bootconfig.rst
476 Disable BERT OS support on buggy BIOSes.
479 Disable BGRT to avoid flickering OEM logo.
484 bttv.pll= See Documentation/admin-guide/media/bttv.rst
493 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
496 to fix known problems, but for some CPUs it is not
497 possible to determine what the correct size should be.
506 the system trusted keyring to be used for certificate
511 algorithm. Accepted values range from 0 to 7
512 inclusive. See arch/mips/include/asm/pgtable-bits.h
519 cgroup_disable= [KNL] Disable a particular controller or optional feature
520 Format: {name of the controller(s) or feature(s) to disable}
522 - foo isn't auto-mounted if you mount all cgroups in
524 - foo isn't visible as an individually mountable
526 - if foo is an optional feature then the feature is
530 cut the overhead, others just disable the usage. So
532 Specifying "pressure" disables per-cgroup pressure
535 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
538 Like cgroup_disable, but only applies to cgroup v1;
544 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
546 nosocket -- Disable socket memory accounting.
547 nokmem -- Disable kernel memory accounting.
549 checkreqprot [SELINUX] Set initial checkreqprot flag value.
552 0 -- check protection applied by kernel (includes
554 1 -- check protection requested by application.
555 Default value is set via a kernel config option.
558 Setting checkreqprot to 1 is deprecated.
568 force such clocks to be always-on nor does it reserve
572 information, see Documentation/driver-api/clk.rst.
574 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
576 Forces specified clocksource (if available) to be used
578 clocksource is not available, it defaults to PIT.
585 Some clocksource names to choose from, depending on
591 [X86-32] pit,hpet,tsc;
598 [X86-64] hpet,tsc
603 Enable/disable the eventstream feature of the ARM
604 architected timer so that code using WFE-based polling
609 Number of clocksource_watchdog() retries due to
611 unstable. Defaults to three retries, that is,
612 four attempts to read the clock under test.
615 Disable CPUID feature X for the kernel. See
616 arch/x86/include/asm/cpufeatures.h for the valid bit
624 Also note the kernel might malfunction if you disable
627 cma=nn[MG]@[start[MG][-end[MG]]]
638 Sets the size of kernel per-numa memory area for
640 per-numa CMA altogether. And If this option is not
642 With per-numa CMA enabled, DMA users on node nid will
643 first try to allocate buffer from the pernuma area
645 they will fallback to the global default memory area.
650 to determine OS memory pressure for page stealing by
656 allocations, by default set to 256K.
658 com20020= [HW,NET] ARCnet - COM20020 chipset
662 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
666 ARCnet - COM90xx chipset (memory-mapped buffers)
684 See Documentation/admin-guide/serial-console.rst for more
694 Start an early, polled-mode console on the 8250/16550
696 switching to the matching ttyS device later.
697 MMIO inter-register address stride is either 8-bit
698 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
700 to be equivalent to 'mmio'. 'options' are specified in
702 the h/w is not re-initialized.
707 If the device connected to the port is not a TTY but a braille
720 Switch to syslog format: "<%u>[time stamp] text\n"
722 prefix. The format is similar to one used by syslog()
723 syscall, or to executing "dmesg -S --raw" or to reading
728 Defaults to 0.
738 Enable/disable the CPU sampling based debugging.
739 0: default value, disable debugging
743 disable the cpuidle sub-system
746 [CPU_IDLE] Name of the cpuidle governor to use.
749 disable the cpufreq sub-system
753 policy to use. This governor must be registered in the
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
772 [KNL, X86-64] Select a region under 4G first, and
773 fall back to reserve region above 4G when '@offset'
775 See Documentation/admin-guide/kdump/kdump.rst for further details.
780 start-[end] where start and end are both
782 Documentation/admin-guide/kdump/kdump.rst for an example.
785 [KNL, X86-64] range could be above 4G. Allow kernel
786 to allocate physical memory region from top, so could
792 [KNL, X86-64] range under 4G. When crashkernel=X,high
797 low memory is needed to make sure DMA buffers for 32-bit
798 devices won't run out. Kernel would try to allocate at
800 This one let user to specify own low range under 4G
802 0: to disable low allocation.
807 [KNL] Disable crypto self-tests
821 See also Documentation/input/devices/joystick-parport.rst
825 Documentation/admin-guide/dynamic-debug-howto.rst for
833 of siphash to hash pointers. Use this option if you are
834 seeing instances of '(___ptrval___)') and need to see a
839 [KNL] verbose self-tests
842 self-tests.
843 We default to 0 (no extra messages), setting it to
844 1 will print _a lot_ more information - normally
845 only useful to kernel developers.
850 [KNL] Disable object debugging
853 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
860 to 1 or 2 should be enough to identify most random
862 driver code when a CPU writes to (or reads from) a
872 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
876 Note: to get most of debug_pagealloc error reports, it's
877 useful to also enable the page_owner functionality.
880 debugfs= [KNL] This parameter enables what is exposed to userspace
882 Format: { on, no-mount, off }
884 no-mount:
886 access APIs and a crashkernel can be used to read
887 its content. There is nothing to mount.
889 get a -EPERM as result when trying to register files
893 Default value is set in build-time with a kernel configuration.
906 filesystems. If not specified, defaults to the
909 Documentation/admin-guide/mm/hugetlbpage.rst.
913 [KNL] Debugging option to set a timeout in seconds for
914 deferred probe to give up waiting on dependencies to
934 Set number of hash buckets for dentry cache.
938 causes the kernel to fall back to 256MB segments which
940 miss to occur.
943 Dynamically disable ZONE_DMA32 on kernels compiled with
948 them frequently to increase the rate of SLB faults
951 disable= [IPV6]
957 usercopy checking is used to protect the kernel
960 against bounds-checking flaws in the kernel's
963 off Disable hardened usercopy checks.
966 Disable RADIX MMU mode on POWER9
969 Disable RADIX GTSE feature and use hcall for TLB
973 Disable TLBIE instruction. Currently does not work
979 corresponding CPU to be disabled at boot,
980 mostly used for the kdump 2nd kernel to
981 disable BSP to wake up multiple CPUs without
982 causing system reset or hang due to sending
983 INIT from AP to BSP.
987 Disable Intel PMU counter freezing feature.
992 Disable Dynamic DMA Window support. Use this
993 to workaround buggy firmware.
999 The kernel tries to adjust MTRR layout from continuous
1000 to discrete, to make X server driver able to add WB
1007 possibly causing your machine to run very slowly.
1010 Disable PIN 1 of APIC timer
1011 Can be useful to work around chipset bugs.
1013 dis_ucode_ldr [X86] Disable the microcode loader.
1019 This option allows to tune the number of preallocated
1020 entries for DMA-API debugging code. One entry is
1021 required per DMA-API allocation. Use this if the
1022 DMA-API debugging code disables itself because the
1026 With this option the DMA-API debugging driver
1028 pass the driver to filter for as the parameter.
1029 The filter can be disabled or changed to another
1033 List of driver names to be probed asynchronously.
1039 This parameter allows to specify an EDID data sets
1041 Generic built-in EDID data sets are used, if one of
1045 instructions how to build your own EDID data are
1046 available in Documentation/admin-guide/edid.rst. An EDID
1047 data set will only be used for a particular connector,
1048 if its name and a colon are prepended to the EDID
1050 set by separating the files with a comma. An EDID
1051 data set with no connector name will be used for
1058 Control how the dt_cpu_ftrs device-tree binding is
1061 off: Do not use it, fall back to legacy cpu table.
1062 known: Do not pass through unknown features to guests
1067 x86 Macs. Useful for driver authors to determine
1068 what data is available or for reverse-engineering.
1073 Documentation/admin-guide/dynamic-debug-howto.rst
1076 nopku [X86] Disable Memory Protection Keys CPU feature found
1090 determined by stdout-path property in device tree's
1095 Start an early, polled-mode console on a Cadence
1106 Start an early, polled-mode console on the 8250/16550
1108 MMIO inter-register address stride is either 8-bit
1109 (mmio) or 32-bit (mmio32 or mmio32be).
1111 to be equivalent to 'mmio'. 'options' are specified
1117 Start an early, polled-mode console on a pl011 serial
1121 the driver will use only 32-bit accessors to read/write
1125 Start an early, polled-mode console on a meson serial
1131 Start an early, polled-mode console on an msm serial
1137 Start an early, polled-mode console on an msm serial
1143 Start an early, polled-mode console on a serial port
1149 Start an early, polled-mode console on a serial port
1155 Use RISC-V SBI (Supervisor Binary Interface) for early
1173 Start an early, polled-mode console on a lantiq serial
1187 Start an early, polled-mode, output-only console on the
1192 Start an early, polled-mode console on the
1198 Start an early, polled-mode console on a Qualcomm
1206 coherent non-x86 systems that use system memory for
1231 Append ",keep" to not disable it when the real console
1256 The optional "force" to "pciserial" enables use of a
1260 edac_report= [HW,EDAC] Control how to report EDAC event
1262 on: enable EDAC to report H/W event. May be overridden
1264 off: disable H/W event reporting through EDAC.
1265 force: enforce the use of EDAC to report H/W event.
1271 This is designed to be used in conjunction with
1287 disable_early_pci_dma: disable the busmaster bit on all
1289 nochunk: disable reading files in "chunks" in the EFI
1292 noruntime : disable EFI runtime services support
1294 attribute may cause the kernel to reserve the
1295 memory range for a memory mapping driver to
1296 claim. Specify efi=nosoftreserve to disable this
1300 no_disable_early_pci_dma: Leave the busmaster bit set
1310 Add arbitrary attribute to specific memory range by
1312 Region of memory which aa attribute is added to is
1313 from ss to ss+nn.
1317 attribute is added to range 0x100000000-0x180000000 and
1318 0x10a0000000-0x1120000000.
1321 EFI_MEMORY_SP(0x40000) attribute is added to
1322 range 0x240000000-0x43fffffff.
1331 that is to be dynamically loaded by Linux. If there are
1334 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1340 elanfreq= [X86-32]
1347 kexec loader will pass this option to capture kernel.
1348 See Documentation/admin-guide/kdump/kdump.rst for details.
1351 The kernel tries to adjust MTRR layout from continuous
1352 to discrete, to make X server driver able to add WB
1357 Can be useful to work around chipset bugs
1359 The kernel tries to set a reasonable default.
1361 enforcing [SELINUX] Set initial enforcing status.
1364 0 -- permissive (log only, no denials).
1365 1 -- enforcing (deny and log).
1371 Disable Error Record Serialization Table (ERST)
1380 Permit 'security.evm' to be updated regardless of
1389 See also Documentation/fault-injection/.
1393 See Documentation/admin-guide/sysctl/net.rst for
1397 See Documentation/admin-guide/blockdev/floppy.rst.
1400 [IA-64] Avoid check_sal_cache_flush which may hang on
1402 parameter will force ia64_sal_cache_flush to call
1405 forcepae [X86-32]
1407 Many Pentium M systems disable PAE but may have a
1413 [FTRACE] will set and start the specified tracer
1414 as early as possible in order to facilitate early
1424 ftrace_filter=[function-list]
1426 tracer at boot up. function-list is a comma separated
1431 ftrace_notrace=[function-list]
1433 function-list. This list can be changed at run time
1437 ftrace_graph_filter=[function-list]
1440 function-list is a comma separated list of functions
1444 ftrace_graph_notrace=[function-list]
1446 function-list. This list is a comma separated list of
1457 devices by scanning the firmware to infer the
1466 off -- Don't create device links from firmware info.
1467 permissive -- Create device links from firmware info
1470 on -- Create device links from firmware info and use it
1471 to enforce probe and suspend/resume ordering.
1472 rpm -- Like "on", but also use to order runtime PM.
1481 support via parallel port (up to 5 devices per port)
1483 See also Documentation/input/devices/joystick-parport.rst
1487 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1491 gcov_persist= [GCOV] When non-zero (default), profiling data for
1502 invalid Protective MBR to be treated as GPT. If the
1504 GPT to be used instead.
1507 the "Enable 0" bit of the configuration register.
1511 the "Enable 0" bit of the configuration register.
1514 grcan.select= [HW] Select which physical interface to use.
1524 gpio-mockup.gpio_mockup_ranges
1529 [KNL] Should the hard-lockup detector generate
1535 for 64-bit NUMA, off otherwise.
1538 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1544 Disable Hardware Error Source Table (HEST) support;
1545 corresponding firmware-first mode error processing
1548 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1550 highmem otherwise. This also works to reduce highmem
1553 highres= [KNL] Enable/disable high resolution timer mode.
1559 hpet= [X86-32,HPET] option to control HPET usage
1560 Format: { enable (default) | disable | force |
1562 disable: disable HPET and use PIT instead
1567 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1568 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1576 boot-time allocation of gigantic hugepages is skipped.
1578 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1580 the number of pages of hugepagesz to be allocated.
1582 line, it specifies the number of pages to allocate for
1584 Documentation/admin-guide/mm/hugetlbpage.rst.
1589 conjunction with hugepages (above) to allocate huge
1594 Documentation/admin-guide/mm/hugetlbpage.rst.
1601 A value of 1 instructs the kernel to panic when a
1603 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1609 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1614 disabled at runtime by default to prevent
1618 which allow the hypervisor to 'idle' the
1636 (disabled by default, and as a pre-condition
1638 i8042.direct [HW] Put keyboard port into non-translated mode
1641 (Don't attempt to blink the leds)
1644 i8042.noloop [HW] Disable the AUX Loopback command while probing
1648 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1652 suspend-to-ram transitions, only during s2r
1658 architectures force reset to be always executed
1660 i8042.kbdreset [HW] Reset device connected to KBD port
1675 capability is set.
1678 [DRM] Invert the sense of the variable that is used to
1679 set the brightness of the panel backlight. Normally a
1682 to maximum brightness. If this parameter is set to 0
1684 is set to 1, a brightness value of 0 sets the backlight
1685 to maximum brightness, and the maximum of the brightness
1687 -1 -- never invert brightness
1688 0 -- machine default
1689 1 -- force brightness inversion
1694 ide-core.nodma= [HW] (E)IDE subsystem
1695 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1700 ide-generic.probe-mask= [HW] (E)IDE subsystem
1703 platform up to 6 ports are supported, enabled by
1704 setting corresponding bits in the mask to 1. The
1712 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1721 idle=halt: Halt is forced to be used for CPU idle.
1723 idle=nomwait: Disable mwait for CPU C-states
1732 of an ELF file header flag individually set by each
1733 binary. Hardware implementations are permitted to
1740 legacy only accept legacy-NaN binaries, if supported
1742 2008 only accept 2008-NaN binaries, if supported
1747 The FPU emulator is always able to support both NaN
1751 'relaxed' straps the emulator for both legacy-NaN and
1752 2008-NaN, whereas 'strict' enables legacy-NaN only on
1761 Ignore loglevel setting - this will print /all/
1762 kernel messages to the console. Useful for debugging.
1773 Set number of hash buckets for inode cache.
1796 The builtin policies to load during IMA setup.
1802 mode bit set by either the effective uid (euid=0) or
1825 Formats: { "ima" | "ima-ng" | "ima-sig" }
1826 Default: "ima-ng"
1834 Set the minimal file size for using asynchronous hash.
1839 to achieve the best performance for a particular HW.
1843 Set hashing buffer size. Default: 4k.
1847 to achieve best performance for particular HW.
1858 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1859 initcall functions. Useful for debugging built-in
1864 initrdmem= [KNL] Specify a physical address and size from which to
1874 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
1878 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
1882 default (disallow access to all but pkey 0). Can
1892 0 -- basic integrity auditing messages. (Default)
1893 1 -- additional integrity auditing messages.
1899 Disable intel iommu driver.
1906 forcedac [X86-64]
1907 With this option iommu will not optimize to look
1908 for io virtual address below 32-bit forcing dual
1910 than 32-bit addressing. The default is to look
1911 for translation below 32-bit and if not available
1916 to batching them for performance.
1924 mode translation. With this option set, scalable mode
1925 will be used on hardware which claims to support it.
1929 could harm performance of some high-throughput
1934 vulnerable to DMA attacks.
1936 Disable bounce buffer for untrusted devices such as
1943 1 to 9 specify maximum depth of C-state.
1946 disable
1951 to work with generic cpufreq governors (instead of
1953 used along with the hardware-managed P-states (HWP)
1957 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1958 instead of acpi-cpufreq may disable platform features, such
1960 P-States information being indicated to OSPM and therefore
1963 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1976 Allow per-logical-CPU P-State performance control limits using
1979 intremap= [X86-64, Intel-IOMMU]
1981 off disable Interrupt Remapping
1982 nosid disable Source ID checking
1984 BIOS x2APIC opt-out request will be ignored
1985 nopost disable Interrupt Posting
1987 iomem= Disable strict checking of access to MMIO memory
2004 Disable IOMMU bypass, using IOMMU for PCI devices.
2008 0 - Lazy mode.
2012 Will fall back to strict mode if not supported by
2014 1 - Strict mode (default).
2019 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2021 0 - Use IOMMU translation for DMA.
2022 1 - Bypass the IOMMU for DMA.
2023 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2025 io7= [HW] IO7 for Marvel-based Alpha systems
2040 See Documentation/admin-guide/nfs/nfsroot.rst.
2043 IPC identifiers from 32,768 to 16,777,216.
2045 irqaffinity= [SMP] Set the default irq affinity mask
2051 Force the kernel to look for the second 4kB page
2057 Force the kernel to ignore the availability of
2060 to let secondary kernels in charge of setting up
2064 Enables support for pseudo-NMIs in the kernel. This
2065 requires the kernel to be built with
2070 for it. Intended to get systems with badly broken
2076 interrupt. Intended to get systems with badly broken
2082 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2083 [Deprecated - use cpusets instead]
2084 Format: [flag-list,]<cpu-list>
2086 Specify one or more CPUs to isolate from disturbances
2090 Disable the tick when a single task runs.
2092 A residual 1Hz tick is offloaded to workqueues, which you
2093 need to affine to housekeeping through the global
2099 so to protect individual CPUs the 'cpumask' file has to
2105 is irreversible: it's not possible to bring back a CPU to
2107 advised to use cpusets instead to disable scheduler load
2110 move in and out of an isolated set anytime.
2115 "number of CPUs in system - 1".
2129 interrupts are directed to the housekeeping CPU
2141 The format of <cpu-list> is described above.
2145 ivrs_ioapic [HW,X86-64]
2146 Provide an override to the IOAPIC-ID<->DEVICE-ID
2148 example, to map IOAPIC-ID decimal 10 to
2152 ivrs_hpet [HW,X86-64]
2153 Provide an override to the HPET-ID<->DEVICE-ID
2155 example, to map HPET-ID decimal 0 to
2159 ivrs_acpihid [HW,X86-64]
2160 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2162 example, to map UART-HID:UID AMD0020:0 to
2170 When CONFIG_RANDOMIZE_BASE is set, this disables
2175 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2182 kernelcore= [KNL,X86,IA-64,PPC]
2185 the kernel for non-movable allocations. The requested
2189 event, a node is too small to have both ZONE_NORMAL and
2195 subsystem. Note that allocations like PTEs-from-HighMem
2199 It is possible to specify the exact amount of memory in
2203 for non-movable allocations and remaining memory is used
2212 each poll cycle to the debug port in case you need
2214 gdb or control-c on the dbgp connection. When
2215 not using this parameter you use sysrq-g to break into
2220 or a supported polling keyboard driver (non-usb).
2229 If the boot console provides the ability to read
2231 this parameter to tell kgdb to use it as a backend
2232 until the normal console is registered. Intended to
2234 specifies the normal console to transition to.
2239 name passed to kgdboc. It's OK to leave the value
2247 Configure the RouterBoard 532 series on-chip
2250 kmemleak= [KNL] Boot-time kmemleak enable/disable
2256 kprobe_event=[probe-list]
2258 The probe-list is a semicolon delimited list of probe
2261 For example, to add a kprobe event on vfs_read with
2262 arg1 and arg2, add to the command line;
2275 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2296 guests do need not to enable it for nested guests.
2300 back to huge pages. 0 disables the recovery, otherwise if
2304 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2307 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2309 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2311 kvm-arm.mode=
2314 nvhe: Standard nVHE-based mode, without support for
2317 protected: nVHE-based mode with support for guests whose
2321 Defaults to VHE/nVHE based on hardware support and
2324 kvm-arm.vgic_v3_group0_trap=
2325 [KVM,ARM] Trap guest accesses to GICv3 group-0
2328 kvm-arm.vgic_v3_group1_trap=
2329 [KVM,ARM] Trap guest accesses to GICv3 group-1
2332 kvm-arm.vgic_v3_common_trap=
2333 [KVM,ARM] Trap guest accesses to GICv3 common
2336 kvm-arm.vgic_v4_enable=
2348 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2352 kvm-intel.emulate_invalid_guest_state=
2353 [KVM,Intel] Disable emulation of invalid guest state.
2354 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2356 This param doesn't apply to nested guests (L2), as KVM
2360 kvm-intel.flexpriority=
2361 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2364 kvm-intel.nested=
2368 kvm-intel.unrestricted_guest=
2369 [KVM,Intel] Disable unrestricted guest feature
2373 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2374 CVE-2018-3620.
2385 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2452 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2458 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2462 value for LAPIC timer one-shot implementation. Default
2463 back to the programmable timer unit in the LAPIC.
2470 libata.dma=0 Disable all PATA and SATA DMA
2482 when set.
2492 configuration applies to all ports, links and devices.
2494 If only DEVICE is omitted, the parameter applies to
2497 first fan-out link behind PMP device. It does not
2499 host link and device attached to it.
2501 The VAL specifies the configuration to force. As long
2511 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2523 hot-unplug link recovery
2529 * disable: Disable this device.
2537 Setting this to true through kernel command line will
2538 call memblock_remove on the regions marked with no-map
2540 for those regions. By default this is set to false.
2558 Enable the kernel lockdown feature. If set to
2559 integrity, kernel features that allow userland to
2560 modify the running kernel are disabled. If set to
2562 to extract confidential information from the kernel
2566 Set the number of locking read-acquisition kthreads.
2567 Defaults to being automatically set based on the
2571 Set the number of locking write-acquisition kthreads.
2574 Set time (s) after boot for CPU-hotplug testing.
2577 Set time (s) between CPU-hotplug operations, or
2578 zero to disable CPU-hotplug testing.
2581 Set task-shuffle interval (jiffies). Shuffling
2582 tasks allows some CPUs to go into dyntick-idle
2586 Set time (s) after boot system shutdown. This
2587 is useful for hands-off automated testing.
2593 Time (s) to stutter testing, for example,
2594 specifying five seconds causes the test to run for
2596 This tests the locking primitive's ability to
2597 transition abruptly to and from idle.
2600 Specify the locking implementation to test.
2609 console loglevel will be printed to the console. It can
2620 7 (KERN_DEBUG) debug-level messages
2627 that allows to increase the default size depending on
2630 logo.nologo [FB] Disables display of the built-in Linux logo.
2631 This may be used to provide more screen space for
2635 lp=0 [LP] Specify parallel ports to use, e.g,
2639 specified in addition to the ports) causes
2640 attached printers to be reset. Using
2642 to associate lp devices with, starting with
2643 lp0. A port specification may be 'none' to skip
2647 from each port should be examined, to see if
2648 an IEEE 1284-compliant printer is attached; if
2653 Sets loops_per_jiffy to given constant, thus avoiding
2654 time-consuming boot-time autodetection (up to 250 ms per
2655 CPU). 0 enables autodetection (default). To determine
2658 on SMP systems the preset will be applied to all CPUs,
2659 which is likely to cause problems if your CPUs need
2661 will cause delays in the kernel to be wrong, leading to
2675 machvec= [IA-64] Force the use of a particular machine-vector
2681 Example: machtype=lemote-yeeloong-2f-7inch
2684 than or equal to this physical address is ignored.
2688 the kernel to bring up 'n' processors. Surely after
2692 While n=0 is a special case, it is equivalent to "nosmp",
2696 (loop.max_loop) unconditionally pre-created at init time. The default
2699 devices can be requested on-demand with the
2700 /dev/loop-control interface.
2702 mce [X86-32] Machine Check Exception
2704 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
2707 See Documentation/admin-guide/md.rst.
2711 Specifies range of consoles to be captured by the MDA.
2714 Control mitigation for the Micro-architectural Data
2717 Certain CPUs are vulnerable to an exploit against CPU
2718 internal buffers which can forward information to a
2723 attack, to access data to which the attacker does
2729 full - Enable MDS mitigation on vulnerable CPUs
2730 full,nosmt - Enable MDS mitigation and disable
2732 off - Unconditionally disable MDS mitigation
2734 On TAA-affected machines, mds=off can be prevented by
2736 mitigated with the same mechanism so in order to disable
2737 this mitigation, you need to specify tsx_async_abort=off
2740 Not specifying this option is equivalent to
2743 For details see: Documentation/admin-guide/hw-vuln/mds.rst
2746 Amount of memory to be used in cases as follows:
2749 2 when the kernel is not able to see the whole system memory;
2751 the hypervisor, then assigned to KVM guests.
2754 with memmap= to avoid physical address space collisions.
2756 belonging to unused RAM.
2762 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2766 [KNL,SH] Allow user to override the default size for
2767 per-device physically contiguous DMA buffers.
2770 [KNL] Set the initial state for the memory hotplug
2772 set according to the
2775 See Documentation/admin-guide/mm/memory-hotplug.rst.
2785 Region of memory to be used is from ss to ss+nn.
2786 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2787 which limits max address to nn[KMG].
2795 Region of memory to be marked is from ss to ss+nn.
2799 Region of memory to be reserved is from ss to ss+nn.
2800 Example: Exclude memory from 0x18690000-0x1869ffff
2810 Region of memory to be used, from ss to ss+nn.
2814 memmap=<size>%<offset>-<oldtype>+<newtype>
2816 from <oldtype> to <newtype>. If "-<oldtype>" is left
2824 Some BIOSes seem to corrupt the first 64k of
2831 repeatable BIOS-originated corruption always
2833 to prevent the kernel from using that memory.
2838 use. Use this parameter to scan for
2843 seconds. Use this parameter to check at some
2848 default : 0 <disable>
2849 Specifies the number of memtest passes to be
2851 pattern from a given set of patterns. Memtest
2856 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2864 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
2868 s2idle - Suspend-To-Idle
2869 shallow - Power-On Suspend or equivalent (if supported)
2870 deep - Suspend-To-RAM or equivalent (if supported)
2871 See Documentation/admin-guide/pm/sleep-states.rst.
2873 meye.*= [HW] Set MotionEye Camera parameters
2874 See Documentation/admin-guide/media/meye.rst.
2876 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2877 Multi-Function General Purpose Timers on AMD Geode
2880 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2882 version 0.98 is known to be affected, 0.99 fixes the
2883 problem by letting the user disable the workaround.
2894 0 - The attached screen is the 3.5" TFT
2895 1 - The attached screen is the 7" TFT
2896 2 - The VGA Shield is attached (1024x768)
2900 b - Enable backlight. The TFT backlight pin will be
2901 linked to the kernel VESA blanking code and a GPIO
2904 c - Enable the s3c camera interface.
2905 t - Reserved for enabling touchscreen support. The
2909 https://repo.or.cz/w/linux-2.6/mini2440.git
2913 CPU vulnerabilities. This is a set of curated,
2914 arch-independent options, each of which is an
2915 aggregation of existing arch-specific options.
2918 Disable all optional CPU mitigations. This
2920 expose users to several CPU vulnerabilities.
2921 Equivalent to: nopti [X86,PPC]
2928 ssbd=force-off [ARM64]
2946 users who don't want to be surprised by SMT
2948 have other ways of avoiding SMT-based attacks.
2949 Equivalent to: (default behavior)
2953 if needed. This is for users who always want to
2955 Equivalent to: l1tf=flush,nosmt [X86]
2962 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2967 so loglevel=8 may also need to be specified.
2977 Therefore, similar to MDS and TAA, the mitigation
2978 is to clear the affected CPU buffers.
2983 full - Enable mitigation on vulnerable CPUs
2985 full,nosmt - Enable mitigation and disable SMT on
2988 off - Unconditionally disable mitigation
2993 mitigated with the same mechanism so in order to
2994 disable this mitigation, you need to specify
2997 Not specifying this option is equivalent to
3001 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3004 [KNL] When CONFIG_MODULE_SIG is set, this means that
3005 modules without (valid) signatures will fail to load.
3006 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3009 module_blacklist= [KNL] Do not load a comma-separated list of
3014 leaving touchpad surface for touch to be considered
3023 movablecore= [KNL,X86,IA-64,PPC]
3025 This parameter is the complement to kernelcore=, it
3034 movable_node [KNL] Boot-time switch to make hotplugable memory
3035 NUMA nodes to be movable. This means that the memory
3041 Format: <name>,<region-number>,<size>,<offset>
3044 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3054 kswapd_per_node allows you to control the number of kswapd threads
3055 running on the system. This provides the ability to devote additional
3059 result can cause aggregate CPU usage on the system to go up, down or
3067 The range of acceptible values are 1-16. Always start with lower
3068 values in the 2-6 range. Higher values should be justified with
3070 of direct reclaims (in latency) that occur can be higher due to
3073 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
3077 boundary - index of last SLC block on Flex-OneNAND.
3079 lock - Configure if Flex-OneNAND boundary should be locked.
3086 See arch/arm/mach-s3c2412/mach-jive.c
3107 Set to 2 or more if your graphical card needs more.
3113 Note that mem_start is often overloaded to mean
3114 something different and driver-specific.
3120 0 to disable accounting
3121 1 to enable accounting
3125 See Documentation/admin-guide/nfs/nfsroot.rst.
3127 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3128 See Documentation/admin-guide/nfs/nfsroot.rst.
3131 See Documentation/admin-guide/nfs/nfsroot.rst.
3134 [NFSv4] set the total number of threads that the
3135 NFS client will assign to service NFSv4 callback
3139 [NFS] set the TCP port on which the NFSv4 callback
3143 [NFS] sets the pathname to the program which is used
3144 to update the NFS client cache entries.
3147 [NFS] sets the timeout after which an attempt to
3148 update a cache entry is deemed to have failed.
3151 [NFS] set the maximum lifetime for idmapper cache
3155 [NFS] enable 64-bit inode numbers.
3156 If zero, the NFS client will fake up a 32-bit inode
3158 of returning the full 64-bit number.
3159 The default is to return 64-bit inode numbers.
3163 slots the client will assign to the callback
3170 the client will attempt to negotiate with the server.
3172 that the client can send to the NFSv4.1 server.
3177 [NFSv4] When set to the default of '1', this option
3179 scheme and the NFS level operations agree to use
3183 legacy NFSv2/v3 systems to NFSv4 easier.
3186 back to using the idmapper.
3187 To turn off this behaviour, set the value to '0'.
3189 [NFS4] Specify an additional fixed unique ident-
3199 The default is to send the implementation identification
3203 [NFSv4] Attempt to recover locks that were lost due
3204 to a lease timeout on the server. Please note that
3208 If you want to enable the kernel legacy behaviour of
3209 attempting to recover these locks, then set this
3210 parameter to '1'.
3212 not to attempt recovery of lost locks.
3216 layoutstats to the pNFS metadata server.
3218 Setting this to value to 0 causes the kernel to use
3219 whatever value is the default set by the layout
3220 driver. A non-zero value sets the minimum interval
3224 [NFSv4] When set to the default of '1', the NFSv4
3225 server will return only numeric uids and gids to
3227 and gids from such clients. This is intended to ease
3231 Dump stacks even of idle CPUs in response to an
3232 NMI stack-backtrace request.
3234 nmi_debug= [KNL,SH] Specify one or more actions to take
3241 0 - turn hardlockup detector in nmi_watchdog off
3242 1 - turn hardlockup detector in nmi_watchdog on
3244 timeout occurs (or 'nopanic' to not panic on an NMI
3245 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3246 To disable both hard and soft lockup detectors,
3259 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3263 no5lvl [X86-64] Disable 5-level paging mode. Forces
3264 kernel to use 4-level paging instead.
3270 Disable suspending of consoles during suspend and
3273 of the system is being put to sleep (ie, while
3276 to work with serial and VGA consoles.
3277 To facilitate more flexible debugging, we also add
3278 console_suspend, a printk module parameter to control
3280 /sys/module/printk/parameters/console_suspend) to
3284 Disable device dump. Device dump allows drivers to
3285 append dump data to vmcore so you can collect driver
3292 is set.
3295 caches in the slab allocator. Saves per-node memory,
3303 noapic [SMP,APIC] Tells the kernel to not make use of any
3306 noautogroup Disable scheduler automatic task group creation.
3315 nodelayacct [KNL] Disable per-task delay accounting
3317 nodsp [SH] Disable hardware DSP at boot time.
3319 noefi Disable EFI runtime services support.
3321 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3323 noexec [IA-64]
3326 On X86-32 available only on PAE configured kernels.
3327 noexec=on: enable non-executable mappings (default)
3328 noexec=off: disable non-executable mappings
3331 Disable SMAP (Supervisor Mode Access Prevention)
3335 Disable SMEP (Supervisor Mode Execution Prevention)
3338 noexec32 [X86-64]
3339 This affects only 32-bit executables.
3340 noexec32=on: enable non-executable mappings (default)
3342 noexec32=off: disable non-executable mappings
3345 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3347 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3349 legacy floating-point registers on task switch.
3351 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3353 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
3354 Equivalent to smt=1.
3356 [KNL,X86] Disable symmetric multithreading (SMT).
3357 nosmt=force: Force disable SMT, cannot be undone
3360 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
3364 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
3370 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
3373 [PPC] Don't flush the L1-D cache after accessing user data.
3376 and restore using xsave. The kernel will fallback to
3377 enabling legacy floating-point and sse state.
3380 register states. The kernel will fall back to use
3381 xsave to save the states. By using this parameter,
3388 form of xsave area. The kernel will fall back to use
3389 xsaveopt and xrstor to save and restore the states
3395 wfi(ARM) instruction doesn't work correctly and not to
3398 no_file_caps Tells the kernel not to honor file capabilities. The
3399 only way then for a file to be executed with privilege
3400 is to be setuid root or executed by root.
3402 nohalt [IA-64] Tells the kernel not to use the power saving
3404 power-consumption. On the positive side, it reduces
3405 interrupt wake-up latency, which may improve performance
3407 real-time systems.
3410 Force pointers printed to the console or buffers to be
3417 compared. However, if this command-line option is
3423 nohibernate [HIBERNATION] Disable hibernation and resume.
3425 nohz= [KNL] Boottime enable/disable dynamic ticks
3431 In kernels built with CONFIG_NO_HZ_FULL=y, set
3434 the range to maintain the timekeeping. Any CPUs
3441 noirqdebug [X86-32] Disables the code which attempts to detect and
3442 disable unhandled interrupt sources.
3449 noinitrd [RAM] Tells the kernel not to load any configured
3452 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3454 [Deprecated - use intremap=off]
3456 nointroute [IA-64]
3458 noinvpcid [X86] Disable the INVPCID cpu feature.
3460 nojitter [IA-64] Disables jitter checking for ITC timers.
3462 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3464 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3467 no-vmw-sched-clock
3468 [X86,PV_OPS] Disable paravirtualized VMware scheduler
3471 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
3475 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3477 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3482 nomca [IA-64] Disable machine check abort handling
3484 nomce [X86-32] Disable Machine Check Exception
3486 nomfgpt [X86-32] Disable Multi-Function General Purpose
3489 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3493 nomodule Disable module load
3495 nopat [X86] Disable PAT (page attribute table extension of
3498 nopcid [X86-64] Disable the PCID cpu feature.
3500 norandmaps Don't use address space randomization. Equivalent to
3503 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
3506 nordrand [X86] Disable kernel use of the RDRAND and
3509 available to user space applications.
3514 no-scroll [VGA] Disables scrollback.
3515 This is required for the Braillex ib80-piezo Braille
3518 nosbagart [IA-64]
3520 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
3522 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
3523 and disable the IO APIC. legacy for "maxcpus=0".
3525 nosoftlockup [KNL] Disable the soft-lockup detector.
3529 nowatchdog [KNL] Disable both lockup detectors, i.e.
3530 soft-lockup and NMI watchdog (hard-lockup).
3534 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
3541 need to online CPU0 before suspend/hibernate.
3559 nptcg= [IA-64] Override max number of concurrent global TLB
3564 could support. nr_cpus=n : n >= 1 limits the kernel to
3568 n. So during boot up some boot time memory for per-cpu
3569 variables need be pre-allocated for later physical cpu
3572 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
3574 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
3575 Allowed values are enable and disable
3579 This can be set from sysctl after boot.
3580 See Documentation/admin-guide/sysctl/vm.rst for details.
3583 See Documentation/core-api/debugging-via-ohci1394.rst for more
3590 waiting for the ACK, so if this is set too high
3595 For example, to override I2C bus2:
3607 CPU specific event set.
3612 oops=panic Always panic on oopses. Default is to just kill the
3616 Useful together with panic=30 to trigger a reboot.
3619 [KNL] Boolean flag to control whether the page allocator
3622 running on a platform with a direct-mapped memory-side
3623 cache, and this parameter can be used to
3624 override/disable that behavior. The state of the flag
3628 page_owner= [KNL] Boot-time page_owner enabling option.
3634 page_poison= [KNL] Boot-time parameter changing the state of
3648 bit 0: print all tasks info
3649 bit 1: print system memory info
3650 bit 2: print timer info
3651 bit 3: print locks info if CONFIG_LOCKDEP is on
3652 bit 4: print ftrace buffer
3653 bit 5: print all printk messages in buffer
3657 Hexadecimal bitmask representing the set of TAINT flags
3658 that will cause the kernel to panic when add_taint() is
3659 called with any of the flags in this set.
3660 The optional switch "nousertaint" can be utilized to
3661 prevent userspace forced crashes by writing to sysctl
3663 bitmask set on panic_on_taint.
3664 See Documentation/admin-guide/tainted-kernels.rst for
3666 to compose the bitmask to assign to panic_on_taint.
3668 panic_on_warn panic() instead of WARN(). Useful to cause kdump
3671 pelt= [KNL] Boot-time parameter changing the PELT half life in ms
3673 32: Set the half life to 32ms
3674 8: Set the half life to 8ms
3678 Run kdump after running panic-notifiers and dumping
3686 connected to, default is 0.
3694 Use 'auto' to force the driver to use any
3695 IRQ/DMA settings detected (the default is to
3701 (to avoid using a FIFO even if it is detected).
3707 Configure VIA parallel port to operate in
3710 up parallel port mode and sets it to spp.
3716 the specified number of seconds. This is to be used if
3723 See also Documentation/admin-guide/blockdev/paride.rst.
3728 or a set of devices (<pci_dev>). These are
3737 firmware changes, or due to changes caused
3740 taken to be zero. Optionally, a path
3741 to a device through multiple device/function
3752 bios [X86-32] force use of PCI BIOS, don't access
3754 has a non-standard PCI host bridge.
3755 nobios [X86-32] disallow use of PCI BIOS, only direct
3761 data in IO port 0xCFC, both 32-bit).
3763 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3764 the function, IO port 0xCFA, also 8-bit, sets
3766 through ports 0xC000-0xCFFF).
3770 enabled, this kernel boot option can be used to
3771 disable the use of PCIE advanced error reporting.
3772 nodomains [PCI] Disable support for multiple PCI
3773 root domains (aka PCI segments, in ACPI-speak).
3774 nommconf [X86] Disable use of MMCONFIG for PCI
3777 properly configured MMIO access to PCI
3780 enabled, this kernel boot option can be used to
3781 disable the use of MSI interrupts system-wide.
3782 noioapicquirk [APIC] Disable all boot interrupt quirks.
3783 Safety option to keep boot IRQs enabled. This
3785 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3786 primary IO-APIC for bridges that cannot disable
3789 noioapicreroute [APIC] Disable workaround that uses the
3790 boot IRQ equivalent of an IRQ that connects to
3793 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3794 routing table. These calls are known to be buggy
3797 way to get the interrupt routing table. Try
3798 this option if the kernel is unable to allocate
3801 rom [X86] Assign address space to expansion ROMs.
3805 norom [X86] Do not assign address space to
3808 nobar [X86] Do not assign address space to the
3810 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3811 assigned automatically to PCI devices. You can
3817 F0000h-100000h range.
3819 useful if the kernel is unable to find your
3820 secondary buses and you want to tell it
3822 assign-busses [X86] Always assign all PCI bus
3835 is enabled by default. If you need to use this,
3838 If you need to use this, please report a bug.
3850 bfsort Sort PCI devices into breadth-first order.
3851 This sorting is done to get a device
3853 nobfsort Don't sort PCI devices into breadth-first order.
3854 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3855 tuning and use the BIOS-configured MPS defaults.
3856 pcie_bus_safe Set every device's MPS to the largest value
3858 pcie_bus_perf Set device MPS to the largest allowable MPS
3859 based on its parent bus. Also set MRRS (Max
3860 Read Request Size) to the largest supported
3863 pcie_bus_peer2peer Set every device's MPS to 128B, which
3864 every device is guaranteed to support. This
3865 configuration allows peer-to-peer DMA between
3868 that hot-added devices will work.
3878 Specifies alignment and device to reassign
3879 aligned memory resources. How to
3883 A PCI-PCI bridge can be specified if resource
3884 windows need to be expanded.
3885 To specify the alignment for several
3889 for 4096-byte alignment.
3890 ecrc= Enable/disable PCIe ECRC (transaction layer
3891 end-to-end CRC checking).
3912 realloc= Enable/disable reallocating PCI bridge resources
3913 if allocations done by BIOS are too small to
3920 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
3925 big_root_window Try to add a big 64bit memory window to the PCIe
3927 can resize a BAR to allow access to all VRAM.
3945 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3947 off Disable ASPM.
3948 force Enable ASPM even on devices that claim not to support it.
3953 even if the platform doesn't give the OS permission to
3955 also tries to use these services.
3956 dpc-native Use native PCIe service for DPC only. May
3958 compat Disable native PCIe services (PME, AER, DPC, PCIe
3962 off Disable power management of all PCIe ports
3973 Keep all power-domains already enabled by bootloader on,
3979 See Documentation/admin-guide/blockdev/paride.rst.
3981 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3986 percpu_alloc= Select which percpu first chunk allocator to use.
3994 See Documentation/admin-guide/blockdev/paride.rst.
3997 See Documentation/admin-guide/blockdev/paride.rst.
3999 pirq= [SMP,APIC] Manual mp-table setup
4000 See Documentation/x86/i386/IO-APIC.rst.
4004 See also Documentation/admin-guide/parport.rst.
4015 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4024 { on | off | curr | res | no-curr | no-res }
4042 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4049 function to NULL. On Idle the CPU just reduces
4060 Disable Hardware Transactional Memory
4062 print-fatal-signals=
4068 coredump - etc.
4070 If you hit the warning due to signal overflow,
4071 you might want to try "ulimit -i unlimited".
4078 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4082 Control writing to /dev/kmsg.
4083 on - unlimited logging to /dev/kmsg from userspace
4084 off - logging to /dev/kmsg disabled
4085 ratelimit - ratelimit the logging
4088 printk.time= Show timing data prefixed to each printk message line
4089 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4092 Limit processor to maximum C-state
4096 Ignore the _CST method to determine C-states,
4102 [defaults to kernel profiling]
4103 Param: "schedule" - profile schedule points.
4104 Param: "sleep" - profile D-state sleeping (millisecs).
4106 Param: "kvm" - profile VM exits.
4107 Param: <number> - step/bucket size as a power of 2 for
4117 psi= [KNL] Enable or disable pressure stall information
4121 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4123 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4126 Try to reset the device after so many bad packets
4129 [HW,MOUSE] Set desired mouse resolution, in dpi.
4134 pstore.backend= Specify the name of the pstore backend to use
4137 See Documentation/admin-guide/blockdev/paride.rst.
4139 pti= [X86-64] Control Page Table Isolation of user and
4144 on - unconditionally enable
4145 off - unconditionally disable
4146 auto - kernel detects whether your CPU model is
4147 vulnerable to issues that PTI mitigates
4149 Not specifying this option is equivalent to pti=auto.
4151 nopti [X86-64]
4152 Equivalent to pti=off
4155 [KNL] Number of legacy pty's. Overwrites compiled-in
4158 quiet [KNL] Disable most log messages
4163 See Documentation/admin-guide/md.rst.
4166 See Documentation/admin-guide/blockdev/ramdisk.rst.
4171 [KNL] Enable or disable trusting the use of the
4172 CPU's random number generator (if available) to
4177 [KNL] Enable or disable trusting the use of a
4178 seed passed by the bootloader (if available) to
4182 ras=option[,option,...] [KNL] RAS-specific options
4185 Disable the Correctable Errors Collector,
4190 except that the string "all" can be used to
4193 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4194 the specified list of CPUs to be no-callback CPUs.
4196 offloaded to "rcuox/N" kthreads created for that
4197 purpose, where "x" is "p" for RCU-preempt, and
4198 "s" for RCU-sched, and "N" is the CPU number.
4200 which can be useful for HPC and real-time
4209 This improves the real-time response for the
4210 offloaded CPUs by relieving them of the need to
4213 periodically wake up to do the polling.
4216 Set maximum number of finished RCU callbacks to
4222 purposes, to verify correct tree setup.
4225 Set the number of jiffies to delay each step of
4226 RCU grace-period cleanup.
4229 Set the number of jiffies to delay each step of
4230 RCU grace-period initialization.
4233 Set the number of jiffies to delay each step of
4234 RCU grace-period pre-initialization, that is,
4235 the propagation of recent CPU-hotplug changes up
4239 If set to zero, move all RCU_SOFTIRQ processing to
4240 per-CPU rcuc kthreads. Defaults to a non-zero
4242 Specify rcutree.use_softirq=0 to use rcuc kthreads.
4245 Disable autobalancing of the rcu_node combining
4248 cache-to-cache transfer latencies.
4251 Change the number of CPUs assigned to each
4254 and for NUMA systems with large remote-access
4261 to PAGE_SIZE. The cache allows to reduce the
4262 pressure to page allocator, also it makes the
4263 whole algorithm to behave better in low memory
4267 Set delay from grace-period initialization to
4268 first attempt to force quiescent states.
4273 Set delay between subsequent attempts to force
4278 Set required age in jiffies for a
4280 soliciting quiescent-state help from
4287 rcutree.jiffies_to_sched_qs. Any attempt to set
4292 Set the SCHED_FIFO priority of the RCU per-CPU
4295 and for the RCU grace-period kthreads (rcu_bh,
4297 set, valid values are 1-99 and the default is 1
4298 (the least-favored priority). Otherwise, when
4299 RCU_BOOST is not set, valid values are 0-99 and
4300 the default is zero (non-realtime operation).
4303 Set the number of NOCB callback kthreads in
4304 each group, which defaults to the square root
4306 the wakeup overhead on the global grace-period
4308 each group's NOCB grace-period kthread.
4311 Set threshold of queued RCU callbacks beyond which
4315 Set threshold of queued RCU callbacks below which
4316 batch limiting is re-enabled.
4319 Set threshold of queued RCU callbacks beyond which
4320 RCU's force-quiescent-state scan will aggressively
4321 enlist help from cond_resched() and sched IPIs to
4323 Set to less than zero to make this be set based
4324 on rcutree.qhimark at boot time and to zero to
4325 disable more aggressive help enlistment.
4328 Set wakeup interval for idle CPUs that have
4332 Set wakeup interval for idle CPUs that have
4338 Cause the grace-period kthread to get an extra
4340 it should at force-quiescent-state time.
4346 this specifies an rcu_read_unlock()-time delay
4347 in microseconds. This defaults to zero.
4350 of RCU-protected pointers after the relevant
4354 Commandeer a sysrq key to dump out Tree RCU's
4360 grace-period primitives such as call_rcu().
4366 corresponding flavor of rcu_barrier() to allow
4367 previously posted callbacks to drain.
4371 grace-period primitives.
4374 Set test-start holdoff period. The purpose of
4375 this parameter is to delay the start of the
4376 test until boot completes in order to avoid
4380 Set to measure performance of kfree_rcu() flooding.
4393 Set number of RCU readers. The value -1 selects
4395 "n" less than -1 selects N-n+1, where N is again
4396 the number of CPUs. For example, -2 selects N
4397 (the number of CPUs), -3 selects N+1, and so on.
4398 A value of "n" less than or equal to -N selects
4402 Set number of RCU writers. The values operate
4407 Specify the RCU implementation to test.
4411 complete. This is useful for hands-off automated
4418 Write-side holdoff between grace periods,
4423 Set duration of force_quiescent_state bursts
4427 Set holdoff time within force_quiescent_state bursts
4431 Set wait time between force_quiescent_state bursts
4435 Enable RCU grace-period forward-progress testing
4439 Specify the fraction of a CPU-stall-warning
4440 period to do tight-loop forward-progress testing.
4443 Number of seconds to wait between successive
4444 forward-progress tests.
4448 need_resched() during tight-loop forward-progress
4452 Use conditional/asynchronous update-side
4456 Use expedited update-side primitives, if available.
4459 Use normal (non-expedited) asynchronous
4460 update-side primitives, if available.
4463 Use normal (non-expedited) synchronous
4464 update-side primitives, if available. If all
4468 they are all non-zero.
4473 flavors take kindly to this sort of thing.
4476 Leak an RCU-protected pointer out of the reader.
4478 intended to test the ability of things like
4479 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
4483 Set callbacks/threads for rcu_barrier() testing.
4486 Set number of concurrent RCU writers. These just
4491 Set number of RCU readers. The value -1 selects
4492 N-1, where N is the number of CPUs. A value
4493 "n" less than -1 selects N-n-2, where N is again
4494 the number of CPUs. For example, -2 selects N
4495 (the number of CPUs), -3 selects N+1, and so on.
4498 Enable debug-object double-call_rcu() testing.
4501 Set time (s) after boot for CPU-hotplug testing.
4504 Set time (jiffies) between CPU-hotplug operations,
4505 or zero to disable CPU-hotplug testing.
4508 Set the number of read-then-exit kthreads used
4509 to test the interaction of RCU updaters and
4510 task-exit processing.
4513 The number of times in a given read-then-exit
4514 episode that a set of read-then-exit kthreads
4519 read-then-exit testing episodes.
4522 Set task-shuffle interval (s). Shuffling tasks
4523 allows some CPUs to go into dyntick-idle mode
4527 Set time (s) after boot system shutdown. This
4528 is useful for hands-off automated testing.
4531 Duration of CPU stall (s) to test RCU CPU stall
4532 warnings, zero to disable.
4535 Sleep while stalling if set. This will result
4537 to any other stall-related activity.
4540 Time to wait (s) after boot before inducing stall.
4543 Disable interrupts while stalling if set.
4547 grace-period kthread to test RCU CPU stall
4548 warnings, zero to disable. If both stall_cpu
4556 Time (s) to stutter testing, for example, specifying
4557 five seconds causes the test to run for five seconds,
4559 ability to transition abruptly to and from idle.
4573 Test RCU's dyntick-idle handling. See also the
4577 Specify the RCU implementation to test.
4596 Set timeout for RCU CPU stall warning messages.
4599 Use expedited grace-period primitives, for
4603 real-time latency, and degrade energy efficiency.
4607 Use only normal grace-period primitives,
4610 real-time latency, CPU utilization, and
4611 energy efficiency, but can expose users to
4612 increased grace-period latency. This parameter
4619 only normal grace-period primitives. No effect
4623 Set time in jiffies during which RCU tasks will
4626 number avoids disturbing real-time workloads,
4630 Set timeout in jiffies for RCU task stall warning
4631 messages. Disable with a value less than or equal
4632 to zero.
4643 force - Override the decision by the kernel to hide the
4653 E.g. to turn on cmt and turn off mba use:
4663 (prefix with 'panic_' to set mode for panic
4668 to be used for rebooting.
4671 Set test-start holdoff period. The purpose of
4672 this parameter is to delay the start of the
4673 test until boot completes in order to avoid
4677 Set the number of loops over the synchronization
4679 reduces noise due to loop start/end overhead,
4680 but the default has already reduced the per-pass
4681 noise to a handful of picoseconds on ca. 2020
4685 Set number of readers. The default value of -1
4690 Set number of runs, each of which is dumped onto
4694 Set the read-side critical-section duration,
4698 Specify the read-protection implementation to test.
4702 test. This defaults to 1 (shut it down) when
4703 refscale is built into the kernel and to 0 (leave
4710 [KNL, SMP] Set scheduler's default relax_domain_level.
4711 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
4713 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
4717 is assumed to be I/O ports; otherwise it is memory.
4719 reservetop= [X86-32]
4726 Set the amount of memory to reserve for BIOS at
4729 reset_devices [KNL] Force drivers to reset the underlying device
4741 See Documentation/power/swsusp-and-swap-files.rst
4743 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
4746 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
4754 no Disable hibernation and resume.
4756 (that will set all pages holding image data
4757 during restoration read-only).
4765 AMD-based UNRET and IBPB mitigations alone do not stop
4767 sibling threads. For that reason, STIBP is used on pro-
4771 off - no mitigation
4772 auto - automatically select a migitation
4773 auto,nosmt - automatically select a mitigation,
4777 ibpb - On AMD, mitigate short speculation
4782 ibpb,nosmt - Like "ibpb" above but will disable SMT
4786 unret - Force enable untrained return thunks,
4787 only effective on AMD f15h-f17h based
4789 unret,nosmt - Like unret, but will disable SMT when STIBP
4794 time according to the CPU.
4796 Not specifying this option is equivalent to retbleed=auto.
4811 Set number of hash buckets for route cache
4813 ring3mwait=disable
4814 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
4817 ro [KNL] Mount root device read-only on boot
4820 on Mark read-only kernel memory as read-only (default).
4821 off Leave read-only kernel memory writable for debugging.
4826 debug-uart get routed to the D+ and D- pins of the usb
4832 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
4835 rootflags= [KNL] Set root filesystem mount option string
4837 rootfstype= [KNL] Set root filesystem type
4839 rootwait [KNL] Wait (indefinitely) for root device to show up.
4845 Memory area to be used by remote processor image,
4848 rw [KNL] Mount root device read-write on boot
4853 Set s390 IOTLB flushing mode
4866 schedstats= [KNL,X86] Enable or disable scheduled statistics.
4867 Allowed values are enable and disable. This feature
4872 [KNL, SMP] Set a decay shift for scheduler thermal
4888 Number of seconds to hold off before starting
4889 test. Defaults to zero for module insertion and
4890 to 10 seconds for built-in smp_call_function()
4895 up to the chosen limit in seconds. Zero (the
4897 that requesting even small non-zero numbers of
4902 Number of kthreads to spawn to invoke the
4904 The default of -1 specifies a number of kthreads
4905 equal to the number of CPUs.
4908 Number seconds to wait after the start of the
4909 test before initiating CPU-hotplug operations.
4912 Number seconds to wait between successive
4913 CPU-hotplug operations. Specifying zero (which
4914 is the default) disables CPU-hotplug operations.
4918 test after which to shut down the system. The
4920 Non-zero values are useful for automated tests.
4924 current test statistics to the console. A value
4928 The number of jiffies to wait between each change
4929 to the set of CPUs under test.
4933 preempt_disable() to disable CPU hotplug
4941 The probability weighting to use for the
4943 "wait" parameter. A value of -1 selects the
4944 default if all other weights are -1. However,
4946 value of -1 will instead select a weight of zero.
4949 The probability weighting to use for the
4951 non-zero "wait" parameter. See weight_single.
4954 The probability weighting to use for the
4962 The probability weighting to use for the
4964 non-zero "wait" parameter. See weight_single
4968 The probability weighting to use for the
4974 The probability weighting to use for the
4976 non-zero "wait" parameter. See weight_single
4979 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
4981 contention on all systems with CONFIG_MAXSMP set.
4983 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
4984 1 -- enable.
4988 security= [SECURITY] Choose a legacy "major" security module to
4992 selinux= [SELINUX] Disable or enable SELinux at boot time.
4995 0 -- disable.
4996 1 -- enable.
4999 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
5002 0 -- disable.
5003 1 -- enable.
5004 Default value is set via kernel config option.
5006 serialnumber [BUGS=X86-32]
5011 simeth= [IA-64]
5017 Disable merging of slabs with similar size. May be
5018 necessary if there is some reason to distinguish
5019 allocs to different slabs, especially in hardened
5023 most of the exposure of a heap attack to a single
5025 unchanged). Debug options disable merging on their
5031 A high setting may cause OOMs due to memory
5032 fragmentation. Defaults to 1 for systems with
5036 Enabling slub_debug allows one to determine the
5044 Determines whether to enable sysfs directories for
5045 memory cgroup sub-caches. 1 to enable, 0 to disable.
5047 Enabling this can lead to a very high number of debug
5053 A high setting may cause OOMs due to memory
5059 increase the slab order up to slub_max_order to
5060 generate a sufficiently large slab able to contain
5063 and the less frequently locks need to be acquired.
5078 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
5079 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
5080 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
5081 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
5082 smsc-ircc2.ircc_irq= [HW] IRQ line
5083 smsc-ircc2.ircc_dma= [HW] DMA channel
5084 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
5089 smt [KNL,S390] Set the maximum number of threads (logical
5090 CPUs) to use per physical CPU on systems capable of
5091 symmetric multithreading (SMT). Will be capped to the
5094 Default: -1 (no limit)
5097 [KNL] Should the soft-lockup detector generate panics.
5100 A value of 1 instructs the soft-lockup detector
5101 to panic the machine when a soft-lockup occurs. It is
5104 respective build-time switch to that functionality.
5107 [KNL] Should the soft-lockup detector generate
5112 See Documentation/admin-guide/laptops/sonypi.rst
5119 on - unconditionally enable, implies
5121 off - unconditionally disable, implies
5123 auto - kernel detects whether your CPU model is
5127 mitigation method at run time according to the
5133 against user space to user space task attacks.
5135 Selecting 'off' will disable both the kernel and
5140 retpoline - replace indirect branches
5141 retpoline,generic - Retpolines
5142 retpoline,lfence - LFENCE; indirect branch
5143 retpoline,amd - alias for retpoline,lfence
5144 eibrs - enhanced IBRS
5145 eibrs,retpoline - enhanced IBRS + Retpolines
5146 eibrs,lfence - enhanced IBRS + LFENCE
5147 ibrs - use IBRS to protect kernel
5149 Not specifying this option is equivalent to
5157 on - Unconditionally enable mitigations. Is
5160 off - Unconditionally disable mitigations. Is
5163 prctl - Indirect branch speculation is enabled,
5169 - Like "prctl" above, but only STIBP is
5175 - Same as "prctl" above, but all seccomp
5180 - Like "seccomp" above, but only STIBP is
5185 auto - Kernel selects the mitigation depending on
5191 Not specifying this option is equivalent to
5195 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
5198 Certain CPUs are vulnerable to an exploit against a
5201 to the same memory location may not be observed by
5204 be detected prior to instruction retirement at the
5209 example to read memory to which the attacker does not
5217 on - Unconditionally disable Speculative Store Bypass
5218 off - Unconditionally enable Speculative Store Bypass
5219 auto - Kernel detects whether the CPU model contains an
5225 prctl - Control Speculative Store Bypass per thread
5229 seccomp - Same as "prctl" above, but all seccomp threads
5230 will disable SSB unless they explicitly opt out.
5237 on,auto - On Power8 and Power9 insert a store-forwarding
5241 off - No action.
5243 Not specifying this option is equivalent to
5258 off - not enabled
5260 warn - the kernel will emit rate limited warnings
5265 fatal - the kernel will send SIGBUS to applications
5277 Certain CPUs are vulnerable to an MDS-like
5283 the RDRAND and RDSEED instructions to become
5290 off: Disable mitigation and remove
5291 performance impact to RDRAND and RDSEED
5294 Specifies how frequently to check for
5295 grace-period sequence counter wrap for the
5296 srcu_data structure's ->srcu_gp_seq_needed field.
5297 The greater the number of bits set in this kernel
5307 expediting. Set to zero to disable automatic
5311 Speculative Store Bypass Disable control
5313 On CPUs that are vulnerable to the Speculative
5318 force-on: Unconditionally enable mitigation for
5320 force-off: Unconditionally disable mitigation for
5324 to allow userspace to register its
5330 to (for stacks growing down) resp. after (for stacks
5335 Setting this to true through kernel command line will
5336 disable the stack depot thereby saving the static memory
5337 consumed by the stack hash table. By default this is set
5338 to false.
5343 stacktrace_filter=[function-list]
5345 will trace at boot up. function-list is a comma separated
5353 Set the STI (builtin display/keyboard on the HP-PARISC
5355 as the initial boot-console.
5370 An administrator who wishes to reserve some of these
5372 kernel's sunrpc client considers to be privileged
5373 using these two parameters to set the minimum and
5384 Control how the NFS server code allocates CPUs to
5396 to global on non-NUMA machines)
5402 RPC calls that can be sent from the client to a
5403 server. Increasing these values may allow you to
5409 Sets the number of seconds to remain in a suspend test
5412 is set. Default value is 5.
5421 controller if no parameter or 1 is given or disable
5422 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
5424 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
5426 <int> -- Number of I/O TLB slabs
5427 force -- force using of bounce buffers even if they
5429 noforce -- Never use bounce buffers (for debugging)
5434 Set a sysctl parameter, right before loading the init
5435 process, as if the value was written to the respective
5439 later by a loaded module cannot be set this way.
5443 Enable/disable old style sysfs layout for old udev
5448 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
5453 Ignore sysrq setting - this boot parameter will
5458 Set the number of tcp_metrics_hash slots.
5460 ram pages. This is used to specify the TCP metrics
5461 cache size. See Documentation/networking/ip-sysctl.rst
5467 Specify "mem" (for Suspend-to-RAM) or "standby" (for
5470 the optional capability to repeat N number of times.
5472 wakeup-capable RTC alarm.
5475 Set number of hash buckets for TCP connection
5478 -1: disable all active trip points in all thermal zones
5482 -1: disable all critical trip points in all thermal zones
5486 Set to disable actions on ACPI thermal zone
5490 1: disable ACPI thermal control
5493 -1: disable all passive trip points
5494 <degrees C>: override all passive trip points to this
5499 <deci-seconds>: poll all this frequency
5517 topology updates sent by the hypervisor to this
5521 Prevent the CPU-hotplug component of torturing
5525 Dump the ftrace buffer at torture-test shutdown,
5529 with rotating-rust storage.
5537 as a workaround for some chips which fail to
5543 [FTRACE] will set tracing buffer size on each cpu.
5545 trace_event=[event-list]
5546 [FTRACE] Set and start specified trace events in order
5547 to facilitate early boot debugging. The event-list is a
5548 comma separated list of trace events to enable. See
5551 trace_options=[option-list]
5552 [FTRACE] Enable or disable tracer options at boot.
5553 The option-list is a comma delimited list of options
5555 to echo the option name into
5559 For example, to enable stacktrace option (to dump the
5560 stack trace of each event), add to the command line:
5568 Have the tracepoints sent to printk as well as the
5574 To turn off having tracepoints sent to printk,
5581 Having tracepoints sent to printk() and activating high
5583 the system to live lock.
5586 [FTRACE] enable this option to disable tracing when a
5592 the WARNING dump is called, which prevents the trace to
5595 This option can also be set at run time via the sysctl
5601 Can be used to control the default behavior of the system
5602 with respect to transparent hugepages.
5603 See Documentation/admin-guide/mm/transhuge.rst
5606 tsc= Disable clocksource stability checks for TSC.
5610 as the stability checks done at bootup. Used to enable
5611 high-resolution timer mode on older hardware, and in
5613 [x86] noirqtime: Do not use TSC to do irq accounting.
5614 Used to run time disable IRQ_TIME_ACCOUNTING on any
5620 [x86] nowatchdog: disable clocksource watchdog. Used
5637 on - Enable TSX on the system. Although there are
5639 TSX has been known to be an accelerator for
5640 several previous speculation-related CVEs, and
5644 off - Disable TSX on the system. (Note that this
5646 not vulnerable to MDS, i.e., have
5652 auto - Disable TSX if X86_BUG_TAA is present,
5655 Not specifying this option is equivalent to tsx=off.
5657 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
5663 Similar to Micro-architectural Data Sampling (MDS)
5665 Synchronization Extensions (TSX) are vulnerable to an
5667 information to a disclosure gadget under certain
5671 data can be used in a cache side channel attack, to
5672 access data to which the attacker does not have direct
5678 full - Enable TAA mitigation on vulnerable CPUs
5681 full,nosmt - Enable TAA mitigation and disable SMT on
5684 vulnerable to cross-thread TAA attacks.
5685 off - Unconditionally disable TAA mitigation
5687 On MDS-affected machines, tsx_async_abort=off can be
5689 are mitigated with the same mechanism so in order to disable
5690 this mitigation, you need to specify mds=off too.
5692 Not specifying this option is equivalent to
5699 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
5705 See also Documentation/input/devices/joystick-parport.rst
5707 udbg-immortal [PPC] When debugging early kernel crashes that
5713 Set number of hash buckets for UDP/UDP-Lite connections
5715 uhci-hcd.ignore_oc=
5717 Some badly-designed motherboards generate lots of
5718 bogus events, for ports that aren't wired to
5719 anything. Set this parameter to avoid log spamming.
5728 (default -1 = authorized except for wireless USB,
5730 if device connected to internal port)
5734 for newly-detected USB devices (default 2). This
5736 autosuspended. Devices for which the delay is set
5737 to a negative value won't be autosuspended at all.
5740 [USB] Set to log all usbfs traffic (default 0 = off).
5743 [USB] Maximum number of bytes to snoop in each URB
5747 [USB] Set to cycle leds on hubs (default 0 = off).
5762 [USB] Specifies timeout for the initial 64-byte
5766 usbcore.nousb [USB] Disable the USB subsystem
5769 [USB] A list of quirk entries to augment the built-in
5772 VendorID:ProductID:Flags. The IDs are 4-digit hex
5773 numbers and Flags is a set of letters. Each letter
5774 will change the built-in quirk; setting it if it is
5775 clear and clearing it if it is set. The letters have
5779 a 255-byte read);
5783 Set-Interface requests);
5792 talking to these interfaces);
5800 microframe = 125 microseconds) to be
5802 (bInterval-1).
5820 to be disconnected before suspend to
5829 [USBHID] The interval which mice are to be polled at.
5832 [USBHID] The interval which joysticks are to be polled at.
5835 [USBHID] The interval which keyboards are to be polled at.
5837 usb-storage.delay_use=
5841 usb-storage.quirks=
5842 [UMS] A list of quirks entries to supplement or
5843 override the built-in unusual_devs list. List
5846 and Product ID values (4-digit hex numbers) and
5847 Flags is a set of characters, each corresponding
5848 to a common usb-storage quirk flag as follows:
5866 i = IGNORE_DEVICE (don't bind to this
5871 l = NOT_LOCKABLE (don't try to lock and
5888 u = IGNORE_UAS (don't bind to the uas driver);
5890 medium is write-protected).
5899 1 - undefined instruction events
5900 2 - system calls
5901 4 - invalid data aborts
5902 8 - SIGSEGV faults
5903 16 - SIGBUS faults
5917 vdso=0: disable VDSO mapping
5919 vdso32= [X86] Control the 32-bit vDSO
5920 vdso32=1: enable 32-bit VDSO
5921 vdso32=0 or vdso32=2: disable 32-bit VDSO
5924 details. If CONFIG_COMPAT_VDSO is set, the default is
5931 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
5933 vector= [IA-64,SMP]
5940 If set to 1, on receiving an ACPI notify event
5942 level and then send out the event to user space through
5943 the allocated input device; If set to 0, video driver
5956 <irq> := interrupt number (as passed to
5964 vga= [BOOT,X86-32] Select a particular video mode
5966 Documentation/admin-guide/svga.rst.
5969 passed to the kernel using a special protocol.
5975 interface is meant to allow for selectively
5981 - Disable all of the above options
5983 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
5984 size of <nn>. This can be used to increase the
5985 minimum size (128MB on x86). It can also be used to
6002 vsyscall= [X86-64]
6003 Controls the behavior of vsyscalls (i.e. calls to
6005 code). Most statically-linked binaries and older
6019 them quite hard to use for exploits but
6029 see VGA-softcursor.txt. Default: 2 = underline.
6034 This is a 16-member array composed of values
6035 ranging from 0-255.
6040 This is a 16-member array composed of values
6041 ranging from 0-255.
6046 This is a 16-member array composed of values
6047 ranging from 0-255.
6052 Set system-wide default UTF-8 mode for all tty's.
6053 Default is 1, i.e. UTF-8 mode is enabled for all
6058 Format=<-1|0|1>
6059 Set system-wide default for whether a cursor
6060 is shown on new VTs. Default is -1,
6065 vt.italic= [VT] Default color for italic text; 0-15.
6068 vt.underline= [VT] Default color for underlined text; 0-15.
6072 see Documentation/watchdog/watchdog-parameters.rst
6073 or other driver-specific files in the
6078 Set the hard lockup detector stall duration
6080 threshold is set to twice the value. A value of 0
6086 warn stall conditions and dump internal state to
6090 it can be updated at runtime by writing to the
6094 By default, all work items queued to unbound
6095 workqueues are affine to the NUMA nodes they're
6097 general. If NUMA affinity needs to be disabled for
6099 that this also can be controlled per-workqueue for
6103 Per-cpu workqueues are generally preferred because
6104 they show better performance thanks to cache
6105 locality; unfortunately, per-cpu workqueues tend to
6108 Enabling this makes the per-cpu workqueues which
6109 were observed to contribute significantly to power
6110 consumption unbound, leading to measurably lower
6118 Workqueue used to implicitly guarantee that work
6123 forces round-robin CPU selection to flush out
6128 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
6132 x86_intel_mid_timer= [X86-32,APBT]
6138 xen_512gb_limit [KNL,X86-64,XEN]
6140 to use only up to 512 GB of RAM. The reason to do so is
6142 save/restore/migration must be enabled to handle larger
6148 ide-disks -- unplug primary master IDE devices
6149 aux-ide-disks -- unplug non-primary-master IDE devices
6150 nics -- unplug network devices
6151 all -- unplug all emulated devices (NICs and IDE disks)
6152 unnecessary -- unplugging emulated devices is
6153 unnecessary even if the host did not respond to
6155 never -- do not unplug even if version check succeeds
6167 Disables the PV optimizations forcing the HVM guest to
6173 [KNL,X86,XEN] Disable the vector callback for Xen
6177 Boolean option to control scrubbing pages before giving them back
6178 to Xen, for use by other domains. Can be also changed at runtime
6182 xen_timer_slop= [X86-64,XEN]
6183 Set the timer slop (in nanoseconds) for the virtual Xen
6190 The time (in seconds) to wait before giving up to boot
6191 in case initial ballooning fails to free enough memory.
6197 How long to delay EOI handling in case of event
6202 should start to delay EOI handling. Default is 2.
6205 Boolean parameter to disable using fifo event handling
6207 preferred over the 2-level event handling, as it is
6212 Disables the PV optimizations forcing the guest to run
6218 which allow the hypervisor to 'idle' the guest on lock
6228 allows the fallback firmware mode to be used:
6230 off Fallback to firmware control of XIVE interrupt
6234 xhci-hcd.quirks [USB,KNL]
6236 host controller quirks. Meaning of each bit can be
6242 Passing only "xmon" is equivalent to "xmon=early".