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.
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
449 arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
452 arm64.nobti [ARM64] Unconditionally disable Branch Target
455 arm64.nogcs [ARM64] Unconditionally disable Guarded Control Stack
458 arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
461 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
464 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
467 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
470 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
494 audit= [KNL] Enable the audit sub-system
496 0 | off - kernel audit is disabled and can not be
498 unset - kernel audit is initialized but disabled and
500 1 | on - kernel audit is initialized and partially
511 behavior is to disable the BAU (i.e. bau=0).
513 0 - Disable the BAU.
514 1 - Enable the BAU.
515 unset - Disable the BAU.
543 O_EXCL. Default is Y and can be changed through the
547 Disable BERT OS support on buggy BIOSes.
550 Disable BGRT to avoid flickering OEM logo.
554 See Documentation/block/cmdline-partition.rst
565 Extended command line options can be added to an initrd
568 See Documentation/admin-guide/bootconfig.rst
573 bttv.pll= See Documentation/admin-guide/media/bttv.rst
582 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
601 inclusive. See arch/mips/include/asm/pgtable-bits.h
608 cgroup_disable= [KNL] Disable a particular controller or optional feature
609 Format: {name of the controller(s) or feature(s) to disable}
611 - foo isn't auto-mounted if you mount all cgroups in
613 - foo isn't visible as an individually mountable
615 - if foo is an optional feature then the feature is
619 cut the overhead, others just disable the usage. So
621 Specifying "pressure" disables per-cgroup pressure
624 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
633 cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
639 nosocket -- Disable socket memory accounting.
640 nokmem -- Disable kernel memory accounting.
641 nobpf -- Disable BPF memory accounting.
646 0 -- check protection applied by kernel (includes
648 1 -- check protection requested by application.
650 Value can be changed at runtime via
658 Disable CPUID feature X for the kernel. See
660 numbers X. Note the Linux-specific bits are not necessarily
661 stable over kernel options, but the vendor-specific
663 X can also be a string as appearing in the flags: line
672 Also note the kernel might malfunction if you disable
681 force such clocks to be always-on nor does it reserve
685 information, see Documentation/driver-api/clk.rst.
687 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
704 [X86-32] pit,hpet,tsc;
711 [X86-64] hpet,tsc
716 Enable/disable the eventstream feature of the ARM
717 architected timer so that code using WFE-based polling
718 loops can be debugged more effectively on production
731 clocksource-wdtest.holdoff= [KNL]
737 cma=nn[MG]@[start[MG][-end[MG]]]
748 Sets the size of kernel per-numa memory area for
750 per-numa CMA altogether. And If this option is not
752 With per-numa CMA enabled, DMA users on node nid will
779 com20020= [HW,NET] ARCnet - COM20020 chipset
783 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
787 ARCnet - COM90xx chipset (memory-mapped buffers)
816 See Documentation/admin-guide/serial-console.rst for more
829 can be viewed with:
831 $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
832 /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
834 In the above example, the console can be addressed with
845 Start an early, polled-mode console on the 8250/16550
848 MMIO inter-register address stride is either 8-bit
849 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
853 the h/w is not re-initialized.
859 Use to disable console output, i.e., to have kernel
880 syscall, or to executing "dmesg -S --raw" or to reading
895 Enable/disable the CPU sampling based debugging.
896 0: default value, disable debugging
904 disable the cpuidle sub-system
910 disable the cpufreq sub-system
918 [X86,EARLY] Delay for N microsec between assert and de-assert
924 [SMP] Enable/disable parallel bringup of secondary CPUs
933 notifiers can make the crashed kernel more unstable.
939 like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
942 [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
947 [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
950 See Documentation/admin-guide/kdump/kdump.rst for further details.
955 start-[end] where start and end are both
957 Documentation/admin-guide/kdump/kdump.rst for an example.
960 [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
968 [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
974 for 32-bit devices won't run out. Kernel would try to allocate
977 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
978 --> arm64: 128MiB
979 --> riscv: 128MiB
980 --> loongarch: 128MiB
983 0: to disable low allocation.
988 [KNL] Disable crypto self-tests
996 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
1011 See also Documentation/input/devices/joystick-parport.rst
1024 [KNL] verbose locking self-tests
1027 self-tests.
1029 (no extra messages), setting it to -1 (all bits set)
1030 will print _a_lot_ more information - normally only
1065 Format: { on, no-mount, off }
1067 no-mount:
1068 Filesystem is not registered but kernel clients can
1069 access APIs and a crashkernel can be used to read
1072 get a -EPERM as result when trying to register files
1076 Default value is set in build-time with a kernel configuration.
1088 Documentation/admin-guide/mm/hugetlbpage.rst.
1102 delayacct [KNL] Enable per-task delay accounting
1146 can be useful when debugging issues that require an SLB
1149 disable= [IPV6]
1153 Disable RADIX MMU mode on POWER9
1156 Disable TLBIE instruction. Currently does not work
1160 Disable Dynamic DMA Window support. Use this
1178 Disable PIN 1 of APIC timer
1179 Can be useful to work around chipset bugs.
1181 dis_ucode_ldr [X86] Disable the microcode loader.
1188 entries for DMA-API debugging code. One entry is
1189 required per DMA-API allocation. Use this if the
1190 DMA-API debugging code disables itself because the
1194 With this option the DMA-API debugging driver
1195 filter feature can be enabled at boot time. Just
1197 The filter can be disabled or changed to another
1214 are enabled. In order to disable RFDS mitigation all
1218 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1243 Control how the dt_cpu_ftrs device-tree binding is
1253 what data is available or for reverse-engineering.
1258 Documentation/admin-guide/dynamic-debug-howto.rst
1269 determined by stdout-path property in device tree's
1274 Start an early, polled-mode console on a Cadence
1285 Start an early, polled-mode console on the 8250/16550
1287 MMIO inter-register address stride is either 8-bit
1288 (mmio) or 32-bit (mmio32 or mmio32be).
1298 Start an early, polled-mode console on a pl011 serial
1302 the driver will use only 32-bit accessors to read/write
1311 Start an early, polled-mode console on a meson serial
1317 Start an early, polled-mode console on an msm serial
1323 Start an early, polled-mode console on an msm serial
1329 Start an early, polled-mode console on a serial port
1335 Start an early, polled-mode console on a serial port
1341 Use RISC-V SBI (Supervisor Binary Interface) for early
1359 Start an early, polled-mode console on a lantiq serial
1373 Start an early, polled-mode, output-only console on the
1378 Start an early, polled-mode console on the
1384 Start an early, polled-mode console on a Qualcomm
1392 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
1791 off Disable hardened usercopy checks.
1794 [KNL] Should the hard-lockup detector generate
1800 for 64-bit NUMA, off otherwise.
1807 Disable Hardware Error Source Table (HEST) support;
1808 corresponding firmware-first mode error processing
1815 no Disable hibernation and resume.
1818 during restoration read-only).
1836 highres= [KNL] Enable/disable high resolution timer mode.
1855 hpet= [X86-32,HPET] option to control HPET usage
1856 Format: { enable (default) | disable | force |
1858 disable: disable HPET and use PIT instead
1872 number of pages to allocate per-node can be specified.
1873 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1881 pair hugepagesz=X hugepages=Y can be specified once
1884 Documentation/admin-guide/mm/hugetlbpage.rst.
1889 allocate hugepages during boot. This option can be
1894 Note that this parameter only applies to non-gigantic huge pages.
1898 of a CMA area per node can be specified.
1904 boot-time allocation of gigantic hugepages is skipped.
1922 off: disable HVO
1939 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1940 option. The value selected by this boot parameter can
1945 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1967 Set device-properties for ACPI-enumerated I2C-attached
1968 touchscreen, to e.g. fix coordinates of upside-down
1976 Omit "=<val>" entirely Set a boolean device-property
1977 Unsigned number Set a u32 device-property
1978 Anything else Set a string device-property
1981 i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1982 touchscreen-inverted-y
1984 i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
1985 touchscreen-size-y=1080:touchscreen-inverted-y:
1986 firmware-name=gsl1680-vendor-model.fw:silead,home-button
1991 (disabled by default, and as a pre-condition
1993 i8042.direct [HW] Put keyboard port into non-translated mode
1994 i8042.dumbkbd [HW] Pretend that controller can only read data from
1999 i8042.noloop [HW] Disable the AUX Loopback command while probing
2007 suspend-to-ram transitions, only during s2r
2031 -1 -- never invert brightness
2032 0 -- machine default
2033 1 -- force brightness inversion
2035 ia32_emulation= [X86-64]
2037 When true, allows loading 32-bit programs and executing 32-bit
2062 idle=nomwait: Disable mwait for CPU C-states
2090 legacy only accept legacy-NaN binaries, if supported
2092 2008 only accept 2008-NaN binaries, if supported
2103 'relaxed' straps the emulator for both legacy-NaN and
2104 2008-NaN, whereas 'strict' enables legacy-NaN only on
2113 Ignore loglevel setting - this will print /all/
2121 print warning at first misuse. Can be changed via
2180 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2181 "ima-sigv2" }
2182 Default: "ima-ng"
2194 different crypto accelerators. This option can be used
2202 different crypto accelerators. This option can be used
2210 off: Disable mitigation.
2215 stuff: Deploy RSB-fill mitigation when retpoline is
2220 Documentation/admin-guide/hw-vuln/indirect-target-selection.rst
2231 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2232 initcall functions. Useful for debugging built-in
2242 but as a debugging aid, one can get the
2267 default (disallow access to all but pkey 0). Can
2277 0 -- basic integrity auditing messages. (Default)
2278 1 -- additional integrity auditing messages.
2284 Disable intel iommu driver.
2306 could harm performance of some high-throughput
2315 1 to 9 specify maximum depth of C-state.
2318 disable
2324 algorithms for p-state selection. There are two
2325 P-state selection algorithms provided by
2328 on whether or not the hardware managed P-states
2335 used along with the hardware-managed P-states (HWP)
2339 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2340 instead of acpi-cpufreq may disable platform features, such
2342 P-States information being indicated to OSPM and therefore
2345 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2358 Allow per-logical-CPU P-State performance control limits using
2361 Do not enable capacity-aware scheduling (CAS) on
2364 intremap= [X86-64,Intel-IOMMU,EARLY]
2366 off disable Interrupt Remapping
2367 nosid disable Source ID checking
2369 BIOS x2APIC opt-out request will be ignored
2370 nopost disable Interrupt Posting
2374 iomem= Disable strict checking of access to MMIO memory
2400 Intel machines). This can be used to prevent the usage
2409 Disable IOMMU bypass, using IOMMU for PCI devices.
2412 AMD Gart HW IOMMU-specific options:
2431 Do scatter-gather (SG) merging. Implies "force"
2435 Don't do scatter-gather (SG) merging.
2448 0 - Try to allocate a 32-bit DMA address first, before
2450 1 - Allocate directly from the full usable range,
2452 greater than 32-bit addressing.
2456 0 - Lazy mode.
2462 1 - Strict mode.
2465 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2467 legacy driver-specific options takes precedence.
2472 0 - Use IOMMU translation for DMA.
2473 1 - Bypass the IOMMU for DMA.
2474 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2476 io7= [HW] IO7 for Marvel-based Alpha systems
2491 See Documentation/admin-guide/nfs/nfsroot.rst.
2527 Enables support for pseudo-NMIs in the kernel. This
2546 [Deprecated - use cpusets instead]
2547 Format: [flag-list,]<cpu-list>
2553 Disable the tick when a single task runs as well as
2572 advised to use cpusets instead to disable scheduler load
2574 It offers a much more flexible interface where CPUs can
2577 You can move a process onto or off an "isolated" CPU via
2580 "number of CPUs in system - 1".
2606 The format of <cpu-list> is described above.
2610 ivrs_ioapic [HW,X86-64]
2611 Provide an override to the IOAPIC-ID<->DEVICE-ID
2613 By default, PCI segment is 0, and can be omitted.
2615 For example, to map IOAPIC-ID decimal 10 to
2621 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2624 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2628 ivrs_hpet [HW,X86-64]
2629 Provide an override to the HPET-ID<->DEVICE-ID
2631 By default, PCI segment is 0, and can be omitted.
2633 For example, to map HPET-ID decimal 10 to
2639 * To map HPET-ID decimal 0 to PCI device 00:14.0
2642 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2646 ivrs_acpihid [HW,X86-64]
2647 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2649 By default, PCI segment is 0, and can be omitted.
2651 For example, to map UART-HID:UID AMD0020:0 to
2657 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2660 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2684 the kernel for non-movable allocations. The requested
2694 subsystem. Note that allocations like PTEs-from-HighMem
2702 for non-movable allocations and remaining memory is used
2713 gdb or control-c on the dbgp connection. When
2714 not using this parameter you use sysrq-g to break into
2719 or a supported polling keyboard driver (non-usb).
2729 characters and can work in polling mode, you can use
2746 Configure the RouterBoard 532 series on-chip
2749 kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable
2755 kprobe_event=[probe-list]
2757 The probe-list is a semicolon delimited list of probe
2776 default value can be overridden via
2787 execution by eliminating the write-protection faults
2810 when KVM is loaded, and disable virtualization when KVM
2813 If disabled, KVM will dynamically enable and disable
2814 virtualization on-demand when creating and destroying
2822 is that doing so may interfere with using out-of-tree
2849 back to huge pages. If the value is a non-zero N, KVM will
2854 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2857 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2858 a.k.a. Two-Dimensional Page Tables. Default is 1
2859 (enabled). Disable by KVM if hardware lacks support
2862 kvm-arm.mode=
2866 none: Forcefully disable KVM.
2868 nvhe: Standard nVHE-based mode, without support for
2875 nested: VHE-based mode with support for nested
2880 mode to "protected" will disable kexec and hibernation
2883 command-line.
2887 kvm-arm.vgic_v3_group0_trap=
2888 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2891 kvm-arm.vgic_v3_group1_trap=
2892 [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2895 kvm-arm.vgic_v3_common_trap=
2899 kvm-arm.vgic_v4_enable=
2903 kvm-arm.wfe_trap_policy=
2912 kvm-arm.wfi_trap_policy=
2929 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2930 a.k.a. Two-Dimensional Page Tables. Default is 1
2931 (enabled). Disable by KVM if hardware lacks support
2934 kvm-intel.emulate_invalid_guest_state=
2936 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2942 kvm-intel.flexpriority=
2944 (TPR shadow). Default is 1 (enabled). Disable by KVM if
2947 kvm-intel.nested=
2951 kvm-intel.unrestricted_guest=
2954 is 1 (enabled). Disable by KVM if EPT is disabled or
2957 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2958 CVE-2018-3620.
2964 VMEXIT and VMENTER can leak host memory.
2969 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2971 (enabled). Disable by KVM if hardware lacks support
2978 internal buffers which can forward information to a
2982 forwarded data can be used in a cache side channel
2989 on - enable the interface for the mitigation
3054 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3060 lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3064 value for LAPIC timer one-shot implementation. Default
3072 libata.dma=0 Disable all PATA and SATA DMA
3087 libata.force= [LIBATA] Force configurations. The format is a comma-
3099 first fan-out link behind PMP device. It does not
3106 The following configurations can be forced.
3113 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3120 * rstonce: only attempt one reset during hot-unplug
3123 * [no]dbdelay: Enable or disable the extra 200ms delay
3129 * [no]ncqtrim: Enable or disable queued DSM TRIM.
3131 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3133 * [no]trim: Enable or disable (unqueued) TRIM.
3146 * [no]dmalog: Enable or disable the use of the
3149 * [no]iddevlog: Enable or disable access to the
3152 * [no]logdir: Enable or disable access to the general
3163 * external: Mark port as external (hotplug-capable).
3165 * [no]lpm: Enable or disable link power management.
3170 * [no]fua: Disable or enable FUA (Force Unit Access)
3175 * disable: Disable this device.
3217 Specify the number of self-propagating call_rcu()
3225 occasional long-duration lock hold time. Defaults
3226 to 100 milliseconds. Select 0 to disable.
3231 (MAX_NESTED_LOCKS). Specify zero to disable.
3236 Set the number of locking read-acquisition kthreads.
3241 Set the number of locking write-acquisition kthreads.
3244 Set time (s) after boot for CPU-hotplug testing.
3247 Set time (s) between CPU-hotplug operations, or
3248 zero to disable CPU-hotplug testing.
3251 Do periodic testing of real-time lock priority
3252 boosting. Select 0 to disable, 1 to boost
3256 non-real-time spinlocks, due to their disabling
3257 of preemption. Note that non-realtime mutexes
3258 disable boosting.
3270 Set task-shuffle interval (jiffies). Shuffling
3271 tasks allows some CPUs to go into dyntick-idle
3276 is useful for hands-off automated testing.
3295 Run the write-side locktorture kthreads at
3296 sched_set_fifo() real-time priority.
3303 console loglevel will be printed to the console. It can
3314 7 (KERN_DEBUG) debug-level messages
3326 logo.nologo [FB] Disables display of the built-in Linux logo.
3334 lp=auto printer driver. 'lp=reset' (which can be
3344 an IEEE 1284-compliant printer is attached; if
3350 time-consuming boot-time autodetection (up to 250 ms per
3370 Example: machtype=lemote-yeeloong-2f-7inch
3375 bootup you can bring up the other plugged cpu by executing
3382 (loop.max_loop) unconditionally pre-created at init time. The default
3385 devices can be requested on-demand with the
3386 /dev/loop-control interface.
3388 mce= [X86-{32,64}]
3393 disable machine check
3396 disable CMCI(Corrected Machine Check Interrupt) that
3412 disable features for corrected errors, e.g.
3425 do not opt-in to Local MCE delivery. Use legacy method
3439 disable boot machine check logging.
3443 checks. 0 to disable.
3446 don't overwrite the bios-set CMCI threshold. This boot
3455 force-enable recoverable machine check code paths
3461 See Documentation/admin-guide/md.rst.
3468 Control mitigation for the Micro-architectural Data
3472 internal buffers which can forward information to a
3476 forwarded data can be used in a cache side channel
3483 full - Enable MDS mitigation on vulnerable CPUs
3484 full,nosmt - Enable MDS mitigation and disable
3486 off - Unconditionally disable MDS mitigation
3488 On TAA-affected machines, mds=off can be prevented by
3490 mitigated with the same mechanism so in order to disable
3497 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3512 [ARC,MICROBLAZE] - the limit applies only to low memory,
3515 [ARM64] - only limits memory covered by the linear
3528 [ARM,MIPS,EARLY] - override the memory layout
3532 Multiple different regions can be specified with
3535 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3542 per-device physically contiguous DMA buffers.
3550 See Documentation/admin-guide/mm/memory-hotplug.rst.
3554 Such memmap=exactmap lines can be constructed based on
3563 Multiple different regions can be specified,
3575 Example: Exclude memory from 0x18690000-0x1869ffff
3589 memmap=<size>%<offset>-<oldtype>+<newtype>
3591 from <oldtype> to <newtype>. If "-<oldtype>" is left
3606 repeatable BIOS-originated corruption always
3607 affects the same memory, you can use memmap=
3635 The state of the flag can be read in
3642 default : 0 <disable>
3650 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3656 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3657 for details on when memory encryption can be activated.
3660 s2idle - Suspend-To-Idle
3661 shallow - Power-On Suspend or equivalent (if supported)
3662 deep - Suspend-To-RAM or equivalent (if supported)
3663 See Documentation/admin-guide/pm/sleep-states.rst.
3665 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3668 problem by letting the user disable the workaround.
3674 Enable or disable the microcode minimal revision
3681 0 - The attached screen is the 3.5" TFT
3682 1 - The attached screen is the 7" TFT
3683 2 - The VGA Shield is attached (1024x768)
3687 b - Enable backlight. The TFT backlight pin will be
3691 c - Enable the s3c camera interface.
3692 t - Reserved for enabling touchscreen support. The
3694 kernel as of 2.6.30, a preliminary port can be found
3696 https://repo.or.cz/w/linux-2.6/mini2440.git
3701 arch-independent options, each of which is an
3702 aggregation of existing arch-specific options.
3708 Disable all optional CPU mitigations. This
3732 ssbd=force-off [ARM64]
3745 have other ways of avoiding SMT-based attacks.
3780 full - Enable mitigation on vulnerable CPUs
3782 full,nosmt - Enable mitigation and disable SMT on
3785 off - Unconditionally disable mitigation
3788 mmio_stale_data=off can be prevented by an active
3791 disable this mitigation, you need to specify
3798 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3803 probe on this module. Otherwise, enable/disable
3809 by default. To enable/disable async probing for a
3828 module_blacklist= [KNL] Do not load a comma-separated list of
3853 movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory
3860 Format: <name>,<region-number>,<size>,<offset>
3863 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3902 something different and driver-specific.
3913 0 to disable accounting
3942 [NFS] enable 64-bit inode numbers.
3943 If zero, the NFS client will fake up a 32-bit inode
3945 of returning the full 64-bit number.
3946 The default is to return 64-bit inode numbers.
3963 that the client can send to the NFSv4.1 server.
3973 disabling idmapping, which can make migration from
3981 [NFS4] Specify an additional fixed unique ident-
3982 ification string that NFSv4 clients can insert into
4012 driver. A non-zero value sets the minimum interval
4017 server-to-server copies for which this server is
4029 server-to-server copy, knfsd temporarily mounts
4036 See Documentation/admin-guide/nfs/nfsroot.rst.
4038 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
4039 See Documentation/admin-guide/nfs/nfsroot.rst.
4042 See Documentation/admin-guide/nfs/nfsroot.rst.
4046 NMI stack-backtrace request.
4055 0 - turn hardlockup detector in nmi_watchdog off
4056 1 - turn hardlockup detector in nmi_watchdog on
4057 rNNN - configure the watchdog with raw perf event 0xNNN
4062 To disable both hard and soft lockup detectors,
4067 These settings can be accessed at runtime via
4070 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
4074 no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes.
4075 Forces kernel to use 3-level paging instead.
4077 no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4078 kernel to use 4-level paging instead.
4087 noautogroup Disable scheduler automatic task group creation.
4093 Disable suspending of consoles during suspend and
4095 messages can reach various consoles while the rest
4107 [KNL,EARLY] Disable object debugging
4109 nodsp [SH] Disable hardware DSP at boot time.
4111 noefi [EFI,EARLY] Disable EFI runtime services support.
4113 no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4115 noexec32 [X86-64]
4116 This affects only 32-bit executables.
4117 noexec32=on: enable non-executable mappings (default)
4119 noexec32=off: disable non-executable mappings
4126 nofpu [MIPS,SH] Disable hardware FPU at boot time.
4130 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4132 legacy floating-point registers on task switch.
4144 difficult since unequal pointers can no longer be
4145 compared. However, if this command-line option is
4151 nohibernate [HIBERNATION] Disable hibernation and resume.
4164 nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
4166 nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
4168 nohz= [KNL] Boottime enable/disable dynamic ticks
4188 nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4190 [Deprecated - use intremap=off]
4192 noinvpcid [X86,EARLY] Disable the INVPCID cpu feature.
4196 noirqdebug [X86-32] Disables the code which attempts to detect and
4197 disable unhandled interrupt sources.
4206 no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page
4209 no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4211 nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC.
4213 nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer.
4215 nomce [X86-32] Disable Machine Check Exception
4217 nomfgpt [X86-32] Disable Multi-Function General Purpose
4220 nomodeset Disable kernel modesetting. Most systems' firmware
4223 not load if they could possibly displace the pre-
4226 perform display-mode changes or accelerated rendering.
4230 nomodule Disable module load
4232 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
4236 nopat [X86,EARLY] Disable PAT (page attribute table extension of
4239 nopcid [X86-64,EARLY] Disable the PCID cpu feature.
4241 nopku [X86] Disable Memory Protection Keys CPU feature found
4244 nopti [X86-64,EARLY]
4260 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4266 no-scroll [VGA] Disables scrollback.
4267 This is required for the Braillex ib80-piezo Braille
4270 nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4273 Disable SMAP (Supervisor Mode Access Prevention)
4277 Disable SMEP (Supervisor Mode Execution Prevention)
4281 and disable the IO APIC. legacy for "maxcpus=0".
4283 nosmt [KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT).
4286 [KNL,X86,PPC,S390] Disable symmetric multithreading (SMT).
4287 nosmt=force: Force disable SMT, cannot be undone
4290 nosoftlockup [KNL] Disable the soft-lockup detector.
4293 [HW,EARLY] Disable all mitigations for the Speculative
4296 nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4300 nospectre_v1 [X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4304 nospectre_v2 [X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4309 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4310 Disable paravirtualized steal time accounting. steal time
4316 timer IRQ sources, i.e., the IO-APIC timer. This can
4321 [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4324 Disable device dump. Device dump allows drivers to
4325 append dump data to vmcore so you can collect driver
4326 specified debug info. Drivers can append the data
4329 device dump can help save memory but the driver debug
4334 no-vmw-sched-clock
4335 [X86,PV_OPS,EARLY] Disable paravirtualized VMware
4338 nowatchdog [KNL] Disable both lockup detectors, i.e.
4339 soft-lockup and NMI watchdog (hard-lockup).
4343 nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode.
4351 enabling legacy floating-point and sse state.
4372 runtime you can physically add extra cpu until it reaches
4373 n. So during boot up some boot time memory for per-cpu
4374 variables need be pre-allocated for later physical cpu
4380 Disable NUMA, Only set up a single NUMA node
4401 soft-reserved memory partitioning.
4403 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4405 Allowed values are enable and disable
4408 'node', 'default' can be specified
4409 This can be set from sysctl after boot.
4410 See Documentation/admin-guide/sysctl/vm.rst for details.
4413 See Documentation/core-api/debugging-via-ohci1394.rst for more
4428 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4432 boundary - index of last SLC block on Flex-OneNAND.
4434 lock - Configure if Flex-OneNAND boundary should be locked.
4447 should randomize its free lists. This parameter can be
4448 used to enable/disable page randomization. The state of
4449 the flag can be read from sysfs at:
4453 page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
4456 we can turn it on.
4459 page_poison= [KNL,EARLY] Boot-time parameter changing the state of
4483 The optional switch "nousertaint" can be utilized to
4487 See Documentation/admin-guide/tainted-kernels.rst for
4488 extra details on the taint flags that users can pick
4495 User can chose combination of the following bits:
4521 possible conflicts). You can specify the base
4540 Set to non-zero to probe primary and secondary ISA
4546 Set to non-zero if a chip is present that snoops speed
4594 Set to non-zero to probe tertiary and further ISA
4603 of individual ports can be disabled by setting the
4610 Set to non-zero to probe QDI controllers. By default
4615 Set to non-zero to probe Winbond controllers. Use
4652 addresses can be specified after the base
4662 bios [X86-32] force use of PCI BIOS, don't access
4664 has a non-standard PCI host bridge.
4665 nobios [X86-32] disallow use of PCI BIOS, only direct
4671 data in IO port 0xCFC, both 32-bit).
4673 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4674 the function, IO port 0xCFA, also 8-bit, sets
4676 through ports 0xC000-0xCFFF).
4680 enabled, this kernel boot option can be used to
4681 disable the use of PCIE advanced error reporting.
4682 nodomains [PCI] Disable support for multiple PCI
4683 root domains (aka PCI segments, in ACPI-speak).
4684 nommconf [X86] Disable use of MMCONFIG for PCI
4690 enabled, this kernel boot option can be used to
4691 disable the use of MSI interrupts system-wide.
4692 noioapicquirk [APIC] Disable all boot interrupt quirks.
4696 primary IO-APIC for bridges that cannot disable
4699 noioapicreroute [APIC] Disable workaround that uses the
4703 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4721 assigned automatically to PCI devices. You can
4727 F0000h-100000h range.
4728 lastbus=N [X86] Scan all buses thru bus #N. Can be
4732 assign-busses [X86] Always assign all PCI bus
4753 <linux-pci@vger.kernel.org>.
4757 a bug to <linux-pci@vger.kernel.org>.
4762 skip_isa_align [X86] do not align io start addr, so can
4769 bfsort Sort PCI devices into breadth-first order.
4772 nobfsort Don't sort PCI devices into breadth-first order.
4773 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4774 tuning and use the BIOS-configured MPS defaults.
4781 or bus can support) for best performance.
4784 configuration allows peer-to-peer DMA between
4787 that hot-added devices will work.
4802 A PCI-PCI bridge can be specified if resource
4808 for 4096-byte alignment.
4809 ecrc= Enable/disable PCIe ECRC (transaction layer
4810 end-to-end CRC checking). Only effective if
4833 realloc= Enable/disable reallocating PCI bridge resources
4841 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4848 can resize a BAR to allow access to all VRAM.
4872 bit-0 : ACS Source Validation
4873 bit-1 : ACS Translation Blocking
4874 bit-2 : ACS P2P Request Redirect
4875 bit-3 : ACS P2P Completion Redirect
4876 bit-4 : ACS Upstream Forwarding
4877 bit-5 : ACS P2P Egress Control
4878 bit-6 : ACS Direct Translated P2P
4879 Each bit can be marked as:
4886 ACS to enable P2P Request Redirect, disable
4888 Validation unchanged from whatever power-up
4898 is enabled, this kernel boot option can be used
4899 to disable PCIe TLP Processing Hints support
4900 system-wide.
4914 dpc-native Use native PCIe service for DPC only. May
4916 compat Disable native PCIe services (PME, AER, DPC, PCIe
4920 off Disable power management of all PCIe ports
4931 Keep all power-domains already enabled by bootloader on,
4936 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4949 pirq= [SMP,APIC] Manual mp-table setup
4950 See Documentation/arch/x86/i386/IO-APIC.rst.
4954 See also Documentation/admin-guide/parport.rst.
4973 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4982 { on | off | curr | res | no-curr | no-res }
5023 Disable Hardware Transactional Memory
5027 none - Limited to cond_resched() calls
5028 voluntary - Limited to cond_resched() and might_sleep() calls
5029 full - Any section that isn't explicitly preempt disabled
5030 can be preempted anytime. Tasks will also yield
5033 lazy - Scheduler controlled. Similar to full but instead
5039 print-fatal-signals=
5045 coredump - etc.
5048 you might want to try "ulimit -i unlimited".
5055 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5059 Disable console loglevel raise on oops, panic
5060 or lockdep-detected issues (only if lock debug is on).
5068 Allows storing messages from non-panic CPUs into
5070 flushed to consoles by the panic-CPU on
5071 a best-effort basis.
5072 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5077 on - unlimited logging to /dev/kmsg from userspace
5078 off - logging to /dev/kmsg disabled
5079 ratelimit - ratelimit the logging
5083 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5089 restrict that. Can be one of:
5090 - 'always': traditional behavior always allows mem overrides.
5091 - 'ptrace': only allow mem overrides for active ptracers.
5092 - 'never': never allow mem overrides.
5096 Limit processor to maximum C-state
5100 Ignore the _CST method to determine C-states,
5107 Param: "schedule" - profile schedule points.
5108 Param: "kvm" - profile VM exits.
5109 Param: <number> - step/bucket size as a power of 2 for
5121 psi= [KNL] Enable or disable pressure stall information
5140 pti= [X86-64] Control Page Table Isolation of user and
5145 on - unconditionally enable
5146 off - unconditionally disable
5147 auto - kernel detects whether your CPU model is
5153 [KNL] Number of legacy pty's. Overwrites compiled-in
5156 quiet [KNL,EARLY] Disable most log messages
5161 Disable RADIX GTSE feature and use hcall for TLB
5165 See Documentation/admin-guide/md.rst.
5168 See Documentation/admin-guide/blockdev/ramdisk.rst.
5173 [KNL,EARLY] Disable trusting the use of the CPU's
5178 [KNL,EARLY] Disable trusting the use of the a seed
5183 [KNL,EARLY] Enable or disable kernel stack offset
5187 cross-syscall address exposures. This is only
5190 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5193 ras=option[,option,...] [KNL] RAS-specific options
5196 Disable the Correctable Errors Collector,
5199 rcu_nocbs[=cpu-list]
5204 enable the no-callback CPU mode, which prevents
5209 "p" for RCU-preempt, "s" for RCU-sched, and "g"
5212 the offloaded CPUs, which can be useful for HPC
5213 and real-time workloads. It can also improve
5217 list of CPUs is set to no-callback mode from boot.
5221 no-callback mode from boot but the mode may be
5232 This improves the real-time response for the
5243 Do only a one-line RCU CPU stall warning when
5244 there is an ongoing too-long CSD-lock wait.
5248 throttled so that userspace tests can safely
5250 If triggered before the RCU grace-period machinery
5260 RCU grace-period cleanup.
5264 RCU grace-period initialization.
5268 RCU grace-period pre-initialization, that is,
5269 the propagation of recent CPU-hotplug changes up
5273 Set delay from grace-period initialization to
5286 soliciting quiescent-state help from
5298 Set the SCHED_FIFO priority of the RCU per-CPU
5301 and for the RCU grace-period kthreads (rcu_bh,
5303 set, valid values are 1-99 and the default is 1
5304 (the least-favored priority). Otherwise, when
5305 RCU_BOOST is not set, valid values are 0-99 and
5306 the default is zero (non-realtime operation).
5311 On callback-offloaded (rcu_nocbs) CPUs,
5314 use of the ->nocb_bypass list. However, in the
5315 common non-flooded case, RCU queues directly to
5316 the main ->cblist in order to avoid the extra
5317 overhead of the ->nocb_bypass list and its lock.
5319 a single jiffy, RCU pre-queues the callbacks into
5320 the ->nocb_bypass queue. The definition of "too
5324 On callback-offloaded (rcu_nocbs) CPUs, avoid
5337 batch limiting is re-enabled.
5341 RCU's force-quiescent-state scan will aggressively
5346 disable more aggressive help enlistment.
5349 Set the page-cache refill delay (in milliseconds)
5350 in response to low-memory conditions. The range
5354 Set the shift-right count to use to compute
5355 the callback-invocation batch limit bl from
5362 Please note that this callback-invocation batch
5363 limit applies only to non-offloaded callback
5369 Disable autobalancing of the rcu_node combining
5372 cache-to-cache transfer latencies.
5378 and for NUMA systems with large remote-access
5394 the wakeup overhead on the global grace-period
5396 each group's NOCB grace-period kthread.
5399 Cause the grace-period kthread to get an extra
5401 it should at force-quiescent-state time.
5414 this specifies an rcu_read_unlock()-time delay
5418 of RCU-protected pointers after the relevant
5428 per-CPU rcuc kthreads. Defaults to a non-zero
5432 But note that CONFIG_PREEMPT_RT=y kernels disable
5457 grace-period primitives such as call_rcu().
5468 grace-period primitives.
5471 Set test-start holdoff period. The purpose of
5489 Test the double-argument variant of kfree_rcu().
5491 rcuscale.kfree_rcu_test_single, both the single-
5492 and double-argument variants are tested.
5495 Test the single-argument variant of kfree_rcu().
5497 rcuscale.kfree_rcu_test_double, both the single-
5498 and double-argument variants are tested.
5512 does not affect the data-collection interval,
5517 Set number of RCU readers. The value -1 selects
5519 "n" less than -1 selects N-n+1, where N is again
5520 the number of CPUs. For example, -2 selects N
5521 (the number of CPUs), -3 selects N+1, and so on.
5522 A value of "n" less than or equal to -N selects
5535 complete. This is useful for hands-off automated
5542 Write-side holdoff between grace periods,
5547 Additional write-side holdoff between grace
5565 for RCU grace-period forward-progress testing
5572 Specify the fraction of a CPU-stall-warning
5573 period to do tight-loop forward-progress testing.
5577 forward-progress tests.
5581 need_resched() during tight-loop forward-progress
5585 Use conditional/asynchronous update-side
5586 normal-grace-period primitives, if available.
5589 Use conditional/asynchronous update-side
5590 expedited-grace-period primitives, if available.
5593 Use conditional/asynchronous update-side
5594 normal-grace-period primitives that also take
5599 Use conditional/asynchronous update-side
5600 expedited-grace-period primitives that also take
5624 Use expedited update-side primitives, if available.
5627 Use normal (non-expedited) asynchronous
5628 update-side primitives, if available.
5631 Use polled update-side normal-grace-period
5635 Use polled update-side expedited-grace-period
5639 Use polled update-side normal-grace-period
5644 Use polled update-side expedited-grace-period
5668 Use normal (non-expedited) synchronous
5669 update-side primitives, if available. If all
5673 they are all non-zero.
5681 Leak an RCU-protected pointer out of the reader.
5682 This can of course result in splats, and is
5696 Set number of RCU callback-offload togglers.
5701 callback-offload toggling attempts.
5704 Set number of RCU readers. The value -1 selects
5705 N-1, where N is the number of CPUs. A value
5706 "n" less than -1 selects N-n-2, where N is again
5707 the number of CPUs. For example, -2 selects N
5708 (the number of CPUs), -3 selects N+1, and so on.
5711 Enable debug-object double-call_rcu() testing.
5714 Set time (s) after boot for CPU-hotplug testing.
5717 Set time (jiffies) between CPU-hotplug operations,
5718 or zero to disable CPU-hotplug testing.
5722 by a high-priority FIFO real-time task. Set to
5723 zero (the default) to disable. The CPUs to
5731 second) between preemptions by a high-priority
5732 FIFO real-time task. This delay is mediated
5737 The number of times in a given read-then-exit
5738 episode that a set of read-then-exit kthreads
5743 read-then-exit testing episodes.
5748 are entered from low-order bit up, and are
5750 0x1 bit is normal readers, 0x2 NMI-safe readers,
5751 and 0x4 light-weight readers.
5754 Set task-shuffle interval (s). Shuffling tasks
5755 allows some CPUs to go into dyntick-idle mode
5760 is useful for hands-off automated testing.
5764 warnings, zero to disable.
5769 any other stall-related activity. Note that
5775 in scheduling-while-atomic splats.
5784 Disable interrupts while stalling if set, but only
5794 grace-period kthread to test RCU CPU stall
5795 warnings, zero to disable. If both stall_cpu
5818 of RCU priority-boost testing. Defaults to zero,
5825 Test RCU's dyntick-idle handling. See also the
5880 Use expedited grace-period primitives, for
5883 but can increase CPU utilization, degrade
5884 real-time latency, and degrade energy efficiency.
5888 Use only normal grace-period primitives,
5891 real-time latency, CPU utilization, and
5892 energy efficiency, but can expose users to
5893 increased grace-period latency. This parameter
5900 only normal grace-period primitives. No effect
5906 post-boot attempt at an expedited RCU grace
5907 period to instead use normal non-expedited
5908 grace-period processing.
5916 set to the default value of -1.
5919 Set the minimum number of callback-queuing-time
5920 lock-contention events per jiffy required to
5921 cause the RCU Tasks flavors to switch to per-CPU
5924 the default value of -1.
5929 of -1 allows this to be automatically (and
5937 number avoids disturbing real-time workloads,
5942 cancel laziness on that CPU. Use -1 to disable
5952 only printed prior to the stall-warning message
5953 for a given grace period. Disable with a value
5971 warning messages. Disable with a value less
5980 of zero will disable batching. Batching is
5988 disable batching. Batching is always disabled
6000 force - Override the decision by the kernel to hide the
6039 There are some built-in platform specific "quirks"
6040 - you may see: "reboot: <name> series board detected.
6044 built-in quirk table, and use the generic default
6053 Don't stop other CPUs on reboot. This can make reboot
6077 Set test-start holdoff period. The purpose of
6092 but the default has already reduced the per-pass
6097 Set number of readers. The default value of -1
6106 Set the read-side critical-section duration,
6110 Specify the read-protection implementation to test.
6136 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6147 other subsystems can use to access it. This is typically
6152 or if booting a different kernel. It can also fail if KASLR
6166 reservetop= [X86-32,EARLY]
6183 See Documentation/power/swsusp-and-swap-files.rst
6199 AMD-based UNRET and IBPB mitigations alone do not stop
6201 sibling threads. For that reason, STIBP is used on pro-
6205 off - no mitigation
6206 auto - automatically select a migitation
6207 auto,nosmt - automatically select a mitigation,
6211 ibpb - On AMD, mitigate short speculation
6216 ibpb,nosmt - Like "ibpb" above but will disable SMT
6220 unret - Force enable untrained return thunks,
6221 only effective on AMD f15h-f17h based
6223 unret,nosmt - Like unret, but will disable SMT when STIBP
6244 ring3mwait=disable
6245 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
6255 ro [KNL] Mount root device read-only on boot
6258 on Mark read-only kernel memory as read-only (default).
6259 off Leave read-only kernel memory writable for debugging.
6260 full Mark read-only kernel memory and aliases as read-only
6267 debug-uart get routed to the D+ and D- pins of the usb
6273 block/early-lookup.c for details.
6274 Alternatively this can be "ram" for the legacy initial
6298 rw [KNL] Mount root device read-write on boot
6314 The default is 1 meaning that one can concurrently use
6317 once. With a value of 2 one can map all of memory twice
6327 schedstats= [KNL,X86] Enable or disable scheduled statistics.
6328 Allowed values are enable and disable. This feature
6352 to 10 seconds for built-in smp_call_function()
6359 that requesting even small non-zero numbers of
6360 seconds can result in RCU CPU stall warnings,
6366 The default of -1 specifies a number of kthreads
6371 test before initiating CPU-hotplug operations.
6375 CPU-hotplug operations. Specifying zero (which
6376 is the default) disables CPU-hotplug operations.
6382 Non-zero values are useful for automated tests.
6395 preempt_disable() to disable CPU hotplug
6405 "wait" parameter. A value of -1 selects the
6406 default if all other weights are -1. However,
6408 value of -1 will instead select a weight of zero.
6413 non-zero "wait" parameter. See weight_single.
6420 this weighting can place serious IPI load
6426 non-zero "wait" parameter. See weight_single
6438 non-zero "wait" parameter. See weight_single
6449 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6450 1 -- enable.
6458 selinux= [SELINUX] Disable or enable SELinux at boot time.
6461 0 -- disable.
6462 1 -- enable.
6465 serialnumber [BUGS=X86-32]
6467 sev=option[,option...] [X86-64]
6473 Do not enable SEV-SNP (applies to host/hypervisor
6476 SEV-SNP guests.
6484 to set it to "all" by meaning -- no limit here.
6493 slab_debug can create guard zones around objects and
6528 Disable merging of slabs with similar size. May be
6532 layout control by attackers can usually be
6536 unchanged). Debug options disable merging on their
6565 using the csdlock_debug- kernel parameter.
6570 system. By default, let CSD-lock acquisition
6572 for this value provides a 5-minute timeout.
6574 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6575 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6576 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6577 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6578 smsc-ircc2.ircc_irq= [HW] IRQ line
6579 smsc-ircc2.ircc_dma= [HW] DMA channel
6580 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6590 Default: -1 (no limit)
6593 [KNL] Should the soft-lockup detector generate panics.
6596 A value of 1 instructs the soft-lockup detector
6597 to panic the machine when a soft-lockup occurs. It is
6600 respective build-time switch to that functionality.
6603 [KNL] Should the soft-lockup detector generate
6608 See Documentation/admin-guide/laptops/sonypi.rst
6615 on - (default) Enable the HW or SW mitigation as
6618 vmexit - On systems which don't have the HW mitigation
6621 protected from VM-originated BHI attacks, but
6623 off - Disable the mitigation.
6630 on - unconditionally enable, implies
6632 off - unconditionally disable, implies
6634 auto - kernel detects whether your CPU model is
6648 Selecting 'off' will disable both the kernel and
6651 Specific mitigations can also be selected manually:
6653 retpoline - replace indirect branches
6654 retpoline,generic - Retpolines
6655 retpoline,lfence - LFENCE; indirect branch
6656 retpoline,amd - alias for retpoline,lfence
6657 eibrs - Enhanced/Auto IBRS
6658 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6659 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6660 ibrs - use IBRS to protect kernel
6670 on - Unconditionally enable mitigations. Is
6673 off - Unconditionally disable mitigations. Is
6676 prctl - Indirect branch speculation is enabled,
6677 but mitigation can be enabled via prctl
6682 - Like "prctl" above, but only STIBP is
6688 - Same as "prctl" above, but all seccomp
6693 - Like "seccomp" above, but only STIBP is
6698 auto - Kernel selects the mitigation depending on
6709 off - Disable mitigation
6710 microcode - Enable microcode mitigation only
6711 safe-ret - Enable sw-only safe RET mitigation (default)
6712 ibpb - Enable mitigation by issuing IBPB on
6714 ibpb-vmexit - Issue IBPB only on VMEXIT
6715 (cloud-specific mitigation)
6718 [HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6726 is that such stores are unlikely and that they can
6731 store can be used in a cache side channel attack, for
6740 on - Unconditionally disable Speculative Store Bypass
6741 off - Unconditionally enable Speculative Store Bypass
6742 auto - Kernel detects whether the CPU model contains an
6748 prctl - Control Speculative Store Bypass per thread
6752 seccomp - Same as "prctl" above, but all seccomp threads
6753 will disable SSB unless they explicitly opt out.
6760 on,auto - On Power8 and Power9 insert a store-forwarding
6764 off - No action.
6778 off - not enabled
6780 warn - the kernel will emit rate-limited warnings
6788 fatal - the kernel will send SIGBUS to applications
6793 ratelimit:N -
6813 Certain CPUs are vulnerable to an MDS-like
6814 exploit which can leak bits from the random
6818 microcode. However, the microcode fix can cause
6823 The microcode mitigation can be disabled with
6826 off: Disable mitigation and remove
6833 This kernel-boot parameter defaults to 128,
6834 but takes effect only when the low-order four
6851 instead of the compile-time CONFIG_NR_CPUS.
6855 grace-period sequence counter wrap for the
6856 srcu_data structure's ->srcu_gp_seq_needed field.
6867 expediting. Set to zero to disable automatic
6871 Specifies the number of no-delay instances
6878 Specifies the per-grace-period phase, number of
6879 non-sleeping polls of readers. Beyond this limit,
6885 Specifies number of microseconds of non-sleeping
6886 delay between each non-sleeping poll of readers.
6889 Specifies the number of update-side contention
6894 set for contention-based conversions to occur.
6897 Speculative Store Bypass Disable control
6904 force-on: Unconditionally enable mitigation for
6906 force-off: Unconditionally disable mitigation for
6922 disable the stack depot thereby saving the static memory
6929 stacktrace_filter=[function-list]
6931 will trace at boot up. function-list is a comma-separated
6932 list of functions. This list can be changed at run
6939 Set the STI (builtin display/keyboard on the HP-PARISC
6941 as the initial boot-console.
6953 Enable or disable strict sigaltstack size checks
6955 depends on the supported FPU features. This can
7001 to global on non-NUMA machines)
7007 RPC calls that can be sent from the client to a
7026 <int> -- Number of I/O TLB slabs
7027 <int> -- Second integer after comma. Number of swiotlb
7030 force -- force using of bounce buffers even if they
7032 noforce -- Never use bounce buffers (for debugging)
7047 Ignore sysrq setting - this boot parameter will
7055 cache size. See Documentation/networking/ip-sysctl.rst
7062 Specify "mem" (for Suspend-to-RAM) or "standby" (for
7067 wakeup-capable RTC alarm.
7073 -1: disable all active trip points in all thermal zones
7077 -1: disable all critical trip points in all thermal zones
7081 1: disable ACPI thermal control
7084 -1: disable all passive trip points
7090 <deci-seconds>: poll all this frequency
7094 Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7098 Can be used multiple times for multiple anon THP sizes.
7099 See Documentation/admin-guide/mm/transhuge.rst for more
7107 Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7112 It can be used multiple times for multiple shmem THP sizes.
7113 See Documentation/admin-guide/mm/transhuge.rst for more
7125 Prevent the CPU-hotplug component of torturing
7129 Dump the ftrace buffer at torture-test shutdown,
7130 even if there were no errors. This can be a
7133 with rotating-rust storage.
7138 disables verbose-printk() sleeping.
7141 Duration of each verbose-printk() sleep in jiffies.
7166 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7180 The tp_printk_stop_on_boot (see below) can also be used
7187 frequency tracepoints such as irq or sched, can cause
7191 When tp_printk (above) is set, it can cause a lot of noise
7204 local - Use the per CPU time stamp counter
7208 global - Event time stamps are synchronize across
7211 counter - Simple counting of events (1, 2, ..)
7215 uptime - Use jiffies as the time stamp.
7216 perf - Use the same clock that perf uses.
7217 mono - Use ktime_get_mono_fast_ns() for time stamps.
7218 mono_raw - Use ktime_get_raw_fast_ns() for time
7220 boot - Use ktime_get_boot_fast_ns() for time stamps.
7224 trace_event=[event-list]
7226 to facilitate early boot debugging. The event-list is a
7227 comma-separated list of trace events to enable. See
7238 trace_instance=[instance-info]
7244 Events can be enabled at the time the instance is created
7258 Flags can be added to the instance to modify its behavior when it is
7263 traceoff - Have the tracing instance tracing disabled after it is created.
7264 traceprintk - Have trace_printk() write into this trace instance
7265 (note, "printk" and "trace_printk" can also be used)
7272 can use that memory:
7280 Alternatively, the memory can be reserved by the reserve_mem option:
7294 it is recommend to disable tracing so that events from a previous boot do not
7302 can force a memory reset on boot which will clear any trace that was stored.
7303 This is just one of many ways that can clear memory. Make sure your system
7311 trace_options=[option-list]
7312 [FTRACE] Enable or disable tracer options at boot.
7313 The option-list is a comma delimited list of options
7314 that can be enabled or disabled just as if you were
7327 trace_trigger=[trigger-list]
7350 disable tracing after the boot is finished, otherwise
7356 [FTRACE] enable this option to disable tracing when a
7357 warning is hit. This turns off "tracing_on". Tracing can
7365 This option can also be set at run time via the sysctl
7371 Can be used to control the default behavior of the system
7373 See Documentation/admin-guide/mm/transhuge.rst
7378 Can be used to control the hugepage allocation policy for
7380 See Documentation/admin-guide/mm/transhuge.rst
7385 Can be used to control the default hugepage allocation policy
7387 See Documentation/admin-guide/mm/transhuge.rst
7395 - "tpm"
7396 - "tee"
7397 - "caam"
7398 - "dcp"
7407 Can be one of:
7408 - "kernel"
7409 - the same value as trusted.source: "tpm" or "tee"
7410 - "default"
7421 trusted.source=dcp and will disable the check if the
7426 tsc= Disable clocksource stability checks for TSC.
7431 high-resolution timer mode on older hardware, and in
7434 Used to run time disable IRQ_TIME_ACCOUNTING on any
7436 can add overhead.
7440 [x86] nowatchdog: disable clocksource watchdog. Used
7452 can be overridden by a later tsc=nowatchdog. A console
7467 on - Enable TSX on the system. Although there are
7470 several previous speculation-related CVEs, and
7474 off - Disable TSX on the system. (Note that this
7482 auto - Disable TSX if X86_BUG_TAA is present,
7487 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7493 Similar to Micro-architectural Data Sampling (MDS)
7496 exploit against CPU internal buffers which can forward
7501 data can be used in a cache side channel attack, to
7508 full - Enable TAA mitigation on vulnerable CPUs
7511 full,nosmt - Enable TAA mitigation and disable SMT on
7514 vulnerable to cross-thread TAA attacks.
7515 off - Unconditionally disable TAA mitigation
7517 On MDS-affected machines, tsx_async_abort=off can be
7519 are mitigated with the same mechanism so in order to disable
7529 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7535 See also Documentation/input/devices/joystick-parport.rst
7537 udbg-immortal [PPC] When debugging early kernel crashes that
7543 Set number of hash buckets for UDP/UDP-Lite connections
7545 uhci-hcd.ignore_oc=
7547 Some badly-designed motherboards generate lots of
7572 unwind_debug [X86-64,EARLY]
7573 Enable unwinder debug output. This can be
7580 (default -1 = authorized (same as 1),
7586 for newly-detected USB devices (default 2). This
7614 [USB] Specifies timeout for the initial 64-byte
7618 usbcore.nousb [USB] Disable the USB subsystem
7621 [USB] A list of quirk entries to augment the built-in
7624 VendorID:ProductID:Flags. The IDs are 4-digit hex
7626 will change the built-in quirk; setting it if it is
7631 a 255-byte read);
7632 b = USB_QUIRK_RESET_RESUME (device can't resume
7634 c = USB_QUIRK_NO_SET_INTF (device can't handle
7635 Set-Interface requests);
7636 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7639 e = USB_QUIRK_RESET (device can't be reset
7643 bNumInterfaces count, and can't handle
7654 (bInterval-1).
7659 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7665 k = USB_QUIRK_NO_LPM (device can't handle Link
7692 usb-storage.delay_use=
7699 usb-storage.quirks=
7701 override the built-in unusual_devs list. List
7704 and Product ID values (4-digit hex numbers) and
7706 to a common usb-storage quirk flag as follows:
7748 medium is write-protected).
7757 1 - undefined instruction events
7758 2 - system calls
7759 4 - invalid data aborts
7760 8 - SIGSEGV faults
7761 16 - SIGBUS faults
7768 vdso=0: disable VDSO mapping
7770 vdso32= [X86] Control the 32-bit vDSO
7771 vdso32=1: enable 32-bit VDSO
7772 vdso32=0 or vdso32=2: disable 32-bit VDSO
7782 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7802 <size> := size (can use standard suffixes
7811 Can be used multiple times for multiple devices.
7813 vga= [BOOT,X86-32] Select a particular video mode
7815 Documentation/admin-guide/svga.rst.
7830 - Disable all of the above options
7833 exact size of <nn>. This can be used to increase
7835 It can also be used to decrease the size and leave more room
7854 vsyscall= [X86-64,EARLY]
7857 code). Most statically-linked binaries and older
7860 targets for exploits that can control RIP.
7881 see vga-softcursor.rst. Default: 2 = underline.
7886 This is a 16-member array composed of values
7887 ranging from 0-255.
7892 This is a 16-member array composed of values
7893 ranging from 0-255.
7898 This is a 16-member array composed of values
7899 ranging from 0-255.
7904 Set system-wide default UTF-8 mode for all tty's.
7905 Default is 1, i.e. UTF-8 mode is enabled for all
7910 Format=<-1|0|1>
7911 Set system-wide default for whether a cursor
7912 is shown on new VTs. Default is -1,
7917 vt.italic= [VT] Default color for italic text; 0-15.
7920 vt.underline= [VT] Default color for underlined text; 0-15.
7924 see Documentation/watchdog/watchdog-parameters.rst
7925 or other driver-specific files in the
7939 Format: <cpu-list>
7944 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7949 it can be updated at runtime by writing to the
7960 Per-cpu work items which run for longer than this
7963 them from noticeably delaying other per-cpu work
7981 Per-cpu workqueues are generally preferred because
7983 locality; unfortunately, per-cpu workqueues tend to
7986 Enabling this makes the per-cpu workqueues which
7997 workqueues. Can be one of "cpu", "smt", "cache",
8000 Documentation/core-api/workqueue.rst.
8002 This can be changed after boot by writing to the
8013 forces round-robin CPU selection to flush out
8021 on - Enable writecombine, use WUC for ioremap_wc()
8022 off - Disable writecombine, use SUC for ioremap_wc()
8024 x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of
8028 xen_512gb_limit [KNL,X86-64,XEN]
8038 ide-disks -- unplug primary master IDE devices
8039 aux-ide-disks -- unplug non-primary-master IDE devices
8040 nics -- unplug network devices
8041 all -- unplug all emulated devices (NICs and IDE disks)
8042 unnecessary -- unplugging emulated devices is
8045 never -- do not unplug even if version check succeeds
8059 Select whether to always use non-faulting (safe) MSR
8070 [KNL,X86,XEN,EARLY] Disable the vector callback for Xen
8075 to Xen, for use by other domains. Can be also changed at runtime
8079 xen_timer_slop= [X86-64,XEN,EARLY]
8102 Boolean parameter to disable using fifo event handling
8104 preferred over the 2-level event handling, as it is
8121 xive.store-eoi=off [PPC]
8127 xhci-hcd.quirks [USB,KNL]
8129 host controller quirks. Meaning of each bit can be
8145 can be written using xmon commands.
8147 memory, and other data can't be written using