Lines Matching +full:can +full:- +full:disable
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64,riscv64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
26 If set to vendor, prefer vendor-specific driver
31 If set to none, disable the ACPI backlight interface.
40 Disable AML predefined validation mechanism
41 This mechanism can repair the evaluation result to make
58 Documentation/firmware-guide/acpi/debug.rst for more information about
79 can interfere with legacy drivers.
111 by unsupported hardware/firmware features can result in
114 This facility can be used to prevent such uncontrolled
116 Format: <byte> or <bitmap-list>
119 Disable auto-serialization of AML methods
122 auto-serialization feature.
126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
130 Disable installation of static SSDTs at early boot time
140 Ignore the ACPI-based watchdog interface (WDAT) and let
161 acpi_osi=! # disable all built-in OS vendor
163 acpi_osi=!! # enable all built-in OS vendor
165 acpi_osi= # disable all strings
167 'acpi_osi=!' can be used in combination with single or
169 vendor string(s). Note that such command can only
180 can make '_OSI("Windows 2000")' TRUE.
184 exist in the ACPI namespace. NOTE that such command can
189 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
192 'acpi_osi=!*' can be used in combination with single or
194 string(s). Note that such command can affect the
204 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
206 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
225 For broken nForce2 BIOS resulting in XT-PIC timer.
234 as soon as the kernel's real-mode entry point is called.
267 off: disable AGP support
272 See Documentation/sound/alsa-configuration.rst
279 align_va_addr= [X86-64]
284 CPU-intensive style benchmark, and it can vary highly in
287 32: only for 32-bit processes
288 64: only for 64-bit processes
289 on: enable for both 32- and 64-bit processes
290 off: disable for both 32- and 64-bit processes
300 Allow execve() of 32-bit applications and setting of the
302 subset of the CPUs support 32-bit EL0. When this
303 parameter is present, the set of CPUs supporting 32-bit
305 and hot-unplug operations may be restricted.
307 See Documentation/arch/arm64/asymmetric-32bit.rst for more
310 amd_iommu= [HW,X86-64]
313 fullflush - Deprecated, equivalent to iommu.strict=1
314 off - do not initialize any AMD IOMMU found in
316 force_isolation - Force device isolation for all
321 force_enable - Force enable the IOMMU on platforms known
324 pgtbl_v1 - Use v1 page table for DMA-API (Default).
325 pgtbl_v2 - Use v2 page table for DMA-API.
326 irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
328 amd_iommu_dump= [HW,X86-64]
334 amd_iommu_intr= [HW,X86-64]
337 legacy - Use legacy interrupt remapping mode.
338 vapic - Use virtual APIC mode, which allows IOMMU
340 This mode requires kvm-amd.avic=1.
344 disable
377 Power management functions (SPARCstation-4/5 + deriv.)
379 Disable APC CPU standby support. SPARCstation-Fox does
380 not play well with APC CPU idle - disable it if you have
387 when initialising the APIC and IO-APIC components.
388 For X86-32, this can also be used to specify an APIC
408 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
411 0 -- disable.
412 1 -- enable.
415 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
418 arm64.nobti [ARM64] Unconditionally disable Branch Target
421 arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
424 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
427 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
430 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
433 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
457 audit= [KNL] Enable the audit sub-system
459 0 | off - kernel audit is disabled and can not be
461 unset - kernel audit is initialized but disabled and
463 1 | on - kernel audit is initialized and partially
474 behavior is to disable the BAU (i.e. bau=0).
476 0 - Disable the BAU.
477 1 - Enable the BAU.
478 unset - Disable the BAU.
498 Disable BERT OS support on buggy BIOSes.
501 Disable BGRT to avoid flickering OEM logo.
505 See Documentation/block/cmdline-partition.rst
515 Extended command line options can be added to an initrd
518 See Documentation/admin-guide/bootconfig.rst
523 bttv.pll= See Documentation/admin-guide/media/bttv.rst
532 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
551 inclusive. See arch/mips/include/asm/pgtable-bits.h
558 cgroup_disable= [KNL] Disable a particular controller or optional feature
559 Format: {name of the controller(s) or feature(s) to disable}
561 - foo isn't auto-mounted if you mount all cgroups in
563 - foo isn't visible as an individually mountable
565 - if foo is an optional feature then the feature is
569 cut the overhead, others just disable the usage. So
571 Specifying "pressure" disables per-cgroup pressure
574 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
585 nosocket -- Disable socket memory accounting.
586 nokmem -- Disable kernel memory accounting.
587 nobpf -- Disable BPF memory accounting.
592 0 -- check protection applied by kernel (includes
594 1 -- check protection requested by application.
596 Value can be changed at runtime via
604 Disable CPUID feature X for the kernel. See
606 numbers X. Note the Linux-specific bits are not necessarily
607 stable over kernel options, but the vendor-specific
609 X can also be a string as appearing in the flags: line
618 Also note the kernel might malfunction if you disable
627 force such clocks to be always-on nor does it reserve
631 information, see Documentation/driver-api/clk.rst.
633 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
650 [X86-32] pit,hpet,tsc;
657 [X86-64] hpet,tsc
662 Enable/disable the eventstream feature of the ARM
663 architected timer so that code using WFE-based polling
664 loops can be debugged more effectively on production
677 clocksource-wdtest.holdoff= [KNL]
683 cma=nn[MG]@[start[MG][-end[MG]]]
694 Sets the size of kernel per-numa memory area for
696 per-numa CMA altogether. And If this option is not
698 With per-numa CMA enabled, DMA users on node nid will
725 com20020= [HW,NET] ARCnet - COM20020 chipset
729 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
733 ARCnet - COM90xx chipset (memory-mapped buffers)
762 See Documentation/admin-guide/serial-console.rst for more
772 Start an early, polled-mode console on the 8250/16550
775 MMIO inter-register address stride is either 8-bit
776 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
780 the h/w is not re-initialized.
786 Use to disable console output, i.e., to have kernel
807 syscall, or to executing "dmesg -S --raw" or to reading
822 Enable/disable the CPU sampling based debugging.
823 0: default value, disable debugging
831 disable the cpuidle sub-system
837 disable the cpufreq sub-system
845 [X86] Delay for N microsec between assert and de-assert
851 [SMP] Enable/disable parallel bringup of secondary CPUs
857 Run kdump after running panic-notifiers and dumping
861 because some panic notifiers can make the crashed
865 [KNL] Using kexec, Linux can switch to a 'crash kernel'
870 [KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and
873 See Documentation/admin-guide/kdump/kdump.rst for further details.
878 start-[end] where start and end are both
880 Documentation/admin-guide/kdump/kdump.rst for an example.
883 [KNL, X86-64, ARM64, RISCV] range could be above 4G.
890 [KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
895 low memory is needed to make sure DMA buffers for 32-bit
899 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
900 --> arm64: 128MiB
901 --> riscv: 128MiB
904 0: to disable low allocation.
909 [KNL] Disable crypto self-tests
917 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
932 See also Documentation/input/devices/joystick-parport.rst
945 [KNL] verbose locking self-tests
948 self-tests.
950 (no extra messages), setting it to -1 (all bits set)
951 will print _a_lot_ more information - normally only
986 Format: { on, no-mount, off }
988 no-mount:
989 Filesystem is not registered but kernel clients can
990 access APIs and a crashkernel can be used to read
993 get a -EPERM as result when trying to register files
997 Default value is set in build-time with a kernel configuration.
1009 Documentation/admin-guide/mm/hugetlbpage.rst.
1023 delayacct [KNL] Enable per-task delay accounting
1067 can be useful when debugging issues that require an SLB
1070 disable= [IPV6]
1074 Disable RADIX MMU mode on POWER9
1077 Disable TLBIE instruction. Currently does not work
1085 disable BSP to wake up multiple CPUs without
1090 Disable Dynamic DMA Window support. Use this
1108 Disable PIN 1 of APIC timer
1109 Can be useful to work around chipset bugs.
1111 dis_ucode_ldr [X86] Disable the microcode loader.
1118 entries for DMA-API debugging code. One entry is
1119 required per DMA-API allocation. Use this if the
1120 DMA-API debugging code disables itself because the
1124 With this option the DMA-API debugging driver
1125 filter feature can be enabled at boot time. Just
1127 The filter can be disabled or changed to another
1144 are enabled. In order to disable RFDS mitigation all
1148 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1162 Generic built-in EDID data sets are used, if one of
1167 available in Documentation/admin-guide/edid.rst. An EDID
1179 Control how the dt_cpu_ftrs device-tree binding is
1189 what data is available or for reverse-engineering.
1194 Documentation/admin-guide/dynamic-debug-howto.rst
1205 determined by stdout-path property in device tree's
1210 Start an early, polled-mode console on a Cadence
1221 Start an early, polled-mode console on the 8250/16550
1223 MMIO inter-register address stride is either 8-bit
1224 (mmio) or 32-bit (mmio32 or mmio32be).
1234 Start an early, polled-mode console on a pl011 serial
1238 the driver will use only 32-bit accessors to read/write
1247 Start an early, polled-mode console on a meson serial
1253 Start an early, polled-mode console on an msm serial
1259 Start an early, polled-mode console on an msm serial
1265 Start an early, polled-mode console on a serial port
1271 Start an early, polled-mode console on a serial port
1277 Use RISC-V SBI (Supervisor Binary Interface) for early
1295 Start an early, polled-mode console on a lantiq serial
1309 Start an early, polled-mode, output-only console on the
1314 Start an early, polled-mode console on the
1320 Start an early, polled-mode console on a Qualcomm
1328 coherent non-x86 systems that use system memory for
1353 Append ",keep" to not disable it when the real console
1356 Only one of vga, serial, or usb debug port can
1364 You can find the port for a given device in
1374 The xen option can only be used in Xen domains.
1376 The sclp output can only be used on s390.
1386 off: disable H/W event reporting through EDAC.
1398 disable_early_pci_dma: disable the busmaster bit on all
1400 nochunk: disable reading files in "chunks" in the EFI
1401 boot stub, as chunking can cause problems with some
1403 noruntime : disable EFI runtime services support
1407 claim. Specify efi=nosoftreserve to disable this
1415 Using this parameter you can use more than 50% of
1428 attribute is added to range 0x100000000-0x180000000 and
1429 0x10a0000000-0x1120000000.
1433 range 0x240000000-0x43fffffff.
1435 Using this parameter you can do debugging of EFI memmap
1436 related features. For example, you can do debugging of
1445 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1458 but can only be used if the backing tty is available
1462 elanfreq= [X86-32]
1470 See Documentation/admin-guide/kdump/kdump.rst for details.
1479 Can be useful to work around chipset bugs
1486 0 -- permissive (log only, no denials).
1487 1 -- enforcing (deny and log).
1489 Value can be changed at runtime via
1493 Disable Error Record Serialization Table (ERST)
1519 See also Documentation/fault-injection/.
1523 See Documentation/admin-guide/sysctl/net.rst for
1527 See Documentation/admin-guide/blockdev/floppy.rst.
1530 [IA-64] Avoid check_sal_cache_flush which may hang on
1535 forcepae [X86-32]
1537 Many Pentium M systems disable PAE but may have a
1549 ftrace ring buffer that can be read at:
1555 Optionally, the snapshot can also be defined for a tracing
1571 ftrace_filter=[function-list]
1573 tracer at boot up. function-list is a comma-separated
1574 list of functions. This list can be changed at run
1578 ftrace_notrace=[function-list]
1580 function-list. This list can be changed at run time
1584 ftrace_graph_filter=[function-list]
1587 function-list is a comma-separated list of functions
1588 that can be changed at run time by the
1591 ftrace_graph_notrace=[function-list]
1593 function-list. This list is a comma-separated list of
1594 functions that can be changed at run time by the
1600 can be changed at run time by the max_graph_depth file
1613 off -- Don't create device links from firmware info.
1614 permissive -- Create device links from firmware info
1617 on -- Create device links from firmware info and use it
1619 rpm -- Like "on", but also use to order runtime PM.
1632 strict -- Default. Continue waiting on consumers to
1634 timeout -- Give up waiting on consumers and call
1644 See also Documentation/input/devices/joystick-parport.rst
1648 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1661 The mitigation may have a performance impact but can be
1665 force: Disable AVX to mitigate systems without
1670 off: Disable GDS mitigation.
1672 gcov_persist= [GCOV] When non-zero (default), profiling data for
1682 gpio-mockup.gpio_mockup_ranges
1685 gpio-mockup.gpio_mockup_named_lines
1717 against bounds-checking flaws in the kernel's
1720 off Disable hardened usercopy checks.
1723 [KNL] Should the hard-lockup detector generate
1729 for 64-bit NUMA, off otherwise.
1732 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1738 Disable Hardware Error Source Table (HEST) support;
1739 corresponding firmware-first mode error processing
1746 no Disable hibernation and resume.
1749 during restoration read-only).
1756 highres= [KNL] Enable/disable high resolution timer mode.
1775 hpet= [X86-32,HPET] option to control HPET usage
1776 Format: { enable (default) | disable | force |
1778 disable: disable HPET and use PIT instead
1792 number of pages to allocate per-node can be specified.
1793 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1801 hugepagesz=X hugepages=Y can be specified once for
1804 Documentation/admin-guide/mm/hugetlbpage.rst.
1809 of a CMA area per node can be specified.
1815 boot-time allocation of gigantic hugepages is skipped.
1826 off: disable HVO
1843 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1844 option. The value selected by this boot parameter can
1849 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1866 (disabled by default, and as a pre-condition
1868 i8042.direct [HW] Put keyboard port into non-translated mode
1869 i8042.dumbkbd [HW] Pretend that controller can only read data from
1874 i8042.noloop [HW] Disable the AUX Loopback command while probing
1882 suspend-to-ram transitions, only during s2r
1906 -1 -- never invert brightness
1907 0 -- machine default
1908 1 -- force brightness inversion
1916 Poll forces a polling idle loop that can slightly
1922 idle=nomwait: Disable mwait for CPU C-states
1950 legacy only accept legacy-NaN binaries, if supported
1952 2008 only accept 2008-NaN binaries, if supported
1961 'relaxed' straps the emulator for both legacy-NaN and
1962 2008-NaN, whereas 'strict' enables legacy-NaN only on
1971 Ignore loglevel setting - this will print /all/
1979 print warning at first misuse. Can be changed via
2038 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2039 "ima-sigv2" }
2040 Default: "ima-ng"
2052 different crypto accelerators. This option can be used
2060 different crypto accelerators. This option can be used
2072 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2073 initcall functions. Useful for debugging built-in
2083 but as a debugging aid, one can get the
2108 default (disallow access to all but pkey 0). Can
2118 0 -- basic integrity auditing messages. (Default)
2119 1 -- additional integrity auditing messages.
2125 Disable intel iommu driver.
2147 could harm performance of some high-throughput
2156 1 to 9 specify maximum depth of C-state.
2159 disable
2165 algorithms for p-state selection. There are two
2166 P-state selection algorithms provided by
2169 on whether or not the hardware managed P-states
2176 used along with the hardware-managed P-states (HWP)
2180 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2181 instead of acpi-cpufreq may disable platform features, such
2183 P-States information being indicated to OSPM and therefore
2186 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2199 Allow per-logical-CPU P-State performance control limits using
2202 intremap= [X86-64, Intel-IOMMU]
2204 off disable Interrupt Remapping
2205 nosid disable Source ID checking
2207 BIOS x2APIC opt-out request will be ignored
2208 nopost disable Interrupt Posting
2210 iomem= Disable strict checking of access to MMIO memory
2227 Disable IOMMU bypass, using IOMMU for PCI devices.
2231 0 - Try to allocate a 32-bit DMA address first, before
2233 1 - Allocate directly from the full usable range,
2235 greater than 32-bit addressing.
2239 0 - Lazy mode.
2245 1 - Strict mode.
2248 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2250 legacy driver-specific options takes precedence.
2255 0 - Use IOMMU translation for DMA.
2256 1 - Bypass the IOMMU for DMA.
2257 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2259 io7= [HW] IO7 for Marvel-based Alpha systems
2274 See Documentation/admin-guide/nfs/nfsroot.rst.
2298 Enables support for pseudo-NMIs in the kernel. This
2317 [Deprecated - use cpusets instead]
2318 Format: [flag-list,]<cpu-list>
2324 Disable the tick when a single task runs.
2341 advised to use cpusets instead to disable scheduler load
2343 It offers a much more flexible interface where CPUs can
2346 You can move a process onto or off an "isolated" CPU via
2349 "number of CPUs in system - 1".
2375 The format of <cpu-list> is described above.
2379 ivrs_ioapic [HW,X86-64]
2380 Provide an override to the IOAPIC-ID<->DEVICE-ID
2382 By default, PCI segment is 0, and can be omitted.
2384 For example, to map IOAPIC-ID decimal 10 to
2390 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2393 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2397 ivrs_hpet [HW,X86-64]
2398 Provide an override to the HPET-ID<->DEVICE-ID
2400 By default, PCI segment is 0, and can be omitted.
2402 For example, to map HPET-ID decimal 10 to
2408 * To map HPET-ID decimal 0 to PCI device 00:14.0
2411 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2415 ivrs_acpihid [HW,X86-64]
2416 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2418 By default, PCI segment is 0, and can be omitted.
2420 For example, to map UART-HID:UID AMD0020:0 to
2426 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2429 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2450 kernelcore= [KNL,X86,IA-64,PPC]
2453 the kernel for non-movable allocations. The requested
2463 subsystem. Note that allocations like PTEs-from-HighMem
2471 for non-movable allocations and remaining memory is used
2482 gdb or control-c on the dbgp connection. When
2483 not using this parameter you use sysrq-g to break into
2488 or a supported polling keyboard driver (non-usb).
2498 characters and can work in polling mode, you can use
2515 Configure the RouterBoard 532 series on-chip
2518 kmemleak= [KNL] Boot-time kmemleak enable/disable
2524 kprobe_event=[probe-list]
2526 The probe-list is a semicolon delimited list of probe
2545 default value can be overridden via
2556 execution by eliminating the write-protection faults
2601 back to huge pages. If the value is a non-zero N, KVM will
2606 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2609 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2610 a.k.a. Two-Dimensional Page Tables. Default is 1
2611 (enabled). Disable by KVM if hardware lacks support
2614 kvm-arm.mode=
2617 none: Forcefully disable KVM.
2619 nvhe: Standard nVHE-based mode, without support for
2622 protected: nVHE-based mode with support for guests whose
2625 nested: VHE-based mode with support for nested
2630 mode to "protected" will disable kexec and hibernation
2634 kvm-arm.vgic_v3_group0_trap=
2635 [KVM,ARM] Trap guest accesses to GICv3 group-0
2638 kvm-arm.vgic_v3_group1_trap=
2639 [KVM,ARM] Trap guest accesses to GICv3 group-1
2642 kvm-arm.vgic_v3_common_trap=
2646 kvm-arm.vgic_v4_enable=
2658 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2659 a.k.a. Two-Dimensional Page Tables. Default is 1
2660 (enabled). Disable by KVM if hardware lacks support
2663 kvm-intel.emulate_invalid_guest_state=
2665 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2671 kvm-intel.flexpriority=
2673 (TPR shadow). Default is 1 (enabled). Disable by KVM if
2676 kvm-intel.nested=
2680 kvm-intel.unrestricted_guest=
2683 is 1 (enabled). Disable by KVM if EPT is disabled or
2686 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2687 CVE-2018-3620.
2693 VMEXIT and VMENTER can leak host memory.
2698 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2700 (enabled). Disable by KVM if hardware lacks support
2707 internal buffers which can forward information to a
2711 forwarded data can be used in a cache side channel
2718 on - enable the interface for the mitigation
2783 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2789 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2793 value for LAPIC timer one-shot implementation. Default
2801 libata.dma=0 Disable all PATA and SATA DMA
2816 libata.force= [LIBATA] Force configurations. The format is a comma-
2828 first fan-out link behind PMP device. It does not
2835 The following configurations can be forced.
2842 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2849 * rstonce: only attempt one reset during hot-unplug
2852 * [no]dbdelay: Enable or disable the extra 200ms delay
2858 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2860 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2862 * [no]trim: Enable or disable (unqueued) TRIM.
2875 * [no]dmalog: Enable or disable the use of the
2878 * [no]iddevlog: Enable or disable access to the
2881 * [no]logdir: Enable or disable access to the general
2892 * [no]lpm: Enable or disable link power management.
2897 * [no]fua: Disable or enable FUA (Force Unit Access)
2902 * disable: Disable this device.
2931 Set the number of locking read-acquisition kthreads.
2936 Set the number of locking write-acquisition kthreads.
2939 Set time (s) after boot for CPU-hotplug testing.
2942 Set time (s) between CPU-hotplug operations, or
2943 zero to disable CPU-hotplug testing.
2946 Set task-shuffle interval (jiffies). Shuffling
2947 tasks allows some CPUs to go into dyntick-idle
2952 is useful for hands-off automated testing.
2968 Run the write-side locktorture kthreads at
2969 sched_set_fifo() real-time priority.
2978 console loglevel will be printed to the console. It can
2989 7 (KERN_DEBUG) debug-level messages
2999 logo.nologo [FB] Disables display of the built-in Linux logo.
3007 lp=auto printer driver. 'lp=reset' (which can be
3017 an IEEE 1284-compliant printer is attached; if
3023 time-consuming boot-time autodetection (up to 250 ms per
3044 machvec= [IA-64] Force the use of a particular machine-vector
3050 Example: machtype=lemote-yeeloong-2f-7inch
3052 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
3058 bootup you can bring up the other plugged cpu by executing
3065 (loop.max_loop) unconditionally pre-created at init time. The default
3068 devices can be requested on-demand with the
3069 /dev/loop-control interface.
3071 mce [X86-32] Machine Check Exception
3073 mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3076 See Documentation/admin-guide/md.rst.
3083 Control mitigation for the Micro-architectural Data
3087 internal buffers which can forward information to a
3091 forwarded data can be used in a cache side channel
3098 full - Enable MDS mitigation on vulnerable CPUs
3099 full,nosmt - Enable MDS mitigation and disable
3101 off - Unconditionally disable MDS mitigation
3103 On TAA-affected machines, mds=off can be prevented by
3105 mitigated with the same mechanism so in order to disable
3112 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3126 [ARC,MICROBLAZE] - the limit applies only to low memory,
3129 [ARM64] - only limits memory covered by the linear
3142 [ARM,MIPS] - override the memory layout reported by
3146 Multiple different regions can be specified with
3149 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3156 per-device physically contiguous DMA buffers.
3164 See Documentation/admin-guide/mm/memory-hotplug.rst.
3168 Such memmap=exactmap lines can be constructed based on
3177 Multiple different regions can be specified,
3189 Example: Exclude memory from 0x18690000-0x1869ffff
3203 memmap=<size>%<offset>-<oldtype>+<newtype>
3205 from <oldtype> to <newtype>. If "-<oldtype>" is left
3220 repeatable BIOS-originated corruption always
3221 affects the same memory, you can use memmap=
3249 The state of the flag can be read in
3256 default : 0 <disable>
3264 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3270 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3271 for details on when memory encryption can be activated.
3274 s2idle - Suspend-To-Idle
3275 shallow - Power-On Suspend or equivalent (if supported)
3276 deep - Suspend-To-RAM or equivalent (if supported)
3277 See Documentation/admin-guide/pm/sleep-states.rst.
3279 mfgpt_irq= [IA-32] Specify the IRQ to use for the
3280 Multi-Function General Purpose Timers on AMD Geode
3283 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3286 problem by letting the user disable the workaround.
3292 Enable or disable the microcode minimal revision
3295 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3302 0 - The attached screen is the 3.5" TFT
3303 1 - The attached screen is the 7" TFT
3304 2 - The VGA Shield is attached (1024x768)
3308 b - Enable backlight. The TFT backlight pin will be
3312 c - Enable the s3c camera interface.
3313 t - Reserved for enabling touchscreen support. The
3315 kernel as of 2.6.30, a preliminary port can be found
3317 https://repo.or.cz/w/linux-2.6/mini2440.git
3322 arch-independent options, each of which is an
3323 aggregation of existing arch-specific options.
3329 Disable all optional CPU mitigations. This
3351 ssbd=force-off [ARM64]
3364 have other ways of avoiding SMT-based attacks.
3399 full - Enable mitigation on vulnerable CPUs
3401 full,nosmt - Enable mitigation and disable SMT on
3404 off - Unconditionally disable mitigation
3407 mmio_stale_data=off can be prevented by an active
3410 disable this mitigation, you need to specify
3417 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3422 probe on this module. Otherwise, enable/disable
3428 by default. To enable/disable async probing for a
3447 module_blacklist= [KNL] Do not load a comma-separated list of
3461 movablecore= [KNL,X86,IA-64,PPC]
3472 movable_node [KNL] Boot-time switch to make hotplugable memory
3479 Format: <name>,<region-number>,<size>,<offset>
3482 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3490 See arch/arm/mach-s3c/mach-jive.c
3526 something different and driver-specific.
3537 0 to disable accounting
3559 [NFS] enable 64-bit inode numbers.
3560 If zero, the NFS client will fake up a 32-bit inode
3562 of returning the full 64-bit number.
3563 The default is to return 64-bit inode numbers.
3580 that the client can send to the NFSv4.1 server.
3590 disabling idmapping, which can make migration from
3598 [NFS4] Specify an additional fixed unique ident-
3599 ification string that NFSv4 clients can insert into
3629 driver. A non-zero value sets the minimum interval
3634 server-to-server copies for which this server is
3646 server-to-server copy, knfsd temporarily mounts
3653 See Documentation/admin-guide/nfs/nfsroot.rst.
3655 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3656 See Documentation/admin-guide/nfs/nfsroot.rst.
3659 See Documentation/admin-guide/nfs/nfsroot.rst.
3663 NMI stack-backtrace request.
3672 0 - turn hardlockup detector in nmi_watchdog off
3673 1 - turn hardlockup detector in nmi_watchdog on
3677 To disable both hard and soft lockup detectors,
3682 These settings can be accessed at runtime via
3685 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3689 no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces
3690 kernel to use 3-level paging instead.
3692 no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces
3693 kernel to use 4-level paging instead.
3696 caches in the slab allocator. Saves per-node memory,
3707 noautogroup Disable scheduler automatic task group creation.
3713 Disable suspending of consoles during suspend and
3715 messages can reach various consoles while the rest
3727 [KNL] Disable object debugging
3729 nodsp [SH] Disable hardware DSP at boot time.
3731 noefi Disable EFI runtime services support.
3733 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3735 noexec [IA-64]
3737 noexec32 [X86-64]
3738 This affects only 32-bit executables.
3739 noexec32=on: enable non-executable mappings (default)
3741 noexec32=off: disable non-executable mappings
3748 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3752 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3754 legacy floating-point registers on task switch.
3756 nohalt [IA-64] Tells the kernel not to use the power saving
3758 power-consumption. On the positive side, it reduces
3759 interrupt wake-up latency, which may improve performance
3761 real-time systems.
3770 difficult since unequal pointers can no longer be
3771 compared. However, if this command-line option is
3777 nohibernate [HIBERNATION] Disable hibernation and resume.
3788 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3790 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
3792 nohz= [KNL] Boottime enable/disable dynamic ticks
3812 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3814 [Deprecated - use intremap=off]
3816 nointroute [IA-64]
3818 noinvpcid [X86] Disable the INVPCID cpu feature.
3822 noirqdebug [X86-32] Disables the code which attempts to detect and
3823 disable unhandled interrupt sources.
3827 nojitter [IA-64] Disables jitter checking for ITC timers.
3834 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3837 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3839 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3841 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3843 nomca [IA-64] Disable machine check abort handling
3845 nomce [X86-32] Disable Machine Check Exception
3847 nomfgpt [X86-32] Disable Multi-Function General Purpose
3850 nomodeset Disable kernel modesetting. Most systems' firmware
3853 not load if they could possibly displace the pre-
3856 perform display-mode changes or accelerated rendering.
3860 nomodule Disable module load
3862 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3866 nopat [X86] Disable PAT (page attribute table extension of
3869 nopcid [X86-64] Disable the PCID cpu feature.
3871 nopku [X86] Disable Memory Protection Keys CPU feature found
3874 nopti [X86-64]
3890 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
3896 nosbagart [IA-64]
3898 no-scroll [VGA] Disables scrollback.
3899 This is required for the Braillex ib80-piezo Braille
3902 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
3905 Disable SMAP (Supervisor Mode Access Prevention)
3909 Disable SMEP (Supervisor Mode Execution Prevention)
3913 and disable the IO APIC. legacy for "maxcpus=0".
3915 nosmt [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
3918 [KNL,X86,PPC] Disable symmetric multithreading (SMT).
3919 nosmt=force: Force disable SMT, cannot be undone
3922 nosoftlockup [KNL] Disable the soft-lockup detector.
3925 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
3927 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
3931 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
3935 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
3940 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
3950 [PPC] Don't flush the L1-D cache after accessing user data.
3953 Disable device dump. Device dump allows drivers to
3954 append dump data to vmcore so you can collect driver
3955 specified debug info. Drivers can append the data
3958 device dump can help save memory but the driver debug
3963 no-vmw-sched-clock
3964 [X86,PV_OPS] Disable paravirtualized VMware scheduler
3967 nowatchdog [KNL] Disable both lockup detectors, i.e.
3968 soft-lockup and NMI watchdog (hard-lockup).
3972 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
3980 enabling legacy floating-point and sse state.
3999 cycles, each HW thread of the CTOP can run
4006 nptcg= [IA-64] Override max number of concurrent global TLB
4014 runtime you can physically add extra cpu until it reaches
4015 n. So during boot up some boot time memory for per-cpu
4016 variables need be pre-allocated for later physical cpu
4021 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4024 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4026 Allowed values are enable and disable
4029 'node', 'default' can be specified
4030 This can be set from sysctl after boot.
4031 See Documentation/admin-guide/sysctl/vm.rst for details.
4034 See Documentation/core-api/debugging-via-ohci1394.rst for more
4049 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4053 boundary - index of last SLC block on Flex-OneNAND.
4055 lock - Configure if Flex-OneNAND boundary should be locked.
4069 running on a platform with a direct-mapped memory-side
4070 cache, and this parameter can be used to
4071 override/disable that behavior. The state of the flag
4072 can be read from sysfs at:
4075 page_owner= [KNL] Boot-time page_owner enabling option.
4078 we can turn it on.
4081 page_poison= [KNL] Boot-time parameter changing the state of
4104 The optional switch "nousertaint" can be utilized to
4108 See Documentation/admin-guide/tainted-kernels.rst for
4109 extra details on the taint flags that users can pick
4116 User can chose combination of the following bits:
4141 possible conflicts). You can specify the base
4160 Set to non-zero to probe primary and secondary ISA
4166 Set to non-zero if a chip is present that snoops speed
4214 Set to non-zero to probe tertiary and further ISA
4223 of individual ports can be disabled by setting the
4230 Set to non-zero to probe QDI controllers. By default
4235 Set to non-zero to probe Winbond controllers. Use
4272 addresses can be specified after the base
4282 bios [X86-32] force use of PCI BIOS, don't access
4284 has a non-standard PCI host bridge.
4285 nobios [X86-32] disallow use of PCI BIOS, only direct
4291 data in IO port 0xCFC, both 32-bit).
4293 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4294 the function, IO port 0xCFA, also 8-bit, sets
4296 through ports 0xC000-0xCFFF).
4300 enabled, this kernel boot option can be used to
4301 disable the use of PCIE advanced error reporting.
4302 nodomains [PCI] Disable support for multiple PCI
4303 root domains (aka PCI segments, in ACPI-speak).
4304 nommconf [X86] Disable use of MMCONFIG for PCI
4310 enabled, this kernel boot option can be used to
4311 disable the use of MSI interrupts system-wide.
4312 noioapicquirk [APIC] Disable all boot interrupt quirks.
4316 primary IO-APIC for bridges that cannot disable
4319 noioapicreroute [APIC] Disable workaround that uses the
4323 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4341 assigned automatically to PCI devices. You can
4347 F0000h-100000h range.
4348 lastbus=N [X86] Scan all buses thru bus #N. Can be
4352 assign-busses [X86] Always assign all PCI bus
4373 <linux-pci@vger.kernel.org>.
4377 a bug to <linux-pci@vger.kernel.org>.
4382 skip_isa_align [X86] do not align io start addr, so can
4389 bfsort Sort PCI devices into breadth-first order.
4392 nobfsort Don't sort PCI devices into breadth-first order.
4393 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4394 tuning and use the BIOS-configured MPS defaults.
4401 or bus can support) for best performance.
4404 configuration allows peer-to-peer DMA between
4407 that hot-added devices will work.
4422 A PCI-PCI bridge can be specified if resource
4428 for 4096-byte alignment.
4429 ecrc= Enable/disable PCIe ECRC (transaction layer
4430 end-to-end CRC checking). Only effective if
4453 realloc= Enable/disable reallocating PCI bridge resources
4461 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4468 can resize a BAR to allow access to all VRAM.
4486 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4488 off Disable ASPM.
4497 dpc-native Use native PCIe service for DPC only. May
4499 compat Disable native PCIe services (PME, AER, DPC, PCIe
4503 off Disable power management of all PCIe ports
4514 Keep all power-domains already enabled by bootloader on,
4519 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4531 pirq= [SMP,APIC] Manual mp-table setup
4532 See Documentation/arch/x86/i386/IO-APIC.rst.
4536 See also Documentation/admin-guide/parport.rst.
4555 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4564 { on | off | curr | res | no-curr | no-res }
4600 Disable Hardware Transactional Memory
4604 none - Limited to cond_resched() calls
4605 voluntary - Limited to cond_resched() and might_sleep() calls
4606 full - Any section that isn't explicitly preempt disabled
4607 can be preempted anytime.
4609 print-fatal-signals=
4615 coredump - etc.
4618 you might want to try "ulimit -i unlimited".
4625 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4629 Disable console loglevel raise on oops, panic
4630 or lockdep-detected issues (only if lock debug is on).
4639 on - unlimited logging to /dev/kmsg from userspace
4640 off - logging to /dev/kmsg disabled
4641 ratelimit - ratelimit the logging
4645 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4651 restrict that. Can be one of:
4652 - 'always': traditional behavior always allows mem overrides.
4653 - 'ptrace': only allow mem overrides for active ptracers.
4654 - 'never': never allow mem overrides.
4658 Limit processor to maximum C-state
4662 Ignore the _CST method to determine C-states,
4669 Param: "schedule" - profile schedule points.
4670 Param: "kvm" - profile VM exits.
4671 Param: <number> - step/bucket size as a power of 2 for
4681 psi= [KNL] Enable or disable pressure stall information
4700 pti= [X86-64] Control Page Table Isolation of user and
4705 on - unconditionally enable
4706 off - unconditionally disable
4707 auto - kernel detects whether your CPU model is
4713 [KNL] Number of legacy pty's. Overwrites compiled-in
4716 quiet [KNL] Disable most log messages
4721 Disable RADIX GTSE feature and use hcall for TLB
4725 See Documentation/admin-guide/md.rst.
4728 See Documentation/admin-guide/blockdev/ramdisk.rst.
4733 [KNL] Disable trusting the use of the CPU's
4738 [KNL] Disable trusting the use of the a seed
4743 [KNL] Enable or disable kernel stack offset
4747 cross-syscall address exposures. This is only
4750 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4753 ras=option[,option,...] [KNL] RAS-specific options
4756 Disable the Correctable Errors Collector,
4759 rcu_nocbs[=cpu-list]
4764 enable the no-callback CPU mode, which prevents
4769 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4772 the offloaded CPUs, which can be useful for HPC
4773 and real-time workloads. It can also improve
4777 list of CPUs is set to no-callback mode from boot.
4781 no-callback mode from boot but the mode may be
4792 This improves the real-time response for the
4809 RCU grace-period cleanup.
4813 RCU grace-period initialization.
4817 RCU grace-period pre-initialization, that is,
4818 the propagation of recent CPU-hotplug changes up
4822 Set delay from grace-period initialization to
4835 soliciting quiescent-state help from
4847 Set the SCHED_FIFO priority of the RCU per-CPU
4850 and for the RCU grace-period kthreads (rcu_bh,
4852 set, valid values are 1-99 and the default is 1
4853 (the least-favored priority). Otherwise, when
4854 RCU_BOOST is not set, valid values are 0-99 and
4855 the default is zero (non-realtime operation).
4860 On callback-offloaded (rcu_nocbs) CPUs,
4863 use of the ->nocb_bypass list. However, in the
4864 common non-flooded case, RCU queues directly to
4865 the main ->cblist in order to avoid the extra
4866 overhead of the ->nocb_bypass list and its lock.
4868 a single jiffy, RCU pre-queues the callbacks into
4869 the ->nocb_bypass queue. The definition of "too
4878 batch limiting is re-enabled.
4882 RCU's force-quiescent-state scan will aggressively
4887 disable more aggressive help enlistment.
4890 Set the page-cache refill delay (in milliseconds)
4891 in response to low-memory conditions. The range
4895 Set the shift-right count to use to compute
4896 the callback-invocation batch limit bl from
4903 Please note that this callback-invocation batch
4904 limit applies only to non-offloaded callback
4910 Disable autobalancing of the rcu_node combining
4913 cache-to-cache transfer latencies.
4919 and for NUMA systems with large remote-access
4935 the wakeup overhead on the global grace-period
4937 each group's NOCB grace-period kthread.
4940 Cause the grace-period kthread to get an extra
4942 it should at force-quiescent-state time.
4955 this specifies an rcu_read_unlock()-time delay
4959 of RCU-protected pointers after the relevant
4969 per-CPU rcuc kthreads. Defaults to a non-zero
4973 But note that CONFIG_PREEMPT_RT=y kernels disable
4979 grace-period primitives such as call_rcu().
4990 grace-period primitives.
4993 Set test-start holdoff period. The purpose of
5011 Test the double-argument variant of kfree_rcu().
5013 rcuscale.kfree_rcu_test_single, both the single-
5014 and double-argument variants are tested.
5017 Test the single-argument variant of kfree_rcu().
5019 rcuscale.kfree_rcu_test_double, both the single-
5020 and double-argument variants are tested.
5034 does not affect the data-collection interval,
5039 Set number of RCU readers. The value -1 selects
5041 "n" less than -1 selects N-n+1, where N is again
5042 the number of CPUs. For example, -2 selects N
5043 (the number of CPUs), -3 selects N+1, and so on.
5044 A value of "n" less than or equal to -N selects
5057 complete. This is useful for hands-off automated
5064 Write-side holdoff between grace periods,
5069 Additional write-side holdoff between grace
5087 for RCU grace-period forward-progress testing
5094 Specify the fraction of a CPU-stall-warning
5095 period to do tight-loop forward-progress testing.
5099 forward-progress tests.
5103 need_resched() during tight-loop forward-progress
5107 Use conditional/asynchronous update-side
5111 Use expedited update-side primitives, if available.
5114 Use normal (non-expedited) asynchronous
5115 update-side primitives, if available.
5118 Use normal (non-expedited) synchronous
5119 update-side primitives, if available. If all
5123 they are all non-zero.
5131 Leak an RCU-protected pointer out of the reader.
5132 This can of course result in splats, and is
5146 Set number of RCU callback-offload togglers.
5151 callback-offload toggling attempts.
5154 Set number of RCU readers. The value -1 selects
5155 N-1, where N is the number of CPUs. A value
5156 "n" less than -1 selects N-n-2, where N is again
5157 the number of CPUs. For example, -2 selects N
5158 (the number of CPUs), -3 selects N+1, and so on.
5161 Enable debug-object double-call_rcu() testing.
5164 Set time (s) after boot for CPU-hotplug testing.
5167 Set time (jiffies) between CPU-hotplug operations,
5168 or zero to disable CPU-hotplug testing.
5171 Set the number of read-then-exit kthreads used
5173 task-exit processing.
5176 The number of times in a given read-then-exit
5177 episode that a set of read-then-exit kthreads
5182 read-then-exit testing episodes.
5185 Set task-shuffle interval (s). Shuffling tasks
5186 allows some CPUs to go into dyntick-idle mode
5191 is useful for hands-off automated testing.
5195 warnings, zero to disable.
5200 any other stall-related activity. Note that
5206 in scheduling-while-atomic splats.
5215 Disable interrupts while stalling if set.
5219 grace-period kthread to test RCU CPU stall
5220 warnings, zero to disable. If both stall_cpu
5245 Test RCU's dyntick-idle handling. See also the
5294 Use expedited grace-period primitives, for
5297 but can increase CPU utilization, degrade
5298 real-time latency, and degrade energy efficiency.
5302 Use only normal grace-period primitives,
5305 real-time latency, CPU utilization, and
5306 energy efficiency, but can expose users to
5307 increased grace-period latency. This parameter
5314 only normal grace-period primitives. No effect
5320 post-boot attempt at an expedited RCU grace
5321 period to instead use normal non-expedited
5322 grace-period processing.
5330 set to the default value of -1.
5333 Set the minimum number of callback-queuing-time
5334 lock-contention events per jiffy required to
5335 cause the RCU Tasks flavors to switch to per-CPU
5338 the default value of -1.
5343 of -1 allows this to be automatically (and
5351 number avoids disturbing real-time workloads,
5356 cancel laziness on that CPU. Use -1 to disable
5366 only printed prior to the stall-warning message
5367 for a given grace period. Disable with a value
5385 warning messages. Disable with a value less
5394 of zero will disable batching. Batching is
5402 disable batching. Batching is always disabled
5410 disable batching. Batching is always disabled
5422 force - Override the decision by the kernel to hide the
5450 Set test-start holdoff period. The purpose of
5459 but the default has already reduced the per-pass
5464 Set number of readers. The default value of -1
5473 Set the read-side critical-section duration,
5477 Specify the read-protection implementation to test.
5496 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5504 reservetop= [X86-32]
5521 See Documentation/power/swsusp-and-swap-files.rst
5536 AMD-based UNRET and IBPB mitigations alone do not stop
5538 sibling threads. For that reason, STIBP is used on pro-
5542 off - no mitigation
5543 auto - automatically select a migitation
5544 auto,nosmt - automatically select a mitigation,
5548 ibpb - On AMD, mitigate short speculation
5553 ibpb,nosmt - Like "ibpb" above but will disable SMT
5557 unret - Force enable untrained return thunks,
5558 only effective on AMD f15h-f17h based
5560 unret,nosmt - Like unret, but will disable SMT when STIBP
5584 ring3mwait=disable
5585 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5595 ro [KNL] Mount root device read-only on boot
5598 on Mark read-only kernel memory as read-only (default).
5599 off Leave read-only kernel memory writable for debugging.
5600 full Mark read-only kernel memory and aliases as read-only
5606 debug-uart get routed to the D+ and D- pins of the usb
5612 block/early-lookup.c for details.
5613 Alternatively this can be "ram" for the legacy initial
5637 rw [KNL] Mount root device read-write on boot
5652 The default is 1 meaning that one can concurrently use
5655 once. With a value of 2 one can map all of memory twice
5665 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5666 Allowed values are enable and disable. This feature
5689 to 10 seconds for built-in smp_call_function()
5696 that requesting even small non-zero numbers of
5697 seconds can result in RCU CPU stall warnings,
5703 The default of -1 specifies a number of kthreads
5708 test before initiating CPU-hotplug operations.
5712 CPU-hotplug operations. Specifying zero (which
5713 is the default) disables CPU-hotplug operations.
5719 Non-zero values are useful for automated tests.
5732 preempt_disable() to disable CPU hotplug
5742 "wait" parameter. A value of -1 selects the
5743 default if all other weights are -1. However,
5745 value of -1 will instead select a weight of zero.
5750 non-zero "wait" parameter. See weight_single.
5757 this weighting can place serious IPI load
5763 non-zero "wait" parameter. See weight_single
5775 non-zero "wait" parameter. See weight_single
5782 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
5783 1 -- enable.
5791 selinux= [SELINUX] Disable or enable SELinux at boot time.
5794 0 -- disable.
5795 1 -- enable.
5798 serialnumber [BUGS=X86-32]
5800 sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
5808 to set it to "all" by meaning -- no limit here.
5814 simeth= [IA-64]
5824 Disable merging of slabs with similar size. May be
5828 layout control by attackers can usually be
5832 unchanged). Debug options disable merging on their
5845 slub_debug can create guard zones around objects and
5889 using the csdlock_debug- kernel parameter.
5894 system. By default, let CSD-lock acquisition
5896 for this value provides a 5-minute timeout.
5898 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
5899 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
5900 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
5901 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
5902 smsc-ircc2.ircc_irq= [HW] IRQ line
5903 smsc-ircc2.ircc_dma= [HW] DMA channel
5904 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
5914 Default: -1 (no limit)
5917 [KNL] Should the soft-lockup detector generate panics.
5920 A value of 1 instructs the soft-lockup detector
5921 to panic the machine when a soft-lockup occurs. It is
5924 respective build-time switch to that functionality.
5927 [KNL] Should the soft-lockup detector generate
5932 See Documentation/admin-guide/laptops/sonypi.rst
5939 on - (default) Enable the HW or SW mitigation
5941 off - Disable the mitigation.
5948 on - unconditionally enable, implies
5950 off - unconditionally disable, implies
5952 auto - kernel detects whether your CPU model is
5964 Selecting 'off' will disable both the kernel and
5967 Specific mitigations can also be selected manually:
5969 retpoline - replace indirect branches
5970 retpoline,generic - Retpolines
5971 retpoline,lfence - LFENCE; indirect branch
5972 retpoline,amd - alias for retpoline,lfence
5973 eibrs - Enhanced/Auto IBRS
5974 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
5975 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
5976 ibrs - use IBRS to protect kernel
5986 on - Unconditionally enable mitigations. Is
5989 off - Unconditionally disable mitigations. Is
5992 prctl - Indirect branch speculation is enabled,
5993 but mitigation can be enabled via prctl
5998 - Like "prctl" above, but only STIBP is
6004 - Same as "prctl" above, but all seccomp
6009 - Like "seccomp" above, but only STIBP is
6014 auto - Kernel selects the mitigation depending on
6025 off - Disable mitigation
6026 microcode - Enable microcode mitigation only
6027 safe-ret - Enable sw-only safe RET mitigation (default)
6028 ibpb - Enable mitigation by issuing IBPB on
6030 ibpb-vmexit - Issue IBPB only on VMEXIT
6031 (cloud-specific mitigation)
6034 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6042 is that such stores are unlikely and that they can
6047 store can be used in a cache side channel attack, for
6056 on - Unconditionally disable Speculative Store Bypass
6057 off - Unconditionally enable Speculative Store Bypass
6058 auto - Kernel detects whether the CPU model contains an
6064 prctl - Control Speculative Store Bypass per thread
6068 seccomp - Same as "prctl" above, but all seccomp threads
6069 will disable SSB unless they explicitly opt out.
6076 on,auto - On Power8 and Power9 insert a store-forwarding
6080 off - No action.
6099 off - not enabled
6101 warn - the kernel will emit rate-limited warnings
6109 fatal - the kernel will send SIGBUS to applications
6114 ratelimit:N -
6134 Certain CPUs are vulnerable to an MDS-like
6135 exploit which can leak bits from the random
6139 microcode. However, the microcode fix can cause
6144 The microcode mitigation can be disabled with
6147 off: Disable mitigation and remove
6154 This kernel-boot parameter defaults to 128,
6155 but takes effect only when the low-order four
6172 instead of the compile-time CONFIG_NR_CPUS.
6176 grace-period sequence counter wrap for the
6177 srcu_data structure's ->srcu_gp_seq_needed field.
6188 expediting. Set to zero to disable automatic
6192 Specifies the number of no-delay instances
6199 Specifies the per-grace-period phase, number of
6200 non-sleeping polls of readers. Beyond this limit,
6206 Specifies number of microseconds of non-sleeping
6207 delay between each non-sleeping poll of readers.
6210 Specifies the number of update-side contention
6215 set for contention-based conversions to occur.
6218 Speculative Store Bypass Disable control
6225 force-on: Unconditionally enable mitigation for
6227 force-off: Unconditionally disable mitigation for
6243 disable the stack depot thereby saving the static memory
6250 stacktrace_filter=[function-list]
6252 will trace at boot up. function-list is a comma-separated
6253 list of functions. This list can be changed at run
6260 Set the STI (builtin display/keyboard on the HP-PARISC
6262 as the initial boot-console.
6274 Enable or disable strict sigaltstack size checks
6276 depends on the supported FPU features. This can
6322 to global on non-NUMA machines)
6328 RPC calls that can be sent from the client to a
6345 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6347 <int> -- Number of I/O TLB slabs
6348 <int> -- Second integer after comma. Number of swiotlb
6351 force -- force using of bounce buffers even if they
6353 noforce -- Never use bounce buffers (for debugging)
6368 Ignore sysrq setting - this boot parameter will
6376 cache size. See Documentation/networking/ip-sysctl.rst
6383 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6388 wakeup-capable RTC alarm.
6394 -1: disable all active trip points in all thermal zones
6398 -1: disable all critical trip points in all thermal zones
6402 1: disable ACPI thermal control
6405 -1: disable all passive trip points
6411 <deci-seconds>: poll all this frequency
6433 Prevent the CPU-hotplug component of torturing
6437 Dump the ftrace buffer at torture-test shutdown,
6438 even if there were no errors. This can be a
6441 with rotating-rust storage.
6446 disables verbose-printk() sleeping.
6449 Duration of each verbose-printk() sleep in jiffies.
6467 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
6481 The tp_printk_stop_on_boot (see below) can also be used
6488 frequency tracepoints such as irq or sched, can cause
6492 When tp_printk (above) is set, it can cause a lot of noise
6505 local - Use the per CPU time stamp counter
6509 global - Event time stamps are synchronize across
6512 counter - Simple counting of events (1, 2, ..)
6516 uptime - Use jiffies as the time stamp.
6517 perf - Use the same clock that perf uses.
6518 mono - Use ktime_get_mono_fast_ns() for time stamps.
6519 mono_raw - Use ktime_get_raw_fast_ns() for time
6521 boot - Use ktime_get_boot_fast_ns() for time stamps.
6525 trace_event=[event-list]
6527 to facilitate early boot debugging. The event-list is a
6528 comma-separated list of trace events to enable. See
6531 trace_instance=[instance-info]
6537 Events can be enabled at the time the instance is created
6551 trace_options=[option-list]
6552 [FTRACE] Enable or disable tracer options at boot.
6553 The option-list is a comma delimited list of options
6554 that can be enabled or disabled just as if you were
6567 trace_trigger=[trigger-list]
6587 [FTRACE] enable this option to disable tracing when a
6588 warning is hit. This turns off "tracing_on". Tracing can
6596 This option can also be set at run time via the sysctl
6602 Can be used to control the default behavior of the system
6604 See Documentation/admin-guide/mm/transhuge.rst
6612 - "tpm"
6613 - "tee"
6614 - "caam"
6623 Can be one of:
6624 - "kernel"
6625 - the same value as trusted.source: "tpm" or "tee"
6626 - "default"
6630 tsc= Disable clocksource stability checks for TSC.
6635 high-resolution timer mode on older hardware, and in
6638 Used to run time disable IRQ_TIME_ACCOUNTING on any
6640 can add overhead.
6644 [x86] nowatchdog: disable clocksource watchdog. Used
6656 can be overridden by a later tsc=nowatchdog. A console
6671 on - Enable TSX on the system. Although there are
6674 several previous speculation-related CVEs, and
6678 off - Disable TSX on the system. (Note that this
6686 auto - Disable TSX if X86_BUG_TAA is present,
6691 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6697 Similar to Micro-architectural Data Sampling (MDS)
6700 exploit against CPU internal buffers which can forward
6705 data can be used in a cache side channel attack, to
6712 full - Enable TAA mitigation on vulnerable CPUs
6715 full,nosmt - Enable TAA mitigation and disable SMT on
6718 vulnerable to cross-thread TAA attacks.
6719 off - Unconditionally disable TAA mitigation
6721 On MDS-affected machines, tsx_async_abort=off can be
6723 are mitigated with the same mechanism so in order to disable
6733 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6739 See also Documentation/input/devices/joystick-parport.rst
6741 udbg-immortal [PPC] When debugging early kernel crashes that
6747 Set number of hash buckets for UDP/UDP-Lite connections
6749 uhci-hcd.ignore_oc=
6751 Some badly-designed motherboards generate lots of
6760 unwind_debug [X86-64]
6761 Enable unwinder debug output. This can be
6768 (default -1 = authorized (same as 1),
6774 for newly-detected USB devices (default 2). This
6802 [USB] Specifies timeout for the initial 64-byte
6806 usbcore.nousb [USB] Disable the USB subsystem
6809 [USB] A list of quirk entries to augment the built-in
6812 VendorID:ProductID:Flags. The IDs are 4-digit hex
6814 will change the built-in quirk; setting it if it is
6819 a 255-byte read);
6820 b = USB_QUIRK_RESET_RESUME (device can't resume
6822 c = USB_QUIRK_NO_SET_INTF (device can't handle
6823 Set-Interface requests);
6824 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
6827 e = USB_QUIRK_RESET (device can't be reset
6831 bNumInterfaces count, and can't handle
6842 (bInterval-1).
6847 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
6853 k = USB_QUIRK_NO_LPM (device can't handle Link
6880 usb-storage.delay_use=
6884 usb-storage.quirks=
6886 override the built-in unusual_devs list. List
6889 and Product ID values (4-digit hex numbers) and
6891 to a common usb-storage quirk flag as follows:
6933 medium is write-protected).
6942 1 - undefined instruction events
6943 2 - system calls
6944 4 - invalid data aborts
6945 8 - SIGSEGV faults
6946 16 - SIGBUS faults
6960 vdso=0: disable VDSO mapping
6962 vdso32= [X86] Control the 32-bit vDSO
6963 vdso32=1: enable 32-bit VDSO
6964 vdso32=0 or vdso32=2: disable 32-bit VDSO
6974 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
6976 vector= [IA-64,SMP]
6997 <size> := size (can use standard suffixes
7006 Can be used multiple times for multiple devices.
7008 vga= [BOOT,X86-32] Select a particular video mode
7010 Documentation/admin-guide/svga.rst.
7025 - Disable all of the above options
7028 size of <nn>. This can be used to increase the
7029 minimum size (128MB on x86). It can also be used to
7046 vsyscall= [X86-64]
7049 code). Most statically-linked binaries and older
7052 targets for exploits that can control RIP.
7073 see VGA-softcursor.txt. Default: 2 = underline.
7078 This is a 16-member array composed of values
7079 ranging from 0-255.
7084 This is a 16-member array composed of values
7085 ranging from 0-255.
7090 This is a 16-member array composed of values
7091 ranging from 0-255.
7096 Set system-wide default UTF-8 mode for all tty's.
7097 Default is 1, i.e. UTF-8 mode is enabled for all
7102 Format=<-1|0|1>
7103 Set system-wide default for whether a cursor
7104 is shown on new VTs. Default is -1,
7109 vt.italic= [VT] Default color for italic text; 0-15.
7112 vt.underline= [VT] Default color for underlined text; 0-15.
7116 see Documentation/watchdog/watchdog-parameters.rst
7117 or other driver-specific files in the
7131 Format: <cpu-list>
7136 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7141 it can be updated at runtime by writing to the
7145 Per-cpu work items which run for longer than this
7148 them from noticeably delaying other per-cpu work
7157 Per-cpu workqueues are generally preferred because
7159 locality; unfortunately, per-cpu workqueues tend to
7162 Enabling this makes the per-cpu workqueues which
7173 workqueues. Can be one of "cpu", "smt", "cache",
7176 Documentation/core-api/workqueue.rst.
7178 This can be changed after boot by writing to the
7189 forces round-robin CPU selection to flush out
7197 on - Enable writecombine, use WUC for ioremap_wc()
7198 off - Disable writecombine, use SUC for ioremap_wc()
7200 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7204 xen_512gb_limit [KNL,X86-64,XEN]
7214 ide-disks -- unplug primary master IDE devices
7215 aux-ide-disks -- unplug non-primary-master IDE devices
7216 nics -- unplug network devices
7217 all -- unplug all emulated devices (NICs and IDE disks)
7218 unnecessary -- unplugging emulated devices is
7221 never -- do not unplug even if version check succeeds
7229 Select whether to always use non-faulting (safe) MSR
7245 [KNL,X86,XEN] Disable the vector callback for Xen
7250 to Xen, for use by other domains. Can be also changed at runtime
7254 xen_timer_slop= [X86-64,XEN]
7277 Boolean parameter to disable using fifo event handling
7279 preferred over the 2-level event handling, as it is
7296 xive.store-eoi=off [PPC]
7302 xhci-hcd.quirks [USB,KNL]
7304 host controller quirks. Meaning of each bit can be
7320 can be written using xmon commands.
7322 memory, and other data can't be written using