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Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 1155 |
1 files changed, 948 insertions, 207 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 213d0719e2b7..a3ea40b22fb9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -12,7 +12,7 @@ acpi= [HW,ACPI,X86,ARM64,RISCV64,EARLY] Advanced Configuration and Power Interface Format: { force | on | off | strict | noirq | rsdt | - copy_dsdt } + copy_dsdt | nospcr } force -- enable ACPI if default was off on -- enable ACPI but allow fallback to DT [arm64,riscv64] off -- disable ACPI if default was on @@ -21,8 +21,16 @@ strictly ACPI specification compliant. rsdt -- prefer RSDT over (default) XSDT copy_dsdt -- copy DSDT to memory - For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or - "acpi=force" are available + nocmcff -- Disable firmware first mode for corrected + errors. This disables parsing the HEST CMC error + source to check if firmware has set the FF flag. This + may result in duplicate corrected error reports. + nospcr -- disable console in ACPI SPCR table as + default _serial_ console on ARM64 + For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or + "acpi=nospcr" are available + For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force" + are available See also Documentation/power/runtime_pm.rst, pci=noacpi @@ -329,12 +337,17 @@ allowed anymore to lift isolation requirements as needed. This option does not override iommu=pt - force_enable - Force enable the IOMMU on platforms known - to be buggy with IOMMU enabled. Use this - option with care. - pgtbl_v1 - Use v1 page table for DMA-API (Default). - pgtbl_v2 - Use v2 page table for DMA-API. - irtcachedis - Disable Interrupt Remapping Table (IRT) caching. + force_enable - Force enable the IOMMU on platforms known + to be buggy with IOMMU enabled. Use this + option with care. + pgtbl_v1 - Use v1 page table for DMA-API (Default). + pgtbl_v2 - Use v2 page table for DMA-API. + irtcachedis - Disable Interrupt Remapping Table (IRT) caching. + nohugepages - Limit page-sizes used for v1 page-tables + to 4 KiB. + v2_pgsizes_only - Limit page-sizes used for v1 page-tables + to 4KiB/2Mib/1GiB. + amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table @@ -396,15 +409,13 @@ not play well with APC CPU idle - disable it if you have APC and your system crashes randomly. + apic [APIC,X86-64] Use IO-APIC. Default. + apic= [APIC,X86,EARLY] Advanced Programmable Interrupt Controller Change the output verbosity while booting Format: { quiet (default) | verbose | debug } Change the amount of debugging information output when initialising the APIC and IO-APIC components. - For X86-32, this can also be used to specify an APIC - driver name. - Format: apic=driver_name - Examples: apic=bigsmp apic_extnmi= [APIC,X86,EARLY] External NMI delivery setting Format: { bsp (default) | all | none } @@ -415,6 +426,10 @@ useful so that a dump capture kernel won't be shot down by NMI + apicpmtimer Do APIC timer calibration using the pmtimer. Implies + apicmaintimer. Useful when your PIT timer is totally + broken. + autoconf= [IPV6] See Documentation/networking/ipv6.rst. @@ -431,9 +446,15 @@ arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards Format: <io>,<irq>,<nodeID> + arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of + 32 bit applications. + arm64.nobti [ARM64] Unconditionally disable Branch Target Identification support + arm64.nogcs [ARM64] Unconditionally disable Guarded Control Stack + support + arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory Set instructions support @@ -510,6 +531,18 @@ Format: <io>,<irq>,<mode> See header of drivers/net/hamradio/baycom_ser_hdx.c. + bdev_allow_write_mounted= + Format: <bool> + Control the ability to open a mounted block device + for writing, i.e., allow / disallow writes that bypass + the FS. This was implemented as a means to prevent + fuzzers from crashing the kernel by overwriting the + metadata underneath a mounted FS without its awareness. + This also prevents destructive formatting of mounted + filesystems by naive storage tooling that don't use + O_EXCL. Default is Y and can be changed through the + Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED. + bert_disable [ACPI] Disable BERT OS support on buggy BIOSes. @@ -785,6 +818,25 @@ Documentation/networking/netconsole.rst for an alternative. + <DEVNAME>:<n>.<n>[,options] + Use the specified serial port on the serial core bus. + The addressing uses DEVNAME of the physical serial port + device, followed by the serial core controller instance, + and the serial port instance. The options are the same + as documented for the ttyS addressing above. + + The mapping of the serial ports to the tty instances + can be viewed with: + + $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/* + /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0 + + In the above example, the console can be addressed with + console=00:04:0.0. Note that a console addressed this + way will only get added when the related device driver + is ready. The use of an earlycon parameter in addition to + the console may be desired for console output early on. + uart[8250],io,<addr>[,options] uart[8250],mmio,<addr>[,options] uart[8250],mmio16,<addr>[,options] @@ -875,12 +927,16 @@ the parameter has no effect. crash_kexec_post_notifiers - Run kdump after running panic-notifiers and dumping - kmsg. This only for the users who doubt kdump always - succeeds in any situation. - Note that this also increases risks of kdump failure, - because some panic notifiers can make the crashed - kernel more unstable. + Only jump to kdump kernel after running the panic + notifiers and dumping kmsg. This option increases + the risks of a kdump failure, since some panic + notifiers can make the crashed kernel more unstable. + In configurations where kdump may not be reliable, + running the panic notifiers could allow collecting + more data on dmesg, like stack traces from other CPUS + or extra data dumped by panic_print. Note that some + configurations enable this option unconditionally, + like Hyper-V, PowerPC (fadump) and AMD SEV-SNP. crashkernel=size[KMG][@offset[KMG]] [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel' @@ -1351,7 +1407,8 @@ earlyprintk=serial[,0x...[,baudrate]] earlyprintk=ttySn[,baudrate] earlyprintk=dbgp[debugController#] - earlyprintk=pciserial[,force],bus:device.function[,baudrate] + earlyprintk=mmio32,membase[,{nocfg|baudrate}] + earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}] earlyprintk=xdbc[xhciController#] earlyprintk=bios @@ -1359,6 +1416,9 @@ the normal console is initialized. It is not enabled by default because it has some cosmetic problems. + Use "nocfg" to skip UART configuration, assume + BIOS/firmware has configured UART correctly. + Append ",keep" to not disable it when the real console takes over. @@ -1428,27 +1488,6 @@ you are really sure that your UEFI does sane gc and fulfills the spec otherwise your board may brick. - efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI,X86,EARLY] - Add arbitrary attribute to specific memory range by - updating original EFI memory map. - Region of memory which aa attribute is added to is - from ss to ss+nn. - - If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 - is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) - attribute is added to range 0x100000000-0x180000000 and - 0x10a0000000-0x1120000000. - - If efi_fake_mem=8G@9G:0x40000 is specified, the - EFI_MEMORY_SP(0x40000) attribute is added to - range 0x240000000-0x43fffffff. - - Using this parameter you can do debugging of EFI memmap - related features. For example, you can do debugging of - Address Range Mirroring feature even if your box - doesn't support it, or mark specific memory as - "soft reserved". - efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT that is to be dynamically loaded by Linux. If there are multiple variables with the same name but with different @@ -1524,6 +1563,7 @@ failslab= fail_usercopy= fail_page_alloc= + fail_skb_realloc= fail_make_request=[KNL] General fault injection mechanism. Format: <interval>,<probability>,<space>,<times> @@ -1696,6 +1736,8 @@ off: Disable GDS mitigation. + gbpages [X86] Use GB pages for kernel direct mappings. + gcov_persist= [GCOV] When non-zero (default), profiling data for kernel modules is saved and remains accessible via debugfs, even when the module is unloaded/reloaded. @@ -1743,7 +1785,9 @@ allocation boundaries as a proactive defense against bounds-checking flaws in the kernel's copy_to_user()/copy_from_user() interface. - on Perform hardened usercopy checks (default). + The default is determined by + CONFIG_HARDENED_USERCOPY_DEFAULT_ON. + on Perform hardened usercopy checks. off Disable hardened usercopy checks. hardlockup_all_cpu_backtrace= @@ -1756,8 +1800,6 @@ for 64-bit NUMA, off otherwise. Format: 0 | 1 (for off | on) - hcl= [IA-64] SGI's Hardware Graph compatibility layer - hd= [EIDE] (E)IDE hard drive subsystem geometry Format: <cyl>,<head>,<sect> @@ -1786,6 +1828,13 @@ lz4: Select LZ4 compression algorithm to compress/decompress hibernation image. + hibernate.pm_test_delay= + [HIBERNATION] + Sets the number of seconds to remain in a hibernation test + mode before resuming the system (see + /sys/power/pm_test). Only available when CONFIG_PM_DEBUG + is set. Default value is 5. + highmem=nn[KMG] [KNL,BOOT,EARLY] forces the highmem zone to have an exact size of <nn>. This works even on boxes that have no highmem otherwise. This also works to reduce highmem @@ -1821,7 +1870,7 @@ hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET registers. Default set by CONFIG_HPET_MMAP_DEFAULT. - hugepages= [HW] Number of HugeTLB pages to allocate at boot. + hugepages= [HW,EARLY] Number of HugeTLB pages to allocate at boot. If this follows hugepagesz (below), it specifies the number of pages of hugepagesz to be allocated. If this is the first HugeTLB parameter on the command @@ -1833,15 +1882,24 @@ <node>:<integer>[,<node>:<integer>] hugepagesz= - [HW] The size of the HugeTLB pages. This is used in - conjunction with hugepages (above) to allocate huge - pages of a specific size at boot. The pair - hugepagesz=X hugepages=Y can be specified once for - each supported huge page size. Huge page sizes are - architecture dependent. See also + [HW,EARLY] The size of the HugeTLB pages. This is + used in conjunction with hugepages (above) to + allocate huge pages of a specific size at boot. The + pair hugepagesz=X hugepages=Y can be specified once + for each supported huge page size. Huge page sizes + are architecture dependent. See also Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] + hugepage_alloc_threads= + [HW] The number of threads that should be used to + allocate hugepages during boot. This option can be + used to improve system bootup time when allocating + a large amount of huge pages. + The default value is 25% of the available hardware threads. + + Note that this parameter only applies to non-gigantic huge pages. + hugetlb_cma= [HW,CMA,EARLY] The size of a CMA area used for allocation of gigantic hugepages. Or using node format, the size of a CMA area per node can be specified. @@ -1852,6 +1910,13 @@ hugepages using the CMA allocator. If enabled, the boot-time allocation of gigantic hugepages is skipped. + hugetlb_cma_only= + [HW,CMA,EARLY] When allocating new HugeTLB pages, only + try to allocate from the CMA areas. + + This option does nothing if hugetlb_cma= is not also + specified. + hugetlb_free_vmemmap= [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP enabled. @@ -1893,12 +1958,40 @@ which allow the hypervisor to 'idle' the guest on lock contention. + hw_protection= [HW] + Format: reboot | shutdown + + Hardware protection action taken on critical events like + overtemperature or imminent voltage loss. + i2c_bus= [HW] Override the default board specific I2C bus speed or register an additional I2C bus that is not registered from board initialization code. Format: <bus_id>,<clkrate> + i2c_touchscreen_props= [HW,ACPI,X86] + Set device-properties for ACPI-enumerated I2C-attached + touchscreen, to e.g. fix coordinates of upside-down + mounted touchscreens. If you need this option please + submit a drivers/platform/x86/touchscreen_dmi.c patch + adding a DMI quirk for this. + + Format: + <ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...] + Where <val> is one of: + Omit "=<val>" entirely Set a boolean device-property + Unsigned number Set a u32 device-property + Anything else Set a string device-property + + Examples (split over multiple lines): + i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x: + touchscreen-inverted-y + + i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920: + touchscreen-size-y=1080:touchscreen-inverted-y: + firmware-name=gsl1680-vendor-model.fw:silead,home-button + i8042.debug [HW] Toggle i8042 debug mode i8042.unmask_kbd_data [HW] Enable printing of interrupt data from the KBD port @@ -1958,12 +2051,21 @@ idle= [X86,EARLY] Format: idle=poll, idle=halt, idle=nomwait - Poll forces a polling idle loop that can slightly - improve the performance of waking up a idle CPU, but - will use a lot of power and make the system run hot. - Not recommended. + + idle=poll: Don't do power saving in the idle loop + using HLT, but poll for rescheduling event. This will + make the CPUs eat a lot more power, but may be useful + to get slightly better performance in multiprocessor + benchmarks. It also makes some profiling using + performance counters more accurate. Please note that + on systems with MONITOR/MWAIT support (like Intel + EM64T CPUs) this option has no performance advantage + over the normal idle loop. It may also interact badly + with hyperthreading. + idle=halt: Halt is forced to be used for CPU idle. In such case C2/C3 won't be used again. + idle=nomwait: Disable mwait for CPU C-states idxd.sva= [HW] @@ -1978,7 +2080,7 @@ for the device. By default it is set to false (0). ieee754= [MIPS] Select IEEE Std 754 conformance mode - Format: { strict | legacy | 2008 | relaxed } + Format: { strict | legacy | 2008 | relaxed | emulated } Default: strict Choose which programs will be accepted for execution @@ -1998,6 +2100,8 @@ by the FPU relaxed accept any binaries regardless of whether supported by the FPU + emulated accept any binaries but enable FPU emulator + if binary mode is unsupported by the FPU. The FPU emulator is always able to support both NaN encodings, so if no FPU hardware is present or it has @@ -2105,6 +2209,23 @@ different crypto accelerators. This option can be used to achieve best performance for particular HW. + indirect_target_selection= [X86,Intel] Mitigation control for Indirect + Target Selection(ITS) bug in Intel CPUs. Updated + microcode is also required for a fix in IBPB. + + on: Enable mitigation (default). + off: Disable mitigation. + force: Force the ITS bug and deploy default + mitigation. + vmexit: Only deploy mitigation if CPU is affected by + guest/host isolation part of ITS. + stuff: Deploy RSB-fill mitigation when retpoline is + also deployed. Otherwise, deploy the default + mitigation. + + For details see: + Documentation/admin-guide/hw-vuln/indirect-target-selection.rst + init= [KNL] Format: <full_path> Run specified binary instead of /sbin/init as init @@ -2243,6 +2364,9 @@ per_cpu_perf_limits Allow per-logical-CPU P-State performance control limits using cpufreq sysfs interface + no_cas + Do not enable capacity-aware scheduling (CAS) on + hybrid systems intremap= [X86-64,Intel-IOMMU,EARLY] on enable Interrupt Remapping (default) @@ -2251,26 +2375,81 @@ no_x2apic_optout BIOS x2APIC opt-out request will be ignored nopost disable Interrupt Posting + posted_msi + enable MSIs delivered as posted interrupts iomem= Disable strict checking of access to MMIO memory strict regions from userspace. relaxed iommu= [X86,EARLY] + off + Don't initialize and use any kind of IOMMU. + force + Force the use of the hardware IOMMU even when + it is not actually needed (e.g. because < 3 GB + memory). + noforce + Don't force hardware IOMMU usage when it is not + needed. (default). + biomerge panic nopanic merge nomerge + soft - pt [X86] - nopt [X86] - nobypass [PPC/POWERNV] + Use software bounce buffering (SWIOTLB) (default for + Intel machines). This can be used to prevent the usage + of an available hardware IOMMU. + + [X86] + pt + [X86] + nopt + [PPC/POWERNV] + nobypass Disable IOMMU bypass, using IOMMU for PCI devices. + [X86] + AMD Gart HW IOMMU-specific options: + + <size> + Set the size of the remapping area in bytes. + + allowed + Overwrite iommu off workarounds for specific chipsets + + fullflush + Flush IOMMU on each allocation (default). + + nofullflush + Don't use IOMMU fullflush. + + memaper[=<order>] + Allocate an own aperture over RAM with size + 32MB<<order. (default: order=1, i.e. 64MB) + + merge + Do scatter-gather (SG) merging. Implies "force" + (experimental). + + nomerge + Don't do scatter-gather (SG) merging. + + noaperture + Ask the IOMMU not to touch the aperture for AGP. + + noagp + Don't initialize the AGP driver and use full aperture. + + panic + Always panic when IOMMU overflows. + iommu.forcedac= [ARM64,X86,EARLY] Control IOVA allocation for PCI devices. Format: { "0" | "1" } 0 - Try to allocate a 32-bit DMA address first, before @@ -2321,6 +2500,18 @@ ipcmni_extend [KNL,EARLY] Extend the maximum number of unique System V IPC identifiers from 32,768 to 16,777,216. + ipe.enforce= [IPE] + Format: <bool> + Determine whether IPE starts in permissive (0) or + enforce (1) mode. The default is enforce. + + ipe.success_audit= + [IPE] + Format: <bool> + Start IPE with success auditing enabled, emitting + an audit event when a binary is allowed. The default + is 0. + irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. @@ -2366,7 +2557,9 @@ specified in the flag list (default: domain): nohz - Disable the tick when a single task runs. + Disable the tick when a single task runs as well as + disabling other kernel noises like having RCU callbacks + offloaded. This is equivalent to the nohz_full parameter. A residual 1Hz tick is offloaded to workqueues, which you need to affine to housekeeping through the global @@ -2492,7 +2685,7 @@ keepinitrd [HW,ARM] See retain_initrd. - kernelcore= [KNL,X86,IA-64,PPC,EARLY] + kernelcore= [KNL,X86,PPC,EARLY] Format: nn[KMGTPE] | nn% | "mirror" This parameter specifies the amount of memory usable by the kernel for non-movable allocations. The requested @@ -2556,6 +2749,31 @@ kgdbwait [KGDB,EARLY] Stop kernel execution and enter the kernel debugger at the earliest opportunity. + kho= [KEXEC,EARLY] + Format: { "0" | "1" | "off" | "on" | "y" | "n" } + Enables or disables Kexec HandOver. + "0" | "off" | "n" - kexec handover is disabled + "1" | "on" | "y" - kexec handover is enabled + + kho_scratch= [KEXEC,EARLY] + Format: ll[KMG],mm[KMG],nn[KMG] | nn% + Defines the size of the KHO scratch region. The KHO + scratch regions are physically contiguous memory + ranges that can only be used for non-kernel + allocations. That way, even when memory is heavily + fragmented with handed over memory, the kexeced + kernel will always have enough contiguous ranges to + bootstrap itself. + + It is possible to specify the exact amount of + memory in the form of "ll[KMG],mm[KMG],nn[KMG]" + where the first parameter defines the size of a low + memory scratch area, the second parameter defines + the size of a global scratch area and the third + parameter defines the size of additional per-node + scratch areas. The form "nn%" defines scale factor + (in percents) of memory that was used during boot. + kmac= [MIPS] Korina ethernet MAC address. Configure the RouterBoard 532 series on-chip Ethernet adapter MAC address. @@ -2619,6 +2837,23 @@ Default is Y (on). + kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86] + If enabled, KVM will enable virtualization in hardware + when KVM is loaded, and disable virtualization when KVM + is unloaded (if KVM is built as a module). + + If disabled, KVM will dynamically enable and disable + virtualization on-demand when creating and destroying + VMs, i.e. on the 0=>1 and 1=>0 transitions of the + number of VMs. + + Enabling virtualization at module load avoids potential + latency for creation of the 0=>1 VM, as KVM serializes + virtualization enabling across all online CPUs. The + "cost" of enabling virtualization when KVM is loaded, + is that doing so may interfere with using out-of-tree + hypervisors that want to "own" virtualization hardware. + kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. Default is false (don't support). @@ -2665,17 +2900,21 @@ nvhe: Standard nVHE-based mode, without support for protected guests. - protected: nVHE-based mode with support for guests whose - state is kept private from the host. + protected: Mode with support for guests whose state is + kept private from the host, using VHE or + nVHE depending on HW support. nested: VHE-based mode with support for nested - virtualization. Requires at least ARMv8.3 - hardware. + virtualization. Requires at least ARMv8.4 + hardware (with FEAT_NV2). Defaults to VHE/nVHE based on hardware support. Setting mode to "protected" will disable kexec and hibernation - for the host. "nested" is experimental and should be - used with extreme caution. + for the host. To force nVHE on VHE hardware, add + "arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" to the + command-line. + "nested" is experimental and should be used with + extreme caution. kvm-arm.vgic_v3_group0_trap= [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0 @@ -2693,6 +2932,24 @@ [KVM,ARM,EARLY] Allow use of GICv4 for direct injection of LPIs. + kvm-arm.wfe_trap_policy= + [KVM,ARM] Control when to set WFE instruction trap for + KVM VMs. Traps are allowed but not guaranteed by the + CPU architecture. + + trap: set WFE instruction trap + + notrap: clear WFE instruction trap + + kvm-arm.wfi_trap_policy= + [KVM,ARM] Control when to set WFI instruction trap for + KVM VMs. Traps are allowed but not guaranteed by the + CPU architecture. + + trap: set WFI instruction trap + + notrap: clear WFI instruction trap + kvm_cma_resv_ratio=n [PPC,EARLY] Reserves given percentage from system memory area for contiguous memory allocation for KVM hash pagetable @@ -2935,6 +3192,8 @@ * max_sec_lba48: Set or clear transfer size limit to 65535 sectors. + * external: Mark port as external (hotplug-capable). + * [no]lpm: Enable or disable link power management. * [no]setxfer: Indicate if transfer speed mode setting @@ -3132,26 +3391,16 @@ unlikely, in the extreme case this might damage your hardware. - ltpc= [NET] - Format: <io>,<irq>,<dma> - lsm.debug [SECURITY] Enable LSM initialization debugging output. lsm=lsm1,...,lsmN [SECURITY] Choose order of LSM initialization. This overrides CONFIG_LSM, and the "security=" parameter. - machvec= [IA-64] Force the use of a particular machine-vector - (machvec) in a generic kernel. - Example: machvec=hpzx1 - machtype= [Loongson] Share the same kernel image file between different yeeloong laptops. Example: machtype=lemote-yeeloong-2f-7inch - max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater - than or equal to this physical address is ignored. - maxcpus= [SMP,EARLY] Maximum number of processors that an SMP kernel will bring up during bootup. maxcpus=n : n >= 0 limits the kernel to bring up 'n' processors. Surely after @@ -3168,9 +3417,77 @@ devices can be requested on-demand with the /dev/loop-control interface. - mce [X86-32] Machine Check Exception + mce= [X86-{32,64}] + + Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables. + + off + disable machine check + + no_cmci + disable CMCI(Corrected Machine Check Interrupt) that + Intel processor supports. Usually this disablement is + not recommended, but it might be handy if your + hardware is misbehaving. + + Note that you'll get more problems without CMCI than + with due to the shared banks, i.e. you might get + duplicated error logs. + + dont_log_ce + don't make logs for corrected errors. All events + reported as corrected are silently cleared by OS. This + option will be useful if you have no interest in any + of corrected errors. + + ignore_ce + disable features for corrected errors, e.g. + polling timer and CMCI. All events reported as + corrected are not cleared by OS and remained in its + error banks. + + Usually this disablement is not recommended, however + if there is an agent checking/clearing corrected + errors (e.g. BIOS or hardware monitoring + applications), conflicting with OS's error handling, + and you cannot deactivate the agent, then this option + will be a help. + + no_lmce + do not opt-in to Local MCE delivery. Use legacy method + to broadcast MCEs. + + bootlog + enable logging of machine checks left over from + booting. Disabled by default on AMD Fam10h and older + because some BIOS leave bogus ones. + + If your BIOS doesn't do that it's a good idea to + enable though to make sure you log even machine check + events that result in a reboot. On Intel systems it is + enabled by default. + + nobootlog + disable boot machine check logging. + + monarchtimeout (number) + sets the time in us to wait for other CPUs on machine + checks. 0 to disable. + + bios_cmci_threshold + don't overwrite the bios-set CMCI threshold. This boot + option prevents Linux from overwriting the CMCI + threshold set by the bios. Without this option, Linux + always sets the CMCI threshold to 1. Enabling this may + make memory predictive failure analysis less effective + if the bios sets thresholds for memory errors since we + will not see details for all errors. + + recovery + force-enable recoverable machine check code paths + + Everything else is in sysfs now. - mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst md= [HW] RAID subsystems devices and level See Documentation/admin-guide/md.rst. @@ -3260,8 +3577,8 @@ [KNL] Set the initial state for the memory hotplug onlining policy. If not specified, the default value is set according to the - CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config - option. + CONFIG_MHP_DEFAULT_ONLINE_TYPE kernel config + options. See Documentation/admin-guide/mm/memory-hotplug.rst. memmap=exactmap [KNL,X86,EARLY] Enable setting of an exact @@ -3377,10 +3694,6 @@ deep - Suspend-To-RAM or equivalent (if supported) See Documentation/admin-guide/pm/sleep-states.rst. - mfgpt_irq= [IA-32] Specify the IRQ to use for the - Multi-Function General Purpose Timers on AMD Geode - platforms. - mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when the BIOS has incorrectly applied a workaround. TinyBIOS version 0.98 is known to be affected, 0.99 fixes the @@ -3393,9 +3706,6 @@ Enable or disable the microcode minimal revision enforcement for the runtime microcode loader. - min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this - physical address is ignored. - mini2440= [ARM,HW,KNL] Format:[0..2][b][c][t] Default: "0tb" @@ -3432,6 +3742,7 @@ expose users to several CPU vulnerabilities. Equivalent to: if nokaslr then kpti=0 [ARM64] gather_data_sampling=off [X86] + indirect_target_selection=off [X86] kvm.nx_huge_pages=off [X86] l1tf=off [X86] mds=off [X86] @@ -3560,7 +3871,7 @@ mousedev.yres= [MOUSE] Vertical screen resolution, used for devices reporting absolute coordinates, such as tablets - movablecore= [KNL,X86,IA-64,PPC,EARLY] + movablecore= [KNL,X86,PPC,EARLY] Format: nn[KMGTPE] | nn% This parameter is the complement to kernelcore=, it specifies the amount of memory used for migratable @@ -3586,11 +3897,6 @@ mtdparts= [MTD] See drivers/mtd/parsers/cmdlinepart.c - mtdset= [ARM] - ARM/S3C2412 JIVE boot control - - See arch/arm/mach-s3c/mach-jive.c - mtouchusb.raw_coordinates= [HW] Make the MicroTouch USB driver use raw coordinates ('y', default) or cooked coordinates ('n') @@ -3776,10 +4082,12 @@ Format: [state][,regs][,debounce][,die] nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels - Format: [panic,][nopanic,][num] + Format: [panic,][nopanic,][rNNN,][num] Valid num: 0 or 1 0 - turn hardlockup detector in nmi_watchdog off 1 - turn hardlockup detector in nmi_watchdog on + rNNN - configure the watchdog with raw perf event 0xNNN + When panic is specified, panic when an NMI watchdog timeout occurs (or 'nopanic' to not panic on an NMI watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) @@ -3803,12 +4111,11 @@ noalign [KNL,ARM] - noaltinstr [S390,EARLY] Disables alternative instructions - patching (CPU alternatives feature). - noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any IOAPICs that may be present in the system. + noapictimer [APIC,X86] Don't set up the APIC timer + noautogroup Disable scheduler automatic task group creation. nocache [ARM,EARLY] @@ -3837,8 +4144,6 @@ no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel. - noexec [IA-64] - noexec32 [X86-64] This affects only 32-bit executables. noexec32=on: enable non-executable mappings (default) @@ -3858,12 +4163,7 @@ register save and restore. The kernel will only save legacy floating-point registers on task switch. - nohalt [IA-64] Tells the kernel not to use the power saving - function PAL_HALT_LIGHT when idle. This increases - power-consumption. On the positive side, it reduces - interrupt wake-up latency, which may improve performance - in certain environments such as networked servers or - real-time systems. + nogbpages [X86] Do not use GB pages for kernel direct mappings. no_hash_pointers [KNL,EARLY] @@ -3882,7 +4182,7 @@ nohibernate [HIBERNATION] Disable hibernation and resume. - nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to + nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to busy wait in do_idle() and not use the arch_cpu_idle() implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP to be effective. This is useful on platforms where the @@ -3891,6 +4191,8 @@ the impact of the sleep instructions. This is also useful when using JTAG debugger. + nohpet [X86] Don't use the HPET timer. + nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings. nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings. @@ -3919,8 +4221,6 @@ remapping. [Deprecated - use intremap=off] - nointroute [IA-64] - noinvpcid [X86,EARLY] Disable the INVPCID cpu feature. noiotrap [SH] Disables trapped I/O port accesses. @@ -3930,8 +4230,6 @@ noisapnp [ISAPNP] Disables ISA PnP code. - nojitter [IA-64] Disables jitter checking for ITC timers. - nokaslr [KNL,EARLY] When CONFIG_RANDOMIZE_BASE is set, this disables kernel and module base offset ASLR (Address Space @@ -3946,8 +4244,6 @@ nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer. - nomca [IA-64] Disable machine check abort handling - nomce [X86-32] Disable Machine Check Exception nomfgpt [X86-32] Disable Multi-Function General Purpose @@ -3999,8 +4295,6 @@ noresume [SWSUSP] Disables resume and restores original swap space. - nosbagart [IA-64] - no-scroll [VGA] Disables scrollback. This is required for the Braillex ib80-piezo Braille reader made by F.H. Papenmeier (Germany). @@ -4018,10 +4312,10 @@ nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel, and disable the IO APIC. legacy for "maxcpus=0". - nosmt [KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT). + nosmt [KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT). Equivalent to smt=1. - [KNL,X86,PPC] Disable symmetric multithreading (SMT). + [KNL,X86,PPC,S390] Disable symmetric multithreading (SMT). nosmt=force: Force disable SMT, cannot be undone via the sysfs control file. @@ -4044,14 +4338,16 @@ prediction) vulnerability. System may allow data leaks with this option. - no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,EARLY] Disable - paravirtualized steal time accounting. steal time is - computed, but won't influence scheduler behaviour + no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY] + Disable paravirtualized steal time accounting. steal time + is computed, but won't influence scheduler behaviour nosync [HW,M68K] Disables sync negotiation for all devices. - no_timer_check [X86,APIC] Disables the code which tests for - broken timer IRQ sources. + no_timer_check [X86,APIC] Disables the code which tests for broken + timer IRQ sources, i.e., the IO-APIC timer. This can + work around problems with incorrect timer + initialization on some boards. no_uaccess_flush [PPC,EARLY] Don't flush the L1-D cache after accessing user data. @@ -4101,19 +4397,6 @@ parameter, xsave area per process might occupy more memory on xsaves enabled systems. - nps_mtm_hs_ctr= [KNL,ARC] - This parameter sets the maximum duration, in - cycles, each HW thread of the CTOP can run - without interruptions, before HW switches it. - The actual maximum duration is 16 times this - parameter's value. - Format: integer between 1 and 255 - Default: 255 - - nptcg= [IA-64] Override max number of concurrent global TLB - purges which is reported from either PAL_VM_SUMMARY or - SAL PALO. - nr_cpus= [SMP,EARLY] Maximum number of processors that an SMP kernel could support. nr_cpus=n : n >= 1 limits the kernel to support 'n' processors. It could be larger than the @@ -4129,6 +4412,26 @@ Disable NUMA, Only set up a single NUMA node spanning all memory. + numa=fake=<size>[MG] + [KNL, ARM64, RISCV, X86, EARLY] + If given as a memory unit, fills all system RAM with + nodes of size interleaved over physical nodes. + + numa=fake=<N> + [KNL, ARM64, RISCV, X86, EARLY] + If given as an integer, fills all system RAM with N + fake nodes interleaved over physical nodes. + + numa=fake=<N>U + [KNL, ARM64, RISCV, X86, EARLY] + If given as an integer followed by 'U', it will + divide each physical node into N emulated nodes. + + numa=noacpi [X86] Don't parse the SRAT table for NUMA setup + + numa=nohmat [X86] Don't parse the HMAT table for NUMA setup, or + soft-reserved memory partitioning. + numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic NUMA balancing. Allowed values are enable and disable @@ -4173,13 +4476,11 @@ page_alloc.shuffle= [KNL] Boolean flag to control whether the page allocator - should randomize its free lists. The randomization may - be automatically enabled if the kernel detects it is - running on a platform with a direct-mapped memory-side - cache, and this parameter can be used to - override/disable that behavior. The state of the flag - can be read from sysfs at: + should randomize its free lists. This parameter can be + used to enable/disable page randomization. The state of + the flag can be read from sysfs at: /sys/module/page_alloc/parameters/shuffle. + This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y. page_owner= [KNL,EARLY] Boot-time page_owner enabling option. Storage of the information about who allocated @@ -4589,14 +4890,51 @@ bridges without forcing it upstream. Note: this removes isolation between devices and may put more devices in an IOMMU group. + config_acs= + Format: + <ACS flags>@<pci_dev>[; ...] + Specify one or more PCI devices (in the format + specified above) optionally prepended with flags + and separated by semicolons. The respective + capabilities will be enabled, disabled or + unchanged based on what is specified in + flags. + + ACS Flags is defined as follows: + bit-0 : ACS Source Validation + bit-1 : ACS Translation Blocking + bit-2 : ACS P2P Request Redirect + bit-3 : ACS P2P Completion Redirect + bit-4 : ACS Upstream Forwarding + bit-5 : ACS P2P Egress Control + bit-6 : ACS Direct Translated P2P + Each bit can be marked as: + '0' – force disabled + '1' – force enabled + 'x' – unchanged + For example, + pci=config_acs=10x@pci:0:0 + would configure all devices that support + ACS to enable P2P Request Redirect, disable + Translation Blocking, and leave Source + Validation unchanged from whatever power-up + or firmware set it to. + + Note: this may remove isolation between devices + and may put more devices in an IOMMU group. force_floating [S390] Force usage of floating interrupts. nomio [S390] Do not use MIO instructions. norid [S390] ignore the RID field and force use of one PCI domain per PCI function + notph [PCIE] If the PCIE_TPH kernel config parameter + is enabled, this kernel boot option can be used + to disable PCIe TLP Processing Hints support + system-wide. - pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power + pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power Management. - off Disable ASPM. + off Don't touch ASPM configuration at all. Leave any + configuration done by firmware unchanged. force Enable ASPM even on devices that claim not to support it. WARNING: Forcing ASPM on may cause system lockups. @@ -4721,7 +5059,14 @@ none - Limited to cond_resched() calls voluntary - Limited to cond_resched() and might_sleep() calls full - Any section that isn't explicitly preempt disabled - can be preempted anytime. + can be preempted anytime. Tasks will also yield + contended spinlocks (if the critical section isn't + explicitly preempt disabled beyond the lock itself). + lazy - Scheduler controlled. Similar to full but instead + of preempting the task immediately, the task gets + one HZ tick time to yield itself before the + preemption will be forced. One preemption is when the + task returns to user space. print-fatal-signals= [KNL] debug: print fatal signals @@ -4751,6 +5096,14 @@ Format: <bool> default: 0 (auto_verbose is enabled) + printk.debug_non_panic_cpus= + Allows storing messages from non-panic CPUs into + the printk log buffer during panic(). They are + flushed to consoles by the panic-CPU on + a best-effort basis. + Format: <bool> (1/Y/y=enable, 0/N/n=disable) + Default: disabled + printk.devkmsg={on,off,ratelimit} Control writing to /dev/kmsg. on - unlimited logging to /dev/kmsg from userspace @@ -4761,6 +5114,16 @@ printk.time= Show timing data prefixed to each printk message line Format: <bool> (1/Y/y=enable, 0/N/n=disable) + proc_mem.force_override= [KNL] + Format: {always | ptrace | never} + Traditionally /proc/pid/mem allows memory permissions to be + overridden without restrictions. This option may be set to + restrict that. Can be one of: + - 'always': traditional behavior always allows mem overrides. + - 'ptrace': only allow mem overrides for active ptracers. + - 'never': never allow mem overrides. + If not specified, default is the CONFIG_PROC_MEM_* choice. + processor.max_cstate= [HW,ACPI] Limit processor to maximum C-state max_cstate=9 overrides any DMI blacklist limit. @@ -4771,11 +5134,9 @@ profile= [KNL] Enable kernel profiling via /proc/profile Format: [<profiletype>,]<number> - Param: <profiletype>: "schedule", "sleep", or "kvm" + Param: <profiletype>: "schedule" or "kvm" [defaults to kernel profiling] Param: "schedule" - profile schedule points. - Param: "sleep" - profile D-state sleeping (millisecs). - Requires CONFIG_SCHEDSTATS Param: "kvm" - profile VM exits. Param: <number> - step/bucket size as a power of 2 for statistical time based profiling. @@ -4784,7 +5145,9 @@ prot_virt= [S390] enable hosting protected virtual machines isolated from the hypervisor (if hardware supports - that). + that). If enabled, the default kernel base address + might be overridden even when Kernel Address Space + Layout Randomization is disabled. Format: <bool> psi= [KNL] Enable or disable pressure stall information @@ -4908,6 +5271,10 @@ Set maximum number of finished RCU callbacks to process in one batch. + rcutree.csd_lock_suppress_rcu_stall= [KNL] + Do only a one-line RCU CPU stall warning when + there is an ongoing too-long CSD-lock wait. + rcutree.do_rcu_barrier= [KNL] Request a call to rcu_barrier(). This is throttled so that userspace tests can safely @@ -4985,6 +5352,14 @@ the ->nocb_bypass queue. The definition of "too many" is supplied by this kernel boot parameter. + rcutree.nohz_full_patience_delay= [KNL] + On callback-offloaded (rcu_nocbs) CPUs, avoid + disturbing RCU unless the grace period has + reached the specified age in milliseconds. + Defaults to zero. Large values will be capped + at five seconds. All values will be rounded down + to the nearest value representable by jiffies. + rcutree.qhimark= [KNL] Set threshold of queued RCU callbacks beyond which batch limiting is disabled. @@ -5095,6 +5470,20 @@ delay, memory pressure or callback list growing too big. + rcutree.rcu_normal_wake_from_gp= [KNL] + Reduces a latency of synchronize_rcu() call. This approach + maintains its own track of synchronize_rcu() callers, so it + does not interact with regular callbacks because it does not + use a call_rcu[_hurry]() path. Please note, this is for a + normal grace period. + + How to enable it: + + echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp + or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1" + + Default is 0. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). @@ -5226,7 +5615,42 @@ rcutorture.gp_cond= [KNL] Use conditional/asynchronous update-side - primitives, if available. + normal-grace-period primitives, if available. + + rcutorture.gp_cond_exp= [KNL] + Use conditional/asynchronous update-side + expedited-grace-period primitives, if available. + + rcutorture.gp_cond_full= [KNL] + Use conditional/asynchronous update-side + normal-grace-period primitives that also take + concurrent expedited grace periods into account, + if available. + + rcutorture.gp_cond_exp_full= [KNL] + Use conditional/asynchronous update-side + expedited-grace-period primitives that also take + concurrent normal grace periods into account, + if available. + + rcutorture.gp_cond_wi= [KNL] + Nominal wait interval for normal conditional + grace periods (specified by rcutorture's + gp_cond and gp_cond_full module parameters), + in microseconds. The actual wait interval will + be randomly selected to nanosecond granularity up + to this wait interval. Defaults to 16 jiffies, + for example, 16,000 microseconds on a system + with HZ=1000. + + rcutorture.gp_cond_wi_exp= [KNL] + Nominal wait interval for expedited conditional + grace periods (specified by rcutorture's + gp_cond_exp and gp_cond_exp_full module + parameters), in microseconds. The actual wait + interval will be randomly selected to nanosecond + granularity up to this wait interval. Defaults to + 128 microseconds. rcutorture.gp_exp= [KNL] Use expedited update-side primitives, if available. @@ -5235,6 +5659,43 @@ Use normal (non-expedited) asynchronous update-side primitives, if available. + rcutorture.gp_poll= [KNL] + Use polled update-side normal-grace-period + primitives, if available. + + rcutorture.gp_poll_exp= [KNL] + Use polled update-side expedited-grace-period + primitives, if available. + + rcutorture.gp_poll_full= [KNL] + Use polled update-side normal-grace-period + primitives that also take concurrent expedited + grace periods into account, if available. + + rcutorture.gp_poll_exp_full= [KNL] + Use polled update-side expedited-grace-period + primitives that also take concurrent normal + grace periods into account, if available. + + rcutorture.gp_poll_wi= [KNL] + Nominal wait interval for normal conditional + grace periods (specified by rcutorture's + gp_poll and gp_poll_full module parameters), + in microseconds. The actual wait interval will + be randomly selected to nanosecond granularity up + to this wait interval. Defaults to 16 jiffies, + for example, 16,000 microseconds on a system + with HZ=1000. + + rcutorture.gp_poll_wi_exp= [KNL] + Nominal wait interval for expedited conditional + grace periods (specified by rcutorture's + gp_poll_exp and gp_poll_exp_full module + parameters), in microseconds. The actual wait + interval will be randomly selected to nanosecond + granularity up to this wait interval. Defaults to + 128 microseconds. + rcutorture.gp_sync= [KNL] Use normal (non-expedited) synchronous update-side primitives, if available. If all @@ -5243,6 +5704,31 @@ are zero, rcutorture acts as if is interpreted they are all non-zero. + rcutorture.gpwrap_lag= [KNL] + Enable grace-period wrap lag testing. Setting + to false prevents the gpwrap lag test from + running. Default is true. + + rcutorture.gpwrap_lag_gps= [KNL] + Set the value for grace-period wrap lag during + active lag testing periods. This controls how many + grace periods differences we tolerate between + rdp and rnp's gp_seq before setting overflow flag. + The default is always set to 8. + + rcutorture.gpwrap_lag_cycle_mins= [KNL] + Set the total cycle duration for gpwrap lag + testing in minutes. This is the total time for + one complete cycle of active and inactive + testing periods. Default is 30 minutes. + + rcutorture.gpwrap_lag_active_mins= [KNL] + Set the duration for which gpwrap lag is active + within each cycle, in minutes. During this time, + the grace-period wrap lag will be set to the + value specified by gpwrap_lag_gps. Default is + 5 minutes. + rcutorture.irqreader= [KNL] Run RCU readers from irq handlers, or, more accurately, from a timer handler. Not all RCU @@ -5288,10 +5774,21 @@ Set time (jiffies) between CPU-hotplug operations, or zero to disable CPU-hotplug testing. - rcutorture.read_exit= [KNL] - Set the number of read-then-exit kthreads used - to test the interaction of RCU updaters and - task-exit processing. + rcutorture.preempt_duration= [KNL] + Set duration (in milliseconds) of preemptions + by a high-priority FIFO real-time task. Set to + zero (the default) to disable. The CPUs to + preempt are selected randomly from the set that + are online at a given point in time. Races with + CPUs going offline are ignored, with that attempt + at preemption skipped. + + rcutorture.preempt_interval= [KNL] + Set interval (in milliseconds, defaulting to one + second) between preemptions by a high-priority + FIFO real-time task. This delay is mediated + by an hrtimer and is further fuzzed to avoid + inadvertent synchronizations. rcutorture.read_exit_burst= [KNL] The number of times in a given read-then-exit @@ -5302,6 +5799,14 @@ The delay, in seconds, between successive read-then-exit testing episodes. + rcutorture.reader_flavor= [KNL] + A bit mask indicating which readers to use. + If there is more than one bit set, the readers + are entered from low-order bit up, and are + exited in the opposite order. For SRCU, the + 0x1 bit is normal readers, 0x2 NMI-safe readers, + and 0x4 light-weight readers. + rcutorture.shuffle_interval= [KNL] Set task-shuffle interval (s). Shuffling tasks allows some CPUs to go into dyntick-idle mode @@ -5333,7 +5838,13 @@ Time to wait (s) after boot before inducing stall. rcutorture.stall_cpu_irqsoff= [KNL] - Disable interrupts while stalling if set. + Disable interrupts while stalling if set, but only + on the first stall in the set. + + rcutorture.stall_cpu_repeat= [KNL] + Number of times to repeat the stall sequence, + so that rcutorture.stall_cpu_repeat=3 will result + in four stall sequences. rcutorture.stall_gp_kthread= [KNL] Duration (s) of forced sleep within RCU @@ -5359,6 +5870,11 @@ rcutorture.test_boost_duration= [KNL] Duration (s) of each individual boost test. + rcutorture.test_boost_holdoff= [KNL] + Holdoff time (s) from start of test to the start + of RCU priority-boost testing. Defaults to zero, + that is, no holdoff. + rcutorture.test_boost_interval= [KNL] Interval (s) between each boost test. @@ -5521,14 +6037,6 @@ of zero will disable batching. Batching is always disabled for synchronize_rcu_tasks(). - rcupdate.rcu_tasks_rude_lazy_ms= [KNL] - Set timeout in milliseconds RCU Tasks - Rude asynchronous callback batching for - call_rcu_tasks_rude(). A negative value - will take the default. A value of zero will - disable batching. Batching is always disabled - for synchronize_rcu_tasks_rude(). - rcupdate.rcu_tasks_trace_lazy_ms= [KNL] Set timeout in milliseconds RCU Tasks Trace asynchronous callback batching for @@ -5573,6 +6081,55 @@ reboot_cpu is s[mp]#### with #### being the processor to be used for rebooting. + acpi + Use the ACPI RESET_REG in the FADT. If ACPI is not + configured or the ACPI reset does not work, the reboot + path attempts the reset using the keyboard controller. + + bios + Use the CPU reboot vector for warm reset + + cold + Set the cold reboot flag + + default + There are some built-in platform specific "quirks" + - you may see: "reboot: <name> series board detected. + Selecting <type> for reboots." In the case where you + think the quirk is in error (e.g. you have newer BIOS, + or newer board) using this option will ignore the + built-in quirk table, and use the generic default + reboot actions. + + efi + Use efi reset_system runtime service. If EFI is not + configured or the EFI reset does not work, the reboot + path attempts the reset using the keyboard controller. + + force + Don't stop other CPUs on reboot. This can make reboot + more reliable in some cases. + + kbd + Use the keyboard controller. cold reset (default) + + pci + Use a write to the PCI config space register 0xcf9 to + trigger reboot. + + triple + Force a triple fault (init) + + warm + Don't set the cold reboot flag + + Using warm reset will be much faster especially on big + memory systems because the BIOS will not go through + the memory check. Disadvantage is that not all + hardware will be completely reinitialized on reboot so + there may be boot problems on some systems. + + refscale.holdoff= [KNL] Set test-start holdoff period. The purpose of this parameter is to delay the start of the @@ -5641,6 +6198,28 @@ them. If <base> is less than 0x10000, the region is assumed to be I/O ports; otherwise it is memory. + reserve_mem= [RAM] + Format: nn[KMG]:<align>:<label> + Reserve physical memory and label it with a name that + other subsystems can use to access it. This is typically + used for systems that do not wipe the RAM, and this command + line will try to reserve the same physical memory on + soft reboots. Note, it is not guaranteed to be the same + location. For example, if anything about the system changes + or if booting a different kernel. It can also fail if KASLR + places the kernel at the location of where the RAM reservation + was from a previous boot, the new reservation will be at a + different location. + Any subsystem using this feature must add a way to verify + that the contents of the physical memory is from a previous + boot, as there may be cases where the memory will not be + located at the same location. + + The format is size:align:label for example, to request + 12 megabytes of 4096 alignment for ramoops: + + reserve_mem=12M:4096:oops ramoops.mem_name=oops + reservetop= [X86-32,EARLY] Format: nn[KMG] Reserves a hole at the top of the kernel virtual @@ -5719,9 +6298,6 @@ 2 The "airplane mode" button toggles between everything blocked and everything unblocked. - rhash_entries= [KNL,NET] - Set number of hash buckets for route cache - ring3mwait=disable [KNL] Disable ring 3 MONITOR/MWAIT feature on supported CPUs. @@ -5749,7 +6325,7 @@ port and the regular usb controller gets disabled. root= [KNL] Root filesystem - Usually this a a block device specifier of some kind, + Usually this is a block device specifier of some kind, see the early_lookup_bdev comment in block/early-lookup.c for details. Alternatively this can be "ram" for the legacy initial @@ -5776,6 +6352,11 @@ Memory area to be used by remote processor image, managed by CMA. + rt_group_sched= [KNL] Enable or disable SCHED_RR/FIFO group scheduling + when CONFIG_RT_GROUP_SCHED=y. Defaults to + !CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED. + Format: <bool> + rw [KNL] Mount root device read-write on boot S [KNL] Run init in single mode @@ -5811,6 +6392,7 @@ but is useful for debugging and performance tuning. sched_thermal_decay_shift= + [Deprecated] [KNL, SMP] Set a decay shift for scheduler thermal pressure signal. Thermal pressure signal follows the default decay period of other scheduler pelt @@ -5918,6 +6500,10 @@ non-zero "wait" parameter. See weight_single and weight_many. + sdw_mclk_divider=[SDW] + Specify the MCLK divider for Intel SoundWire buses in + case the BIOS does not provide the clock rate properly. + skew_tick= [KNL,EARLY] Offset the periodic timer tick per cpu to mitigate xtime_lock contention on larger systems, and/or RCU lock contention on all systems with CONFIG_MAXSMP set. @@ -5940,7 +6526,16 @@ serialnumber [BUGS=X86-32] - sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst + sev=option[,option...] [X86-64] + + debug + Enable debug messages. + + nosnp + Do not enable SEV-SNP (applies to host/hypervisor + only). Setting 'nosnp' avoids the RMP check overhead + in memory accesses when users do not want to run + SEV-SNP guests. shapers= [NET] Maximal number of shapers. @@ -5954,9 +6549,6 @@ apic=verbose is specified. Example: apic=debug show_lapic=all - simeth= [IA-64] - simscsi= - slab_debug[=options[,slabs][;[options[,slabs]]...] [MM] Enabling slab_debug allows one to determine the culprit if slab objects become corrupted. Enabling @@ -6008,6 +6600,16 @@ For more information see Documentation/mm/slub.rst. (slub_nomerge legacy name also accepted for now) + slab_strict_numa [MM] + Support memory policies on a per object level + in the slab allocator. The default is for memory + policies to be applied at the folio level when + a new folio is needed or a partial folio is + retrieved from the lists. Increases overhead + in the slab fastpaths but gains more accurate + NUMA kernel object placement which helps with slow + interconnects in NUMA systems. + slram= [HW,MTD] smart2= [HW] @@ -6072,9 +6674,15 @@ deployment of the HW BHI control and the SW BHB clearing sequence. - on - (default) Enable the HW or SW mitigation - as needed. - off - Disable the mitigation. + on - (default) Enable the HW or SW mitigation as + needed. This protects the kernel from + both syscalls and VMs. + vmexit - On systems which don't have the HW mitigation + available, enable the SW mitigation on vmexit + ONLY. On such systems, the host kernel is + protected from VM-originated BHI attacks, but + may still be vulnerable to syscall attacks. + off - Disable the mitigation. spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. @@ -6096,6 +6704,8 @@ Selecting 'on' will also enable the mitigation against user space to user space task attacks. + Selecting specific mitigation does not force enable + user mitigations. Selecting 'off' will disable both the kernel and the user space protections. @@ -6218,11 +6828,6 @@ Not specifying this option is equivalent to spec_store_bypass_disable=auto. - spia_io_base= [HW,MTD] - spia_fio_base= - spia_pedr= - spia_peddr= - split_lock_detect= [X86] Enable split lock detection or bus lock detection @@ -6478,7 +7083,7 @@ This parameter controls use of the Protected Execution Facility on pSeries. - swiotlb= [ARM,IA-64,PPC,MIPS,X86,EARLY] + swiotlb= [ARM,PPC,MIPS,X86,S390,EARLY] Format: { <int> [,<int>] | force | noforce } <int> -- Number of I/O TLB slabs <int> -- Second integer after comma. Number of swiotlb @@ -6547,10 +7152,29 @@ <deci-seconds>: poll all this frequency 0: no polling (default) + thp_anon= [KNL] + Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state> + state is one of "always", "madvise", "never" or "inherit". + Control the default behavior of the system with respect + to anonymous transparent hugepages. + Can be used multiple times for multiple anon THP sizes. + See Documentation/admin-guide/mm/transhuge.rst for more + details. + threadirqs [KNL,EARLY] Force threading of all interrupt handlers except those marked explicitly IRQF_NO_THREAD. + thp_shmem= [KNL] + Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy> + Control the default policy of each hugepage size for the + internal shmem mount. <policy> is one of policies available + for the shmem mount ("always", "inherit", "never", "within_size", + and "advise"). + It can be used multiple times for multiple shmem THP sizes. + See Documentation/admin-guide/mm/transhuge.rst for more + details. + topology= [S390,EARLY] Format: {off | on} Specify if the kernel should make use of the cpu @@ -6559,12 +7183,6 @@ e.g. base its process migration decisions on it. Default is on. - topology_updates= [KNL, PPC, NUMA] - Format: {off} - Specify if the kernel should ignore (off) - topology updates sent by the hypervisor to this - LPAR. - torture.disable_onoff_at_boot= [KNL] Prevent the CPU-hotplug component of torturing until after init has spawned. @@ -6584,7 +7202,14 @@ torture.verbose_sleep_duration= [KNL] Duration of each verbose-printk() sleep in jiffies. - tp720= [HW,PS2] + tpm.disable_pcr_integrity= [HW,TPM] + Do not protect PCR registers from unintended physical + access, or interposers in the bus by the means of + having an integrity protected session wrapped around + TPM2_PCR_Extend command. Consider this in a situation + where TPM is heavily utilized by IMA, thus protection + causing a major performance hit, and the space where + machines are deployed is by other means guarded. tpm_suspend_pcr=[HW,TPM] Format: integer pcr id @@ -6664,6 +7289,14 @@ comma-separated list of trace events to enable. See also Documentation/trace/events.rst + To enable modules, use :mod: keyword: + + trace_event=:mod:<module> + + The value before :mod: will only enable specific events + that are part of the module. See the above mentioned + document for more information. + trace_instance=[instance-info] [FTRACE] Create a ring buffer instance early in boot up. This will be listed in: @@ -6684,6 +7317,59 @@ the same thing would happen if it was left off). The irq_handler_entry event, and all events under the "initcall" system. + Flags can be added to the instance to modify its behavior when it is + created. The flags are separated by '^'. + + The available flags are: + + traceoff - Have the tracing instance tracing disabled after it is created. + traceprintk - Have trace_printk() write into this trace instance + (note, "printk" and "trace_printk" can also be used) + + trace_instance=foo^traceoff^traceprintk,sched,irq + + The flags must come before the defined events. + + If memory has been reserved (see memmap for x86), the instance + can use that memory: + + memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M + + The above will create a "boot_map" instance that uses the physical + memory at 0x284500000 that is 12Megs. The per CPU buffers of that + instance will be split up accordingly. + + Alternatively, the memory can be reserved by the reserve_mem option: + + reserve_mem=12M:4096:trace trace_instance=boot_map@trace + + This will reserve 12 megabytes at boot up with a 4096 byte alignment + and place the ring buffer in this memory. Note that due to KASLR, the + memory may not be the same location each time, which will not preserve + the buffer content. + + Also note that the layout of the ring buffer data may change between + kernel versions where the validator will fail and reset the ring buffer + if the layout is not the same as the previous kernel. + + If the ring buffer is used for persistent bootups and has events enabled, + it is recommend to disable tracing so that events from a previous boot do not + mix with events of the current boot (unless you are debugging a random crash + at boot up). + + reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq + + Note, saving the trace buffer across reboots does require that the system + is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION + can force a memory reset on boot which will clear any trace that was stored. + This is just one of many ways that can clear memory. Make sure your system + keeps the content of memory across reboots before relying on this option. + + NB: Both the mapped address and size must be page aligned for the architecture. + + See also Documentation/trace/debugging.rst + + trace_options=[option-list] [FTRACE] Enable or disable tracer options at boot. The option-list is a comma delimited list of options @@ -6719,6 +7405,15 @@ See also "Event triggers" in Documentation/trace/events.rst + traceoff_after_boot + [FTRACE] Sometimes tracing is used to debug issues + during the boot process. Since the trace buffer has a + limited amount of storage, it may be prudent to + disable tracing after the boot is finished, otherwise + the critical information may be overwritten. With this + option, the main tracing buffer will be turned off at + the end of the boot process. + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can @@ -6740,6 +7435,20 @@ See Documentation/admin-guide/mm/transhuge.rst for more details. + transparent_hugepage_shmem= [KNL] + Format: [always|within_size|advise|never|deny|force] + Can be used to control the hugepage allocation policy for + the internal shmem mount. + See Documentation/admin-guide/mm/transhuge.rst + for more details. + + transparent_hugepage_tmpfs= [KNL] + Format: [always|within_size|advise|never] + Can be used to control the default hugepage allocation policy + for the tmpfs mount. + See Documentation/admin-guide/mm/transhuge.rst + for more details. + trusted.source= [KEYS] Format: <string> This parameter identifies the trust source as a backend @@ -6748,6 +7457,7 @@ - "tpm" - "tee" - "caam" + - "dcp" If not specified then it defaults to iterating through the trust source list starting with TPM and assigns the first trust source as a backend which is initialized @@ -6763,6 +7473,18 @@ If not specified, "default" is used. In this case, the RNG's choice is left to each individual trust source. + trusted.dcp_use_otp_key + This is intended to be used in combination with + trusted.source=dcp and will select the DCP OTP key + instead of the DCP UNIQUE key blob encryption. + + trusted.dcp_skip_zk_test + This is intended to be used in combination with + trusted.source=dcp and will disable the check if the + blob key is all zeros. This is helpful for situations where + having this key zero'ed is acceptable. E.g. in testing + scenarios. + tsc= Disable clocksource stability checks for TSC. Format: <string> [x86] reliable: mark tsc clocksource as reliable, this @@ -6890,6 +7612,22 @@ Note that genuine overcurrent events won't be reported either. + unaligned_scalar_speed= + [RISCV] + Format: {slow | fast | unsupported} + Allow skipping scalar unaligned access speed tests. This + is useful for testing alternative code paths and to skip + the tests in environments where they run too slowly. All + CPUs must have the same scalar unaligned access speed. + + unaligned_vector_speed= + [RISCV] + Format: {slow | fast | unsupported} + Allow skipping vector unaligned access speed tests. This + is useful for testing alternative code paths and to skip + the tests in environments where they run too slowly. All + CPUs must have the same vector unaligned access speed. + unknown_nmi_panic [X86] Cause panic on unknown NMI. @@ -7016,6 +7754,9 @@ usb-storage.delay_use= [UMS] The delay in seconds before a new device is scanned for Logical Units (default 1). + Optionally the delay in milliseconds if the value has + suffix with "ms". + Example: delay_use=2567ms usb-storage.quirks= [UMS] A list of quirks entries to supplement or @@ -7082,13 +7823,6 @@ 16 - SIGBUS faults Example: user_debug=31 - userpte= - [X86,EARLY] Flags controlling user PTE allocations. - - nohigh = do not allocate PTE pages in - HIGHMEM regardless of setting - of CONFIG_HIGHPTE. - vdso= [X86,SH,SPARC] On X86_32, this is an alias for vdso32=. Otherwise: @@ -7109,9 +7843,6 @@ Try vdso32=0 if you encounter an error that says: dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! - vector= [IA-64,SMP] - vector=percpu: enable percpu vector domain - video= [FB,EARLY] Frame buffer configuration See Documentation/fb/modedb.rst. @@ -7162,9 +7893,12 @@ vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forces the vmalloc area to have an exact size of <nn>. This can be used to increase - the minimum size (128MB on x86). It can also be - used to decrease the size and leave more room - for directly mapped kernel RAM. + the minimum size (128MB on x86, arm32 platforms). + It can also be used to decrease the size and leave more room + for directly mapped kernel RAM. Note that this parameter does + not exist on many other platforms (including arm64, alpha, + loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc, + parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc). vmcp_cma=nn[MG] [KNL,S390,EARLY] Sets the memory size reserved for contiguous memory @@ -7206,7 +7940,7 @@ vt.cur_default= [VT] Default cursor shape. Format: 0xCCBBAA, where AA, BB, and CC are the same as the parameters of the <Esc>[?A;B;Cc escape sequence; - see VGA-softcursor.txt. Default: 2 = underline. + see vga-softcursor.rst. Default: 2 = underline. vt.default_blu= [VT] Format: <blue0>,<blue1>,<blue2>,...,<blue15> @@ -7277,6 +8011,13 @@ it can be updated at runtime by writing to the corresponding sysfs file. + workqueue.panic_on_stall=<uint> + Panic when workqueue stall is detected by + CONFIG_WQ_WATCHDOG. It sets the number times of the + stall to trigger panic. + + The default is 0, which disables the panic on stall. + workqueue.cpu_intensive_thresh_us= Per-cpu work items which run for longer than this threshold are automatically considered CPU intensive @@ -7323,7 +8064,7 @@ This can be changed after boot by writing to the matching /sys/module/workqueue/parameters file. All workqueues with the "default" affinity scope will be - updated accordignly. + updated accordingly. workqueue.debug_force_rr_cpu Workqueue used to implicitly guarantee that work @@ -7369,17 +8110,18 @@ Crash from Xen panic notifier, without executing late panic() code such as dumping handler. + xen_mc_debug [X86,XEN,EARLY] + Enable multicall debugging when running as a Xen PV guest. + Enabling this feature will reduce performance a little + bit, so it should only be enabled for obtaining extended + debug data in case of multicall errors. + xen_msr_safe= [X86,XEN,EARLY] Format: <bool> Select whether to always use non-faulting (safe) MSR access functions when running as Xen PV guest. The default value is controlled by CONFIG_XEN_PV_MSR_SAFE. - xen_nopvspin [X86,XEN,EARLY] - Disables the qspinlock slowpath using Xen PV optimizations. - This parameter is obsoleted by "nopvspin" parameter, which - has equivalent effect for XEN platform. - xen_nopv [X86] Disables the PV optimizations forcing the HVM guest to run as generic HVM guest with no PV drivers. @@ -7467,4 +8209,3 @@ memory, and other data can't be written using xmon commands. off xmon is disabled. - |