Lines Matching +full:lock +full:- +full:detect +full:- +full:function +full:- +full:integer +full:- +full:n +full:- +full:enable
16 force -- enable ACPI if default was off
17 on -- enable ACPI but allow fallback to DT [arm64,riscv64]
18 off -- disable ACPI if default was on
19 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tolerant of platforms that are not
22 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT to memory
24 nocmcff -- Disable firmware first mode for corrected
28 nospcr -- disable console in ACPI SPCR table as
45 If set to vendor, prefer vendor-specific driver
77 Documentation/firmware-guide/acpi/debug.rst for more information about
80 Enable processor driver info messages:
82 Enable AML "Debug" output, i.e., stores to the Debug
85 Enable all messages related to ACPI hardware:
109 Enable table checksum verification during early stage.
135 Format: <byte> or <bitmap-list>
138 Disable auto-serialization of AML methods
141 auto-serialization feature.
159 Ignore the ACPI-based watchdog interface (WDAT) and let
180 acpi_osi=! # disable all built-in OS vendor
182 acpi_osi=!! # enable all built-in OS vendor
244 For broken nForce2 BIOS resulting in XT-PIC timer.
253 as soon as the kernel's real-mode entry point is called.
291 See Documentation/sound/alsa-configuration.rst
298 align_va_addr= [X86-64]
303 CPU-intensive style benchmark, and it can vary highly in
306 32: only for 32-bit processes
307 64: only for 64-bit processes
308 on: enable for both 32- and 64-bit processes
309 off: disable for both 32- and 64-bit processes
319 Allow execve() of 32-bit applications and setting of the
321 subset of the CPUs support 32-bit EL0. When this
322 parameter is present, the set of CPUs supporting 32-bit
324 and hot-unplug operations may be restricted.
326 See Documentation/arch/arm64/asymmetric-32bit.rst for more
329 amd_iommu= [HW,X86-64]
332 fullflush - Deprecated, equivalent to iommu.strict=1
333 off - do not initialize any AMD IOMMU found in
335 force_isolation - Force device isolation for all
340 force_enable - Force enable the IOMMU on platforms known
343 pgtbl_v1 - Use v1 page table for DMA-API (Default).
344 pgtbl_v2 - Use v2 page table for DMA-API.
345 irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
346 nohugepages - Limit page-sizes used for v1 page-tables
348 v2_pgsizes_only - Limit page-sizes used for v1 page-tables
352 amd_iommu_dump= [HW,X86-64]
353 Enable AMD IOMMU driver option to dump the ACPI table
358 amd_iommu_intr= [HW,X86-64]
361 legacy - Use legacy interrupt remapping mode.
362 vapic - Use virtual APIC mode, which allows IOMMU
364 This mode requires kvm-amd.avic=1.
369 Do not enable amd_pstate as the default
393 Disable amd-pstate preferred core.
406 Power management functions (SPARCstation-4/5 + deriv.)
408 Disable APC CPU standby support. SPARCstation-Fox does
409 not play well with APC CPU idle - disable it if you have
412 apic [APIC,X86-64] Use IO-APIC. Default.
418 when initialising the APIC and IO-APIC components.
439 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
442 0 -- disable.
443 1 -- enable.
446 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
480 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
488 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
497 audit= [KNL] Enable the audit sub-system
499 0 | off - kernel audit is disabled and can not be
501 unset - kernel audit is initialized but disabled and
503 1 | on - kernel audit is initialized and partially
513 bau= [X86_UV] Enable the BAU on SGI UV. The default
516 0 - Disable the BAU.
517 1 - Enable the BAU.
518 unset - Disable the BAU.
557 See Documentation/block/cmdline-partition.rst
565 Format: integer
571 See Documentation/admin-guide/bootconfig.rst
576 bttv.pll= See Documentation/admin-guide/media/bttv.rst
585 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
604 inclusive. See arch/mips/include/asm/pgtable-bits.h
614 - foo isn't auto-mounted if you mount all cgroups in
616 - foo isn't visible as an individually mountable
618 - if foo is an optional feature then the feature is
624 Specifying "pressure" disables per-cgroup pressure
641 semi-legacy software can check this file to decide
644 cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
650 nosocket -- Disable socket memory accounting.
651 nokmem -- Disable kernel memory accounting.
652 nobpf -- Disable BPF memory accounting.
657 0 -- check protection applied by kernel (includes
659 1 -- check protection requested by application.
671 numbers X. Note the Linux-specific bits are not necessarily
672 stable over kernel options, but the vendor-specific
692 force such clocks to be always-on nor does it reserve
696 information, see Documentation/driver-api/clk.rst.
698 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
715 [X86-32] pit,hpet,tsc;
722 [X86-64] hpet,tsc
727 Enable/disable the eventstream feature of the ARM
728 architected timer so that code using WFE-based polling
742 clocksource-wdtest.holdoff= [KNL]
748 cma=nn[MG]@[start[MG][-end[MG]]]
759 Sets the size of kernel per-numa memory area for
761 per-numa CMA altogether. And If this option is not
763 With per-numa CMA enabled, DMA users on node nid will
790 com20020= [HW,NET] ARCnet - COM20020 chipset
794 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
798 ARCnet - COM90xx chipset (memory-mapped buffers)
805 Format: y|n|Y|N|1|0
817 tty<n> Use the virtual console device <n>.
819 ttyS<n>[,options]
823 "p" is parity ("n", "o", or "e"), "n" is number of
827 See Documentation/admin-guide/serial-console.rst for more
832 <DEVNAME>:<n>.<n>[,options]
842 $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
843 /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
856 Start an early, polled-mode console on the 8250/16550
859 MMIO inter-register address stride is either 8-bit
860 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
864 the h/w is not re-initialized.
866 hvc<n> Use the hypervisor console device <n>. This is for
884 "[time stamp] text\n" format (time stamp may not be
888 Switch to syslog format: "<%u>[time stamp] text\n"
891 syscall, or to executing "dmesg -S --raw" or to reading
903 coresight_cpu_debug.enable
906 Enable/disable the CPU sampling based debugging.
908 1: enable debugging at boot time
915 disable the cpuidle sub-system
921 disable the cpufreq sub-system
928 cpu_init_udelay=N
929 [X86,EARLY] Delay for N microsec between assert and de-assert
935 [SMP] Enable/disable parallel bringup of secondary CPUs
949 configurations enable this option unconditionally,
950 like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
958 [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
961 See Documentation/admin-guide/kdump/kdump.rst for further details.
966 start-[end] where start and end are both
968 Documentation/admin-guide/kdump/kdump.rst for an example.
971 [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
979 [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
985 for 32-bit devices won't run out. Kernel would try to allocate
988 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
989 --> arm64: 128MiB
990 --> riscv: 128MiB
991 --> loongarch: 128MiB
1021 [KNL] Disable crypto self-tests
1029 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
1030 function call handling. When switched on,
1044 See also Documentation/input/devices/joystick-parport.rst
1046 debug [KNL,EARLY] Enable kernel debugging (events log level).
1049 [KNL,EARLY] Enable printing [hashed] pointers early in the
1057 [KNL] verbose locking self-tests
1060 self-tests.
1062 (no extra messages), setting it to -1 (all bits set)
1063 will print _a_lot_ more information - normally only
1066 debug_objects [KNL,EARLY] Enable object debugging
1093 useful to also enable the page_owner functionality.
1094 on: enable the feature
1098 Format: { on, no-mount, off }
1100 no-mount:
1105 get a -EPERM as result when trying to register files
1109 Default value is set in build-time with a kernel configuration.
1111 debugpat [X86] Enable PAT debugging
1121 Documentation/admin-guide/mm/hugetlbpage.rst.
1135 delayacct [KNL] Enable per-task delay accounting
1144 not match list of supported models and enable otherwise
1221 entries for DMA-API debugging code. One entry is
1222 required per DMA-API allocation. Use this if the
1223 DMA-API debugging code disables itself because the
1227 With this option the DMA-API debugging driver
1238 registers, vector registers, or integer registers.
1251 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1276 Control how the dt_cpu_ftrs device-tree binding is
1286 what data is available or for reverse-engineering.
1290 Enable debug messages at boot time. See
1291 Documentation/admin-guide/dynamic-debug-howto.rst
1295 Enable debug messages in early_ioremap support. This
1302 determined by stdout-path property in device tree's
1307 Start an early, polled-mode console on a Cadence
1318 Start an early, polled-mode console on the 8250/16550
1320 MMIO inter-register address stride is either 8-bit
1321 (mmio) or 32-bit (mmio32 or mmio32be).
1324 in the same format described for "console=ttyS<n>"; if
1331 Start an early, polled-mode console on a pl011 serial
1335 the driver will use only 32-bit accessors to read/write
1344 Start an early, polled-mode console on a meson serial
1350 Start an early, polled-mode console on an msm serial
1356 Start an early, polled-mode console on an msm serial
1362 Start an early, polled-mode console on a serial port
1368 Start an early, polled-mode console on a serial port
1374 Use RISC-V SBI (Supervisor Binary Interface) for early
1392 Start an early, polled-mode console on a lantiq serial
1406 Start an early, polled-mode, output-only console on the
1411 Start an early, polled-mode console on the
1417 Start an early, polled-mode console on a Qualcomm
1425 coherent non-x86 systems that use system memory for
1444 earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
1488 on: enable EDAC to report H/W event. May be overridden
1501 debug: enable misc debug output.
1528 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1545 elanfreq= [X86-32]
1546 See comment before function elanfreq_setup() in
1553 See Documentation/admin-guide/kdump/kdump.rst for details.
1561 Enable PIN 1 of APIC timer
1569 0 -- permissive (log only, no denials).
1570 1 -- enforcing (deny and log).
1603 See also Documentation/fault-injection/.
1607 See Documentation/admin-guide/sysctl/net.rst for
1611 See Documentation/admin-guide/blockdev/floppy.rst.
1613 forcepae [X86-32]
1614 Forcefully enable Physical Address Extension (PAE).
1620 fred= [X86-64]
1621 Enable/disable Flexible Return and Event Delivery.
1623 on: enable FRED when it's present.
1671 ftrace_filter=[function-list]
1672 [FTRACE] Limit the functions traced by the function
1673 tracer at boot up. function-list is a comma-separated
1678 ftrace_notrace=[function-list]
1680 function-list. This list can be changed at run time
1684 ftrace_graph_filter=[function-list]
1686 by the function graph tracer at boot up.
1687 function-list is a comma-separated list of functions
1691 ftrace_graph_notrace=[function-list]
1693 function-list. This list is a comma-separated list of
1698 [FTRACE] Used with the function graph tracer. This is
1699 the max depth it will trace into a function. This value
1713 off -- Don't create device links from firmware info.
1714 permissive -- Create device links from firmware info
1717 on -- Create device links from firmware info and use it
1719 rpm -- Like "on", but also use to order runtime PM.
1732 strict -- Default. Continue waiting on consumers to
1734 timeout -- Give up waiting on consumers and call
1744 See also Documentation/input/devices/joystick-parport.rst
1748 gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART
1774 gcov_persist= [GCOV] When non-zero (default), profiling data for
1780 goldfish [X86] Enable the goldfish android emulator platform.
1784 gpio-mockup.gpio_mockup_ranges
1787 gpio-mockup.gpio_mockup_named_lines
1796 the "Enable 0" bit of the configuration register.
1800 the "Enable 0" bit of the configuration register.
1819 against bounds-checking flaws in the kernel's
1827 [KNL] Should the hard-lockup detector generate
1843 auto - Hash pointers unless slab_debug is enabled.
1844 always - Always hash pointers (even if slab_debug is
1846 never - Never hash pointers. This option should only
1854 for 64-bit NUMA, off otherwise.
1862 corresponding firmware-first mode error processing
1872 during restoration read-only).
1897 highres= [KNL] Enable/disable high resolution timer mode.
1916 hpet= [X86-32,HPET] option to control HPET usage
1917 Format: { enable (default) | disable | force |
1933 number of pages to allocate per-node can be specified.
1934 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1935 Format: <integer> or (node format)
1936 <node>:<integer>[,<node>:<integer>]
1945 Documentation/admin-guide/mm/hugetlbpage.rst.
1955 Note that this parameter only applies to non-gigantic huge pages.
1965 boot-time allocation of gigantic hugepages is skipped.
1982 on: enable HVO
2000 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
2006 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
2013 on lock contention.
2028 Set device-properties for ACPI-enumerated I2C-attached
2029 touchscreen, to e.g. fix coordinates of upside-down
2037 Omit "=<val>" entirely Set a boolean device-property
2038 Unsigned number Set a u32 device-property
2039 Anything else Set a string device-property
2042 i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
2043 touchscreen-inverted-y
2045 i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
2046 touchscreen-size-y=1080:touchscreen-inverted-y:
2047 firmware-name=gsl1680-vendor-model.fw:silead,home-button
2051 [HW] Enable printing of interrupt data from the KBD port
2052 (disabled by default, and as a pre-condition
2054 i8042.direct [HW] Put keyboard port into non-translated mode
2068 suspend-to-ram transitions, only during s2r
2070 Format: { 1 | Y | y | 0 | N | n }
2072 0, N, n: don't ever reset controller
2092 -1 -- never invert brightness
2093 0 -- machine default
2094 1 -- force brightness inversion
2096 ia32_emulation= [X86-64]
2098 When true, allows loading 32-bit programs and executing 32-bit
2123 idle=nomwait: Disable mwait for CPU C-states
2151 legacy only accept legacy-NaN binaries, if supported
2153 2008 only accept 2008-NaN binaries, if supported
2157 emulated accept any binaries but enable FPU emulator
2164 'relaxed' straps the emulator for both legacy-NaN and
2165 2008-NaN, whereas 'strict' enables legacy-NaN only on
2174 Ignore loglevel setting - this will print /all/
2241 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2242 "ima-sigv2" }
2243 Default: "ima-ng"
2266 ima= [IMA] Enable or disable IMA
2275 on: Enable mitigation (default).
2281 stuff: Deploy RSB-fill mitigation when retpoline is
2286 Documentation/admin-guide/hw-vuln/indirect-target-selection.rst
2297 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2298 initcall functions. Useful for debugging built-in
2339 int_pln_enable [X86] Enable power limit notification interrupt
2343 0 -- basic integrity auditing messages. (Default)
2344 1 -- additional integrity auditing messages.
2348 Enable intel iommu driver.
2364 Enable the Intel IOMMU scalable mode if the hardware
2372 could harm performance of some high-throughput
2381 1 to 9 specify maximum depth of C-state.
2385 Do not enable intel_pstate as the default
2390 algorithms for p-state selection. There are two
2391 P-state selection algorithms provided by
2394 on whether or not the hardware managed P-states
2401 used along with the hardware-managed P-states (HWP)
2404 Enable intel_pstate on systems that prohibit it by default
2405 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2406 instead of acpi-cpufreq may disable platform features, such
2408 P-States information being indicated to OSPM and therefore
2411 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2413 Do not enable hardware P state control (HWP)
2424 Allow per-logical-CPU P-State performance control limits using
2427 Do not enable capacity-aware scheduling (CAS) on
2430 intremap= [X86-64,Intel-IOMMU,EARLY]
2431 on enable Interrupt Remapping (default)
2435 BIOS x2APIC opt-out request will be ignored
2438 enable MSIs delivered as posted interrupts
2478 AMD Gart HW IOMMU-specific options:
2497 Do scatter-gather (SG) merging. Implies "force"
2501 Don't do scatter-gather (SG) merging.
2514 0 - Try to allocate a 32-bit DMA address first, before
2516 1 - Allocate directly from the full usable range,
2518 greater than 32-bit addressing.
2522 0 - Lazy mode.
2528 1 - Strict mode.
2531 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2533 legacy driver-specific options takes precedence.
2538 0 - Use IOMMU translation for DMA.
2539 1 - Bypass the IOMMU for DMA.
2540 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2542 io7= [HW] IO7 for Marvel-based Alpha systems
2557 See Documentation/admin-guide/nfs/nfsroot.rst.
2593 Enables support for pseudo-NMIs in the kernel. This
2598 [RISC-V,EARLY]
2600 as IPIs. Intended for system where IMSIC is trap-n-emulated,
2619 [Deprecated - use cpusets instead]
2620 Format: [flag-list,]<cpu-list>
2653 "number of CPUs in system - 1".
2679 The format of <cpu-list> is described above.
2683 ivrs_ioapic [HW,X86-64]
2684 Provide an override to the IOAPIC-ID<->DEVICE-ID
2688 For example, to map IOAPIC-ID decimal 10 to
2694 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2697 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2701 ivrs_hpet [HW,X86-64]
2702 Provide an override to the HPET-ID<->DEVICE-ID
2706 For example, to map HPET-ID decimal 10 to
2712 * To map HPET-ID decimal 0 to PCI device 00:14.0
2715 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2719 ivrs_acpihid [HW,X86-64]
2720 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2724 For example, to map UART-HID:UID AMD0020:0 to
2730 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2733 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2757 the kernel for non-movable allocations. The requested
2767 subsystem. Note that allocations like PTEs-from-HighMem
2775 for non-movable allocations and remaining memory is used
2786 gdb or control-c on the dbgp connection. When
2787 not using this parameter you use sysrq-g to break into
2792 or a supported polling keyboard driver (non-usb).
2819 Format: { "0" | "1" | "off" | "on" | "y" | "n" }
2821 "0" | "off" | "n" - kexec handover is disabled
2822 "1" | "on" | "y" - kexec handover is enabled
2828 ranges that can only be used for non-kernel
2839 parameter defines the size of additional per-node
2844 Configure the RouterBoard 532 series on-chip
2847 kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable
2853 kprobe_event=[probe-list]
2854 [FTRACE] Add kprobe events and enable at boot time.
2855 The probe-list is a semicolon delimited list of probe
2872 kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
2885 execution by eliminating the write-protection faults
2886 and MMU lock contention that would otherwise be
2907 If enabled, KVM will enable virtualization in hardware
2911 If disabled, KVM will dynamically enable and disable
2912 virtualization on-demand when creating and destroying
2920 is that doing so may interfere with using out-of-tree
2937 guests do need not to enable it for nested guests.
2942 the value is N KVM will zap 1/Nth of the 4KiB pages every
2947 back to huge pages. If the value is a non-zero N, KVM will
2948 zap a portion (see ratio above) of the pages every N msecs.
2952 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2955 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2956 a.k.a. Two-Dimensional Page Tables. Default is 1
2960 kvm-arm.mode=
2966 nvhe: Standard nVHE-based mode, without support for
2973 nested: VHE-based mode with support for nested
2981 command-line.
2985 kvm-arm.vgic_v3_group0_trap=
2986 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2989 kvm-arm.vgic_v3_group1_trap=
2990 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2993 kvm-arm.vgic_v3_common_trap=
2997 kvm-arm.vgic_v4_enable=
3001 kvm-arm.wfe_trap_policy=
3010 kvm-arm.wfi_trap_policy=
3019 kvm_cma_resv_ratio=n [PPC,EARLY]
3024 Format: <integer>
3027 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
3028 a.k.a. Two-Dimensional Page Tables. Default is 1
3032 kvm-intel.emulate_invalid_guest_state=
3034 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
3040 kvm-intel.flexpriority=
3045 kvm-intel.nested=
3049 kvm-intel.unrestricted_guest=
3055 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
3056 CVE-2018-3620.
3067 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
3087 on - enable the interface for the mitigation
3152 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3158 lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3162 value for LAPIC timer one-shot implementation. Default
3185 libata.force= [LIBATA] Force configurations. The format is a comma-
3197 first fan-out link behind PMP device. It does not
3211 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3218 * rstonce: only attempt one reset during hot-unplug
3221 * [no]dbdelay: Enable or disable the extra 200ms delay
3227 * [no]ncqtrim: Enable or disable queued DSM TRIM.
3229 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3231 * [no]trim: Enable or disable (unqueued) TRIM.
3239 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
3241 * atapi_mod16_dma: Enable the use of ATAPI DMA for
3244 * [no]dmalog: Enable or disable the use of the
3247 * [no]iddevlog: Enable or disable access to the
3250 * [no]logdir: Enable or disable access to the general
3261 * external: Mark port as external (hotplug-capable).
3263 * [no]lpm: Enable or disable link power management.
3268 * [no]fua: Disable or enable FUA (Force Unit Access)
3281 Format: <integer>
3283 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3284 Format: <integer>
3287 Format: <integer>
3290 Format: <integer>
3294 Enable the kernel lockdown feature. If set to
3302 Set the time limit in jiffies for a lock
3315 Specify the number of self-propagating call_rcu()
3323 occasional long-duration lock hold time. Defaults
3327 Specify the maximum lock nesting depth that
3334 Set the number of locking read-acquisition kthreads.
3339 Set the number of locking write-acquisition kthreads.
3342 Set time (s) after boot for CPU-hotplug testing.
3345 Set time (s) between CPU-hotplug operations, or
3346 zero to disable CPU-hotplug testing.
3349 Do periodic testing of real-time lock priority
3354 non-real-time spinlocks, due to their disabling
3355 of preemption. Note that non-realtime mutexes
3368 Set task-shuffle interval (jiffies). Shuffling
3369 tasks allows some CPUs to go into dyntick-idle
3374 is useful for hands-off automated testing.
3390 Enable additional printk() statements.
3393 Run the write-side locktorture kthreads at
3394 sched_set_fifo() real-time priority.
3412 7 (KERN_DEBUG) debug-level messages
3414 log_buf_len=n[KMG] [KNL,EARLY]
3416 n must be a power of two and greater than the
3424 logo.nologo [FB] Disables display of the built-in Linux logo.
3442 an IEEE 1284-compliant printer is attached; if
3446 lpj=n [KNL]
3448 time-consuming boot-time autodetection (up to 250 ms per
3460 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3468 Example: machtype=lemote-yeeloong-2f-7inch
3471 will bring up during bootup. maxcpus=n : n >= 0 limits
3472 the kernel to bring up 'n' processors. Surely after
3476 While n=0 is a special case, it is equivalent to "nosmp",
3480 (loop.max_loop) unconditionally pre-created at init time. The default
3483 devices can be requested on-demand with the
3484 /dev/loop-control interface.
3486 mce= [X86-{32,64}]
3523 do not opt-in to Local MCE delivery. Use legacy method
3527 enable logging of machine checks left over from
3532 enable though to make sure you log even machine check
3544 don't overwrite the bios-set CMCI threshold. This boot
3553 force-enable recoverable machine check code paths
3559 See Documentation/admin-guide/md.rst.
3566 Control mitigation for the Micro-architectural Data
3581 full - Enable MDS mitigation on vulnerable CPUs
3582 full,nosmt - Enable MDS mitigation and disable
3584 off - Unconditionally disable MDS mitigation
3586 On TAA-affected machines, mds=off can be prevented by
3595 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3610 [ARC,MICROBLAZE] - the limit applies only to low memory,
3613 [ARM64] - only limits memory covered by the linear
3626 [ARM,MIPS,EARLY] - override the memory layout
3633 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3636 memblock=debug [KNL,EARLY] Enable memblock debug messages.
3640 per-device physically contiguous DMA buffers.
3648 See Documentation/admin-guide/mm/memory-hotplug.rst.
3650 memmap=exactmap [KNL,X86,EARLY] Enable setting of an exact
3673 Example: Exclude memory from 0x18690000-0x1869ffff
3687 memmap=<size>%<offset>-<oldtype>+<newtype>
3689 from <oldtype> to <newtype>. If "-<oldtype>" is left
3701 both detect corruption and prevent the kernel
3704 repeatable BIOS-originated corruption always
3720 [KNL,X86,ARM] Boolean flag to enable this feature.
3738 memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
3739 Format: <integer>
3748 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3754 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3758 s2idle - Suspend-To-Idle
3759 shallow - Power-On Suspend or equivalent (if supported)
3760 deep - Suspend-To-RAM or equivalent (if supported)
3761 See Documentation/admin-guide/pm/sleep-states.rst.
3763 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3772 Enable or disable the microcode minimal revision
3779 0 - The attached screen is the 3.5" TFT
3780 1 - The attached screen is the 7" TFT
3781 2 - The VGA Shield is attached (1024x768)
3785 b - Enable backlight. The TFT backlight pin will be
3789 c - Enable the s3c camera interface.
3790 t - Reserved for enabling touchscreen support. The
3794 https://repo.or.cz/w/linux-2.6/mini2440.git
3799 arch-independent options, each of which is an
3800 aggregation of existing arch-specific options.
3830 ssbd=force-off [ARM64]
3843 have other ways of avoiding SMT-based attacks.
3857 supports attack-vector based controls as documented in
3858 Documentation/admin-guide/hw-vuln/attack_vector_controls.rst
3882 full - Enable mitigation on vulnerable CPUs
3884 full,nosmt - Enable mitigation and disable SMT on
3887 off - Unconditionally disable mitigation
3900 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3904 specified is not a valid <bool>, enable asynchronous
3905 probe on this module. Otherwise, enable/disable
3911 by default. To enable/disable async probing for a
3930 module_blacklist= [KNL] Do not load a comma-separated list of
3955 movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory
3962 Format: <name>,<region-number>,<size>,<offset>
3965 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3972 ('y', default) or cooked coordinates ('n')
3975 Enable printing debug information related to MTRR
3988 mtrr_spare_reg_nr=n [X86,EARLY]
3989 Format: <integer>
4004 something different and driver-specific.
4014 [NETFILTER] Enable connection tracking flow accounting
4016 1 to enable accounting
4044 [NFS] enable 64-bit inode numbers.
4045 If zero, the NFS client will fake up a 32-bit inode
4047 of returning the full 64-bit number.
4048 The default is to return 64-bit inode numbers.
4083 [NFS4] Specify an additional fixed unique ident-
4094 If you want to enable the kernel legacy behaviour of
4114 driver. A non-zero value sets the minimum interval
4119 server-to-server copies for which this server is
4131 server-to-server copy, knfsd temporarily mounts
4138 See Documentation/admin-guide/nfs/nfsroot.rst.
4140 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
4141 See Documentation/admin-guide/nfs/nfsroot.rst.
4143 nfsrootdebug [NFS] enable nfsroot debugging messages.
4144 See Documentation/admin-guide/nfs/nfsroot.rst.
4148 NMI stack-backtrace request.
4157 0 - turn hardlockup detector in nmi_watchdog off
4158 1 - turn hardlockup detector in nmi_watchdog on
4159 rNNN - configure the watchdog with raw perf event 0xNNN
4172 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
4176 no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes.
4177 Forces kernel to use 3-level paging instead.
4179 no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4180 kernel to use 4-level paging instead.
4215 no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4217 noexec32 [X86-64]
4218 This affects only 32-bit executables.
4219 noexec32=on: enable non-executable mappings (default)
4221 noexec32=off: disable non-executable mappings
4232 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4234 legacy floating-point registers on task switch.
4259 nohz= [KNL] Boottime enable/disable dynamic ticks
4279 nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4281 [Deprecated - use intremap=off]
4287 noirqdebug [X86-32] Disables the code which attempts to detect and
4297 no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page
4300 no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4302 nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC.
4304 nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer.
4306 nomce [X86-32] Disable Machine Check Exception
4308 nomfgpt [X86-32] Disable Multi-Function General Purpose
4314 not load if they could possibly displace the pre-
4317 perform display-mode changes or accelerated rendering.
4330 nopcid [X86-64,EARLY] Disable the PCID cpu feature.
4335 nopti [X86-64,EARLY]
4345 which allow the hypervisor to 'idle' the guest on lock
4351 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4357 no-scroll [VGA] Disables scrollback.
4358 This is required for the Braillex ib80-piezo Braille
4361 nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4381 nosoftlockup [KNL] Disable the soft-lockup detector.
4387 nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4400 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4407 timer IRQ sources, i.e., the IO-APIC timer. This can
4412 [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4425 no-vmw-sched-clock
4430 soft-lockup and NMI watchdog (hard-lockup).
4434 nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode.
4442 enabling legacy floating-point and sse state.
4460 could support. nr_cpus=n : n >= 1 limits the kernel to
4461 support 'n' processors. It could be larger than the
4464 n. So during boot up some boot time memory for per-cpu
4465 variables need be pre-allocated for later physical cpu
4479 numa=fake=<N>
4481 If given as an integer, fills all system RAM with N
4484 numa=fake=<N>U
4486 If given as an integer followed by 'U', it will
4487 divide each physical node into N emulated nodes.
4492 soft-reserved memory partitioning.
4494 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4496 Allowed values are enable and disable
4501 See Documentation/admin-guide/sysctl/vm.rst for details.
4503 ohci1394_dma=early [HW,EARLY] enable debugging via the ohci1394 driver.
4504 See Documentation/core-api/debugging-via-ohci1394.rst for more
4519 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4523 boundary - index of last SLC block on Flex-OneNAND.
4525 lock - Configure if Flex-OneNAND boundary should be locked.
4527 1 indicates lock status, 0 indicates unlock status.
4539 used to enable/disable page randomization. The state of
4544 page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
4548 on: enable the feature
4550 page_poison= [KNL,EARLY] Boot-time parameter changing the state of
4558 Format: <integer>
4578 See Documentation/admin-guide/tainted-kernels.rst for
4645 Currently this function knows 686a and 8231 chips.
4650 Set to non-zero to probe primary and secondary ISA
4656 Set to non-zero if a chip is present that snoops speed
4673 IORDY enable mask. Set individual bits to allow IORDY
4704 Set to non-zero to probe tertiary and further ISA
4720 Set to non-zero to probe QDI controllers. By default
4725 Set to non-zero to probe Winbond controllers. Use
4755 bus/device/function address which may change
4761 to a device through multiple device/function
4772 bios [X86-32] force use of PCI BIOS, don't access
4774 has a non-standard PCI host bridge.
4775 nobios [X86-32] disallow use of PCI BIOS, only direct
4781 data in IO port 0xCFC, both 32-bit).
4783 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4784 the function, IO port 0xCFA, also 8-bit, sets
4786 through ports 0xC000-0xCFFF).
4793 root domains (aka PCI segments, in ACPI-speak).
4796 check_enable_amd_mmconf [X86] check for and enable
4801 disable the use of MSI interrupts system-wide.
4805 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4806 primary IO-APIC for bridges that cannot disable
4813 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4837 F0000h-100000h range.
4838 lastbus=N [X86] Scan all buses thru bus #N. Can be
4842 assign-busses [X86] Always assign all PCI bus
4863 <linux-pci@vger.kernel.org>.
4867 a bug to <linux-pci@vger.kernel.org>.
4879 bfsort Sort PCI devices into breadth-first order.
4882 nobfsort Don't sort PCI devices into breadth-first order.
4884 tuning and use the BIOS-configured MPS defaults.
4894 configuration allows peer-to-peer DMA between
4897 that hot-added devices will work.
4912 A PCI-PCI bridge can be specified if resource
4918 for 4096-byte alignment.
4919 ecrc= Enable/disable PCIe ECRC (transaction layer
4920 end-to-end CRC checking). Only effective if
4943 realloc= Enable/disable reallocating PCI bridge resources
4951 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4982 bit-0 : ACS Source Validation
4983 bit-1 : ACS Translation Blocking
4984 bit-2 : ACS P2P Request Redirect
4985 bit-3 : ACS P2P Completion Redirect
4986 bit-4 : ACS Upstream Forwarding
4987 bit-5 : ACS P2P Egress Control
4988 bit-6 : ACS Direct Translated P2P
4996 ACS to enable P2P Request Redirect, disable
4998 Validation unchanged from whatever power-up
5006 one PCI domain per PCI function
5010 system-wide.
5012 pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power
5016 force Enable ASPM even on devices that claim not to support it.
5024 dpc-native Use native PCIe service for DPC only. May
5031 force Forcibly enable power management of all PCIe ports
5041 Keep all power-domains already enabled by bootloader on,
5046 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
5059 pirq= [SMP,APIC] Manual mp-table setup
5060 See Documentation/arch/x86/i386/IO-APIC.rst.
5064 See also Documentation/admin-guide/parport.rst.
5083 resume of devices during system-wide power transitions.
5085 dependencies are not well-defined, or for debugging
5091 Enable suspend/resume debug messages during boot up.
5094 Enable PNP debug messages (depends on the
5095 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
5104 { on | off | curr | res | no-curr | no-res }
5134 function to NULL. On Idle the CPU just reduces
5138 [PPC,ENABLE] This option catches any kernel floating point,
5149 none - Limited to cond_resched() calls
5150 voluntary - Limited to cond_resched() and might_sleep() calls
5151 full - Any section that isn't explicitly preempt disabled
5154 explicitly preempt disabled beyond the lock itself).
5155 lazy - Scheduler controlled. Similar to full but instead
5161 print-fatal-signals=
5167 coredump - etc.
5170 you might want to try "ulimit -i unlimited".
5177 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5182 or lockdep-detected issues (only if lock debug is on).
5190 Allows storing messages from non-panic CPUs into
5192 flushed to consoles by the panic-CPU on
5193 a best-effort basis.
5194 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5199 on - unlimited logging to /dev/kmsg from userspace
5200 off - logging to /dev/kmsg disabled
5201 ratelimit - ratelimit the logging
5205 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5212 - 'always': traditional behavior always allows mem overrides.
5213 - 'ptrace': only allow mem overrides for active ptracers.
5214 - 'never': never allow mem overrides.
5218 Limit processor to maximum C-state
5222 Ignore the _CST method to determine C-states,
5225 profile= [KNL] Enable kernel profiling via /proc/profile
5229 Param: "schedule" - profile schedule points.
5230 Param: "kvm" - profile VM exits.
5231 Param: <number> - step/bucket size as a power of 2 for
5236 prot_virt= [S390] enable hosting protected virtual machines
5243 psi= [KNL] Enable or disable pressure stall information
5262 pti= [X86-64] Control Page Table Isolation of user and
5267 on - unconditionally enable
5268 off - unconditionally disable
5269 auto - kernel detects whether your CPU model is
5275 [KNL] Number of legacy pty's. Overwrites compiled-in
5287 See Documentation/admin-guide/md.rst.
5290 See Documentation/admin-guide/blockdev/ramdisk.rst.
5305 [KNL,EARLY] Enable or disable kernel stack offset
5309 cross-syscall address exposures. This is only
5312 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5315 ras=option[,option,...] [KNL] RAS-specific options
5321 rcu_nocbs[=cpu-list]
5326 enable the no-callback CPU mode, which prevents
5329 callbacks will instead be offloaded to "rcuox/N"
5331 "p" for RCU-preempt, "s" for RCU-sched, and "g"
5333 "N" is the CPU number. This reduces OS jitter on
5335 and real-time workloads. It can also improve
5339 list of CPUs is set to no-callback mode from boot.
5343 no-callback mode from boot but the mode may be
5354 This improves the real-time response for the
5365 Do only a one-line RCU CPU stall warning when
5366 there is an ongoing too-long CSD-lock wait.
5372 If triggered before the RCU grace-period machinery
5382 RCU grace-period cleanup.
5386 RCU grace-period initialization.
5390 RCU grace-period pre-initialization, that is,
5391 the propagation of recent CPU-hotplug changes up
5395 Set delay from grace-period initialization to
5408 soliciting quiescent-state help from
5420 Set the SCHED_FIFO priority of the RCU per-CPU
5421 kthreads (rcuc/N). This value is also used for
5422 the priority of the RCU boost threads (rcub/N)
5423 and for the RCU grace-period kthreads (rcu_bh,
5425 set, valid values are 1-99 and the default is 1
5426 (the least-favored priority). Otherwise, when
5427 RCU_BOOST is not set, valid values are 0-99 and
5428 the default is zero (non-realtime operation).
5433 On callback-offloaded (rcu_nocbs) CPUs,
5434 RCU reduces the lock contention that would
5436 use of the ->nocb_bypass list. However, in the
5437 common non-flooded case, RCU queues directly to
5438 the main ->cblist in order to avoid the extra
5439 overhead of the ->nocb_bypass list and its lock.
5441 a single jiffy, RCU pre-queues the callbacks into
5442 the ->nocb_bypass queue. The definition of "too
5446 On callback-offloaded (rcu_nocbs) CPUs, avoid
5459 batch limiting is re-enabled.
5463 RCU's force-quiescent-state scan will aggressively
5471 Set the page-cache refill delay (in milliseconds)
5472 in response to low-memory conditions. The range
5476 Set the shift-right count to use to compute
5477 the callback-invocation batch limit bl from
5484 Please note that this callback-invocation batch
5485 limit applies only to non-offloaded callback
5494 cache-to-cache transfer latencies.
5500 and for NUMA systems with large remote-access
5516 the wakeup overhead on the global grace-period
5518 each group's NOCB grace-period kthread.
5521 Cause the grace-period kthread to get an extra
5523 it should at force-quiescent-state time.
5536 this specifies an rcu_read_unlock()-time delay
5540 of RCU-protected pointers after the relevant
5550 per-CPU rcuc kthreads. Defaults to a non-zero
5570 How to enable it:
5580 grace-period primitives such as call_rcu().
5591 grace-period primitives.
5594 Set test-start holdoff period. The purpose of
5612 Test the double-argument variant of kfree_rcu().
5614 rcuscale.kfree_rcu_test_single, both the single-
5615 and double-argument variants are tested.
5618 Test the single-argument variant of kfree_rcu().
5620 rcuscale.kfree_rcu_test_double, both the single-
5621 and double-argument variants are tested.
5635 does not affect the data-collection interval,
5640 Set number of RCU readers. The value -1 selects
5641 N, where N is the number of CPUs. A value
5642 "n" less than -1 selects N-n+1, where N is again
5643 the number of CPUs. For example, -2 selects N
5644 (the number of CPUs), -3 selects N+1, and so on.
5645 A value of "n" less than or equal to -N selects
5651 N, where N is the number of CPUs
5658 complete. This is useful for hands-off automated
5662 Enable additional printk() statements.
5665 Write-side holdoff between grace periods,
5670 Additional write-side holdoff between grace
5688 for RCU grace-period forward-progress testing
5695 Specify the fraction of a CPU-stall-warning
5696 period to do tight-loop forward-progress testing.
5700 forward-progress tests.
5704 need_resched() during tight-loop forward-progress
5708 Use conditional/asynchronous update-side
5709 normal-grace-period primitives, if available.
5712 Use conditional/asynchronous update-side
5713 expedited-grace-period primitives, if available.
5716 Use conditional/asynchronous update-side
5717 normal-grace-period primitives that also take
5722 Use conditional/asynchronous update-side
5723 expedited-grace-period primitives that also take
5747 Use expedited update-side primitives, if available.
5750 Use normal (non-expedited) asynchronous
5751 update-side primitives, if available.
5754 Use polled update-side normal-grace-period
5758 Use polled update-side expedited-grace-period
5762 Use polled update-side normal-grace-period
5767 Use polled update-side expedited-grace-period
5791 Use normal (non-expedited) synchronous
5792 update-side primitives, if available. If all
5796 they are all non-zero.
5799 Enable grace-period wrap lag testing. Setting
5804 Set the value for grace-period wrap lag during
5819 the grace-period wrap lag will be set to the
5829 Leak an RCU-protected pointer out of the reader.
5832 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5844 Set number of RCU callback-offload togglers.
5849 callback-offload toggling attempts.
5852 Set number of RCU readers. The value -1 selects
5853 N-1, where N is the number of CPUs. A value
5854 "n" less than -1 selects N-n-2, where N is again
5855 the number of CPUs. For example, -2 selects N
5856 (the number of CPUs), -3 selects N+1, and so on.
5859 Enable debug-object double-call_rcu() testing.
5862 Set time (s) after boot for CPU-hotplug testing.
5865 Set time (jiffies) between CPU-hotplug operations,
5866 or zero to disable CPU-hotplug testing.
5870 by a high-priority FIFO real-time task. Set to
5879 second) between preemptions by a high-priority
5880 FIFO real-time task. This delay is mediated
5885 The number of times in a given read-then-exit
5886 episode that a set of read-then-exit kthreads
5891 read-then-exit testing episodes.
5896 are entered from low-order bit up, and are
5898 0x1 bit is normal readers, 0x2 NMI-safe readers,
5899 and 0x4 light-weight readers.
5902 Set task-shuffle interval (s). Shuffling tasks
5903 allows some CPUs to go into dyntick-idle mode
5908 is useful for hands-off automated testing.
5917 any other stall-related activity. Note that
5918 in kernels built with CONFIG_PREEMPTION=n and
5921 Given CONFIG_PREEMPTION=n, this will suppress
5923 in scheduling-while-atomic splats.
5942 grace-period kthread to test RCU CPU stall
5966 of RCU priority-boost testing. Defaults to zero,
5973 Test RCU's dyntick-idle handling. See also the
5980 Enable additional printk() statements.
6028 Use expedited grace-period primitives, for
6032 real-time latency, and degrade energy efficiency.
6036 Use only normal grace-period primitives,
6039 real-time latency, CPU utilization, and
6041 increased grace-period latency. This parameter
6048 only normal grace-period primitives. No effect
6054 post-boot attempt at an expedited RCU grace
6055 period to instead use normal non-expedited
6056 grace-period processing.
6064 set to the default value of -1.
6067 Set the minimum number of callback-queuing-time
6068 lock-contention events per jiffy required to
6069 cause the RCU Tasks flavors to switch to per-CPU
6072 the default value of -1.
6077 of -1 allows this to be automatically (and
6085 number avoids disturbing real-time workloads,
6090 cancel laziness on that CPU. Use -1 to disable
6100 only printed prior to the stall-warning message
6148 force - Override the decision by the kernel to hide the
6187 There are some built-in platform specific "quirks"
6188 - you may see: "reboot: <name> series board detected.
6192 built-in quirk table, and use the generic default
6225 Set test-start holdoff period. The purpose of
6240 but the default has already reduced the per-pass
6245 Set number of readers. The default value of -1
6246 selects N, where N is roughly 75% of the number
6254 Set the read-side critical-section duration,
6258 Specify the read-protection implementation to test.
6267 Enable additional printk() statements.
6272 print every Nth verbose statement, where N is the value
6284 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6314 reservetop= [X86-32,EARLY]
6331 See Documentation/power/swsusp-and-swap-files.rst
6347 AMD-based UNRET and IBPB mitigations alone do not stop
6349 sibling threads. For that reason, STIBP is used on pro-
6353 off - no mitigation
6354 auto - automatically select a migitation
6355 auto,nosmt - automatically select a mitigation,
6359 ibpb - On AMD, mitigate short speculation
6364 ibpb,nosmt - Like "ibpb" above but will disable SMT
6368 unret - Force enable untrained return thunks,
6369 only effective on AMD f15h-f17h based
6371 unret,nosmt - Like unret, but will disable SMT when STIBP
6403 ro [KNL] Mount root device read-only on boot
6406 on Mark read-only kernel memory as read-only (default).
6407 off Leave read-only kernel memory writable for debugging.
6408 full Mark read-only kernel memory and aliases as read-only
6413 Enable the uart passthrough on the designated usb port
6415 debug-uart get routed to the D+ and D- pins of the usb
6421 block/early-lookup.c for details.
6446 rt_group_sched= [KNL] Enable or disable SCHED_RR/FIFO group scheduling
6451 rw [KNL] Mount root device read-write on boot
6480 solution to mutex-based priority inversion.
6485 schedstats= [KNL,X86] Enable or disable scheduled statistics.
6486 Allowed values are enable and disable. This feature
6504 Format: integer between 0 and 10
6510 to 10 seconds for built-in smp_call_function()
6517 that requesting even small non-zero numbers of
6524 The default of -1 specifies a number of kthreads
6529 test before initiating CPU-hotplug operations.
6533 CPU-hotplug operations. Specifying zero (which
6534 is the default) disables CPU-hotplug operations.
6540 Non-zero values are useful for automated tests.
6558 Enable additional printk() statements.
6562 smp_call_function_single() function with a zero
6563 "wait" parameter. A value of -1 selects the
6564 default if all other weights are -1. However,
6566 value of -1 will instead select a weight of zero.
6570 smp_call_function_single() function with a
6571 non-zero "wait" parameter. See weight_single.
6575 smp_call_function_many() function with a zero
6583 smp_call_function_many() function with a
6584 non-zero "wait" parameter. See weight_single
6589 smp_call_function_all() function with a zero
6595 smp_call_function_all() function with a
6596 non-zero "wait" parameter. See weight_single
6604 xtime_lock contention on larger systems, and/or RCU lock
6607 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6608 1 -- enable.
6613 enable at boot. This has been deprecated by the
6616 selinux= [SELINUX] Disable or enable SELinux at boot time.
6619 0 -- disable.
6620 1 -- enable.
6623 serialnumber [BUGS=X86-32]
6625 sev=option[,option...] [X86-64]
6628 Enable debug messages.
6631 Do not enable SEV-SNP (applies to host/hypervisor
6634 SEV-SNP guests.
6642 to set it to "all" by meaning -- no limit here.
6654 Documentation/admin-guide/mm/slab.rst.
6665 Documentation/admin-guide/mm/slab.rst.
6669 Enable merging of slabs with similar size when the
6681 Documentation/admin-guide/mm/slab.rst.
6687 Documentation/admin-guide/mm/slab.rst.
6702 Documentation/admin-guide/mm/slab.rst.
6723 for a CPU to release the CSD lock. This is
6729 using the csdlock_debug- kernel parameter.
6734 system. By default, let CSD-lock acquisition
6736 for this value provides a 5-minute timeout.
6738 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6739 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6740 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6741 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6742 smsc-ircc2.ircc_irq= [HW] IRQ line
6743 smsc-ircc2.ircc_dma= [HW] DMA channel
6744 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6753 Format: <integer>
6754 Default: -1 (no limit)
6757 [KNL] Should the soft-lockup detector generate panics.
6760 A value of 1 instructs the soft-lockup detector
6761 to panic the machine when a soft-lockup occurs. It is
6764 respective build-time switch to that functionality.
6767 [KNL] Should the soft-lockup detector generate
6772 See Documentation/admin-guide/laptops/sonypi.rst
6779 on - (default) Enable the HW or SW mitigation as
6782 vmexit - On systems which don't have the HW mitigation
6783 available, enable the SW mitigation on vmexit
6785 protected from VM-originated BHI attacks, but
6787 off - Disable the mitigation.
6794 on - unconditionally enable, implies
6796 off - unconditionally disable, implies
6798 auto - kernel detects whether your CPU model is
6807 Selecting 'on' will also enable the mitigation
6809 Selecting specific mitigation does not force enable
6817 retpoline - replace indirect branches
6818 retpoline,generic - Retpolines
6819 retpoline,lfence - LFENCE; indirect branch
6820 retpoline,amd - alias for retpoline,lfence
6821 eibrs - Enhanced/Auto IBRS
6822 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6823 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6824 ibrs - use IBRS to protect kernel
6834 on - Unconditionally enable mitigations. Is
6837 off - Unconditionally disable mitigations. Is
6840 prctl - Indirect branch speculation is enabled,
6846 - Like "prctl" above, but only STIBP is
6852 - Same as "prctl" above, but all seccomp
6853 threads will enable the mitigation unless
6857 - Like "seccomp" above, but only STIBP is
6862 auto - Kernel selects the mitigation depending on
6873 off - Disable mitigation
6874 microcode - Enable microcode mitigation only
6875 safe-ret - Enable sw-only safe RET mitigation (default)
6876 ibpb - Enable mitigation by issuing IBPB on
6878 ibpb-vmexit - Issue IBPB only on VMEXIT
6879 (cloud-specific mitigation)
6904 on - Unconditionally disable Speculative Store Bypass
6905 off - Unconditionally enable Speculative Store Bypass
6906 auto - Kernel detects whether the CPU model contains an
6912 prctl - Control Speculative Store Bypass per thread
6916 seccomp - Same as "prctl" above, but all seccomp threads
6924 on,auto - On Power8 and Power9 insert a store-forwarding
6928 off - No action.
6934 [X86] Enable split lock detection or bus lock detection
6939 for split lock detection or a debug exception for
6940 bus lock detection.
6942 off - not enabled
6944 warn - the kernel will emit rate-limited warnings
6947 the default on CPUs that support split lock
6948 detection or bus lock detection. Default
6952 fatal - the kernel will send SIGBUS to applications
6957 ratelimit:N -
6958 Set system wide rate limit to N bus locks
6959 per second for bus lock detection.
6960 0 < N <= 1000.
6962 N/A for split lock detection.
6970 #DB exception for bus lock is triggered only when
6977 Certain CPUs are vulnerable to an MDS-like
6997 This kernel-boot parameter defaults to 128,
6998 but takes effect only when the low-order four
7015 instead of the compile-time CONFIG_NR_CPUS.
7019 grace-period sequence counter wrap for the
7020 srcu_data structure's ->srcu_gp_seq_needed field.
7035 Specifies the number of no-delay instances
7042 Specifies the per-grace-period phase, number of
7043 non-sleeping polls of readers. Beyond this limit,
7049 Specifies number of microseconds of non-sleeping
7050 delay between each non-sleeping poll of readers.
7053 Specifies the number of update-side contention
7058 set for contention-based conversions to occur.
7068 force-on: Unconditionally enable mitigation for
7070 force-off: Unconditionally disable mitigation for
7072 kernel: Always enable mitigation in the
7092 stack traces. Pools are allocated on-demand up to this
7098 stacktrace_filter=[function-list]
7100 will trace at boot up. function-list is a comma-separated
7108 Set the STI (builtin display/keyboard on the HP-PARISC
7110 as the initial boot-console.
7122 Enable or disable strict sigaltstack size checks
7170 to global on non-NUMA machines)
7189 Format: { on | off | y | n | 1 | 0 }
7195 <int> -- Number of I/O TLB slabs
7196 <int> -- Second integer after comma. Number of swiotlb
7197 areas with their own lock. Will be rounded up
7199 force -- force using of bounce buffers even if they
7201 noforce -- Never use bounce buffers (for debugging)
7216 Ignore sysrq setting - this boot parameter will
7224 cache size. See Documentation/networking/ip-sysctl.rst
7230 Format: { "mem" | "standby" | "freeze" }[,N]
7231 Specify "mem" (for Suspend-to-RAM) or "standby" (for
7234 the optional capability to repeat N number of times.
7236 wakeup-capable RTC alarm.
7242 -1: disable all active trip points in all thermal zones
7246 -1: disable all critical trip points in all thermal zones
7253 -1: disable all passive trip points
7259 <deci-seconds>: poll all this frequency
7263 Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7268 See Documentation/admin-guide/mm/transhuge.rst for more
7276 Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7282 See Documentation/admin-guide/mm/transhuge.rst for more
7294 Prevent the CPU-hotplug component of torturing
7298 Dump the ftrace buffer at torture-test shutdown,
7302 with rotating-rust storage.
7307 disables verbose-printk() sleeping.
7310 Duration of each verbose-printk() sleep in jiffies.
7330 Format: integer pcr id
7339 Enable interrupts for the MMIO based physical layer
7343 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7365 the system to live lock.
7381 local - Use the per CPU time stamp counter
7385 global - Event time stamps are synchronize across
7388 counter - Simple counting of events (1, 2, ..)
7392 uptime - Use jiffies as the time stamp.
7393 perf - Use the same clock that perf uses.
7394 mono - Use ktime_get_mono_fast_ns() for time stamps.
7395 mono_raw - Use ktime_get_raw_fast_ns() for time
7397 boot - Use ktime_get_boot_fast_ns() for time stamps.
7401 trace_event=[event-list]
7403 to facilitate early boot debugging. The event-list is a
7404 comma-separated list of trace events to enable. See
7407 To enable modules, use :mod: keyword:
7411 The value before :mod: will only enable specific events
7415 trace_instance=[instance-info]
7431 will enable the "sched_switch" event (note, the "sched:" is optional, and
7440 traceoff - Have the tracing instance tracing disabled after it is created.
7441 traceprintk - Have trace_printk() write into this trace instance
7488 trace_options=[option-list]
7489 [FTRACE] Enable or disable tracer options at boot.
7490 The option-list is a comma delimited list of options
7496 For example, to enable stacktrace option (to dump the
7504 trace_trigger=[trigger-list]
7516 The above will enable the "stacktrace" trigger on the "sched_switch"
7533 [FTRACE] enable this option to disable tracing when a
7550 See Documentation/admin-guide/mm/transhuge.rst
7557 See Documentation/admin-guide/mm/transhuge.rst
7564 See Documentation/admin-guide/mm/transhuge.rst
7572 - "tpm"
7573 - "tee"
7574 - "caam"
7575 - "dcp"
7585 - "kernel"
7586 - the same value as trusted.source: "tpm" or "tee"
7587 - "default"
7610 off - disable the mitigation
7611 on - enable the mitigation (default)
7612 user - mitigate only user/kernel transitions
7613 vm - mitigate only guest/host transitions
7620 as the stability checks done at bootup. Used to enable
7621 high-resolution timer mode on older hardware, and in
7657 on - Enable TSX on the system. Although there are
7660 several previous speculation-related CVEs, and
7664 off - Disable TSX on the system. (Note that this
7672 auto - Disable TSX if X86_BUG_TAA is present,
7673 otherwise enable TSX on the system.
7677 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7683 Similar to Micro-architectural Data Sampling (MDS)
7698 full - Enable TAA mitigation on vulnerable CPUs
7701 full,nosmt - Enable TAA mitigation and disable SMT on
7704 vulnerable to cross-thread TAA attacks.
7705 off - Unconditionally disable TAA mitigation
7707 On MDS-affected machines, tsx_async_abort=off can be
7719 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7725 See also Documentation/input/devices/joystick-parport.rst
7727 udbg-immortal [PPC] When debugging early kernel crashes that
7733 Set number of hash buckets for UDP/UDP-Lite connections
7735 uhci-hcd.ignore_oc=
7736 [USB] Ignore overcurrent events (default N).
7737 Some badly-designed motherboards generate lots of
7762 unwind_debug [X86-64,EARLY]
7763 Enable unwinder debug output. This can be
7770 (default -1 = authorized (same as 1),
7776 for newly-detected USB devices (default 2). This
7804 [USB] Specifies timeout for the initial 64-byte
7811 [USB] A list of quirk entries to augment the built-in
7814 VendorID:ProductID:Flags. The IDs are 4-digit hex
7816 will change the built-in quirk; setting it if it is
7821 a 255-byte read);
7825 Set-Interface requests);
7844 (bInterval-1).
7864 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7882 usb-storage.delay_use=
7889 usb-storage.quirks=
7891 override the built-in unusual_devs list. List
7894 and Product ID values (4-digit hex numbers) and
7896 to a common usb-storage quirk flag as follows:
7919 l = NOT_LOCKABLE (don't try to lock and
7924 n = INITIAL_READ10 (force a retry of the
7938 medium is write-protected).
7947 1 - undefined instruction events
7948 2 - system calls
7949 4 - invalid data aborts
7950 8 - SIGSEGV faults
7951 16 - SIGBUS faults
7957 vdso=1: enable VDSO (the default)
7960 vdso32= [X86] Control the 32-bit vDSO
7961 vdso32=1: enable 32-bit VDSO
7962 vdso32=0 or vdso32=2: disable 32-bit VDSO
7972 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
8003 vga= [BOOT,X86-32] Select a particular video mode
8005 Documentation/admin-guide/svga.rst.
8019 P Enable page structure init time poisoning
8020 - Disable all of the above options
8044 vsyscall= [X86-64,EARLY]
8047 code). Most statically-linked binaries and older
8071 see vga-softcursor.rst. Default: 2 = underline.
8076 This is a 16-member array composed of values
8077 ranging from 0-255.
8082 This is a 16-member array composed of values
8083 ranging from 0-255.
8088 This is a 16-member array composed of values
8089 ranging from 0-255.
8094 Set system-wide default UTF-8 mode for all tty's.
8095 Default is 1, i.e. UTF-8 mode is enabled for all
8100 Format=<-1|0|1>
8101 Set system-wide default for whether a cursor
8102 is shown on new VTs. Default is -1,
8107 vt.italic= [VT] Default color for italic text; 0-15.
8110 vt.underline= [VT] Default color for underlined text; 0-15.
8114 see Documentation/watchdog/watchdog-parameters.rst
8115 or other driver-specific files in the
8129 Format: <cpu-list>
8150 Per-cpu work items which run for longer than this
8153 them from noticeably delaying other per-cpu work
8166 function has violated this threshold number of times.
8171 Per-cpu workqueues are generally preferred because
8173 locality; unfortunately, per-cpu workqueues tend to
8176 Enabling this makes the per-cpu workqueues which
8190 Documentation/core-api/workqueue.rst.
8203 forces round-robin CPU selection to flush out
8211 on - Enable writecombine, use WUC for ioremap_wc()
8212 off - Disable writecombine, use SUC for ioremap_wc()
8214 x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of
8218 xen_512gb_limit [KNL,X86-64,XEN]
8228 ide-disks -- unplug primary master IDE devices
8229 aux-ide-disks -- unplug non-primary-master IDE devices
8230 nics -- unplug network devices
8231 all -- unplug all emulated devices (NICs and IDE disks)
8232 unnecessary -- unplugging emulated devices is
8235 never -- do not unplug even if version check succeeds
8242 Enable multicall debugging when running as a Xen PV guest.
8249 Select whether to always use non-faulting (safe) MSR
8269 xen_timer_slop= [X86-64,XEN,EARLY]
8294 preferred over the 2-level event handling, as it is
8311 xive.store-eoi=off [PPC]
8317 xhci-hcd.quirks [USB,KNL]