Lines Matching +full:can +full:- +full:disable
9 accept_memory=eager can be used to accept all memory
16 force -- enable ACPI if default was off
17 on -- enable ACPI but allow fallback to DT [arm64,riscv64]
18 off -- disable ACPI if default was on
19 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tolerant of platforms that are not
22 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT to memory
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
50 If set to none, disable the ACPI backlight interface.
59 Disable AML predefined validation mechanism
60 This mechanism can repair the evaluation result to make
77 Documentation/firmware-guide/acpi/debug.rst for more information about
98 can interfere with legacy drivers.
130 by unsupported hardware/firmware features can result in
133 This facility can be used to prevent such uncontrolled
135 Format: <byte> or <bitmap-list>
138 Disable auto-serialization of AML methods
141 auto-serialization feature.
145 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
149 Disable installation of static SSDTs at early boot time
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
184 acpi_osi= # disable all strings
186 'acpi_osi=!' can be used in combination with single or
188 vendor string(s). Note that such command can only
199 can make '_OSI("Windows 2000")' TRUE.
203 exist in the ACPI namespace. NOTE that such command can
208 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
211 'acpi_osi=!*' can be used in combination with single or
213 string(s). Note that such command can affect the
223 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
225 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
244 For broken nForce2 BIOS resulting in XT-PIC timer.
253 as soon as the kernel's real-mode entry point is called.
286 off: disable AGP support
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]
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.
368 disable
392 disable
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.
419 For X86-32, this can also be used to specify an APIC
443 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
446 0 -- disable.
447 1 -- enable.
450 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
453 arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
456 arm64.nobti [ARM64] Unconditionally disable Branch Target
459 arm64.nogcs [ARM64] Unconditionally disable Guarded Control Stack
462 arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
465 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
468 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
471 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
474 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
498 audit= [KNL] Enable the audit sub-system
500 0 | off - kernel audit is disabled and can not be
502 unset - kernel audit is initialized but disabled and
504 1 | on - kernel audit is initialized and partially
515 behavior is to disable the BAU (i.e. bau=0).
517 0 - Disable the BAU.
518 1 - Enable the BAU.
519 unset - Disable the BAU.
547 O_EXCL. Default is Y and can be changed through the
551 Disable BERT OS support on buggy BIOSes.
554 Disable BGRT to avoid flickering OEM logo.
558 See Documentation/block/cmdline-partition.rst
569 Extended command line options can be added to an initrd
572 See Documentation/admin-guide/bootconfig.rst
577 bttv.pll= See Documentation/admin-guide/media/bttv.rst
586 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
605 inclusive. See arch/mips/include/asm/pgtable-bits.h
612 cgroup_disable= [KNL] Disable a particular controller or optional feature
613 Format: {name of the controller(s) or feature(s) to disable}
615 - foo isn't auto-mounted if you mount all cgroups in
617 - foo isn't visible as an individually mountable
619 - if foo is an optional feature then the feature is
623 cut the overhead, others just disable the usage. So
625 Specifying "pressure" disables per-cgroup pressure
628 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
637 cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
643 nosocket -- Disable socket memory accounting.
644 nokmem -- Disable kernel memory accounting.
645 nobpf -- Disable BPF memory accounting.
650 0 -- check protection applied by kernel (includes
652 1 -- check protection requested by application.
654 Value can be changed at runtime via
662 Disable CPUID feature X for the kernel. See
664 numbers X. Note the Linux-specific bits are not necessarily
665 stable over kernel options, but the vendor-specific
667 X can also be a string as appearing in the flags: line
676 Also note the kernel might malfunction if you disable
685 force such clocks to be always-on nor does it reserve
689 information, see Documentation/driver-api/clk.rst.
691 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
708 [X86-32] pit,hpet,tsc;
715 [X86-64] hpet,tsc
720 Enable/disable the eventstream feature of the ARM
721 architected timer so that code using WFE-based polling
722 loops can be debugged more effectively on production
735 clocksource-wdtest.holdoff= [KNL]
741 cma=nn[MG]@[start[MG][-end[MG]]]
752 Sets the size of kernel per-numa memory area for
754 per-numa CMA altogether. And If this option is not
756 With per-numa CMA enabled, DMA users on node nid will
783 com20020= [HW,NET] ARCnet - COM20020 chipset
787 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
791 ARCnet - COM90xx chipset (memory-mapped buffers)
820 See Documentation/admin-guide/serial-console.rst for more
833 can be viewed with:
835 $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
836 /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
838 In the above example, the console can be addressed with
849 Start an early, polled-mode console on the 8250/16550
852 MMIO inter-register address stride is either 8-bit
853 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
857 the h/w is not re-initialized.
863 Use to disable console output, i.e., to have kernel
884 syscall, or to executing "dmesg -S --raw" or to reading
899 Enable/disable the CPU sampling based debugging.
900 0: default value, disable debugging
908 disable the cpuidle sub-system
914 disable the cpufreq sub-system
922 [X86,EARLY] Delay for N microsec between assert and de-assert
928 [SMP] Enable/disable parallel bringup of secondary CPUs
937 notifiers can make the crashed kernel more unstable.
943 like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
946 [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
951 [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
954 See Documentation/admin-guide/kdump/kdump.rst for further details.
959 start-[end] where start and end are both
961 Documentation/admin-guide/kdump/kdump.rst for an example.
964 [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
972 [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
978 for 32-bit devices won't run out. Kernel would try to allocate
981 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
982 --> arm64: 128MiB
983 --> riscv: 128MiB
984 --> loongarch: 128MiB
987 0: to disable low allocation.
992 [KNL] Disable crypto self-tests
1000 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
1015 See also Documentation/input/devices/joystick-parport.rst
1028 [KNL] verbose locking self-tests
1031 self-tests.
1033 (no extra messages), setting it to -1 (all bits set)
1034 will print _a_lot_ more information - normally only
1069 Format: { on, no-mount, off }
1071 no-mount:
1072 Filesystem is not registered but kernel clients can
1073 access APIs and a crashkernel can be used to read
1076 get a -EPERM as result when trying to register files
1080 Default value is set in build-time with a kernel configuration.
1092 Documentation/admin-guide/mm/hugetlbpage.rst.
1106 delayacct [KNL] Enable per-task delay accounting
1150 can be useful when debugging issues that require an SLB
1153 disable= [IPV6]
1157 Disable RADIX MMU mode on POWER9
1160 Disable TLBIE instruction. Currently does not work
1164 Disable Dynamic DMA Window support. Use this
1182 Disable PIN 1 of APIC timer
1183 Can be useful to work around chipset bugs.
1185 dis_ucode_ldr [X86] Disable the microcode loader.
1192 entries for DMA-API debugging code. One entry is
1193 required per DMA-API allocation. Use this if the
1194 DMA-API debugging code disables itself because the
1198 With this option the DMA-API debugging driver
1199 filter feature can be enabled at boot time. Just
1201 The filter can be disabled or changed to another
1218 are enabled. In order to disable RFDS mitigation all
1222 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1247 Control how the dt_cpu_ftrs device-tree binding is
1257 what data is available or for reverse-engineering.
1262 Documentation/admin-guide/dynamic-debug-howto.rst
1273 determined by stdout-path property in device tree's
1278 Start an early, polled-mode console on a Cadence
1289 Start an early, polled-mode console on the 8250/16550
1291 MMIO inter-register address stride is either 8-bit
1292 (mmio) or 32-bit (mmio32 or mmio32be).
1302 Start an early, polled-mode console on a pl011 serial
1306 the driver will use only 32-bit accessors to read/write
1315 Start an early, polled-mode console on a meson serial
1321 Start an early, polled-mode console on an msm serial
1327 Start an early, polled-mode console on an msm serial
1333 Start an early, polled-mode console on a serial port
1339 Start an early, polled-mode console on a serial port
1345 Use RISC-V SBI (Supervisor Binary Interface) for early
1363 Start an early, polled-mode console on a lantiq serial
1377 Start an early, polled-mode, output-only console on the
1382 Start an early, polled-mode console on the
1388 Start an early, polled-mode console on a Qualcomm
1396 coherent non-x86 systems that use system memory for
1422 Append ",keep" to not disable it when the real console
1425 Only one of vga, serial, or usb debug port can
1433 You can find the port for a given device in
1443 The xen option can only be used in Xen domains.
1445 The sclp output can only be used on s390.
1447 The bios output can only be used on SuperH.
1457 off: disable H/W event reporting through EDAC.
1469 disable_early_pci_dma: disable the busmaster bit on all
1471 nochunk: disable reading files in "chunks" in the EFI
1472 boot stub, as chunking can cause problems with some
1474 noruntime : disable EFI runtime services support
1478 claim. Specify efi=nosoftreserve to disable this
1486 Using this parameter you can use more than 50% of
1495 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1508 but can only be used if the backing tty is available
1512 elanfreq= [X86-32]
1520 See Documentation/admin-guide/kdump/kdump.rst for details.
1529 Can be useful to work around chipset bugs
1536 0 -- permissive (log only, no denials).
1537 1 -- enforcing (deny and log).
1539 Value can be changed at runtime via
1543 Disable Error Record Serialization Table (ERST)
1570 See also Documentation/fault-injection/.
1574 See Documentation/admin-guide/sysctl/net.rst for
1578 See Documentation/admin-guide/blockdev/floppy.rst.
1580 forcepae [X86-32]
1582 Many Pentium M systems disable PAE but may have a
1587 fred= [X86-64]
1588 Enable/disable Flexible Return and Event Delivery.
1591 off: disable FRED, the default setting.
1600 ftrace ring buffer that can be read at:
1606 Optionally, the snapshot can also be defined for a tracing
1638 ftrace_filter=[function-list]
1640 tracer at boot up. function-list is a comma-separated
1641 list of functions. This list can be changed at run
1645 ftrace_notrace=[function-list]
1647 function-list. This list can be changed at run time
1651 ftrace_graph_filter=[function-list]
1654 function-list is a comma-separated list of functions
1655 that can be changed at run time by the
1658 ftrace_graph_notrace=[function-list]
1660 function-list. This list is a comma-separated list of
1661 functions that can be changed at run time by the
1667 can be changed at run time by the max_graph_depth file
1680 off -- Don't create device links from firmware info.
1681 permissive -- Create device links from firmware info
1684 on -- Create device links from firmware info and use it
1686 rpm -- Like "on", but also use to order runtime PM.
1699 strict -- Default. Continue waiting on consumers to
1701 timeout -- Give up waiting on consumers and call
1711 See also Documentation/input/devices/joystick-parport.rst
1715 gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART
1728 The mitigation may have a performance impact but can be
1732 force: Disable AVX to mitigate systems without
1737 off: Disable GDS mitigation.
1741 gcov_persist= [GCOV] When non-zero (default), profiling data for
1751 gpio-mockup.gpio_mockup_ranges
1754 gpio-mockup.gpio_mockup_named_lines
1786 against bounds-checking flaws in the kernel's
1789 off Disable hardened usercopy checks.
1792 [KNL] Should the hard-lockup detector generate
1798 for 64-bit NUMA, off otherwise.
1805 Disable Hardware Error Source Table (HEST) support;
1806 corresponding firmware-first mode error processing
1813 no Disable hibernation and resume.
1816 during restoration read-only).
1834 highres= [KNL] Enable/disable high resolution timer mode.
1853 hpet= [X86-32,HPET] option to control HPET usage
1854 Format: { enable (default) | disable | force |
1856 disable: disable HPET and use PIT instead
1870 number of pages to allocate per-node can be specified.
1871 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1879 hugepagesz=X hugepages=Y can be specified once for
1882 Documentation/admin-guide/mm/hugetlbpage.rst.
1887 of a CMA area per node can be specified.
1893 boot-time allocation of gigantic hugepages is skipped.
1904 off: disable HVO
1921 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1922 option. The value selected by this boot parameter can
1927 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1943 Set device-properties for ACPI-enumerated I2C-attached
1944 touchscreen, to e.g. fix coordinates of upside-down
1952 Omit "=<val>" entirely Set a boolean device-property
1953 Unsigned number Set a u32 device-property
1954 Anything else Set a string device-property
1957 i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1958 touchscreen-inverted-y
1960 i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
1961 touchscreen-size-y=1080:touchscreen-inverted-y:
1962 firmware-name=gsl1680-vendor-model.fw:silead,home-button
1967 (disabled by default, and as a pre-condition
1969 i8042.direct [HW] Put keyboard port into non-translated mode
1970 i8042.dumbkbd [HW] Pretend that controller can only read data from
1975 i8042.noloop [HW] Disable the AUX Loopback command while probing
1983 suspend-to-ram transitions, only during s2r
2007 -1 -- never invert brightness
2008 0 -- machine default
2009 1 -- force brightness inversion
2011 ia32_emulation= [X86-64]
2013 When true, allows loading 32-bit programs and executing 32-bit
2038 idle=nomwait: Disable mwait for CPU C-states
2066 legacy only accept legacy-NaN binaries, if supported
2068 2008 only accept 2008-NaN binaries, if supported
2079 'relaxed' straps the emulator for both legacy-NaN and
2080 2008-NaN, whereas 'strict' enables legacy-NaN only on
2089 Ignore loglevel setting - this will print /all/
2097 print warning at first misuse. Can be changed via
2156 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2157 "ima-sigv2" }
2158 Default: "ima-ng"
2170 different crypto accelerators. This option can be used
2178 different crypto accelerators. This option can be used
2190 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2191 initcall functions. Useful for debugging built-in
2201 but as a debugging aid, one can get the
2226 default (disallow access to all but pkey 0). Can
2236 0 -- basic integrity auditing messages. (Default)
2237 1 -- additional integrity auditing messages.
2243 Disable intel iommu driver.
2265 could harm performance of some high-throughput
2274 1 to 9 specify maximum depth of C-state.
2277 disable
2283 algorithms for p-state selection. There are two
2284 P-state selection algorithms provided by
2287 on whether or not the hardware managed P-states
2294 used along with the hardware-managed P-states (HWP)
2298 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2299 instead of acpi-cpufreq may disable platform features, such
2301 P-States information being indicated to OSPM and therefore
2304 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2317 Allow per-logical-CPU P-State performance control limits using
2320 intremap= [X86-64,Intel-IOMMU,EARLY]
2322 off disable Interrupt Remapping
2323 nosid disable Source ID checking
2325 BIOS x2APIC opt-out request will be ignored
2326 nopost disable Interrupt Posting
2330 iomem= Disable strict checking of access to MMIO memory
2356 Intel machines). This can be used to prevent the usage
2365 Disable IOMMU bypass, using IOMMU for PCI devices.
2368 AMD Gart HW IOMMU-specific options:
2387 Do scatter-gather (SG) merging. Implies "force"
2391 Don't do scatter-gather (SG) merging.
2404 0 - Try to allocate a 32-bit DMA address first, before
2406 1 - Allocate directly from the full usable range,
2408 greater than 32-bit addressing.
2412 0 - Lazy mode.
2418 1 - Strict mode.
2421 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2423 legacy driver-specific options takes precedence.
2428 0 - Use IOMMU translation for DMA.
2429 1 - Bypass the IOMMU for DMA.
2430 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2432 io7= [HW] IO7 for Marvel-based Alpha systems
2447 See Documentation/admin-guide/nfs/nfsroot.rst.
2483 Enables support for pseudo-NMIs in the kernel. This
2502 [Deprecated - use cpusets instead]
2503 Format: [flag-list,]<cpu-list>
2509 Disable the tick when a single task runs as well as
2528 advised to use cpusets instead to disable scheduler load
2530 It offers a much more flexible interface where CPUs can
2533 You can move a process onto or off an "isolated" CPU via
2536 "number of CPUs in system - 1".
2562 The format of <cpu-list> is described above.
2566 ivrs_ioapic [HW,X86-64]
2567 Provide an override to the IOAPIC-ID<->DEVICE-ID
2569 By default, PCI segment is 0, and can be omitted.
2571 For example, to map IOAPIC-ID decimal 10 to
2577 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2580 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2584 ivrs_hpet [HW,X86-64]
2585 Provide an override to the HPET-ID<->DEVICE-ID
2587 By default, PCI segment is 0, and can be omitted.
2589 For example, to map HPET-ID decimal 10 to
2595 * To map HPET-ID decimal 0 to PCI device 00:14.0
2598 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2602 ivrs_acpihid [HW,X86-64]
2603 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2605 By default, PCI segment is 0, and can be omitted.
2607 For example, to map UART-HID:UID AMD0020:0 to
2613 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2616 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2640 the kernel for non-movable allocations. The requested
2650 subsystem. Note that allocations like PTEs-from-HighMem
2658 for non-movable allocations and remaining memory is used
2669 gdb or control-c on the dbgp connection. When
2670 not using this parameter you use sysrq-g to break into
2675 or a supported polling keyboard driver (non-usb).
2685 characters and can work in polling mode, you can use
2702 Configure the RouterBoard 532 series on-chip
2705 kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable
2711 kprobe_event=[probe-list]
2713 The probe-list is a semicolon delimited list of probe
2732 default value can be overridden via
2743 execution by eliminating the write-protection faults
2766 when KVM is loaded, and disable virtualization when KVM
2769 If disabled, KVM will dynamically enable and disable
2770 virtualization on-demand when creating and destroying
2778 is that doing so may interfere with using out-of-tree
2805 back to huge pages. If the value is a non-zero N, KVM will
2810 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2813 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2814 a.k.a. Two-Dimensional Page Tables. Default is 1
2815 (enabled). Disable by KVM if hardware lacks support
2818 kvm-arm.mode=
2822 none: Forcefully disable KVM.
2824 nvhe: Standard nVHE-based mode, without support for
2831 nested: VHE-based mode with support for nested
2836 mode to "protected" will disable kexec and hibernation
2839 command-line.
2843 kvm-arm.vgic_v3_group0_trap=
2844 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2847 kvm-arm.vgic_v3_group1_trap=
2848 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2851 kvm-arm.vgic_v3_common_trap=
2855 kvm-arm.vgic_v4_enable=
2859 kvm-arm.wfe_trap_policy=
2868 kvm-arm.wfi_trap_policy=
2885 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2886 a.k.a. Two-Dimensional Page Tables. Default is 1
2887 (enabled). Disable by KVM if hardware lacks support
2890 kvm-intel.emulate_invalid_guest_state=
2892 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2898 kvm-intel.flexpriority=
2900 (TPR shadow). Default is 1 (enabled). Disable by KVM if
2903 kvm-intel.nested=
2907 kvm-intel.unrestricted_guest=
2910 is 1 (enabled). Disable by KVM if EPT is disabled or
2913 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2914 CVE-2018-3620.
2920 VMEXIT and VMENTER can leak host memory.
2925 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2927 (enabled). Disable by KVM if hardware lacks support
2934 internal buffers which can forward information to a
2938 forwarded data can be used in a cache side channel
2945 on - enable the interface for the mitigation
3010 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3016 lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3020 value for LAPIC timer one-shot implementation. Default
3028 libata.dma=0 Disable all PATA and SATA DMA
3043 libata.force= [LIBATA] Force configurations. The format is a comma-
3055 first fan-out link behind PMP device. It does not
3062 The following configurations can be forced.
3069 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3076 * rstonce: only attempt one reset during hot-unplug
3079 * [no]dbdelay: Enable or disable the extra 200ms delay
3085 * [no]ncqtrim: Enable or disable queued DSM TRIM.
3087 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3089 * [no]trim: Enable or disable (unqueued) TRIM.
3102 * [no]dmalog: Enable or disable the use of the
3105 * [no]iddevlog: Enable or disable access to the
3108 * [no]logdir: Enable or disable access to the general
3119 * external: Mark port as external (hotplug-capable).
3121 * [no]lpm: Enable or disable link power management.
3126 * [no]fua: Disable or enable FUA (Force Unit Access)
3131 * disable: Disable this device.
3173 Specify the number of self-propagating call_rcu()
3181 occasional long-duration lock hold time. Defaults
3182 to 100 milliseconds. Select 0 to disable.
3187 (MAX_NESTED_LOCKS). Specify zero to disable.
3192 Set the number of locking read-acquisition kthreads.
3197 Set the number of locking write-acquisition kthreads.
3200 Set time (s) after boot for CPU-hotplug testing.
3203 Set time (s) between CPU-hotplug operations, or
3204 zero to disable CPU-hotplug testing.
3207 Do periodic testing of real-time lock priority
3208 boosting. Select 0 to disable, 1 to boost
3212 non-real-time spinlocks, due to their disabling
3213 of preemption. Note that non-realtime mutexes
3214 disable boosting.
3226 Set task-shuffle interval (jiffies). Shuffling
3227 tasks allows some CPUs to go into dyntick-idle
3232 is useful for hands-off automated testing.
3251 Run the write-side locktorture kthreads at
3252 sched_set_fifo() real-time priority.
3259 console loglevel will be printed to the console. It can
3270 7 (KERN_DEBUG) debug-level messages
3282 logo.nologo [FB] Disables display of the built-in Linux logo.
3290 lp=auto printer driver. 'lp=reset' (which can be
3300 an IEEE 1284-compliant printer is attached; if
3306 time-consuming boot-time autodetection (up to 250 ms per
3326 Example: machtype=lemote-yeeloong-2f-7inch
3331 bootup you can bring up the other plugged cpu by executing
3338 (loop.max_loop) unconditionally pre-created at init time. The default
3341 devices can be requested on-demand with the
3342 /dev/loop-control interface.
3344 mce= [X86-{32,64}]
3349 disable machine check
3352 disable CMCI(Corrected Machine Check Interrupt) that
3368 disable features for corrected errors, e.g.
3381 do not opt-in to Local MCE delivery. Use legacy method
3395 disable boot machine check logging.
3399 checks. 0 to disable.
3402 don't overwrite the bios-set CMCI threshold. This boot
3411 force-enable recoverable machine check code paths
3417 See Documentation/admin-guide/md.rst.
3424 Control mitigation for the Micro-architectural Data
3428 internal buffers which can forward information to a
3432 forwarded data can be used in a cache side channel
3439 full - Enable MDS mitigation on vulnerable CPUs
3440 full,nosmt - Enable MDS mitigation and disable
3442 off - Unconditionally disable MDS mitigation
3444 On TAA-affected machines, mds=off can be prevented by
3446 mitigated with the same mechanism so in order to disable
3453 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3468 [ARC,MICROBLAZE] - the limit applies only to low memory,
3471 [ARM64] - only limits memory covered by the linear
3484 [ARM,MIPS,EARLY] - override the memory layout
3488 Multiple different regions can be specified with
3491 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3498 per-device physically contiguous DMA buffers.
3506 See Documentation/admin-guide/mm/memory-hotplug.rst.
3510 Such memmap=exactmap lines can be constructed based on
3519 Multiple different regions can be specified,
3531 Example: Exclude memory from 0x18690000-0x1869ffff
3545 memmap=<size>%<offset>-<oldtype>+<newtype>
3547 from <oldtype> to <newtype>. If "-<oldtype>" is left
3562 repeatable BIOS-originated corruption always
3563 affects the same memory, you can use memmap=
3591 The state of the flag can be read in
3598 default : 0 <disable>
3606 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3612 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3613 for details on when memory encryption can be activated.
3616 s2idle - Suspend-To-Idle
3617 shallow - Power-On Suspend or equivalent (if supported)
3618 deep - Suspend-To-RAM or equivalent (if supported)
3619 See Documentation/admin-guide/pm/sleep-states.rst.
3621 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3624 problem by letting the user disable the workaround.
3630 Enable or disable the microcode minimal revision
3637 0 - The attached screen is the 3.5" TFT
3638 1 - The attached screen is the 7" TFT
3639 2 - The VGA Shield is attached (1024x768)
3643 b - Enable backlight. The TFT backlight pin will be
3647 c - Enable the s3c camera interface.
3648 t - Reserved for enabling touchscreen support. The
3650 kernel as of 2.6.30, a preliminary port can be found
3652 https://repo.or.cz/w/linux-2.6/mini2440.git
3657 arch-independent options, each of which is an
3658 aggregation of existing arch-specific options.
3664 Disable all optional CPU mitigations. This
3687 ssbd=force-off [ARM64]
3700 have other ways of avoiding SMT-based attacks.
3735 full - Enable mitigation on vulnerable CPUs
3737 full,nosmt - Enable mitigation and disable SMT on
3740 off - Unconditionally disable mitigation
3743 mmio_stale_data=off can be prevented by an active
3746 disable this mitigation, you need to specify
3753 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3758 probe on this module. Otherwise, enable/disable
3764 by default. To enable/disable async probing for a
3783 module_blacklist= [KNL] Do not load a comma-separated list of
3808 movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory
3815 Format: <name>,<region-number>,<size>,<offset>
3818 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3857 something different and driver-specific.
3868 0 to disable accounting
3897 [NFS] enable 64-bit inode numbers.
3898 If zero, the NFS client will fake up a 32-bit inode
3900 of returning the full 64-bit number.
3901 The default is to return 64-bit inode numbers.
3918 that the client can send to the NFSv4.1 server.
3928 disabling idmapping, which can make migration from
3936 [NFS4] Specify an additional fixed unique ident-
3937 ification string that NFSv4 clients can insert into
3967 driver. A non-zero value sets the minimum interval
3972 server-to-server copies for which this server is
3984 server-to-server copy, knfsd temporarily mounts
3991 See Documentation/admin-guide/nfs/nfsroot.rst.
3993 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3994 See Documentation/admin-guide/nfs/nfsroot.rst.
3997 See Documentation/admin-guide/nfs/nfsroot.rst.
4001 NMI stack-backtrace request.
4010 0 - turn hardlockup detector in nmi_watchdog off
4011 1 - turn hardlockup detector in nmi_watchdog on
4012 rNNN - configure the watchdog with raw perf event 0xNNN
4017 To disable both hard and soft lockup detectors,
4022 These settings can be accessed at runtime via
4025 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
4029 no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes.
4030 Forces kernel to use 3-level paging instead.
4032 no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4033 kernel to use 4-level paging instead.
4042 noautogroup Disable scheduler automatic task group creation.
4048 Disable suspending of consoles during suspend and
4050 messages can reach various consoles while the rest
4062 [KNL,EARLY] Disable object debugging
4064 nodsp [SH] Disable hardware DSP at boot time.
4066 noefi [EFI,EARLY] Disable EFI runtime services support.
4068 no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4070 noexec32 [X86-64]
4071 This affects only 32-bit executables.
4072 noexec32=on: enable non-executable mappings (default)
4074 noexec32=off: disable non-executable mappings
4081 nofpu [MIPS,SH] Disable hardware FPU at boot time.
4085 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4087 legacy floating-point registers on task switch.
4099 difficult since unequal pointers can no longer be
4100 compared. However, if this command-line option is
4106 nohibernate [HIBERNATION] Disable hibernation and resume.
4119 nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
4121 nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
4123 nohz= [KNL] Boottime enable/disable dynamic ticks
4143 nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4145 [Deprecated - use intremap=off]
4147 noinvpcid [X86,EARLY] Disable the INVPCID cpu feature.
4151 noirqdebug [X86-32] Disables the code which attempts to detect and
4152 disable unhandled interrupt sources.
4161 no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page
4164 no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4166 nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC.
4168 nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer.
4170 nomce [X86-32] Disable Machine Check Exception
4172 nomfgpt [X86-32] Disable Multi-Function General Purpose
4175 nomodeset Disable kernel modesetting. Most systems' firmware
4178 not load if they could possibly displace the pre-
4181 perform display-mode changes or accelerated rendering.
4185 nomodule Disable module load
4187 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
4191 nopat [X86,EARLY] Disable PAT (page attribute table extension of
4194 nopcid [X86-64,EARLY] Disable the PCID cpu feature.
4196 nopku [X86] Disable Memory Protection Keys CPU feature found
4199 nopti [X86-64,EARLY]
4215 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4221 no-scroll [VGA] Disables scrollback.
4222 This is required for the Braillex ib80-piezo Braille
4225 nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4228 Disable SMAP (Supervisor Mode Access Prevention)
4232 Disable SMEP (Supervisor Mode Execution Prevention)
4236 and disable the IO APIC. legacy for "maxcpus=0".
4238 nosmt [KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT).
4241 [KNL,X86,PPC] Disable symmetric multithreading (SMT).
4242 nosmt=force: Force disable SMT, cannot be undone
4245 nosoftlockup [KNL] Disable the soft-lockup detector.
4248 [HW,EARLY] Disable all mitigations for the Speculative
4251 nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4255 nospectre_v1 [X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4259 nospectre_v2 [X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4264 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4265 Disable paravirtualized steal time accounting. steal time
4271 timer IRQ sources, i.e., the IO-APIC timer. This can
4276 [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4279 Disable device dump. Device dump allows drivers to
4280 append dump data to vmcore so you can collect driver
4281 specified debug info. Drivers can append the data
4284 device dump can help save memory but the driver debug
4289 no-vmw-sched-clock
4290 [X86,PV_OPS,EARLY] Disable paravirtualized VMware
4293 nowatchdog [KNL] Disable both lockup detectors, i.e.
4294 soft-lockup and NMI watchdog (hard-lockup).
4298 nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode.
4306 enabling legacy floating-point and sse state.
4327 runtime you can physically add extra cpu until it reaches
4328 n. So during boot up some boot time memory for per-cpu
4329 variables need be pre-allocated for later physical cpu
4335 Disable NUMA, Only set up a single NUMA node
4356 soft-reserved memory partitioning.
4358 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4360 Allowed values are enable and disable
4363 'node', 'default' can be specified
4364 This can be set from sysctl after boot.
4365 See Documentation/admin-guide/sysctl/vm.rst for details.
4368 See Documentation/core-api/debugging-via-ohci1394.rst for more
4383 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4387 boundary - index of last SLC block on Flex-OneNAND.
4389 lock - Configure if Flex-OneNAND boundary should be locked.
4402 should randomize its free lists. This parameter can be
4403 used to enable/disable page randomization. The state of
4404 the flag can be read from sysfs at:
4408 page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
4411 we can turn it on.
4414 page_poison= [KNL,EARLY] Boot-time parameter changing the state of
4438 The optional switch "nousertaint" can be utilized to
4442 See Documentation/admin-guide/tainted-kernels.rst for
4443 extra details on the taint flags that users can pick
4450 User can chose combination of the following bits:
4476 possible conflicts). You can specify the base
4495 Set to non-zero to probe primary and secondary ISA
4501 Set to non-zero if a chip is present that snoops speed
4549 Set to non-zero to probe tertiary and further ISA
4558 of individual ports can be disabled by setting the
4565 Set to non-zero to probe QDI controllers. By default
4570 Set to non-zero to probe Winbond controllers. Use
4607 addresses can be specified after the base
4617 bios [X86-32] force use of PCI BIOS, don't access
4619 has a non-standard PCI host bridge.
4620 nobios [X86-32] disallow use of PCI BIOS, only direct
4626 data in IO port 0xCFC, both 32-bit).
4628 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4629 the function, IO port 0xCFA, also 8-bit, sets
4631 through ports 0xC000-0xCFFF).
4635 enabled, this kernel boot option can be used to
4636 disable the use of PCIE advanced error reporting.
4637 nodomains [PCI] Disable support for multiple PCI
4638 root domains (aka PCI segments, in ACPI-speak).
4639 nommconf [X86] Disable use of MMCONFIG for PCI
4645 enabled, this kernel boot option can be used to
4646 disable the use of MSI interrupts system-wide.
4647 noioapicquirk [APIC] Disable all boot interrupt quirks.
4651 primary IO-APIC for bridges that cannot disable
4654 noioapicreroute [APIC] Disable workaround that uses the
4658 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4676 assigned automatically to PCI devices. You can
4682 F0000h-100000h range.
4683 lastbus=N [X86] Scan all buses thru bus #N. Can be
4687 assign-busses [X86] Always assign all PCI bus
4708 <linux-[email protected]>.
4712 a bug to <linux-[email protected]>.
4717 skip_isa_align [X86] do not align io start addr, so can
4724 bfsort Sort PCI devices into breadth-first order.
4727 nobfsort Don't sort PCI devices into breadth-first order.
4728 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4729 tuning and use the BIOS-configured MPS defaults.
4736 or bus can support) for best performance.
4739 configuration allows peer-to-peer DMA between
4742 that hot-added devices will work.
4757 A PCI-PCI bridge can be specified if resource
4763 for 4096-byte alignment.
4764 ecrc= Enable/disable PCIe ECRC (transaction layer
4765 end-to-end CRC checking). Only effective if
4788 realloc= Enable/disable reallocating PCI bridge resources
4796 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4803 can resize a BAR to allow access to all VRAM.
4827 bit-0 : ACS Source Validation
4828 bit-1 : ACS Translation Blocking
4829 bit-2 : ACS P2P Request Redirect
4830 bit-3 : ACS P2P Completion Redirect
4831 bit-4 : ACS Upstream Forwarding
4832 bit-5 : ACS P2P Egress Control
4833 bit-6 : ACS Direct Translated P2P
4834 Each bit can be marked as:
4841 ACS to enable P2P Request Redirect, disable
4843 Validation unchanged from whatever power-up
4853 is enabled, this kernel boot option can be used
4854 to disable PCIe TLP Processing Hints support
4855 system-wide.
4869 dpc-native Use native PCIe service for DPC only. May
4871 compat Disable native PCIe services (PME, AER, DPC, PCIe
4875 off Disable power management of all PCIe ports
4886 Keep all power-domains already enabled by bootloader on,
4891 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4904 pirq= [SMP,APIC] Manual mp-table setup
4905 See Documentation/arch/x86/i386/IO-APIC.rst.
4909 See also Documentation/admin-guide/parport.rst.
4928 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4937 { on | off | curr | res | no-curr | no-res }
4978 Disable Hardware Transactional Memory
4982 none - Limited to cond_resched() calls
4983 voluntary - Limited to cond_resched() and might_sleep() calls
4984 full - Any section that isn't explicitly preempt disabled
4985 can be preempted anytime. Tasks will also yield
4988 lazy - Scheduler controlled. Similar to full but instead
4994 print-fatal-signals=
5000 coredump - etc.
5003 you might want to try "ulimit -i unlimited".
5010 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5014 Disable console loglevel raise on oops, panic
5015 or lockdep-detected issues (only if lock debug is on).
5024 on - unlimited logging to /dev/kmsg from userspace
5025 off - logging to /dev/kmsg disabled
5026 ratelimit - ratelimit the logging
5030 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5036 restrict that. Can be one of:
5037 - 'always': traditional behavior always allows mem overrides.
5038 - 'ptrace': only allow mem overrides for active ptracers.
5039 - 'never': never allow mem overrides.
5043 Limit processor to maximum C-state
5047 Ignore the _CST method to determine C-states,
5054 Param: "schedule" - profile schedule points.
5055 Param: "kvm" - profile VM exits.
5056 Param: <number> - step/bucket size as a power of 2 for
5068 psi= [KNL] Enable or disable pressure stall information
5087 pti= [X86-64] Control Page Table Isolation of user and
5092 on - unconditionally enable
5093 off - unconditionally disable
5094 auto - kernel detects whether your CPU model is
5100 [KNL] Number of legacy pty's. Overwrites compiled-in
5103 quiet [KNL,EARLY] Disable most log messages
5108 Disable RADIX GTSE feature and use hcall for TLB
5112 See Documentation/admin-guide/md.rst.
5115 See Documentation/admin-guide/blockdev/ramdisk.rst.
5120 [KNL,EARLY] Disable trusting the use of the CPU's
5125 [KNL,EARLY] Disable trusting the use of the a seed
5130 [KNL,EARLY] Enable or disable kernel stack offset
5134 cross-syscall address exposures. This is only
5137 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5140 ras=option[,option,...] [KNL] RAS-specific options
5143 Disable the Correctable Errors Collector,
5146 rcu_nocbs[=cpu-list]
5151 enable the no-callback CPU mode, which prevents
5156 "p" for RCU-preempt, "s" for RCU-sched, and "g"
5159 the offloaded CPUs, which can be useful for HPC
5160 and real-time workloads. It can also improve
5164 list of CPUs is set to no-callback mode from boot.
5168 no-callback mode from boot but the mode may be
5179 This improves the real-time response for the
5190 Do only a one-line RCU CPU stall warning when
5191 there is an ongoing too-long CSD-lock wait.
5195 throttled so that userspace tests can safely
5197 If triggered before the RCU grace-period machinery
5207 RCU grace-period cleanup.
5211 RCU grace-period initialization.
5215 RCU grace-period pre-initialization, that is,
5216 the propagation of recent CPU-hotplug changes up
5220 Set delay from grace-period initialization to
5233 soliciting quiescent-state help from
5245 Set the SCHED_FIFO priority of the RCU per-CPU
5248 and for the RCU grace-period kthreads (rcu_bh,
5250 set, valid values are 1-99 and the default is 1
5251 (the least-favored priority). Otherwise, when
5252 RCU_BOOST is not set, valid values are 0-99 and
5253 the default is zero (non-realtime operation).
5258 On callback-offloaded (rcu_nocbs) CPUs,
5261 use of the ->nocb_bypass list. However, in the
5262 common non-flooded case, RCU queues directly to
5263 the main ->cblist in order to avoid the extra
5264 overhead of the ->nocb_bypass list and its lock.
5266 a single jiffy, RCU pre-queues the callbacks into
5267 the ->nocb_bypass queue. The definition of "too
5271 On callback-offloaded (rcu_nocbs) CPUs, avoid
5284 batch limiting is re-enabled.
5288 RCU's force-quiescent-state scan will aggressively
5293 disable more aggressive help enlistment.
5296 Set the page-cache refill delay (in milliseconds)
5297 in response to low-memory conditions. The range
5301 Set the shift-right count to use to compute
5302 the callback-invocation batch limit bl from
5309 Please note that this callback-invocation batch
5310 limit applies only to non-offloaded callback
5316 Disable autobalancing of the rcu_node combining
5319 cache-to-cache transfer latencies.
5325 and for NUMA systems with large remote-access
5341 the wakeup overhead on the global grace-period
5343 each group's NOCB grace-period kthread.
5346 Cause the grace-period kthread to get an extra
5348 it should at force-quiescent-state time.
5361 this specifies an rcu_read_unlock()-time delay
5365 of RCU-protected pointers after the relevant
5375 per-CPU rcuc kthreads. Defaults to a non-zero
5379 But note that CONFIG_PREEMPT_RT=y kernels disable
5404 grace-period primitives such as call_rcu().
5415 grace-period primitives.
5418 Set test-start holdoff period. The purpose of
5436 Test the double-argument variant of kfree_rcu().
5438 rcuscale.kfree_rcu_test_single, both the single-
5439 and double-argument variants are tested.
5442 Test the single-argument variant of kfree_rcu().
5444 rcuscale.kfree_rcu_test_double, both the single-
5445 and double-argument variants are tested.
5459 does not affect the data-collection interval,
5464 Set number of RCU readers. The value -1 selects
5466 "n" less than -1 selects N-n+1, where N is again
5467 the number of CPUs. For example, -2 selects N
5468 (the number of CPUs), -3 selects N+1, and so on.
5469 A value of "n" less than or equal to -N selects
5482 complete. This is useful for hands-off automated
5489 Write-side holdoff between grace periods,
5494 Additional write-side holdoff between grace
5512 for RCU grace-period forward-progress testing
5519 Specify the fraction of a CPU-stall-warning
5520 period to do tight-loop forward-progress testing.
5524 forward-progress tests.
5528 need_resched() during tight-loop forward-progress
5532 Use conditional/asynchronous update-side
5533 normal-grace-period primitives, if available.
5536 Use conditional/asynchronous update-side
5537 expedited-grace-period primitives, if available.
5540 Use conditional/asynchronous update-side
5541 normal-grace-period primitives that also take
5546 Use conditional/asynchronous update-side
5547 expedited-grace-period primitives that also take
5571 Use expedited update-side primitives, if available.
5574 Use normal (non-expedited) asynchronous
5575 update-side primitives, if available.
5578 Use polled update-side normal-grace-period
5582 Use polled update-side expedited-grace-period
5586 Use polled update-side normal-grace-period
5591 Use polled update-side expedited-grace-period
5615 Use normal (non-expedited) synchronous
5616 update-side primitives, if available. If all
5620 they are all non-zero.
5628 Leak an RCU-protected pointer out of the reader.
5629 This can of course result in splats, and is
5643 Set number of RCU callback-offload togglers.
5648 callback-offload toggling attempts.
5651 Set number of RCU readers. The value -1 selects
5652 N-1, where N is the number of CPUs. A value
5653 "n" less than -1 selects N-n-2, where N is again
5654 the number of CPUs. For example, -2 selects N
5655 (the number of CPUs), -3 selects N+1, and so on.
5658 Enable debug-object double-call_rcu() testing.
5661 Set time (s) after boot for CPU-hotplug testing.
5664 Set time (jiffies) between CPU-hotplug operations,
5665 or zero to disable CPU-hotplug testing.
5669 by a high-priority FIFO real-time task. Set to
5670 zero (the default) to disable. The CPUs to
5678 second) between preemptions by a high-priority
5679 FIFO real-time task. This delay is mediated
5684 The number of times in a given read-then-exit
5685 episode that a set of read-then-exit kthreads
5690 read-then-exit testing episodes.
5695 are entered from low-order bit up, and are
5697 0x1 bit is normal readers, 0x2 NMI-safe readers,
5698 and 0x4 light-weight readers.
5701 Set task-shuffle interval (s). Shuffling tasks
5702 allows some CPUs to go into dyntick-idle mode
5707 is useful for hands-off automated testing.
5711 warnings, zero to disable.
5716 any other stall-related activity. Note that
5722 in scheduling-while-atomic splats.
5731 Disable interrupts while stalling if set, but only
5741 grace-period kthread to test RCU CPU stall
5742 warnings, zero to disable. If both stall_cpu
5767 Test RCU's dyntick-idle handling. See also the
5822 Use expedited grace-period primitives, for
5825 but can increase CPU utilization, degrade
5826 real-time latency, and degrade energy efficiency.
5830 Use only normal grace-period primitives,
5833 real-time latency, CPU utilization, and
5834 energy efficiency, but can expose users to
5835 increased grace-period latency. This parameter
5842 only normal grace-period primitives. No effect
5848 post-boot attempt at an expedited RCU grace
5849 period to instead use normal non-expedited
5850 grace-period processing.
5858 set to the default value of -1.
5861 Set the minimum number of callback-queuing-time
5862 lock-contention events per jiffy required to
5863 cause the RCU Tasks flavors to switch to per-CPU
5866 the default value of -1.
5871 of -1 allows this to be automatically (and
5879 number avoids disturbing real-time workloads,
5884 cancel laziness on that CPU. Use -1 to disable
5894 only printed prior to the stall-warning message
5895 for a given grace period. Disable with a value
5913 warning messages. Disable with a value less
5922 of zero will disable batching. Batching is
5930 disable batching. Batching is always disabled
5942 force - Override the decision by the kernel to hide the
5981 There are some built-in platform specific "quirks"
5982 - you may see: "reboot: <name> series board detected.
5986 built-in quirk table, and use the generic default
5995 Don't stop other CPUs on reboot. This can make reboot
6019 Set test-start holdoff period. The purpose of
6034 but the default has already reduced the per-pass
6039 Set number of readers. The default value of -1
6048 Set the read-side critical-section duration,
6052 Specify the read-protection implementation to test.
6078 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6089 other subsystems can use to access it. This is typically
6094 or if booting a different kernel. It can also fail if KASLR
6108 reservetop= [X86-32,EARLY]
6125 See Documentation/power/swsusp-and-swap-files.rst
6141 AMD-based UNRET and IBPB mitigations alone do not stop
6143 sibling threads. For that reason, STIBP is used on pro-
6147 off - no mitigation
6148 auto - automatically select a migitation
6149 auto,nosmt - automatically select a mitigation,
6153 ibpb - On AMD, mitigate short speculation
6158 ibpb,nosmt - Like "ibpb" above but will disable SMT
6162 unret - Force enable untrained return thunks,
6163 only effective on AMD f15h-f17h based
6165 unret,nosmt - Like unret, but will disable SMT when STIBP
6186 ring3mwait=disable
6187 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
6197 ro [KNL] Mount root device read-only on boot
6200 on Mark read-only kernel memory as read-only (default).
6201 off Leave read-only kernel memory writable for debugging.
6202 full Mark read-only kernel memory and aliases as read-only
6209 debug-uart get routed to the D+ and D- pins of the usb
6215 block/early-lookup.c for details.
6216 Alternatively this can be "ram" for the legacy initial
6240 rw [KNL] Mount root device read-write on boot
6256 The default is 1 meaning that one can concurrently use
6259 once. With a value of 2 one can map all of memory twice
6269 schedstats= [KNL,X86] Enable or disable scheduled statistics.
6270 Allowed values are enable and disable. This feature
6294 to 10 seconds for built-in smp_call_function()
6301 that requesting even small non-zero numbers of
6302 seconds can result in RCU CPU stall warnings,
6308 The default of -1 specifies a number of kthreads
6313 test before initiating CPU-hotplug operations.
6317 CPU-hotplug operations. Specifying zero (which
6318 is the default) disables CPU-hotplug operations.
6324 Non-zero values are useful for automated tests.
6337 preempt_disable() to disable CPU hotplug
6347 "wait" parameter. A value of -1 selects the
6348 default if all other weights are -1. However,
6350 value of -1 will instead select a weight of zero.
6355 non-zero "wait" parameter. See weight_single.
6362 this weighting can place serious IPI load
6368 non-zero "wait" parameter. See weight_single
6380 non-zero "wait" parameter. See weight_single
6391 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6392 1 -- enable.
6400 selinux= [SELINUX] Disable or enable SELinux at boot time.
6403 0 -- disable.
6404 1 -- enable.
6407 serialnumber [BUGS=X86-32]
6409 sev=option[,option...] [X86-64]
6415 Do not enable SEV-SNP (applies to host/hypervisor
6418 SEV-SNP guests.
6426 to set it to "all" by meaning -- no limit here.
6435 slab_debug can create guard zones around objects and
6470 Disable merging of slabs with similar size. May be
6474 layout control by attackers can usually be
6478 unchanged). Debug options disable merging on their
6507 using the csdlock_debug- kernel parameter.
6512 system. By default, let CSD-lock acquisition
6514 for this value provides a 5-minute timeout.
6516 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6517 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6518 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6519 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6520 smsc-ircc2.ircc_irq= [HW] IRQ line
6521 smsc-ircc2.ircc_dma= [HW] DMA channel
6522 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6532 Default: -1 (no limit)
6535 [KNL] Should the soft-lockup detector generate panics.
6538 A value of 1 instructs the soft-lockup detector
6539 to panic the machine when a soft-lockup occurs. It is
6542 respective build-time switch to that functionality.
6545 [KNL] Should the soft-lockup detector generate
6550 See Documentation/admin-guide/laptops/sonypi.rst
6557 on - (default) Enable the HW or SW mitigation as
6560 vmexit - On systems which don't have the HW mitigation
6563 protected from VM-originated BHI attacks, but
6565 off - Disable the mitigation.
6572 on - unconditionally enable, implies
6574 off - unconditionally disable, implies
6576 auto - kernel detects whether your CPU model is
6588 Selecting 'off' will disable both the kernel and
6591 Specific mitigations can also be selected manually:
6593 retpoline - replace indirect branches
6594 retpoline,generic - Retpolines
6595 retpoline,lfence - LFENCE; indirect branch
6596 retpoline,amd - alias for retpoline,lfence
6597 eibrs - Enhanced/Auto IBRS
6598 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6599 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6600 ibrs - use IBRS to protect kernel
6610 on - Unconditionally enable mitigations. Is
6613 off - Unconditionally disable mitigations. Is
6616 prctl - Indirect branch speculation is enabled,
6617 but mitigation can be enabled via prctl
6622 - Like "prctl" above, but only STIBP is
6628 - Same as "prctl" above, but all seccomp
6633 - Like "seccomp" above, but only STIBP is
6638 auto - Kernel selects the mitigation depending on
6649 off - Disable mitigation
6650 microcode - Enable microcode mitigation only
6651 safe-ret - Enable sw-only safe RET mitigation (default)
6652 ibpb - Enable mitigation by issuing IBPB on
6654 ibpb-vmexit - Issue IBPB only on VMEXIT
6655 (cloud-specific mitigation)
6658 [HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6666 is that such stores are unlikely and that they can
6671 store can be used in a cache side channel attack, for
6680 on - Unconditionally disable Speculative Store Bypass
6681 off - Unconditionally enable Speculative Store Bypass
6682 auto - Kernel detects whether the CPU model contains an
6688 prctl - Control Speculative Store Bypass per thread
6692 seccomp - Same as "prctl" above, but all seccomp threads
6693 will disable SSB unless they explicitly opt out.
6700 on,auto - On Power8 and Power9 insert a store-forwarding
6704 off - No action.
6718 off - not enabled
6720 warn - the kernel will emit rate-limited warnings
6728 fatal - the kernel will send SIGBUS to applications
6733 ratelimit:N -
6753 Certain CPUs are vulnerable to an MDS-like
6754 exploit which can leak bits from the random
6758 microcode. However, the microcode fix can cause
6763 The microcode mitigation can be disabled with
6766 off: Disable mitigation and remove
6773 This kernel-boot parameter defaults to 128,
6774 but takes effect only when the low-order four
6791 instead of the compile-time CONFIG_NR_CPUS.
6795 grace-period sequence counter wrap for the
6796 srcu_data structure's ->srcu_gp_seq_needed field.
6807 expediting. Set to zero to disable automatic
6811 Specifies the number of no-delay instances
6818 Specifies the per-grace-period phase, number of
6819 non-sleeping polls of readers. Beyond this limit,
6825 Specifies number of microseconds of non-sleeping
6826 delay between each non-sleeping poll of readers.
6829 Specifies the number of update-side contention
6834 set for contention-based conversions to occur.
6837 Speculative Store Bypass Disable control
6844 force-on: Unconditionally enable mitigation for
6846 force-off: Unconditionally disable mitigation for
6862 disable the stack depot thereby saving the static memory
6869 stacktrace_filter=[function-list]
6871 will trace at boot up. function-list is a comma-separated
6872 list of functions. This list can be changed at run
6879 Set the STI (builtin display/keyboard on the HP-PARISC
6881 as the initial boot-console.
6893 Enable or disable strict sigaltstack size checks
6895 depends on the supported FPU features. This can
6941 to global on non-NUMA machines)
6947 RPC calls that can be sent from the client to a
6966 <int> -- Number of I/O TLB slabs
6967 <int> -- Second integer after comma. Number of swiotlb
6970 force -- force using of bounce buffers even if they
6972 noforce -- Never use bounce buffers (for debugging)
6987 Ignore sysrq setting - this boot parameter will
6995 cache size. See Documentation/networking/ip-sysctl.rst
7002 Specify "mem" (for Suspend-to-RAM) or "standby" (for
7007 wakeup-capable RTC alarm.
7013 -1: disable all active trip points in all thermal zones
7017 -1: disable all critical trip points in all thermal zones
7021 1: disable ACPI thermal control
7024 -1: disable all passive trip points
7030 <deci-seconds>: poll all this frequency
7034 Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7038 Can be used multiple times for multiple anon THP sizes.
7039 See Documentation/admin-guide/mm/transhuge.rst for more
7047 Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7052 It can be used multiple times for multiple shmem THP sizes.
7053 See Documentation/admin-guide/mm/transhuge.rst for more
7065 Prevent the CPU-hotplug component of torturing
7069 Dump the ftrace buffer at torture-test shutdown,
7070 even if there were no errors. This can be a
7073 with rotating-rust storage.
7078 disables verbose-printk() sleeping.
7081 Duration of each verbose-printk() sleep in jiffies.
7106 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7120 The tp_printk_stop_on_boot (see below) can also be used
7127 frequency tracepoints such as irq or sched, can cause
7131 When tp_printk (above) is set, it can cause a lot of noise
7144 local - Use the per CPU time stamp counter
7148 global - Event time stamps are synchronize across
7151 counter - Simple counting of events (1, 2, ..)
7155 uptime - Use jiffies as the time stamp.
7156 perf - Use the same clock that perf uses.
7157 mono - Use ktime_get_mono_fast_ns() for time stamps.
7158 mono_raw - Use ktime_get_raw_fast_ns() for time
7160 boot - Use ktime_get_boot_fast_ns() for time stamps.
7164 trace_event=[event-list]
7166 to facilitate early boot debugging. The event-list is a
7167 comma-separated list of trace events to enable. See
7178 trace_instance=[instance-info]
7184 Events can be enabled at the time the instance is created
7198 Flags can be added to the instance to modify its behavior when it is
7203 traceoff - Have the tracing instance tracing disabled after it is created.
7204 traceprintk - Have trace_printk() write into this trace instance
7205 (note, "printk" and "trace_printk" can also be used)
7212 can use that memory:
7220 Alternatively, the memory can be reserved by the reserve_mem option:
7234 it is recommend to disable tracing so that events from a previous boot do not
7242 can force a memory reset on boot which will clear any trace that was stored.
7243 This is just one of many ways that can clear memory. Make sure your system
7249 trace_options=[option-list]
7250 [FTRACE] Enable or disable tracer options at boot.
7251 The option-list is a comma delimited list of options
7252 that can be enabled or disabled just as if you were
7265 trace_trigger=[trigger-list]
7285 [FTRACE] enable this option to disable tracing when a
7286 warning is hit. This turns off "tracing_on". Tracing can
7294 This option can also be set at run time via the sysctl
7300 Can be used to control the default behavior of the system
7302 See Documentation/admin-guide/mm/transhuge.rst
7307 Can be used to control the hugepage allocation policy for
7309 See Documentation/admin-guide/mm/transhuge.rst
7314 Can be used to control the default hugepage allocation policy
7316 See Documentation/admin-guide/mm/transhuge.rst
7324 - "tpm"
7325 - "tee"
7326 - "caam"
7327 - "dcp"
7336 Can be one of:
7337 - "kernel"
7338 - the same value as trusted.source: "tpm" or "tee"
7339 - "default"
7350 trusted.source=dcp and will disable the check if the
7355 tsc= Disable clocksource stability checks for TSC.
7360 high-resolution timer mode on older hardware, and in
7363 Used to run time disable IRQ_TIME_ACCOUNTING on any
7365 can add overhead.
7369 [x86] nowatchdog: disable clocksource watchdog. Used
7381 can be overridden by a later tsc=nowatchdog. A console
7396 on - Enable TSX on the system. Although there are
7399 several previous speculation-related CVEs, and
7403 off - Disable TSX on the system. (Note that this
7411 auto - Disable TSX if X86_BUG_TAA is present,
7416 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7422 Similar to Micro-architectural Data Sampling (MDS)
7425 exploit against CPU internal buffers which can forward
7430 data can be used in a cache side channel attack, to
7437 full - Enable TAA mitigation on vulnerable CPUs
7440 full,nosmt - Enable TAA mitigation and disable SMT on
7443 vulnerable to cross-thread TAA attacks.
7444 off - Unconditionally disable TAA mitigation
7446 On MDS-affected machines, tsx_async_abort=off can be
7448 are mitigated with the same mechanism so in order to disable
7458 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7464 See also Documentation/input/devices/joystick-parport.rst
7466 udbg-immortal [PPC] When debugging early kernel crashes that
7472 Set number of hash buckets for UDP/UDP-Lite connections
7474 uhci-hcd.ignore_oc=
7476 Some badly-designed motherboards generate lots of
7485 unwind_debug [X86-64,EARLY]
7486 Enable unwinder debug output. This can be
7493 (default -1 = authorized (same as 1),
7499 for newly-detected USB devices (default 2). This
7527 [USB] Specifies timeout for the initial 64-byte
7531 usbcore.nousb [USB] Disable the USB subsystem
7534 [USB] A list of quirk entries to augment the built-in
7537 VendorID:ProductID:Flags. The IDs are 4-digit hex
7539 will change the built-in quirk; setting it if it is
7544 a 255-byte read);
7545 b = USB_QUIRK_RESET_RESUME (device can't resume
7547 c = USB_QUIRK_NO_SET_INTF (device can't handle
7548 Set-Interface requests);
7549 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7552 e = USB_QUIRK_RESET (device can't be reset
7556 bNumInterfaces count, and can't handle
7567 (bInterval-1).
7572 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7578 k = USB_QUIRK_NO_LPM (device can't handle Link
7605 usb-storage.delay_use=
7612 usb-storage.quirks=
7614 override the built-in unusual_devs list. List
7617 and Product ID values (4-digit hex numbers) and
7619 to a common usb-storage quirk flag as follows:
7661 medium is write-protected).
7670 1 - undefined instruction events
7671 2 - system calls
7672 4 - invalid data aborts
7673 8 - SIGSEGV faults
7674 16 - SIGBUS faults
7688 vdso=0: disable VDSO mapping
7690 vdso32= [X86] Control the 32-bit vDSO
7691 vdso32=1: enable 32-bit VDSO
7692 vdso32=0 or vdso32=2: disable 32-bit VDSO
7702 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7722 <size> := size (can use standard suffixes
7731 Can be used multiple times for multiple devices.
7733 vga= [BOOT,X86-32] Select a particular video mode
7735 Documentation/admin-guide/svga.rst.
7750 - Disable all of the above options
7753 exact size of <nn>. This can be used to increase
7755 It can also be used to decrease the size and leave more room
7774 vsyscall= [X86-64,EARLY]
7777 code). Most statically-linked binaries and older
7780 targets for exploits that can control RIP.
7801 see vga-softcursor.rst. Default: 2 = underline.
7806 This is a 16-member array composed of values
7807 ranging from 0-255.
7812 This is a 16-member array composed of values
7813 ranging from 0-255.
7818 This is a 16-member array composed of values
7819 ranging from 0-255.
7824 Set system-wide default UTF-8 mode for all tty's.
7825 Default is 1, i.e. UTF-8 mode is enabled for all
7830 Format=<-1|0|1>
7831 Set system-wide default for whether a cursor
7832 is shown on new VTs. Default is -1,
7837 vt.italic= [VT] Default color for italic text; 0-15.
7840 vt.underline= [VT] Default color for underlined text; 0-15.
7844 see Documentation/watchdog/watchdog-parameters.rst
7845 or other driver-specific files in the
7859 Format: <cpu-list>
7864 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7869 it can be updated at runtime by writing to the
7880 Per-cpu work items which run for longer than this
7883 them from noticeably delaying other per-cpu work
7901 Per-cpu workqueues are generally preferred because
7903 locality; unfortunately, per-cpu workqueues tend to
7906 Enabling this makes the per-cpu workqueues which
7917 workqueues. Can be one of "cpu", "smt", "cache",
7920 Documentation/core-api/workqueue.rst.
7922 This can be changed after boot by writing to the
7933 forces round-robin CPU selection to flush out
7941 on - Enable writecombine, use WUC for ioremap_wc()
7942 off - Disable writecombine, use SUC for ioremap_wc()
7944 x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of
7948 xen_512gb_limit [KNL,X86-64,XEN]
7958 ide-disks -- unplug primary master IDE devices
7959 aux-ide-disks -- unplug non-primary-master IDE devices
7960 nics -- unplug network devices
7961 all -- unplug all emulated devices (NICs and IDE disks)
7962 unnecessary -- unplugging emulated devices is
7965 never -- do not unplug even if version check succeeds
7979 Select whether to always use non-faulting (safe) MSR
7990 [KNL,X86,XEN,EARLY] Disable the vector callback for Xen
7995 to Xen, for use by other domains. Can be also changed at runtime
7999 xen_timer_slop= [X86-64,XEN,EARLY]
8022 Boolean parameter to disable using fifo event handling
8024 preferred over the 2-level event handling, as it is
8041 xive.store-eoi=off [PPC]
8047 xhci-hcd.quirks [USB,KNL]
8049 host controller quirks. Meaning of each bit can be
8065 can be written using xmon commands.
8067 memory, and other data can't be written using