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Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 2171 |
1 files changed, 1371 insertions, 800 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0e990f7c2aa3..bb884c14b2f6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1,21 +1,32 @@ - acpi= [HW,ACPI,X86,ARM64] + accept_memory= [MM] + Format: { eager | lazy } + default: lazy + By default, unaccepted memory is accepted lazily to + avoid prolonged boot times. The lazy option will add + some runtime overhead until all memory is eventually + accepted. In most cases the overhead is negligible. + For some workloads or for debugging purposes + accept_memory=eager can be used to accept all memory + at once during boot. + + acpi= [HW,ACPI,X86,ARM64,RISCV64,EARLY] Advanced Configuration and Power Interface Format: { force | on | off | strict | noirq | rsdt | copy_dsdt } force -- enable ACPI if default was off - on -- enable ACPI but allow fallback to DT [arm64] + on -- enable ACPI but allow fallback to DT [arm64,riscv64] off -- disable ACPI if default was on noirq -- do not use ACPI for IRQ routing strict -- Be less tolerant of platforms that are not strictly ACPI specification compliant. rsdt -- prefer RSDT over (default) XSDT copy_dsdt -- copy DSDT to memory - For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" - are available + For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or + "acpi=force" are available See also Documentation/power/runtime_pm.rst, pci=noacpi - acpi_apic_instance= [ACPI, IOAPIC] + acpi_apic_instance= [ACPI,IOAPIC,EARLY] Format: <int> 2: use 2nd APIC table, if available 1,0: use 1st APIC table @@ -30,7 +41,7 @@ If set to native, use the device's native backlight mode. If set to none, disable the ACPI backlight interface. - acpi_force_32bit_fadt_addr + acpi_force_32bit_fadt_addr [ACPI,EARLY] force FADT to use 32 bit addresses rather than the 64 bit X_* addresses. Some firmware have broken 64 bit addresses for force ACPI ignore these and use @@ -86,7 +97,7 @@ no: ACPI OperationRegions are not marked as reserved, no further checks are performed. - acpi_force_table_verification [HW,ACPI] + acpi_force_table_verification [HW,ACPI,EARLY] Enable table checksum verification during early stage. By default, this is disabled due to x86 early mapping size limitation. @@ -126,7 +137,7 @@ acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump kernels. - acpi_no_static_ssdt [HW,ACPI] + acpi_no_static_ssdt [HW,ACPI,EARLY] Disable installation of static SSDTs at early boot time By default, SSDTs contained in the RSDT/XSDT will be installed automatically and they will appear under @@ -140,7 +151,7 @@ Ignore the ACPI-based watchdog interface (WDAT) and let a native driver control the watchdog device instead. - acpi_rsdp= [ACPI,EFI,KEXEC] + acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] Pass the RSDP address to the kernel, mostly used on machines running EFI runtime service to boot the second kernel for kdump. @@ -217,10 +228,10 @@ to assume that this machine's pmtimer latches its value and always returns good values. - acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode + acpi_sci= [HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low } - acpi_skip_timer_override [HW,ACPI] + acpi_skip_timer_override [HW,ACPI,EARLY] Recognize and ignore IRQ0/pin2 Interrupt Override. For broken nForce2 BIOS resulting in XT-PIC timer. @@ -255,11 +266,11 @@ behave incorrectly in some ways with respect to system suspend and resume to be ignored (use wisely). - acpi_use_timer_override [HW,ACPI] + acpi_use_timer_override [HW,ACPI,EARLY] Use timer override. For some broken Nvidia NF5 boards that require a timer override, but don't have HPET - add_efi_memmap [EFI; X86] Include EFI memory map in + add_efi_memmap [EFI,X86,EARLY] Include EFI memory map in kernel's map of available physical RAM. agp= [AGP] @@ -296,7 +307,7 @@ do not want to use tracing_snapshot_alloc() as it needs to be done where GFP_KERNEL allocations are allowed. - allow_mismatched_32bit_el0 [ARM64] + allow_mismatched_32bit_el0 [ARM64,EARLY] Allow execve() of 32-bit applications and setting of the PER_LINUX32 personality on systems where only a strict subset of the CPUs support 32-bit EL0. When this @@ -304,7 +315,7 @@ EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 and hot-unplug operations may be restricted. - See Documentation/arm64/asymmetric-32bit.rst for more + See Documentation/arch/arm64/asymmetric-32bit.rst for more information. amd_iommu= [HW,X86-64] @@ -321,6 +332,9 @@ 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. amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table @@ -337,6 +351,34 @@ This mode requires kvm-amd.avic=1. (Default when IOMMU HW support is present.) + amd_pstate= [X86,EARLY] + disable + Do not enable amd_pstate as the default + scaling driver for the supported processors + passive + Use amd_pstate with passive mode as a scaling driver. + In this mode autonomous selection is disabled. + Driver requests a desired performance level and platform + tries to match the same performance level if it is + satisfied by guaranteed performance level. + active + Use amd_pstate_epp driver instance as the scaling driver, + driver provides a hint to the hardware if software wants + to bias toward performance (0x0) or energy efficiency (0xff) + to the CPPC firmware. then CPPC power algorithm will + calculate the runtime workload and adjust the realtime cores + frequency. + guided + Activate guided autonomous mode. Driver requests minimum and + maximum performance level and the platform autonomously + selects a performance level in this range and appropriate + to the current workload. + + amd_prefcore= + [X86] + disable + Disable amd-pstate preferred core. + amijoy.map= [HW,JOY] Amiga joystick support Map of devices attached to JOY0DAT and JOY1DAT Format: <a>,<b> @@ -354,7 +396,7 @@ not play well with APC CPU idle - disable it if you have APC and your system crashes randomly. - apic= [APIC,X86] Advanced Programmable Interrupt Controller + 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 @@ -364,7 +406,7 @@ Format: apic=driver_name Examples: apic=bigsmp - apic_extnmi= [APIC,X86] External NMI delivery setting + apic_extnmi= [APIC,X86,EARLY] External NMI delivery setting Format: { bsp (default) | all | none } bsp: External NMI is delivered only to CPU 0 all: External NMIs are broadcast to all CPUs as a @@ -376,36 +418,37 @@ autoconf= [IPV6] See Documentation/networking/ipv6.rst. - show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller - Limit apic dumping. The parameter defines the maximal - number of local apics being dumped. Also it is possible - to set it to "all" by meaning -- no limit here. - Format: { 1 (default) | 2 | ... | all }. - The parameter valid if only apic=debug or - apic=verbose is specified. - Example: apic=debug show_lapic=all - apm= [APM] Advanced Power Management See header of arch/x86/kernel/apm_32.c. + apparmor= [APPARMOR] Disable or enable AppArmor at boot time + Format: { "0" | "1" } + See security/apparmor/Kconfig help text + 0 -- disable. + 1 -- enable. + Default value is set via kernel config option. + arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards Format: <io>,<irq>,<nodeID> arm64.nobti [ARM64] Unconditionally disable Branch Target Identification support - arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication - support + arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory + Set instructions support arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension support - arm64.nosve [ARM64] Unconditionally disable Scalable Vector - Extension support + arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication + support arm64.nosme [ARM64] Unconditionally disable Scalable Matrix Extension support + arm64.nosve [ARM64] Unconditionally disable Scalable Vector + Extension support + ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse @@ -470,19 +513,22 @@ bert_disable [ACPI] Disable BERT OS support on buggy BIOSes. - bgrt_disable [ACPI][X86] + bgrt_disable [ACPI,X86,EARLY] Disable BGRT to avoid flickering OEM logo. blkdevparts= Manual partition parsing of block device(s) for embedded devices based on command line input. See Documentation/block/cmdline-partition.rst - boot_delay= Milliseconds to delay each printk during boot. - Values larger than 10 seconds (10000) are changed to - no delay (0). + boot_delay= [KNL,EARLY] + Milliseconds to delay each printk during boot. + Only works if CONFIG_BOOT_PRINTK_DELAY is enabled, + and you may also have to specify "lpj=". Boot_delay + values larger than 10 seconds (10000) are assumed + erroneous and ignored. Format: integer - bootconfig [KNL] + bootconfig [KNL,EARLY] Extended command line options can be added to an initrd and this will cause the kernel to look for it. @@ -517,14 +563,14 @@ trust validation. format: { id:<keyid> | builtin } - cca= [MIPS] Override the kernel pages' cache coherency + cca= [MIPS,EARLY] Override the kernel pages' cache coherency algorithm. Accepted values range from 0 to 7 inclusive. See arch/mips/include/asm/pgtable-bits.h for platform specific values (SB1, Loongson3 and others). ccw_timeout_log [S390] - See Documentation/s390/common_io.rst for details. + See Documentation/arch/s390/common_io.rst for details. cgroup_disable= [KNL] Disable a particular controller or optional feature Format: {name of the controller(s) or feature(s) to disable} @@ -551,10 +597,15 @@ named mounts. Specifying both "all" and "named" disables all v1 hierarchies. + cgroup_favordynmods= [KNL] Enable or Disable favordynmods. + Format: { "true" | "false" } + Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS. + cgroup.memory= [KNL] Pass options to the cgroup memory controller. Format: <string> nosocket -- Disable socket memory accounting. nokmem -- Disable kernel memory accounting. + nobpf -- Disable BPF memory accounting. checkreqprot= [SELINUX] Set initial checkreqprot flag value. Format: { "0" | "1" } @@ -568,7 +619,7 @@ Setting checkreqprot to 1 is deprecated. cio_ignore= [S390] - See Documentation/s390/common_io.rst for details. + See Documentation/arch/s390/common_io.rst for details. clearcpuid=X[,X...] [X86] Disable CPUID feature X for the kernel. See @@ -627,19 +678,13 @@ [X86-64] hpet,tsc clocksource.arm_arch_timer.evtstrm= - [ARM,ARM64] + [ARM,ARM64,EARLY] Format: <bool> Enable/disable the eventstream feature of the ARM architected timer so that code using WFE-based polling loops can be debugged more effectively on production systems. - clocksource.max_cswd_read_retries= [KNL] - Number of clocksource_watchdog() retries due to - external delays before the clock will be marked - unstable. Defaults to two retries, that is, - three attempts to read the clock under test. - clocksource.verify_n_cpus= [KNL] Limit the number of CPUs checked for clocksources marked with CLOCK_SOURCE_VERIFY_PERCPU that @@ -657,7 +702,7 @@ 10 seconds when built into the kernel. cma=nn[MG]@[start[MG][-end[MG]]] - [KNL,CMA] + [KNL,CMA,EARLY] Sets the size of kernel global memory area for contiguous memory allocations and optionally the placement constraint by the physical address range of @@ -666,16 +711,27 @@ kernel/dma/contiguous.c cma_pernuma=nn[MG] - [ARM64,KNL,CMA] + [KNL,CMA,EARLY] Sets the size of kernel per-numa memory area for contiguous memory allocations. A value of 0 disables per-numa CMA altogether. And If this option is not - specificed, the default value is 0. + specified, the default value is 0. With per-numa CMA enabled, DMA users on node nid will first try to allocate buffer from the pernuma area which is located in node nid, if the allocation fails, they will fallback to the global default memory area. + numa_cma=<node>:nn[MG][,<node>:nn[MG]] + [KNL,CMA,EARLY] + Sets the size of kernel numa memory area for + contiguous memory allocations. It will reserve CMA + area for the specified node. + + With numa CMA enabled, DMA users on node nid will + first try to allocate buffer from the numa area + which is located in node nid, if the allocation fails, + they will fallback to the global default memory area. + cmo_free_hint= [PPC] Format: { yes | no } Specify whether pages are marked as being inactive when they are freed. This is used in CMO environments @@ -683,7 +739,7 @@ a hypervisor. Default: yes - coherent_pool=nn[KMG] [ARM,KNL] + coherent_pool=nn[KMG] [ARM,KNL,EARLY] Sets the size of memory pool for coherent, atomic dma allocations, by default set to 256K. @@ -701,6 +757,17 @@ condev= [HW,S390] console device conmode= + con3215_drop= [S390,EARLY] 3215 console drop mode. + Format: y|n|Y|N|1|0 + When set to true, drop data on the 3215 console when + the console buffer is full. In this case the + operator using a 3270 terminal emulator (for example + x3270) does not have to enter the clear key for the + console output to advance and the kernel to continue. + This leads to a much faster boot time when a 3270 + terminal emulator is active. If no 3270 terminal + emulator is used, this parameter has no effect. + console= [KNL] Output console device and options. tty<n> Use the virtual console device <n>. @@ -781,20 +848,6 @@ Format: <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] - cpu0_hotplug [X86] Turn on CPU0 hotplug feature when - CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. - Some features depend on CPU0. Known dependencies are: - 1. Resume from suspend/hibernate depends on CPU0. - Suspend/hibernate will fail if CPU0 is offline and you - need to online CPU0 before suspend/hibernate. - 2. PIC interrupts also depend on CPU0. CPU0 can't be - removed if a PIC interrupt is detected. - It's said poweroff/reboot may depend on CPU0 on some - machines although I haven't seen such issues so far - after CPU0 is offline on a few tested machines. - If the dependencies are under your control, you can - turn on cpu0_hotplug. - cpuidle.off=1 [CPU_IDLE] disable the cpuidle sub-system @@ -810,11 +863,17 @@ kernel before the cpufreq driver probes. cpu_init_udelay=N - [X86] Delay for N microsec between assert and de-assert + [X86,EARLY] Delay for N microsec between assert and de-assert of APIC INIT to start processors. This delay occurs on every CPU online, such as boot, and resume from suspend. Default: 10000 + cpuhp.parallel= + [SMP] Enable/disable parallel bringup of secondary CPUs + Format: <bool> + Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise + 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 @@ -824,14 +883,14 @@ kernel more unstable. crashkernel=size[KMG][@offset[KMG]] - [KNL] Using kexec, Linux can switch to a 'crash kernel' + [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel' upon panic. This parameter reserves the physical memory region [offset, offset + size] for that kernel image. If '@offset' is omitted, then a suitable offset is selected automatically. - [KNL, X86-64] Select a region under 4G first, and - fall back to reserve region above 4G when '@offset' - hasn't been specified. + [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region + under 4G first, and fall back to reserve region above + 4G when '@offset' hasn't been specified. See Documentation/admin-guide/kdump/kdump.rst for further details. crashkernel=range1:size1[,range2:size2,...][@offset] @@ -842,33 +901,33 @@ Documentation/admin-guide/kdump/kdump.rst for an example. crashkernel=size[KMG],high - [KNL, X86-64, ARM64] range could be above 4G. Allow kernel - to allocate physical memory region from top, so could - be above 4G if system have more than 4G ram installed. - Otherwise memory region will be allocated below 4G, if - available. + [KNL, X86-64, ARM64, RISCV, LoongArch] range could be + above 4G. + Allow kernel to allocate physical memory region from top, + so could be above 4G if system have more than 4G ram + installed. Otherwise memory region will be allocated + below 4G, if available. It will be ignored if crashkernel=X is specified. crashkernel=size[KMG],low - [KNL, X86-64] range under 4G. When crashkernel=X,high - is passed, kernel could allocate physical memory region - above 4G, that cause second kernel crash on system - that require some amount of low memory, e.g. swiotlb - requires at least 64M+32K low memory, also enough extra - low memory is needed to make sure DMA buffers for 32-bit - devices won't run out. Kernel would try to allocate - at least 256M below 4G automatically. + [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G. + When crashkernel=X,high is passed, kernel could allocate + physical memory region above 4G, that cause second kernel + crash on system that require some amount of low memory, + e.g. swiotlb requires at least 64M+32K low memory, also + enough extra low memory is needed to make sure DMA buffers + for 32-bit devices won't run out. Kernel would try to allocate + default size of memory below 4G automatically. The default + size is platform dependent. + --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB) + --> arm64: 128MiB + --> riscv: 128MiB + --> loongarch: 128MiB This one lets the user specify own low range under 4G for second kernel instead. 0: to disable low allocation. It will be ignored when crashkernel=X,high is not used or memory reserved is below 4G. - [KNL, ARM64] range in low memory. - This one lets the user specify a low range in the - DMA zone for the crash dump kernel. - It will be ignored when crashkernel=X,high is not used - or memory reserved is located in the DMA zones. - cryptomgr.notests [KNL] Disable crypto self-tests @@ -878,15 +937,14 @@ cs89x0_media= [HW,NET] Format: { rj45 | aui | bnc } - csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call - handling. When switched on, additional debug data is - printed to the console in case a hanging CPU is - detected, and that CPU is pinged again in order to try - to resolve the hang situation. - 0: disable csdlock debugging (default) - 1: enable basic csdlock debugging (minor impact) - ext: enable extended csdlock debugging (more impact, - but more data) + csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU + function call handling. When switched on, + additional debug data is printed to the console + in case a hanging CPU is detected, and that + CPU is pinged again in order to try to resolve + the hang situation. The default value of this + option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT + Kconfig option. dasd= [HW,NET] See header of drivers/s390/block/dasd_devmap.c. @@ -896,10 +954,10 @@ Format: <port#>,<type> See also Documentation/input/devices/joystick-parport.rst - debug [KNL] Enable kernel debugging (events log level). + debug [KNL,EARLY] Enable kernel debugging (events log level). debug_boot_weak_hash - [KNL] Enable printing [hashed] pointers early in the + [KNL,EARLY] Enable printing [hashed] pointers early in the boot sequence. If enabled, we use a weak hash instead of siphash to hash pointers. Use this option if you are seeing instances of '(___ptrval___)') and need to see a @@ -916,32 +974,29 @@ will print _a_lot_ more information - normally only useful to lockdep developers. - debug_objects [KNL] Enable object debugging - - no_debug_objects - [KNL] Disable object debugging + debug_objects [KNL,EARLY] Enable object debugging debug_guardpage_minorder= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this + [KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter allows control of the order of pages that will be intentionally kept free (and hence protected) by the buddy allocator. Bigger value increase the probability of catching random memory corruption, but reduce the amount of memory for normal system use. The maximum - possible value is MAX_ORDER/2. Setting this parameter - to 1 or 2 should be enough to identify most random - memory corruption problems caused by bugs in kernel or - driver code when a CPU writes to (or reads from) a - random memory location. Note that there exists a class - of memory corruptions problems caused by buggy H/W or - F/W or by drivers badly programing DMA (basically when - memory is written at bus level and the CPU MMU is - bypassed) which are not detectable by - CONFIG_DEBUG_PAGEALLOC, hence this option will not help - tracking down these problems. + possible value is MAX_PAGE_ORDER/2. Setting this + parameter to 1 or 2 should be enough to identify most + random memory corruption problems caused by bugs in + kernel or driver code when a CPU writes to (or reads + from) a random memory location. Note that there exists + a class of memory corruptions problems caused by buggy + H/W or F/W or by drivers badly programming DMA + (basically when memory is written at bus level and the + CPU MMU is bypassed) which are not detectable by + CONFIG_DEBUG_PAGEALLOC, hence this option will not + help tracking down these problems. debug_pagealloc= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter + [KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter enables the feature at boot time. By default, it is disabled and the system will work mostly the same as a kernel built without CONFIG_DEBUG_PAGEALLOC. @@ -949,8 +1004,8 @@ useful to also enable the page_owner functionality. on: enable the feature - debugfs= [KNL] This parameter enables what is exposed to userspace - and debugfs internal clients. + debugfs= [KNL,EARLY] This parameter enables what is exposed to + userspace and debugfs internal clients. Format: { on, no-mount, off } on: All functions are enabled. no-mount: @@ -966,10 +1021,6 @@ debugpat [X86] Enable PAT debugging - decnet.addr= [HW,NET] - Format: <area>[,<node>] - See also Documentation/networking/decnet.rst. - default_hugepagesz= [HW] The size of the default HugeTLB page. This is the size represented by the legacy /proc/ hugepages @@ -1033,59 +1084,41 @@ dhash_entries= [KNL] Set number of hash buckets for dentry cache. - disable_1tb_segments [PPC] + disable_1tb_segments [PPC,EARLY] Disables the use of 1TB hash page table segments. This causes the kernel to fall back to 256MB segments which can be useful when debugging issues that require an SLB miss to occur. - stress_slb [PPC] - Limits the number of kernel SLB entries, and flushes - them frequently to increase the rate of SLB faults - on kernel addresses. - disable= [IPV6] See Documentation/networking/ipv6.rst. - disable_radix [PPC] + disable_radix [PPC,EARLY] Disable RADIX MMU mode on POWER9 - radix_hcall_invalidate=on [PPC/PSERIES] - Disable RADIX GTSE feature and use hcall for TLB - invalidate. - disable_tlbie [PPC] Disable TLBIE instruction. Currently does not work with KVM, with HASH MMU, or with coherent accelerators. - disable_cpu_apicid= [X86,APIC,SMP] - Format: <int> - The number of initial APIC ID for the - corresponding CPU to be disabled at boot, - mostly used for the kdump 2nd kernel to - disable BSP to wake up multiple CPUs without - causing system reset or hang due to sending - INIT from AP to BSP. - - disable_ddw [PPC/PSERIES] + disable_ddw [PPC/PSERIES,EARLY] Disable Dynamic DMA Window support. Use this to workaround buggy firmware. disable_ipv6= [IPV6] See Documentation/networking/ipv6.rst. - disable_mtrr_cleanup [X86] + disable_mtrr_cleanup [X86,EARLY] The kernel tries to adjust MTRR layout from continuous to discrete, to make X server driver able to add WB entry later. This parameter disables that. - disable_mtrr_trim [X86, Intel and AMD only] + disable_mtrr_trim [X86, Intel and AMD only,EARLY] By default the kernel will trim any uncacheable memory out of your available memory pool based on MTRR settings. This parameter disables that behavior, possibly causing your machine to run very slowly. - disable_timer_pin_1 [X86] + disable_timer_pin_1 [X86,EARLY] Disable PIN 1 of APIC timer Can be useful to work around chipset bugs. @@ -1108,6 +1141,26 @@ The filter can be disabled or changed to another driver later using sysfs. + reg_file_data_sampling= + [X86] Controls mitigation for Register File Data + Sampling (RFDS) vulnerability. RFDS is a CPU + vulnerability which may allow userspace to infer + kernel data values previously stored in floating point + registers, vector registers, or integer registers. + RFDS only affects Intel Atom processors. + + on: Turns ON the mitigation. + off: Turns OFF the mitigation. + + This parameter overrides the compile time default set + by CONFIG_MITIGATION_RFDS. Mitigation cannot be + disabled when other VERW based mitigations (like MDS) + are enabled. In order to disable RFDS mitigation all + VERW based mitigations need to be disabled. + + For details see: + Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst + driver_async_probe= [KNL] List of driver names to be probed asynchronously. * matches with all driver names. If * is specified, the @@ -1120,22 +1173,16 @@ panels may send no or incorrect EDID data sets. This parameter allows to specify an EDID data sets in the /lib/firmware directory that are used instead. - Generic built-in EDID data sets are used, if one of - edid/1024x768.bin, edid/1280x1024.bin, - edid/1680x1050.bin, or edid/1920x1080.bin is given - and no file with the same name exists. Details and - instructions how to build your own EDID data are - available in Documentation/admin-guide/edid.rst. An EDID - data set will only be used for a particular connector, - if its name and a colon are prepended to the EDID - name. Each connector may use a unique EDID data - set by separating the files with a comma. An EDID + An EDID data set will only be used for a particular + connector, if its name and a colon are prepended to + the EDID name. Each connector may use a unique EDID + data set by separating the files with a comma. An EDID data set with no connector name will be used for any connectors not explicitly specified. dscc4.setup= [NET] - dt_cpu_ftrs= [PPC] + dt_cpu_ftrs= [PPC,EARLY] Format: {"off" | "known"} Control how the dt_cpu_ftrs device-tree binding is used for CPU feature discovery and setup (if it @@ -1155,18 +1202,12 @@ Documentation/admin-guide/dynamic-debug-howto.rst for details. - nopku [X86] Disable Memory Protection Keys CPU feature found - in some Intel CPUs. - - <module>.async_probe [KNL] - Enable asynchronous probe on this module. - - early_ioremap_debug [KNL] + early_ioremap_debug [KNL,EARLY] Enable debug messages in early_ioremap support. This is useful for tracking down temporary early mappings which are not unmapped. - earlycon= [KNL] Output early console device and options. + earlycon= [KNL,EARLY] Output early console device and options. When used with no options, the early console is determined by stdout-path property in device tree's @@ -1180,10 +1221,10 @@ specified, the serial port must already be setup and configured. - uart[8250],io,<addr>[,options] - uart[8250],mmio,<addr>[,options] - uart[8250],mmio32,<addr>[,options] - uart[8250],mmio32be,<addr>[,options] + uart[8250],io,<addr>[,options[,uartclk]] + uart[8250],mmio,<addr>[,options[,uartclk]] + uart[8250],mmio32,<addr>[,options[,uartclk]] + uart[8250],mmio32be,<addr>[,options[,uartclk]] uart[8250],0x<addr>[,options] Start an early, polled-mode console on the 8250/16550 UART at the specified I/O port or MMIO address. @@ -1192,7 +1233,9 @@ If none of [io|mmio|mmio32|mmio32be], <addr> is assumed to be equivalent to 'mmio'. 'options' are specified in the same format described for "console=ttyS<n>"; if - unspecified, the h/w is not initialized. + unspecified, the h/w is not initialized. 'uartclk' is + the uart clock frequency; if unspecified, it is set + to 'BASE_BAUD' * 16. pl011,<addr> pl011,mmio32,<addr> @@ -1300,7 +1343,7 @@ address must be provided, and the serial port must already be setup and configured. - earlyprintk= [X86,SH,ARM,M68k,S390] + earlyprintk= [X86,SH,ARM,M68k,S390,UM,EARLY] earlyprintk=vga earlyprintk=sclp earlyprintk=xen @@ -1310,6 +1353,7 @@ earlyprintk=dbgp[debugController#] earlyprintk=pciserial[,force],bus:device.function[,baudrate] earlyprintk=xdbc[xhciController#] + earlyprintk=bios earlyprintk is useful when the kernel crashes before the normal console is initialized. It is not enabled by @@ -1340,6 +1384,8 @@ The sclp output can only be used on s390. + The bios output can only be used on SuperH. + The optional "force" to "pciserial" enables use of a PCI device even when its classcode is not of the UART class. @@ -1355,7 +1401,7 @@ edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} - efi= [EFI] + efi= [EFI,EARLY] Format: { "debug", "disable_early_pci_dma", "nochunk", "noruntime", "nosoftreserve", "novamap", "no_disable_early_pci_dma" } @@ -1376,13 +1422,13 @@ no_disable_early_pci_dma: Leave the busmaster bit set on all PCI bridges while in the EFI boot stub - efi_no_storage_paranoia [EFI; X86] + efi_no_storage_paranoia [EFI,X86,EARLY] Using this parameter you can use more than 50% of your efi variable storage. Use this parameter only if 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] + 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 @@ -1413,7 +1459,7 @@ eisa_irq_edge= [PARISC,HW] See header of drivers/parisc/eisa.c. - ekgdboc= [X86,KGDB] Allow early kernel console debugging + ekgdboc= [X86,KGDB,EARLY] Allow early kernel console debugging Format: ekgdboc=kbd This is designed to be used in conjunction with @@ -1428,13 +1474,13 @@ See comment before function elanfreq_setup() in arch/x86/kernel/cpu/cpufreq/elanfreq.c. - elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] + elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY] Specifies physical address of start of kernel core image elf header and optionally the size. Generally kexec loader will pass this option to capture kernel. See Documentation/admin-guide/kdump/kdump.rst for details. - enable_mtrr_cleanup [X86] + enable_mtrr_cleanup [X86,EARLY] The kernel tries to adjust MTRR layout from continuous to discrete, to make X server driver able to add WB entry later. This parameter enables that. @@ -1467,6 +1513,14 @@ Permit 'security.evm' to be updated regardless of current integrity status. + early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier + stages so cover more early boot allocations. + Please note that as side effect some optimizations + might be disabled to achieve that (e.g. parallelized + memory initialization is disabled) so the boot process + might take longer, especially on systems with a lot of + memory. Available with CONFIG_PAGE_EXTENSION=y. + failslab= fail_usercopy= fail_page_alloc= @@ -1483,12 +1537,6 @@ floppy= [HW] See Documentation/admin-guide/blockdev/floppy.rst. - force_pal_cache_flush - [IA-64] Avoid check_sal_cache_flush which may hang on - buggy SAL_CACHE_FLUSH implementations. Using this - parameter will force ia64_sal_cache_flush to call - ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. - forcepae [X86-32] Forcefully enable Physical Address Extension (PAE). Many Pentium M systems disable PAE but may have a @@ -1496,6 +1544,12 @@ Warning: use of this parameter will taint the kernel and may cause unknown problems. + fred= [X86-64] + Enable/disable Flexible Return and Event Delivery. + Format: { on | off } + on: enable FRED when it's present. + off: disable FRED, the default setting. + ftrace=[tracer] [FTRACE] will set and start the specified tracer as early as possible in order to facilitate early @@ -1509,12 +1563,37 @@ boot up that is likely to be overridden by user space start up functionality. - ftrace_dump_on_oops[=orig_cpu] + Optionally, the snapshot can also be defined for a tracing + instance that was created by the trace_instance= command + line parameter. + + trace_instance=foo,sched_switch ftrace_boot_snapshot=foo + + The above will cause the "foo" tracing instance to trigger + a snapshot at the end of boot up. + + ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> | + ,<instance>=2(orig_cpu)] [FTRACE] will dump the trace buffers on oops. - If no parameter is passed, ftrace will dump - buffers of all CPUs, but if you pass orig_cpu, it will - dump only the buffer of the CPU that triggered the - oops. + If no parameter is passed, ftrace will dump global + buffers of all CPUs, if you pass 2 or orig_cpu, it + will dump only the buffer of the CPU that triggered + the oops, or the specific instance will be dumped if + its name is passed. Multiple instance dump is also + supported, and instances are separated by commas. Each + instance supports only dump on CPU that triggered the + oops by passing 2 or orig_cpu to it. + + ftrace_dump_on_oops=foo=orig_cpu + + The above will dump only the buffer of "foo" instance + on CPU that triggered the oops. + + ftrace_dump_on_oops,foo,bar=orig_cpu + + The above will dump global buffer on all CPUs, the + buffer of "foo" instance on all CPUs and the buffer + of "bar" instance on CPU that triggered the oops. ftrace_filter=[function-list] [FTRACE] Limit the functions traced by the function @@ -1548,7 +1627,7 @@ can be changed at run time by the max_graph_depth file in the tracefs tracing directory. default: 0 (no limit) - fw_devlink= [KNL] Create device links between consumer and supplier + fw_devlink= [KNL,EARLY] Create device links between consumer and supplier devices by scanning the firmware to infer the consumer/supplier relationships. This feature is especially useful when drivers are loaded as modules as @@ -1567,10 +1646,24 @@ rpm -- Like "on", but also use to order runtime PM. fw_devlink.strict=<bool> - [KNL] Treat all inferred dependencies as mandatory + [KNL,EARLY] Treat all inferred dependencies as mandatory dependencies. This only applies for fw_devlink=on|rpm. Format: <bool> + fw_devlink.sync_state = + [KNL,EARLY] When all devices that could probe have finished + probing, this parameter controls what to do with + devices that haven't yet received their sync_state() + calls. + Format: { strict | timeout } + strict -- Default. Continue waiting on consumers to + probe successfully. + timeout -- Give up waiting on consumers and call + sync_state() on any devices that haven't yet + received their sync_state() calls after + deferred_probe_timeout has expired or by + late_initcall() if !CONFIG_MODULES. + gamecon.map[2|3]= [HW,JOY] Multisystem joystick and NES/SNES/PSX pad support via parallel port (up to 5 devices per port) @@ -1579,10 +1672,30 @@ gamma= [HW,DRM] - gart_fix_e820= [X86-64] disable the fix e820 for K8 GART + gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART Format: off | on default: on + gather_data_sampling= + [X86,INTEL,EARLY] Control the Gather Data Sampling (GDS) + mitigation. + + Gather Data Sampling is a hardware vulnerability which + allows unprivileged speculative access to data which was + previously stored in vector registers. + + This issue is mitigated by default in updated microcode. + The mitigation may have a performance impact but can be + disabled. On systems without the microcode mitigation + disabling AVX serves as a mitigation. + + force: Disable AVX to mitigate systems without + microcode mitigation. No effect if the microcode + mitigation is present. Known to cause crashes in + userspace with buggy AVX enumeration. + + off: Disable GDS mitigation. + 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. @@ -1662,7 +1775,18 @@ (that will set all pages holding image data during restoration read-only). - highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact + hibernate.compressor= [HIBERNATION] Compression algorithm to be + used with hibernation. + Format: { lzo | lz4 } + Default: lzo + + lzo: Select LZO compression algorithm to + compress/decompress hibernation image. + + lz4: Select LZ4 compression algorithm to + compress/decompress hibernation image. + + 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 size on bigger boxes. @@ -1673,6 +1797,19 @@ hlt [BUGS=ARM,SH] + hostname= [KNL,EARLY] Set the hostname (aka UTS nodename). + Format: <string> + This allows setting the system's hostname during early + startup. This sets the name returned by gethostname. + Using this parameter to set the hostname makes it + possible to ensure the hostname is correctly set before + any userspace processes run, avoiding the possibility + that a process may call gethostname before the hostname + has been explicitly set, resulting in the calling + process getting an incorrect result. The string must + not exceed the maximum allowed hostname length (usually + 64 characters) and will be truncated otherwise. + hpet= [X86-32,HPET] option to control HPET usage Format: { enable (default) | disable | force | verbose } @@ -1705,7 +1842,7 @@ Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] - hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation + 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. Format: nn[KMGTPE] or (node format) @@ -1716,21 +1853,24 @@ boot-time allocation of gigantic hugepages is skipped. hugetlb_free_vmemmap= - [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP + [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP enabled. + Control if HugeTLB Vmemmap Optimization (HVO) is enabled. Allows heavy hugetlb users to free up some more memory (7 * PAGE_SIZE for each 2MB hugetlb page). - Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) } + Format: { on | off (default) } - [oO][Nn]/Y/y/1: enable the feature - [oO][Ff]/N/n/0: disable the feature + on: enable HVO + off: disable HVO Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, the default is on. - This is not compatible with memory_hotplug.memmap_on_memory. - If both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. + Note that the vmemmap pages may be allocated from the added + memory block itself when memory_hotplug.memmap_on_memory is + enabled, those vmemmap pages cannot be optimized even if this + feature is enabled. Other vmemmap pages not allocated from + the added memory block itself do not be affected. hung_task_panic= [KNL] Should the hung task detector generate panics. @@ -1748,15 +1888,10 @@ If specified, z/VM IUCV HVC accepts connections from listed z/VM user IDs only. - hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations - which allow the hypervisor to 'idle' the - guest on lock contention. - - keep_bootcon [KNL] - Do not unregister boot console at start. This is only - useful for debugging when something happens in the window - between unregistering the boot console and initializing - the real console. + hv_nopvspin [X86,HYPER_V,EARLY] + Disables the paravirt spinlock optimizations + which allow the hypervisor to 'idle' the guest + on lock contention. i2c_bus= [HW] Override the default board specific I2C bus speed or register an additional I2C bus that is not @@ -1811,11 +1946,17 @@ 0 -- machine default 1 -- force brightness inversion + ia32_emulation= [X86-64] + Format: <bool> + When true, allows loading 32-bit programs and executing 32-bit + syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at + boot time. When false, unconditionally disables IA32 emulation. + icn= [HW,ISDN] Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] - idle= [X86] + 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 @@ -1871,7 +2012,7 @@ mode generally follows that for the NaN encoding, except where unsupported by hardware. - ignore_loglevel [KNL] + ignore_loglevel [KNL,EARLY] Ignore loglevel setting - this will print /all/ kernel messages to the console. Useful for debugging. We also add it as printk module parameter, so users @@ -1989,21 +2130,21 @@ unpacking being completed before device_ and late_ initcalls. - initrd= [BOOT] Specify the location of the initial ramdisk + initrd= [BOOT,EARLY] Specify the location of the initial ramdisk - initrdmem= [KNL] Specify a physical address and size from which to + initrdmem= [KNL,EARLY] Specify a physical address and size from which to load the initrd. If an initrd is compiled in or specified in the bootparams, it takes priority over this setting. Format: ss[KMG],nn[KMG] Default is 0, 0 - init_on_alloc= [MM] Fill newly allocated pages and heap objects with + init_on_alloc= [MM,EARLY] Fill newly allocated pages and heap objects with zeroes. Format: 0 | 1 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. - init_on_free= [MM] Fill freed pages and heap objects with zeroes. + init_on_free= [MM,EARLY] Fill freed pages and heap objects with zeroes. Format: 0 | 1 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. @@ -2059,10 +2200,20 @@ 0 disables intel_idle and fall back on acpi_idle. 1 to 9 specify maximum depth of C-state. - intel_pstate= [X86] + intel_pstate= [X86,EARLY] disable Do not enable intel_pstate as the default scaling driver for the supported processors + active + Use intel_pstate driver to bypass the scaling + governors layer of cpufreq and provides it own + algorithms for p-state selection. There are two + P-state selection algorithms provided by + intel_pstate in the active mode: powersave and + performance. The way they both operate depends + on whether or not the hardware managed P-states + (HWP) feature has been enabled in the processor + and possibly on the processor model. passive Use intel_pstate as a scaling driver, but configure it to work with generic cpufreq governors (instead of @@ -2093,7 +2244,7 @@ Allow per-logical-CPU P-State performance control limits using cpufreq sysfs interface - intremap= [X86-64, Intel-IOMMU] + intremap= [X86-64,Intel-IOMMU,EARLY] on enable Interrupt Remapping (default) off disable Interrupt Remapping nosid disable Source ID checking @@ -2105,7 +2256,7 @@ strict regions from userspace. relaxed - iommu= [X86] + iommu= [X86,EARLY] off force noforce @@ -2120,7 +2271,7 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. - iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. + 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 falling back to the full range if needed. @@ -2128,7 +2279,7 @@ forcing Dual Address Cycle for PCI cards supporting greater than 32-bit addressing. - iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour + iommu.strict= [ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. Request that DMA unmap operations use deferred @@ -2144,7 +2295,7 @@ legacy driver-specific options takes precedence. iommu.passthrough= - [ARM64, X86] Configure DMA to bypass the IOMMU by default. + [ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default. Format: { "0" | "1" } 0 - Use IOMMU translation for DMA. 1 - Bypass the IOMMU for DMA. @@ -2154,7 +2305,7 @@ See comment before marvel_specify_io7 in arch/alpha/kernel/core_marvel.c. - io_delay= [X86] I/O delay method + io_delay= [X86,EARLY] I/O delay method 0x80 Standard port 0x80 based delay 0xed @@ -2167,28 +2318,28 @@ ip= [IP_PNP] See Documentation/admin-guide/nfs/nfsroot.rst. - ipcmni_extend [KNL] Extend the maximum number of unique System V + ipcmni_extend [KNL,EARLY] Extend the maximum number of unique System V IPC identifiers from 32,768 to 16,777,216. irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. irqchip.gicv2_force_probe= - [ARM, ARM64] + [ARM,ARM64,EARLY] Format: <bool> Force the kernel to look for the second 4kB page of a GICv2 controller even if the memory range exposed by the device tree is too small. irqchip.gicv3_nolpi= - [ARM, ARM64] + [ARM,ARM64,EARLY] Force the kernel to ignore the availability of LPIs (and by consequence ITSs). Intended for system that use the kernel as a bootloader, and thus want to let secondary kernels in charge of setting up LPIs. - irqchip.gicv3_pseudo_nmi= [ARM64] + irqchip.gicv3_pseudo_nmi= [ARM64,EARLY] Enables support for pseudo-NMIs in the kernel. This requires the kernel to be built with CONFIG_ARM64_PSEUDO_NMI. @@ -2272,42 +2423,76 @@ ivrs_ioapic [HW,X86-64] Provide an override to the IOAPIC-ID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map IOAPIC-ID decimal 10 to - PCI device 00:14.0 write the parameter as: + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map IOAPIC-ID decimal 10 to + PCI segment 0x1 and PCI device 00:14.0, + write the parameter as: + ivrs_ioapic=10@0001:00:14.0 + + Deprecated formats: + * To map IOAPIC-ID decimal 10 to PCI device 00:14.0 + write the parameter as: ivrs_ioapic[10]=00:14.0 + * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and + PCI device 00:14.0 write the parameter as: + ivrs_ioapic[10]=0001:00:14.0 ivrs_hpet [HW,X86-64] Provide an override to the HPET-ID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map HPET-ID decimal 0 to - PCI device 00:14.0 write the parameter as: + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map HPET-ID decimal 10 to + PCI segment 0x1 and PCI device 00:14.0, + write the parameter as: + ivrs_hpet=10@0001:00:14.0 + + Deprecated formats: + * To map HPET-ID decimal 0 to PCI device 00:14.0 + write the parameter as: ivrs_hpet[0]=00:14.0 + * To map HPET-ID decimal 10 to PCI segment 0x1 and + PCI device 00:14.0 write the parameter as: + ivrs_ioapic[10]=0001:00:14.0 ivrs_acpihid [HW,X86-64] Provide an override to the ACPI-HID:UID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map UART-HID:UID AMD0020:0 to - PCI device 00:14.5 write the parameter as: + mapping provided in the IVRS ACPI table. + By default, PCI segment is 0, and can be omitted. + + For example, to map UART-HID:UID AMD0020:0 to + PCI segment 0x1 and PCI device ID 00:14.5, + write the parameter as: + ivrs_acpihid=AMD0020:0@0001:00:14.5 + + Deprecated formats: + * To map UART-HID:UID AMD0020:0 to PCI segment is 0, + PCI device ID 00:14.5, write the parameter as: ivrs_acpihid[00:14.5]=AMD0020:0 + * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and + PCI device ID 00:14.5, write the parameter as: + ivrs_acpihid[0001:00:14.5]=AMD0020:0 js= [HW,JOY] Analog joystick See Documentation/input/joydev/joystick.rst. - nokaslr [KNL] - When CONFIG_RANDOMIZE_BASE is set, this disables - kernel and module base offset ASLR (Address Space - Layout Randomization). - kasan_multi_shot [KNL] Enforce KASAN (Kernel Address Sanitizer) to print report on every invalid memory access. Without this parameter KASAN will print report only for the first invalid access. - keepinitrd [HW,ARM] + keep_bootcon [KNL,EARLY] + Do not unregister boot console at start. This is only + useful for debugging when something happens in the window + between unregistering the boot console and initializing + the real console. - kernelcore= [KNL,X86,IA-64,PPC] + keepinitrd [HW,ARM] See retain_initrd. + + kernelcore= [KNL,X86,IA-64,PPC,EARLY] Format: nn[KMGTPE] | nn% | "mirror" This parameter specifies the amount of memory usable by the kernel for non-movable allocations. The requested @@ -2332,7 +2517,7 @@ for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" are exclusive, so you cannot specify multiple forms. - kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. + kgdbdbgp= [KGDB,HW,EARLY] kgdb over EHCI usb debug port. Format: <Controller#>[,poll interval] The controller # is the number of the ehci usb debug port as it is probed via PCI. The poll interval is @@ -2353,7 +2538,7 @@ kms, kbd format: kms,kbd kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] - kgdboc_earlycon= [KGDB,HW] + kgdboc_earlycon= [KGDB,HW,EARLY] If the boot console provides the ability to read characters and can work in polling mode, you can use this parameter to tell kgdb to use it as a backend @@ -2368,14 +2553,14 @@ blank and the first boot console that implements read() will be picked. - kgdbwait [KGDB] Stop kernel execution and enter the + kgdbwait [KGDB,EARLY] Stop kernel execution and enter the kernel debugger at the earliest opportunity. kmac= [MIPS] Korina ethernet MAC address. Configure the RouterBoard 532 series on-chip Ethernet adapter MAC address. - kmemleak= [KNL] Boot-time kmemleak enable/disable + kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable Valid arguments: on, off Default: on Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, @@ -2394,12 +2579,18 @@ See also Documentation/trace/kprobetrace.rst "Kernel Boot Parameter" section. - kpti= [ARM64] Control page table isolation of user - and kernel address spaces. + kpti= [ARM64,EARLY] Control page table isolation of + user and kernel address spaces. Default: enabled on cores which need mitigation. 0: force disabled 1: force enabled + kunit.enable= [KUNIT] Enable executing KUnit tests. Requires + CONFIG_KUNIT to be set to be fully enabled. The + default value can be overridden via + KUNIT_DEFAULT_ENABLED. + Default is 1 (enabled) + kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. Default is 0 (don't ignore, but inject #GP) @@ -2424,8 +2615,7 @@ the KVM_CLEAR_DIRTY ioctl, and only for the pages being cleared. - Eager page splitting currently only supports splitting - huge pages mapped by the TDP MMU. + Eager page splitting is only supported when kvm.tdp_mmu=Y. Default is Y (on). @@ -2458,15 +2648,17 @@ If the value is 0 (the default), KVM will pick a period based on the ratio, such that a page is zapped after 1 hour on average. - kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. - Default is 1 (enabled) + kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in + KVM/SVM. Default is 1 (enabled). - kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) - for all guests. - Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. + kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for NPT. kvm-arm.mode= - [KVM,ARM] Select one of KVM/arm64's modes of operation. + [KVM,ARM,EARLY] Select one of KVM/arm64's modes of + operation. none: Forcefully disable KVM. @@ -2476,27 +2668,32 @@ protected: nVHE-based mode with support for guests whose state is kept private from the host. + nested: VHE-based mode with support for nested + virtualization. Requires at least ARMv8.3 + hardware. + Defaults to VHE/nVHE based on hardware support. Setting mode to "protected" will disable kexec and hibernation - for the host. + for the host. "nested" is experimental and should be + used with extreme caution. kvm-arm.vgic_v3_group0_trap= - [KVM,ARM] Trap guest accesses to GICv3 group-0 + [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0 system registers kvm-arm.vgic_v3_group1_trap= - [KVM,ARM] Trap guest accesses to GICv3 group-1 + [KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1 system registers kvm-arm.vgic_v3_common_trap= - [KVM,ARM] Trap guest accesses to GICv3 common + [KVM,ARM,EARLY] Trap guest accesses to GICv3 common system registers kvm-arm.vgic_v4_enable= - [KVM,ARM] Allow use of GICv4 for direct injection of - LPIs. + [KVM,ARM,EARLY] Allow use of GICv4 for direct + injection of LPIs. - kvm_cma_resv_ratio=n [PPC] + kvm_cma_resv_ratio=n [PPC,EARLY] Reserves given percentage from system memory area for contiguous memory allocation for KVM hash pagetable allocation. @@ -2504,30 +2701,33 @@ Format: <integer> Default: 5 - kvm-intel.ept= [KVM,Intel] Disable extended page tables - (virtualized MMU) support on capable Intel chips. - Default is 1 (enabled) + kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for EPT. kvm-intel.emulate_invalid_guest_state= - [KVM,Intel] Disable emulation of invalid guest state. - Ignored if kvm-intel.enable_unrestricted_guest=1, as - guest state is never invalid for unrestricted guests. - This param doesn't apply to nested guests (L2), as KVM - never emulates invalid L2 guest state. - Default is 1 (enabled) + [KVM,Intel] Control whether to emulate invalid guest + state. Ignored if kvm-intel.enable_unrestricted_guest=1, + as guest state is never invalid for unrestricted + guests. This param doesn't apply to nested guests (L2), + as KVM never emulates invalid L2 guest state. + Default is 1 (enabled). kvm-intel.flexpriority= - [KVM,Intel] Disable FlexPriority feature (TPR shadow). - Default is 1 (enabled) + [KVM,Intel] Control KVM's use of FlexPriority feature + (TPR shadow). Default is 1 (enabled). Disable by KVM if + hardware lacks support for it. kvm-intel.nested= - [KVM,Intel] Enable VMX nesting (nVMX). - Default is 0 (disabled) + [KVM,Intel] Control nested virtualization feature in + KVM/VMX. Default is 1 (enabled). kvm-intel.unrestricted_guest= - [KVM,Intel] Disable unrestricted guest feature - (virtualized real and unpaged mode) on capable - Intel chips. Default is 1 (enabled) + [KVM,Intel] Control KVM's use of unrestricted guest + feature (virtualized real and unpaged mode). Default + is 1 (enabled). Disable by KVM if EPT is disabled or + hardware lacks support for it. kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault CVE-2018-3620. @@ -2541,11 +2741,12 @@ Default is cond (do L1 cache flush in specific instances) - kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification - feature (tagged TLBs) on capable Intel chips. - Default is 1 (enabled) + kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor + Identification feature (tagged TLBs). Default is 1 + (enabled). Disable by KVM if hardware lacks support + for it. - l1d_flush= [X86,INTEL] + l1d_flush= [X86,INTEL,EARLY] Control mitigation for L1D based snooping vulnerability. Certain CPUs are vulnerable to an exploit against CPU @@ -2562,7 +2763,7 @@ on - enable the interface for the mitigation - l1tf= [X86] Control mitigation of the L1TF vulnerability on + l1tf= [X86,EARLY] Control mitigation of the L1TF vulnerability on affected CPUs The kernel PTE inversion protection is unconditionally @@ -2631,7 +2832,7 @@ l3cr= [PPC] - lapic [X86-32,APIC] Enable the local APIC even if BIOS + lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS disabled it. lapic= [X86,APIC] Do not use TSC deadline @@ -2639,7 +2840,7 @@ back to the programmable timer unit in the LAPIC. Format: notscdeadline - lapic_timer_c2_ok [X86,APIC] trust the local apic timer + lapic_timer_c2_ok [X86,APIC,EARLY] trust the local apic timer in C2 power state. libata.dma= [LIBATA] DMA control @@ -2739,6 +2940,9 @@ * [no]setxfer: Indicate if transfer speed mode setting should be skipped. + * [no]fua: Disable or enable FUA (Force Unit Access) + support for devices supporting this feature. + * dump_id: Dump IDENTIFY data. * disable: Disable this device. @@ -2760,7 +2964,7 @@ lockd.nlm_udpport=M [NFS] Assign UDP port. Format: <integer> - lockdown= [SECURITY] + lockdown= [SECURITY,EARLY] { integrity | confidentiality } Enable the kernel lockdown feature. If set to integrity, kernel features that allow userland to @@ -2769,6 +2973,38 @@ to extract confidential information from the kernel are also disabled. + locktorture.acq_writer_lim= [KNL] + Set the time limit in jiffies for a lock + acquisition. Acquisitions exceeding this limit + will result in a splat once they do complete. + + locktorture.bind_readers= [KNL] + Specify the list of CPUs to which the readers are + to be bound. + + locktorture.bind_writers= [KNL] + Specify the list of CPUs to which the writers are + to be bound. + + locktorture.call_rcu_chains= [KNL] + Specify the number of self-propagating call_rcu() + chains to set up. These are used to ensure that + there is a high probability of an RCU grace period + in progress at any given time. Defaults to 0, + which disables these call_rcu() chains. + + locktorture.long_hold= [KNL] + Specify the duration in milliseconds for the + occasional long-duration lock hold time. Defaults + to 100 milliseconds. Select 0 to disable. + + locktorture.nested_locks= [KNL] + Specify the maximum lock nesting depth that + locktorture is to exercise, up to a limit of 8 + (MAX_NESTED_LOCKS). Specify zero to disable. + Note that this parameter is ineffective on types + of locks that do not support nested acquisition. + locktorture.nreaders_stress= [KNL] Set the number of locking read-acquisition kthreads. Defaults to being automatically set based on the @@ -2784,6 +3020,25 @@ Set time (s) between CPU-hotplug operations, or zero to disable CPU-hotplug testing. + locktorture.rt_boost= [KNL] + Do periodic testing of real-time lock priority + boosting. Select 0 to disable, 1 to boost + only rt_mutex, and 2 to boost unconditionally. + Defaults to 2, which might seem to be an + odd choice, but which should be harmless for + non-real-time spinlocks, due to their disabling + of preemption. Note that non-realtime mutexes + disable boosting. + + locktorture.rt_boost_factor= [KNL] + Number that determines how often and for how + long priority boosting is exercised. This is + scaled down by the number of writers, so that the + number of boosts per unit time remains roughly + constant as the number of writers increases. + On the other hand, the duration of each boost + increases with the number of writers. + locktorture.shuffle_interval= [KNL] Set task-shuffle interval (jiffies). Shuffling tasks allows some CPUs to go into dyntick-idle @@ -2809,10 +3064,15 @@ locktorture.verbose= [KNL] Enable additional printk() statements. + locktorture.writer_fifo= [KNL] + Run the write-side locktorture kthreads at + sched_set_fifo() real-time priority. + logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver Format: <irq> - loglevel= All Kernel Messages with a loglevel smaller than the + loglevel= [KNL,EARLY] + All Kernel Messages with a loglevel smaller than the console loglevel will be printed to the console. It can also be changed with klogd or other programs. The loglevels are defined as follows: @@ -2826,13 +3086,15 @@ 6 (KERN_INFO) informational 7 (KERN_DEBUG) debug-level messages - log_buf_len=n[KMG] Sets the size of the printk ring buffer, - in bytes. n must be a power of two and greater - than the minimal size. The minimal size is defined - by LOG_BUF_SHIFT kernel config parameter. There is - also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter - that allows to increase the default size depending on - the number of CPUs. See init/Kconfig for more details. + log_buf_len=n[KMG] [KNL,EARLY] + Sets the size of the printk ring buffer, in bytes. + n must be a power of two and greater than the + minimal size. The minimal size is defined by + LOG_BUF_SHIFT kernel config parameter. There + is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config + parameter that allows to increase the default size + depending on the number of CPUs. See init/Kconfig + for more details. logo.nologo [FB] Disables display of the built-in Linux logo. This may be used to provide more screen space for @@ -2890,7 +3152,7 @@ max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater than or equal to this physical address is ignored. - maxcpus= [SMP] Maximum number of processors that an SMP kernel + 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 bootup you can bring up the other plugged cpu by executing @@ -2908,7 +3170,7 @@ mce [X86-32] Machine Check Exception - mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst + 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. @@ -2917,7 +3179,7 @@ Format: <first>,<last> Specifies range of consoles to be captured by the MDA. - mds= [X86,INTEL] + mds= [X86,INTEL,EARLY] Control mitigation for the Micro-architectural Data Sampling (MDS) vulnerability. @@ -2949,11 +3211,12 @@ For details see: Documentation/admin-guide/hw-vuln/mds.rst - mem=nn[KMG] [HEXAGON] Set the memory size. + mem=nn[KMG] [HEXAGON,EARLY] Set the memory size. Must be specified, otherwise memory size will be 0. - mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory - Amount of memory to be used in cases as follows: + mem=nn[KMG] [KNL,BOOT,EARLY] Force usage of a specific amount + of memory Amount of memory to be used in cases + as follows: 1 for test; 2 when the kernel is not able to see the whole system memory; @@ -2977,8 +3240,8 @@ if system memory of hypervisor is not sufficient. mem=nn[KMG]@ss[KMG] - [ARM,MIPS] - override the memory layout reported by - firmware. + [ARM,MIPS,EARLY] - override the memory layout + reported by firmware. Define a memory region of size nn[KMG] starting at ss[KMG]. Multiple different regions can be specified with @@ -2987,13 +3250,13 @@ mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel memory. - memblock=debug [KNL] Enable memblock debug messages. + memblock=debug [KNL,EARLY] Enable memblock debug messages. memchunk=nn[KMG] [KNL,SH] Allow user to override the default size for per-device physically contiguous DMA buffers. - memhp_default_state=online/offline + memhp_default_state=online/offline/online_kernel/online_movable [KNL] Set the initial state for the memory hotplug onlining policy. If not specified, the default value is set according to the @@ -3001,14 +3264,14 @@ option. See Documentation/admin-guide/mm/memory-hotplug.rst. - memmap=exactmap [KNL,X86] Enable setting of an exact + memmap=exactmap [KNL,X86,EARLY] Enable setting of an exact E820 memory map, as specified by the user. Such memmap=exactmap lines can be constructed based on BIOS output or other requirements. See the memmap=nn@ss option description. memmap=nn[KMG]@ss[KMG] - [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory. + [KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory. Region of memory to be used is from ss to ss+nn. If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], which limits max address to nn[KMG]. @@ -3018,11 +3281,11 @@ memmap=100M@2G,100M#3G,1G!1024G memmap=nn[KMG]#ss[KMG] - [KNL,ACPI] Mark specific memory as ACPI data. + [KNL,ACPI,EARLY] Mark specific memory as ACPI data. Region of memory to be marked is from ss to ss+nn. memmap=nn[KMG]$ss[KMG] - [KNL,ACPI] Mark specific memory as reserved. + [KNL,ACPI,EARLY] Mark specific memory as reserved. Region of memory to be reserved is from ss to ss+nn. Example: Exclude memory from 0x18690000-0x1869ffff memmap=64K$0x18690000 @@ -3032,14 +3295,14 @@ like Grub2, otherwise '$' and the following number will be eaten. - memmap=nn[KMG]!ss[KMG] + memmap=nn[KMG]!ss[KMG,EARLY] [KNL,X86] Mark specific memory as protected. Region of memory to be used, from ss to ss+nn. The memory region may be marked as e820 type 12 (0xc) and is NVDIMM or ADR memory. memmap=<size>%<offset>-<oldtype>+<newtype> - [KNL,ACPI] Convert memory within the specified region + [KNL,ACPI,EARLY] Convert memory within the specified region from <oldtype> to <newtype>. If "-<oldtype>" is left out, the whole region will be marked as <newtype>, even if previously unavailable. If "+<newtype>" is left @@ -3047,7 +3310,7 @@ specified as e820 types, e.g., 1 = RAM, 2 = reserved, 3 = ACPI, 12 = PRAM. - memory_corruption_check=0/1 [X86] + memory_corruption_check=0/1 [X86,EARLY] Some BIOSes seem to corrupt the first 64k of memory when doing things like suspend/resume. Setting this option will scan the memory @@ -3059,13 +3322,13 @@ affects the same memory, you can use memmap= to prevent the kernel from using that memory. - memory_corruption_check_size=size [X86] + memory_corruption_check_size=size [X86,EARLY] By default it checks for corruption in the low 64k, making this memory unavailable for normal use. Use this parameter to scan for corruption in more or less memory. - memory_corruption_check_period=seconds [X86] + memory_corruption_check_period=seconds [X86,EARLY] By default it checks for corruption every 60 seconds. Use this parameter to check at some other rate. 0 disables periodic checking. @@ -3074,10 +3337,12 @@ [KNL,X86,ARM] Boolean flag to enable this feature. Format: {on | off (default)} When enabled, runtime hotplugged memory will - allocate its internal metadata (struct pages) - from the hotadded memory which will allow to - hotadd a lot of memory without requiring - additional memory to do so. + allocate its internal metadata (struct pages, + those vmemmap pages cannot be optimized even + if hugetlb_free_vmemmap is enabled) from the + hotadded memory which will allow to hotadd a + lot of memory without requiring additional + memory to do so. This feature is disabled by default because it has some implication on large (e.g. GB) allocations in some configurations (e.g. small @@ -3087,11 +3352,7 @@ Note that even when enabled, there are a few cases where the feature is not effective. - This is not compatible with hugetlb_free_vmemmap. If - both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. - - memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest + memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest Format: <integer> default : 0 <disable> Specifies the number of memtest passes to be @@ -3103,9 +3364,7 @@ mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control Valid arguments: on, off - Default (depends on kernel configuration option): - on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) - off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) + Default: off mem_encrypt=on: Activate SME mem_encrypt=off: Do not activate SME @@ -3118,9 +3377,6 @@ deep - Suspend-To-RAM or equivalent (if supported) See Documentation/admin-guide/pm/sleep-states.rst. - meye.*= [HW] Set MotionEye Camera parameters - See Documentation/admin-guide/media/meye.rst. - mfgpt_irq= [IA-32] Specify the IRQ to use for the Multi-Function General Purpose Timers on AMD Geode platforms. @@ -3132,6 +3388,11 @@ mga= [HW,DRM] + microcode.force_minrev= [X86] + Format: <bool> + 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. @@ -3157,7 +3418,7 @@ https://repo.or.cz/w/linux-2.6/mini2440.git mitigations= - [X86,PPC,S390,ARM64] Control optional mitigations for + [X86,PPC,S390,ARM64,EARLY] Control optional mitigations for CPU vulnerabilities. This is a set of curated, arch-independent options, each of which is an aggregation of existing arch-specific options. @@ -3166,23 +3427,27 @@ Disable all optional CPU mitigations. This improves system performance, but it may also expose users to several CPU vulnerabilities. - Equivalent to: nopti [X86,PPC] - if nokaslr then kpti=0 [ARM64] - nospectre_v1 [X86,PPC] - nobp=0 [S390] - nospectre_v2 [X86,PPC,S390,ARM64] - spectre_v2_user=off [X86] - spec_store_bypass_disable=off [X86,PPC] - ssbd=force-off [ARM64] + Equivalent to: if nokaslr then kpti=0 [ARM64] + gather_data_sampling=off [X86] + kvm.nx_huge_pages=off [X86] l1tf=off [X86] mds=off [X86] - tsx_async_abort=off [X86] - kvm.nx_huge_pages=off [X86] - srbds=off [X86,INTEL] + mmio_stale_data=off [X86] no_entry_flush [PPC] no_uaccess_flush [PPC] - mmio_stale_data=off [X86] + nobp=0 [S390] + nopti [X86,PPC] + nospectre_bhb [ARM64] + nospectre_v1 [X86,PPC] + nospectre_v2 [X86,PPC,S390,ARM64] + reg_file_data_sampling=off [X86] retbleed=off [X86] + spec_rstack_overflow=off [X86] + spec_store_bypass_disable=off [X86,PPC] + spectre_v2_user=off [X86] + srbds=off [X86,INTEL] + ssbd=force-off [ARM64] + tsx_async_abort=off [X86] Exceptions: This does not have any effect on @@ -3208,7 +3473,7 @@ retbleed=auto,nosmt [X86] mminit_loglevel= - [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this + [KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this parameter allows control of the logging verbosity for the additional memory initialisation checks. A value of 0 disables mminit logging and a level of 4 will @@ -3216,7 +3481,7 @@ so loglevel=8 may also need to be specified. mmio_stale_data= - [X86,INTEL] Control mitigation for the Processor + [X86,INTEL,EARLY] Control mitigation for the Processor MMIO Stale Data vulnerabilities. Processor MMIO Stale Data is a class of @@ -3249,6 +3514,28 @@ For details see: Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst + <module>.async_probe[=<bool>] [KNL] + If no <bool> value is specified or if the value + specified is not a valid <bool>, enable asynchronous + probe on this module. Otherwise, enable/disable + asynchronous probe on this module as indicated by the + <bool> value. See also: module.async_probe + + module.async_probe=<bool> + [KNL] When set to true, modules will use async probing + by default. To enable/disable async probing for a + specific module, use the module specific control that + is documented under <module>.async_probe. When both + module.async_probe and <module>.async_probe are + specified, <module>.async_probe takes precedence for + the specific module. + + module.enable_dups_trace + [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set, + this means that duplicate request_module() calls will + trigger a WARN_ON() instead of a pr_warn(). Note that + if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s + will always be issued and this option does nothing. module.sig_enforce [KNL] When CONFIG_MODULE_SIG is set, this means that modules without (valid) signatures will fail to load. @@ -3269,7 +3556,7 @@ mousedev.yres= [MOUSE] Vertical screen resolution, used for devices reporting absolute coordinates, such as tablets - movablecore= [KNL,X86,IA-64,PPC] + movablecore= [KNL,X86,IA-64,PPC,EARLY] Format: nn[KMGTPE] | nn% This parameter is the complement to kernelcore=, it specifies the amount of memory used for migratable @@ -3280,7 +3567,7 @@ that the amount of memory usable for all allocations is not too small. - movable_node [KNL] Boot-time switch to make hotplugable memory + movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory NUMA nodes to be movable. This means that the memory of such nodes will be usable only for movable allocations which rules out almost all kernel @@ -3304,17 +3591,21 @@ [HW] Make the MicroTouch USB driver use raw coordinates ('y', default) or cooked coordinates ('n') - mtrr_chunk_size=nn[KMG] [X86] + mtrr=debug [X86,EARLY] + Enable printing debug information related to MTRR + registers at boot time. + + mtrr_chunk_size=nn[KMG,X86,EARLY] used for mtrr cleanup. It is largest continuous chunk that could hold holes aka. UC entries. - mtrr_gran_size=nn[KMG] [X86] + mtrr_gran_size=nn[KMG,X86,EARLY] Used for mtrr cleanup. It is granularity of mtrr block. Default is 1. Large value could prevent small alignment from using up MTRRs. - mtrr_spare_reg_nr=n [X86] + mtrr_spare_reg_nr=n [X86,EARLY] Format: <integer> Range: 0,7 : spare reg number Default : 1 @@ -3345,14 +3636,13 @@ 1 to enable accounting Default value is 0. - nfsaddrs= [NFS] Deprecated. Use ip= instead. - See Documentation/admin-guide/nfs/nfsroot.rst. - - nfsroot= [NFS] nfs root filesystem for disk-less boxes. - See Documentation/admin-guide/nfs/nfsroot.rst. + nfs.cache_getent= + [NFS] sets the pathname to the program which is used + to update the NFS client cache entries. - nfsrootdebug [NFS] enable nfsroot debugging messages. - See Documentation/admin-guide/nfs/nfsroot.rst. + nfs.cache_getent_timeout= + [NFS] sets the timeout after which an attempt to + update a cache entry is deemed to have failed. nfs.callback_nr_threads= [NFSv4] set the total number of threads that the @@ -3363,17 +3653,12 @@ [NFS] set the TCP port on which the NFSv4 callback channel should listen. - nfs.cache_getent= - [NFS] sets the pathname to the program which is used - to update the NFS client cache entries. - - nfs.cache_getent_timeout= - [NFS] sets the timeout after which an attempt to - update a cache entry is deemed to have failed. - - nfs.idmap_cache_timeout= - [NFS] set the maximum lifetime for idmapper cache - entries. + nfs.delay_retrans= + [NFS] specifies the number of times the NFSv4 client + retries the request before returning an EAGAIN error, + after a reply of NFS4ERR_DELAY from the server. + Only applies if the softerr mount option is enabled, + and the specified value is >= 0. nfs.enable_ino64= [NFS] enable 64-bit inode numbers. @@ -3382,6 +3667,10 @@ of returning the full 64-bit number. The default is to return 64-bit inode numbers. + nfs.idmap_cache_timeout= + [NFS] set the maximum lifetime for idmapper cache + entries. + nfs.max_session_cb_slots= [NFSv4.1] Sets the maximum number of session slots the client will assign to the callback @@ -3409,21 +3698,14 @@ will be autodetected by the client, and it will fall back to using the idmapper. To turn off this behaviour, set the value to '0'. + nfs.nfs4_unique_id= [NFS4] Specify an additional fixed unique ident- ification string that NFSv4 clients can insert into their nfs_client_id4 string. This is typically a UUID that is generated at system install time. - nfs.send_implementation_id = - [NFSv4.1] Send client implementation identification - information in exchange_id requests. - If zero, no implementation identification information - will be sent. - The default is to send the implementation identification - information. - - nfs.recover_lost_locks = + nfs.recover_lost_locks= [NFSv4] Attempt to recover locks that were lost due to a lease timeout on the server. Please note that doing this risks data corruption, since there are @@ -3435,7 +3717,15 @@ The default parameter value of '0' causes the kernel not to attempt recovery of lost locks. - nfs4.layoutstats_timer = + nfs.send_implementation_id= + [NFSv4.1] Send client implementation identification + information in exchange_id requests. + If zero, no implementation identification information + will be sent. + The default is to send the implementation identification + information. + + nfs4.layoutstats_timer= [NFSv4.2] Change the rate at which the kernel sends layoutstats to the pNFS metadata server. @@ -3444,12 +3734,19 @@ driver. A non-zero value sets the minimum interval in seconds between layoutstats transmissions. - nfsd.inter_copy_offload_enable = + nfsd.inter_copy_offload_enable= [NFSv4.2] When set to 1, the server will support server-to-server copies for which this server is the destination of the copy. - nfsd.nfsd4_ssc_umount_timeout = + nfsd.nfs4_disable_idmapping= + [NFSv4] When set to the default of '1', the NFSv4 + server will return only numeric uids and gids to + clients using auth_sys, and will accept numeric uids + and gids from such clients. This is intended to ease + migration from NFSv2/v3. + + nfsd.nfsd4_ssc_umount_timeout= [NFSv4.2] When used as the destination of a server-to-server copy, knfsd temporarily mounts the source server. It caches the mount in case @@ -3457,13 +3754,14 @@ used for the number of milliseconds specified by this parameter. - nfsd.nfs4_disable_idmapping= - [NFSv4] When set to the default of '1', the NFSv4 - server will return only numeric uids and gids to - clients using auth_sys, and will accept numeric uids - and gids from such clients. This is intended to ease - migration from NFSv2/v3. + nfsaddrs= [NFS] Deprecated. Use ip= instead. + See Documentation/admin-guide/nfs/nfsroot.rst. + nfsroot= [NFS] nfs root filesystem for disk-less boxes. + See Documentation/admin-guide/nfs/nfsroot.rst. + + nfsrootdebug [NFS] enable nfsroot debugging messages. + See Documentation/admin-guide/nfs/nfsroot.rst. nmi_backtrace.backtrace_idle [KNL] Dump stacks even of idle CPUs in response to an @@ -3493,10 +3791,23 @@ emulation library even if a 387 maths coprocessor is present. - no5lvl [X86-64] Disable 5-level paging mode. Forces + no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes. + Forces kernel to use 3-level paging instead. + + no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. - nofsgsbase [X86] Disables FSGSBASE instructions. + 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. + + noautogroup Disable scheduler automatic task group creation. + + nocache [ARM,EARLY] no_console_suspend [HW] Never suspend the console @@ -3513,52 +3824,17 @@ /sys/module/printk/parameters/console_suspend) to turn on/off it dynamically. - novmcoredd [KNL,KDUMP] - Disable device dump. Device dump allows drivers to - append dump data to vmcore so you can collect driver - specified debug info. Drivers can append the data - without any limit and this data is stored in memory, - so this may cause significant memory stress. Disabling - device dump can help save memory but the driver debug - data will be no longer available. This parameter - is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP - is set. - - noaliencache [MM, NUMA, SLAB] Disables the allocation of alien - caches in the slab allocator. Saves per-node memory, - but will impact performance. - - noalign [KNL,ARM] - - noaltinstr [S390] Disables alternative instructions patching - (CPU alternatives feature). - - noapic [SMP,APIC] Tells the kernel to not make use of any - IOAPICs that may be present in the system. - - noautogroup Disable scheduler automatic task group creation. - - nobats [PPC] Do not use BATs for mapping kernel lowmem - on "Classic" PPC cores. - - nocache [ARM] + no_debug_objects + [KNL,EARLY] Disable object debugging nodsp [SH] Disable hardware DSP at boot time. - noefi Disable EFI runtime services support. + noefi [EFI,EARLY] Disable EFI runtime services support. - no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel. + no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel. noexec [IA-64] - nosmap [PPC] - Disable SMAP (Supervisor Mode Access Prevention) - even if it is supported by processor. - - nosmep [PPC64s] - Disable SMEP (Supervisor Mode Execution Prevention) - even if it is supported by processor. - noexec32 [X86-64] This affects only 32-bit executables. noexec32=on: enable non-executable mappings (default) @@ -3566,70 +3842,18 @@ noexec32=off: disable non-executable mappings read implies executable mappings + no_file_caps Tells the kernel not to honor file capabilities. The + only way then for a file to be executed with privilege + is to be setuid root or executed by root. + nofpu [MIPS,SH] Disable hardware FPU at boot time. + nofsgsbase [X86] Disables FSGSBASE instructions. + nofxsr [BUGS=X86-32] Disables x86 floating point extended register save and restore. The kernel will only save legacy floating-point registers on task switch. - nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. - - nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. - - nosmt [KNL,S390] Disable symmetric multithreading (SMT). - Equivalent to smt=1. - - [KNL,X86] Disable symmetric multithreading (SMT). - nosmt=force: Force disable SMT, cannot be undone - via the sysfs control file. - - nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 - (bounds check bypass). With this option data leaks are - possible in the system. - - nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for - the Spectre variant 2 (indirect branch prediction) - vulnerability. System may allow data leaks with this - option. - - nospec_store_bypass_disable - [HW] Disable all mitigations for the Speculative Store Bypass vulnerability - - no_uaccess_flush - [PPC] Don't flush the L1-D cache after accessing user data. - - noxsave [BUGS=X86] Disables x86 extended register state save - and restore using xsave. The kernel will fallback to - enabling legacy floating-point and sse state. - - noxsaveopt [X86] Disables xsaveopt used in saving x86 extended - register states. The kernel will fall back to use - xsave to save the states. By using this parameter, - performance of saving the states is degraded because - xsave doesn't support modified optimization while - xsaveopt supports it on xsaveopt enabled systems. - - noxsaves [X86] Disables xsaves and xrstors used in saving and - restoring x86 extended register state in compacted - form of xsave area. The kernel will fall back to use - xsaveopt and xrstor to save and restore the states - in standard form of xsave area. By using this - parameter, xsave area per process might occupy more - memory on xsaves enabled systems. - - nohlt [ARM,ARM64,MICROBLAZE,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 - sleep(SH) or wfi(ARM,ARM64) instructions do not work - correctly or when doing power measurements to evalute - the impact of the sleep instructions. This is also - useful when using JTAG debugger. - - no_file_caps Tells the kernel not to honor file capabilities. The - only way then for a file to be executed with privilege - is to be setuid root or executed by root. - 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 @@ -3638,6 +3862,7 @@ real-time systems. no_hash_pointers + [KNL,EARLY] Force pointers printed to the console or buffers to be unhashed. By default, when a pointer is printed via %p format string, that pointer is "hashed", i.e. obscured @@ -3653,6 +3878,19 @@ nohibernate [HIBERNATION] Disable hibernation and resume. + nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,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 + sleep(SH) or wfi(ARM,ARM64) instructions do not work + correctly or when doing power measurements to evaluate + the impact of the sleep instructions. This is also + useful when using JTAG debugger. + + nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings. + + nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings. + nohz= [KNL] Boottime enable/disable dynamic ticks Valid arguments: on, off Default: on @@ -3670,48 +3908,39 @@ Note that this argument takes precedence over the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. - noiotrap [SH] Disables trapped I/O port accesses. - - noirqdebug [X86-32] Disables the code which attempts to detect and - disable unhandled interrupt sources. - - no_timer_check [X86,APIC] Disables the code which tests for - broken timer IRQ sources. - - noisapnp [ISAPNP] Disables ISA PnP code. - noinitrd [RAM] Tells the kernel not to load any configured initial RAM disk. - nointremap [X86-64, Intel-IOMMU] Do not enable interrupt + nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt remapping. [Deprecated - use intremap=off] nointroute [IA-64] - noinvpcid [X86] Disable the INVPCID cpu feature. + noinvpcid [X86,EARLY] Disable the INVPCID cpu feature. - nojitter [IA-64] Disables jitter checking for ITC timers. + noiotrap [SH] Disables trapped I/O port accesses. - no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver + noirqdebug [X86-32] Disables the code which attempts to detect and + disable unhandled interrupt sources. - no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page - fault handling. + noisapnp [ISAPNP] Disables ISA PnP code. - no-vmw-sched-clock - [X86,PV_OPS] Disable paravirtualized VMware scheduler - clock and use the default one. + nojitter [IA-64] Disables jitter checking for ITC timers. - no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time - accounting. steal time is computed, but won't - influence scheduler behaviour + nokaslr [KNL,EARLY] + When CONFIG_RANDOMIZE_BASE is set, this disables + kernel and module base offset ASLR (Address Space + Layout Randomization). - nolapic [X86-32,APIC] Do not enable or use the local APIC. + no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page + fault handling. + + no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver - nolapic_timer [X86-32,APIC] Do not use the local APIC timer. + nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC. - noltlbs [PPC] Do not use large page/tlb entries for kernel - lowmem mapping on PPC40x and PPC8xx + nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer. nomca [IA-64] Disable machine check abort handling @@ -3720,23 +3949,42 @@ nomfgpt [X86-32] Disable Multi-Function General Purpose Timer usage (for AMD Geode machines). + nomodeset Disable kernel modesetting. Most systems' firmware + sets up a display mode and provides framebuffer memory + for output. With nomodeset, DRM and fbdev drivers will + not load if they could possibly displace the pre- + initialized output. Only the system framebuffer will + be available for use. The respective drivers will not + perform display-mode changes or accelerated rendering. + + Useful as error fallback, or for testing and debugging. + + nomodule Disable module load + nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to shutdown the other cpus. Instead use the REBOOT_VECTOR irq. - nomodeset Disable kernel modesetting. DRM drivers will not perform - display-mode changes or accelerated rendering. Only the - system framebuffer will be available for use if this was - set-up by the firmware or boot loader. + nopat [X86,EARLY] Disable PAT (page attribute table extension of + pagetables) support. - Useful as fallback, or for testing and debugging. + nopcid [X86-64,EARLY] Disable the PCID cpu feature. - nomodule Disable module load + nopku [X86] Disable Memory Protection Keys CPU feature found + in some Intel CPUs. - nopat [X86] Disable PAT (page attribute table extension of - pagetables) support. + nopti [X86-64,EARLY] + Equivalent to pti=off + + nopv= [X86,XEN,KVM,HYPER_V,VMWARE,EARLY] + Disables the PV optimizations forcing the guest to run + as generic guest with no PV drivers. Currently support + XEN HVM, KVM, HYPER_V and VMWARE guest. - nopcid [X86-64] Disable the PCID cpu feature. + nopvspin [X86,XEN,KVM,EARLY] + Disables the qspinlock slow path using PV optimizations + which allow the hypervisor to 'idle' the guest on lock + contention. norandmaps Don't use address space randomization. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space @@ -3747,27 +3995,107 @@ 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). - nosbagart [IA-64] + nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support. - nosgx [X86-64,SGX] Disables Intel SGX kernel support. + nosmap [PPC,EARLY] + Disable SMAP (Supervisor Mode Access Prevention) + even if it is supported by processor. + + nosmep [PPC64s,EARLY] + Disable SMEP (Supervisor Mode Execution Prevention) + even if it is supported by processor. - nosmp [SMP] Tells an SMP kernel to act as a UP kernel, + 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). + Equivalent to smt=1. + + [KNL,X86,PPC] Disable symmetric multithreading (SMT). + nosmt=force: Force disable SMT, cannot be undone + via the sysfs control file. + nosoftlockup [KNL] Disable the soft-lockup detector. + nospec_store_bypass_disable + [HW,EARLY] Disable all mitigations for the Speculative + Store Bypass vulnerability + + nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch + history injection) vulnerability. System may allow data leaks + with this option. + + nospectre_v1 [X86,PPC,EARLY] Disable mitigations for Spectre Variant 1 + (bounds check bypass). With this option data leaks are + possible in the system. + + nospectre_v2 [X86,PPC_E500,ARM64,EARLY] Disable all mitigations + for the Spectre variant 2 (indirect branch + 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 + 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_uaccess_flush + [PPC,EARLY] Don't flush the L1-D cache after accessing user data. + + novmcoredd [KNL,KDUMP] + Disable device dump. Device dump allows drivers to + append dump data to vmcore so you can collect driver + specified debug info. Drivers can append the data + without any limit and this data is stored in memory, + so this may cause significant memory stress. Disabling + device dump can help save memory but the driver debug + data will be no longer available. This parameter + is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP + is set. + + no-vmw-sched-clock + [X86,PV_OPS,EARLY] Disable paravirtualized VMware + scheduler clock and use the default one. + nowatchdog [KNL] Disable both lockup detectors, i.e. soft-lockup and NMI watchdog (hard-lockup). - nowb [ARM] + nowb [ARM,EARLY] + + nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode. - nox2apic [X86-64,APIC] Do not enable x2APIC mode. + NOTE: this parameter will be ignored on systems with the + LEGACY_XAPIC_DISABLED bit set in the + IA32_XAPIC_DISABLE_STATUS MSR. + + noxsave [BUGS=X86] Disables x86 extended register state save + and restore using xsave. The kernel will fallback to + enabling legacy floating-point and sse state. + + noxsaveopt [X86] Disables xsaveopt used in saving x86 extended + register states. The kernel will fall back to use + xsave to save the states. By using this parameter, + performance of saving the states is degraded because + xsave doesn't support modified optimization while + xsaveopt supports it on xsaveopt enabled systems. + + noxsaves [X86] Disables xsaves and xrstors used in saving and + restoring x86 extended register state in compacted + form of xsave area. The kernel will fall back to use + xsaveopt and xrstor to save and restore the states + in standard form of xsave area. By using this + 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 @@ -3782,7 +4110,7 @@ purges which is reported from either PAL_VM_SUMMARY or SAL PALO. - nr_cpus= [SMP] Maximum number of processors that an SMP kernel + 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 number of already plugged CPU during bootup, later in @@ -3793,8 +4121,9 @@ nr_uarts= [SERIAL] maximum number of UARTs to be registered. - numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only - set up a single NUMA node spanning all memory. + numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY] + Disable NUMA, Only set up a single NUMA node + spanning all memory. numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic NUMA balancing. @@ -3805,7 +4134,7 @@ This can be set from sysctl after boot. See Documentation/admin-guide/sysctl/vm.rst for details. - ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. + ohci1394_dma=early [HW,EARLY] enable debugging via the ohci1394 driver. See Documentation/core-api/debugging-via-ohci1394.rst for more info. @@ -3831,7 +4160,8 @@ Once locked, the boundary cannot be changed. 1 indicates lock status, 0 indicates unlock status. - oops=panic Always panic on oopses. Default is to just kill the + oops=panic [KNL,EARLY] + Always panic on oopses. Default is to just kill the process, but there is a small probability of deadlocking the machine. This will also cause panics on machine check exceptions. @@ -3847,13 +4177,13 @@ can be read from sysfs at: /sys/module/page_alloc/parameters/shuffle. - page_owner= [KNL] Boot-time page_owner enabling option. + page_owner= [KNL,EARLY] Boot-time page_owner enabling option. Storage of the information about who allocated each page is disabled in default. With this switch, we can turn it on. on: enable the feature - page_poison= [KNL] Boot-time parameter changing the state of + page_poison= [KNL,EARLY] Boot-time parameter changing the state of poisoning on the buddy allocator, available with CONFIG_PAGE_POISONING=y. off: turn off poisoning (default) @@ -3863,7 +4193,7 @@ [KNL] Minimal page reporting order Format: <integer> Adjust the minimal page reporting order. The page - reporting is disabled when it exceeds (MAX_ORDER-1). + reporting is disabled when it exceeds MAX_PAGE_ORDER. panic= [KNL] Kernel behaviour on panic: delay <timeout> timeout > 0: seconds before rebooting @@ -3871,21 +4201,8 @@ timeout < 0: reboot immediately Format: <timeout> - panic_print= Bitmask for printing system info when panic happens. - User can chose combination of the following bits: - bit 0: print all tasks info - bit 1: print system memory info - bit 2: print timer info - bit 3: print locks info if CONFIG_LOCKDEP is on - bit 4: print ftrace buffer - bit 5: print all printk messages in buffer - bit 6: print all CPUs backtrace (if available in the arch) - *Be aware* that this option may print a _lot_ of lines, - so there are risks of losing older messages in the log. - Use this option carefully, maybe worth to setup a - bigger log buffer with "log_buf_len" along with this. - - panic_on_taint= Bitmask for conditionally calling panic() in add_taint() + panic_on_taint= [KNL,EARLY] + Bitmask for conditionally calling panic() in add_taint() Format: <hex>[,nousertaint] Hexadecimal bitmask representing the set of TAINT flags that will cause the kernel to panic when add_taint() is @@ -3898,9 +4215,24 @@ extra details on the taint flags that users can pick to compose the bitmask to assign to panic_on_taint. - panic_on_warn panic() instead of WARN(). Useful to cause kdump + panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump on a WARN(). + panic_print= Bitmask for printing system info when panic happens. + User can chose combination of the following bits: + bit 0: print all tasks info + bit 1: print system memory info + bit 2: print timer info + bit 3: print locks info if CONFIG_LOCKDEP is on + bit 4: print ftrace buffer + bit 5: print all printk messages in buffer + bit 6: print all CPUs backtrace (if available in the arch) + bit 7: print only tasks in uninterruptible (blocked) state + *Be aware* that this option may print a _lot_ of lines, + so there are risks of losing older messages in the log. + Use this option carefully, maybe worth to setup a + bigger log buffer with "log_buf_len" along with this. + parkbd.port= [HW] Parallel port number the keyboard adapter is connected to, default is 0. Format: <parport#> @@ -4020,18 +4352,14 @@ mode 0, bit 1 is for mode 1, and so on. Mode 0 only allowed by default. - pause_on_oops= + pause_on_oops=<int> Halt all CPUs after the first oops has been printed for the specified number of seconds. This is to be used if your oopses keep scrolling off the screen. pcbit= [HW,ISDN] - pcd. [PARIDE] - See header of drivers/block/paride/pcd.c. - See also Documentation/admin-guide/blockdev/paride.rst. - - pci=option[,option...] [PCI] various PCI subsystem options. + pci=option[,option...] [PCI,EARLY] various PCI subsystem options. Some options herein operate on a specific device or a set of devices (<pci_dev>). These are @@ -4206,7 +4534,9 @@ specified, e.g., 12@pci:8086:9c22:103c:198f for 4096-byte alignment. ecrc= Enable/disable PCIe ECRC (transaction layer - end-to-end CRC checking). + end-to-end CRC checking). Only effective if + OS has native AER control (either granted by + ACPI _OSC or forced via "pcie_ports=native") bios: Use BIOS/firmware settings. This is the the default. off: Turn ECRC off @@ -4293,29 +4623,21 @@ for debug and development, but should not be needed on a platform with proper driver support. - pd. [PARIDE] - See Documentation/admin-guide/blockdev/paride.rst. - pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at boot time. Format: { 0 | 1 } See arch/parisc/kernel/pdc_chassis.c - percpu_alloc= Select which percpu first chunk allocator to use. + percpu_alloc= [MM,EARLY] + Select which percpu first chunk allocator to use. Currently supported values are "embed" and "page". Archs may support subset or none of the selections. See comments in mm/percpu.c for details on each allocator. This parameter is primarily for debugging and performance comparison. - pf. [PARIDE] - See Documentation/admin-guide/blockdev/paride.rst. - - pg. [PARIDE] - See Documentation/admin-guide/blockdev/paride.rst. - pirq= [SMP,APIC] Manual mp-table setup - See Documentation/x86/i386/IO-APIC.rst. + See Documentation/arch/x86/i386/IO-APIC.rst. plip= [PPT,NET] Parallel port network link Format: { parport<nr> | timid | 0 } @@ -4369,6 +4691,11 @@ may be specified. Format: <port>,<port>.... + possible_cpus= [SMP,S390,X86] + Format: <unsigned int> + Set the number of possible CPUs, overriding the + regular discovery mechanisms (such as ACPI/FW, etc). + powersave=off [PPC] This option disables power saving features. It specifically disables cpuidle and sets the platform machine description specific power_save @@ -4376,12 +4703,12 @@ execution priority. ppc_strict_facility_enable - [PPC] This option catches any kernel floating point, + [PPC,ENABLE] This option catches any kernel floating point, Altivec, VSX and SPE outside of regions specifically allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). There is some performance impact when enabling this. - ppc_tm= [PPC] + ppc_tm= [PPC,EARLY] Format: {"off"} Disable Hardware Transactional Memory @@ -4475,9 +4802,6 @@ pstore.backend= Specify the name of the pstore backend to use - pt. [PARIDE] - See Documentation/admin-guide/blockdev/paride.rst. - pti= [X86-64] Control Page Table Isolation of user and kernel address spaces. Disabling this feature removes hardening, but improves performance of @@ -4490,17 +4814,18 @@ Not specifying this option is equivalent to pti=auto. - nopti [X86-64] - Equivalent to pti=off - pty.legacy_count= [KNL] Number of legacy pty's. Overwrites compiled-in default number. - quiet [KNL] Disable most log messages + quiet [KNL,EARLY] Disable most log messages r128= [HW,DRM] + radix_hcall_invalidate=on [PPC/PSERIES] + Disable RADIX GTSE feature and use hcall for TLB + invalidate. + raid= [HW,RAID] See Documentation/admin-guide/md.rst. @@ -4509,20 +4834,18 @@ ramdisk_start= [RAM] RAM disk image start address - random.trust_cpu={on,off} - [KNL] Enable or disable trusting the use of the - CPU's random number generator (if available) to - fully seed the kernel's CRNG. Default is controlled - by CONFIG_RANDOM_TRUST_CPU. + random.trust_cpu=off + [KNL,EARLY] Disable trusting the use of the CPU's + random number generator (if available) to + initialize the kernel's RNG. - random.trust_bootloader={on,off} - [KNL] Enable or disable trusting the use of a - seed passed by the bootloader (if available) to - fully seed the kernel's CRNG. Default is controlled - by CONFIG_RANDOM_TRUST_BOOTLOADER. + random.trust_bootloader=off + [KNL,EARLY] Disable trusting the use of the a seed + passed by the bootloader (if available) to + initialize the kernel's RNG. randomize_kstack_offset= - [KNL] Enable or disable kernel stack offset + [KNL,EARLY] Enable or disable kernel stack offset randomization, which provides roughly 5 bits of entropy, frustrating memory corruption attacks that depend on stack address determinism or @@ -4581,6 +4904,13 @@ Set maximum number of finished RCU callbacks to process in one batch. + rcutree.do_rcu_barrier= [KNL] + Request a call to rcu_barrier(). This is + throttled so that userspace tests can safely + hammer on the sysfs variable if they so choose. + If triggered before the RCU grace-period machinery + is fully active, this will error out with EAGAIN. + rcutree.dump_tree= [KNL] Dump the structure of the rcu_node combining tree out at early boot. This is used for diagnostic @@ -4600,43 +4930,6 @@ the propagation of recent CPU-hotplug changes up the rcu_node combining tree. - rcutree.use_softirq= [KNL] - If set to zero, move all RCU_SOFTIRQ processing to - per-CPU rcuc kthreads. Defaults to a non-zero - value, meaning that RCU_SOFTIRQ is used by default. - Specify rcutree.use_softirq=0 to use rcuc kthreads. - - But note that CONFIG_PREEMPT_RT=y kernels disable - this kernel boot parameter, forcibly setting it - to zero. - - rcutree.rcu_fanout_exact= [KNL] - Disable autobalancing of the rcu_node combining - tree. This is used by rcutorture, and might - possibly be useful for architectures having high - cache-to-cache transfer latencies. - - rcutree.rcu_fanout_leaf= [KNL] - Change the number of CPUs assigned to each - leaf rcu_node structure. Useful for very - large systems, which will choose the value 64, - and for NUMA systems with large remote-access - latencies, which will choose a value aligned - with the appropriate hardware boundaries. - - rcutree.rcu_min_cached_objs= [KNL] - Minimum number of objects which are cached and - maintained per one CPU. Object size is equal - to PAGE_SIZE. The cache allows to reduce the - pressure to page allocator, also it makes the - whole algorithm to behave better in low memory - condition. - - rcutree.rcu_delay_page_cache_fill_msec= [KNL] - Set the page-cache refill delay (in milliseconds) - in response to low-memory conditions. The range - of permitted values is in the range 0:100000. - rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to first attempt to force quiescent states. @@ -4675,21 +4968,6 @@ When RCU_NOCB_CPU is set, also adjust the priority of NOCB callback kthreads. - rcutree.rcu_divisor= [KNL] - Set the shift-right count to use to compute - the callback-invocation batch limit bl from - the number of callbacks queued on this CPU. - The result will be bounded below by the value of - the rcutree.blimit kernel parameter. Every bl - callbacks, the softirq handler will exit in - order to allow the CPU to do other work. - - Please note that this callback-invocation batch - limit applies only to non-offloaded callback - invocation. Offloaded callbacks are instead - invoked in the context of an rcuoc kthread, which - scheduler will preempt as it does any other task. - rcutree.nocb_nobypass_lim_per_jiffy= [KNL] On callback-offloaded (rcu_nocbs) CPUs, RCU reduces the lock contention that would @@ -4703,14 +4981,6 @@ the ->nocb_bypass queue. The definition of "too many" is supplied by this kernel boot parameter. - rcutree.rcu_nocb_gp_stride= [KNL] - Set the number of NOCB callback kthreads in - each group, which defaults to the square root - of the number of CPUs. Larger numbers reduce - the wakeup overhead on the global grace-period - kthread, but increases that same overhead on - each group's NOCB grace-period kthread. - rcutree.qhimark= [KNL] Set threshold of queued RCU callbacks beyond which batch limiting is disabled. @@ -4728,6 +4998,56 @@ on rcutree.qhimark at boot time and to zero to disable more aggressive help enlistment. + rcutree.rcu_delay_page_cache_fill_msec= [KNL] + Set the page-cache refill delay (in milliseconds) + in response to low-memory conditions. The range + of permitted values is in the range 0:100000. + + rcutree.rcu_divisor= [KNL] + Set the shift-right count to use to compute + the callback-invocation batch limit bl from + the number of callbacks queued on this CPU. + The result will be bounded below by the value of + the rcutree.blimit kernel parameter. Every bl + callbacks, the softirq handler will exit in + order to allow the CPU to do other work. + + Please note that this callback-invocation batch + limit applies only to non-offloaded callback + invocation. Offloaded callbacks are instead + invoked in the context of an rcuoc kthread, which + scheduler will preempt as it does any other task. + + rcutree.rcu_fanout_exact= [KNL] + Disable autobalancing of the rcu_node combining + tree. This is used by rcutorture, and might + possibly be useful for architectures having high + cache-to-cache transfer latencies. + + rcutree.rcu_fanout_leaf= [KNL] + Change the number of CPUs assigned to each + leaf rcu_node structure. Useful for very + large systems, which will choose the value 64, + and for NUMA systems with large remote-access + latencies, which will choose a value aligned + with the appropriate hardware boundaries. + + rcutree.rcu_min_cached_objs= [KNL] + Minimum number of objects which are cached and + maintained per one CPU. Object size is equal + to PAGE_SIZE. The cache allows to reduce the + pressure to page allocator, also it makes the + whole algorithm to behave better in low memory + condition. + + rcutree.rcu_nocb_gp_stride= [KNL] + Set the number of NOCB callback kthreads in + each group, which defaults to the square root + of the number of CPUs. Larger numbers reduce + the wakeup overhead on the global grace-period + kthread, but increases that same overhead on + each group's NOCB grace-period kthread. + rcutree.rcu_kick_kthreads= [KNL] Cause the grace-period kthread to get an extra wake_up() if it sleeps three times longer than @@ -4735,6 +5055,13 @@ This wake_up() will be accompanied by a WARN_ONCE() splat and an ftrace_dump(). + rcutree.rcu_resched_ns= [KNL] + Limit the time spend invoking a batch of RCU + callbacks to the specified number of nanoseconds. + By default, this limit is checked only once + every 32 callbacks in order to limit the pain + inflicted by local_clock() overhead. + rcutree.rcu_unlock_delay= [KNL] In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, this specifies an rcu_read_unlock()-time delay @@ -4749,6 +5076,21 @@ rcu_node tree with an eye towards determining why a new grace period has not yet started. + rcutree.use_softirq= [KNL] + If set to zero, move all RCU_SOFTIRQ processing to + per-CPU rcuc kthreads. Defaults to a non-zero + value, meaning that RCU_SOFTIRQ is used by default. + Specify rcutree.use_softirq=0 to use rcuc kthreads. + + But note that CONFIG_PREEMPT_RT=y kernels disable + this kernel boot parameter, forcibly setting it + to zero. + + rcutree.enable_rcu_lazy= [KNL] + To save power, batch RCU callbacks and flush after + delay, memory pressure or callback list growing too + big. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). @@ -4770,6 +5112,15 @@ test until boot completes in order to avoid interference. + rcuscale.kfree_by_call_rcu= [KNL] + In kernels built with CONFIG_RCU_LAZY=y, test + call_rcu() instead of kfree_rcu(). + + rcuscale.kfree_mult= [KNL] + Instead of allocating an object of size kfree_obj, + allocate one of kfree_mult * sizeof(kfree_obj). + Defaults to 1. + rcuscale.kfree_rcu_test= [KNL] Set to measure performance of kfree_rcu() flooding. @@ -4795,6 +5146,12 @@ Number of loops doing rcuscale.kfree_alloc_num number of allocations and frees. + rcuscale.minruntime= [KNL] + Set the minimum test run time in seconds. This + does not affect the data-collection interval, + but instead allows better measurement of things + like CPU consumption. + rcuscale.nreaders= [KNL] Set number of RCU readers. The value -1 selects N, where N is the number of CPUs. A value @@ -4809,7 +5166,7 @@ the same as for rcuscale.nreaders. N, where N is the number of CPUs - rcuscale.perf_type= [KNL] + rcuscale.scale_type= [KNL] Specify the RCU implementation to test. rcuscale.shutdown= [KNL] @@ -4825,6 +5182,11 @@ in microseconds. The default of zero says no holdoff. + rcuscale.writer_holdoff_jiffies= [KNL] + Additional write-side holdoff between grace + periods, but in jiffies. The default of zero + says no holdoff. + rcutorture.fqs_duration= [KNL] Set duration of force_quiescent_state bursts in microseconds. @@ -4951,8 +5313,17 @@ rcutorture.stall_cpu_block= [KNL] Sleep while stalling if set. This will result - in warnings from preemptible RCU in addition - to any other stall-related activity. + in warnings from preemptible RCU in addition to + any other stall-related activity. Note that + in kernels built with CONFIG_PREEMPTION=n and + CONFIG_PREEMPT_COUNT=y, this parameter will + cause the CPU to pass through a quiescent state. + Given CONFIG_PREEMPTION=n, this will suppress + RCU CPU stall warnings, but will instead result + in scheduling-while-atomic splats. + + Use of this module parameter results in splats. + rcutorture.stall_cpu_holdoff= [KNL] Time to wait (s) after boot before inducing stall. @@ -5001,6 +5372,12 @@ Dump ftrace buffer after reporting RCU CPU stall warning. + rcupdate.rcu_cpu_stall_notifiers= [KNL] + Provide RCU CPU stall notifiers, but see the + warnings in the RCU_CPU_STALL_NOTIFIER Kconfig + option's help text. TL;DR: You almost certainly + do not want rcupdate.rcu_cpu_stall_notifiers. + rcupdate.rcu_cpu_stall_suppress= [KNL] Suppress RCU CPU stall warning messages. @@ -5025,6 +5402,17 @@ rcupdate.rcu_cpu_stall_timeout to be used (after conversion from seconds to milliseconds). + rcupdate.rcu_cpu_stall_cputime= [KNL] + Provide statistics on the cputime and count of + interrupts and tasks during the sampling period. For + multiple continuous RCU stalls, all sampling periods + begin at half of the first RCU stall timeout. + + rcupdate.rcu_exp_stall_task_details= [KNL] + Print stack dumps of any tasks blocking the + current expedited RCU grace period during an + expedited RCU CPU stall warning. + rcupdate.rcu_expedited= [KNL] Use expedited grace-period primitives, for example, synchronize_rcu_expedited() instead @@ -5086,6 +5474,13 @@ number avoids disturbing real-time workloads, but lengthens grace periods. + rcupdate.rcu_task_lazy_lim= [KNL] + Number of callbacks on a given CPU that will + cancel laziness on that CPU. Use -1 to disable + cancellation of laziness, but be advised that + doing so increases the danger of OOM due to + callback flooding. + rcupdate.rcu_task_stall_info= [KNL] Set initial timeout in jiffies for RCU task stall informational messages, which give some indication @@ -5115,6 +5510,29 @@ A change in value does not take effect until the beginning of the next grace period. + rcupdate.rcu_tasks_lazy_ms= [KNL] + Set timeout in milliseconds RCU Tasks asynchronous + callback batching for call_rcu_tasks(). + A negative value will take the default. A value + 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 + call_rcu_tasks_trace(). A negative value + will take the default. A value of zero will + disable batching. Batching is always disabled + for synchronize_rcu_tasks_trace(). + rcupdate.rcu_self_test= [KNL] Run the RCU early boot self tests @@ -5123,7 +5541,7 @@ Run specified binary instead of /init from the ramdisk, used for early userspace startup. See initrd. - rdrand= [X86] + rdrand= [X86,EARLY] force - Override the decision by the kernel to hide the advertisement of RDRAND support (this affects certain AMD processors because of buggy BIOS @@ -5133,7 +5551,7 @@ rdt= [HW,X86,RDT] Turn on/off individual RDT features. List is: cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, - mba. + mba, smba, bmec. E.g. to turn on cmt and turn off mba use: rdt=cmt,!mba @@ -5157,6 +5575,12 @@ test until boot completes in order to avoid interference. + refscale.lookup_instances= [KNL] + Number of data elements to use for the forms of + SLAB_TYPESAFE_BY_RCU testing. A negative number + is negated and multiplied by nr_cpu_ids, while + zero specifies nr_cpu_ids. + refscale.loops= [KNL] Set the number of loops over the synchronization primitive under test. Increasing this number @@ -5196,6 +5620,13 @@ print every Nth verbose statement, where N is the value specified. + regulator_ignore_unused + [REGULATOR] + Prevents regulator framework from disabling regulators + that are unused, due no driver claiming them. This may + be useful for debug and development, but should not be + needed on a platform with proper driver support. + relax_domain_level= [KNL, SMP] Set scheduler's default relax_domain_level. See Documentation/admin-guide/cgroup-v1/cpusets.rst. @@ -5206,7 +5637,7 @@ them. If <base> is less than 0x10000, the region is assumed to be I/O ports; otherwise it is memory. - reservetop= [X86-32] + reservetop= [X86-32,EARLY] Format: nn[KMG] Reserves a hole at the top of the kernel virtual address space. @@ -5232,26 +5663,40 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). - retain_initrd [RAM] Keep initrd memory after extraction + retain_initrd [RAM] Keep initrd memory after extraction. After boot, it will + be accessible via /sys/firmware/initrd. retbleed= [X86] Control mitigation of RETBleed (Arbitrary Speculative Code Execution with Return Instructions) vulnerability. + AMD-based UNRET and IBPB mitigations alone do not stop + sibling threads from influencing the predictions of other + sibling threads. For that reason, STIBP is used on pro- + cessors that support it, and mitigate SMT on processors + that don't. + off - no mitigation auto - automatically select a migitation auto,nosmt - automatically select a mitigation, disabling SMT if necessary for the full mitigation (only on Zen1 and older without STIBP). - ibpb - mitigate short speculation windows on - basic block boundaries too. Safe, highest - perf impact. - unret - force enable untrained return thunks, - only effective on AMD f15h-f17h - based systems. - unret,nosmt - like unret, will disable SMT when STIBP - is not available. + ibpb - On AMD, mitigate short speculation + windows on basic block boundaries too. + Safe, highest perf impact. It also + enables STIBP if present. Not suitable + on Intel. + ibpb,nosmt - Like "ibpb" above but will disable SMT + when STIBP is not available. This is + the alternative for systems which do not + have STIBP. + unret - Force enable untrained return thunks, + only effective on AMD f15h-f17h based + systems. + unret,nosmt - Like unret, but will disable SMT when STIBP + is not available. This is the alternative for + systems which do not have STIBP. Selecting 'auto' will choose a mitigation method at run time according to the CPU. @@ -5277,20 +5722,35 @@ [KNL] Disable ring 3 MONITOR/MWAIT feature on supported CPUs. + riscv_isa_fallback [RISCV,EARLY] + When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit + falling back to detecting extension support by parsing + "riscv,isa" property on devicetree systems when the + replacement properties are not found. See the Kconfig + entry for RISCV_ISA_FALLBACK. + ro [KNL] Mount root device read-only on boot - rodata= [KNL] + rodata= [KNL,EARLY] on Mark read-only kernel memory as read-only (default). off Leave read-only kernel memory writable for debugging. + full Mark read-only kernel memory and aliases as read-only + [arm64] rockchip.usb_uart + [EARLY] Enable the uart passthrough on the designated usb port on Rockchip SoCs. When active, the signals of the debug-uart get routed to the D+ and D- pins of the usb port and the regular usb controller gets disabled. root= [KNL] Root filesystem - See name_to_dev_t comment in init/do_mounts.c. + Usually this a 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 + ramdisk, "nfs" and "cifs" for root on a network file + system, or "mtd" and "ubi" for mounting from raw flash. rootdelay= [KNL] Delay (in seconds) to pause before attempting to mount the root filesystem @@ -5303,6 +5763,10 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). + rootwait= [KNL] Maximum time (in seconds) to wait for root device + to show up before attempting to mount the root + filesystem. + rproc_mem=nn[KMG][@address] [KNL,ARM,CMA] Remoteproc physical memory block. Memory area to be used by remote processor image, @@ -5315,9 +5779,10 @@ s390_iommu= [HW,S390] Set s390 IOTLB flushing mode strict - With strict flushing every unmap operation will result in - an IOTLB flush. Default is lazy flushing before reuse, - which is faster. + With strict flushing every unmap operation will result + in an IOTLB flush. Default is lazy flushing before + reuse, which is faster. Deprecated, equivalent to + iommu.strict=1. s390_iommu_aperture= [KNL,S390] Specifies the size of the per device DMA address space @@ -5334,7 +5799,7 @@ sa1100ir [NET] See drivers/net/irda/sa1100_ir.c. - sched_verbose [KNL] Enables verbose scheduler debug messages. + sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages. schedstats= [KNL,X86] Enable or disable scheduled statistics. Allowed values are enable and disable. This feature @@ -5449,7 +5914,7 @@ non-zero "wait" parameter. See weight_single and weight_many. - skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate + 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. Format: { "0" | "1" } @@ -5469,82 +5934,77 @@ 1 -- enable. Default value is 1. - apparmor= [APPARMOR] Disable or enable AppArmor at boot time - Format: { "0" | "1" } - See security/apparmor/Kconfig help text - 0 -- disable. - 1 -- enable. - Default value is set via kernel config option. - serialnumber [BUGS=X86-32] - sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst + sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst shapers= [NET] Maximal number of shapers. + show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller + Limit apic dumping. The parameter defines the maximal + number of local apics being dumped. Also it is possible + to set it to "all" by meaning -- no limit here. + Format: { 1 (default) | 2 | ... | all }. + The parameter valid if only apic=debug or + apic=verbose is specified. + Example: apic=debug show_lapic=all + simeth= [IA-64] simscsi= - slram= [HW,MTD] - - slab_merge [MM] - Enable merging of slabs with similar size when the - kernel is built without CONFIG_SLAB_MERGE_DEFAULT. - - slab_nomerge [MM] - Disable merging of slabs with similar size. May be - necessary if there is some reason to distinguish - allocs to different slabs, especially in hardened - environments where the risk of heap overflows and - layout control by attackers can usually be - frustrated by disabling merging. This will reduce - most of the exposure of a heap attack to a single - cache (risks via metadata attacks are mostly - unchanged). Debug options disable merging on their - own. - For more information see Documentation/vm/slub.rst. - - slab_max_order= [MM, SLAB] - Determines the maximum allowed order for slabs. - A high setting may cause OOMs due to memory - fragmentation. Defaults to 1 for systems with - more than 32MB of RAM, 0 otherwise. - - slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] - Enabling slub_debug allows one to determine the + slab_debug[=options[,slabs][;[options[,slabs]]...] [MM] + Enabling slab_debug allows one to determine the culprit if slab objects become corrupted. Enabling - slub_debug can create guard zones around objects and + slab_debug can create guard zones around objects and may poison objects when not in use. Also tracks the last alloc / free. For more information see - Documentation/vm/slub.rst. + Documentation/mm/slub.rst. + (slub_debug legacy name also accepted for now) - slub_max_order= [MM, SLUB] + slab_max_order= [MM] Determines the maximum allowed order for slabs. A high setting may cause OOMs due to memory fragmentation. For more information see - Documentation/vm/slub.rst. + Documentation/mm/slub.rst. + (slub_max_order legacy name also accepted for now) - slub_min_objects= [MM, SLUB] + slab_merge [MM] + Enable merging of slabs with similar size when the + kernel is built without CONFIG_SLAB_MERGE_DEFAULT. + (slub_merge legacy name also accepted for now) + + slab_min_objects= [MM] The minimum number of objects per slab. SLUB will - increase the slab order up to slub_max_order to + increase the slab order up to slab_max_order to generate a sufficiently large slab able to contain the number of objects indicated. The higher the number of objects the smaller the overhead of tracking slabs and the less frequently locks need to be acquired. - For more information see Documentation/vm/slub.rst. + For more information see Documentation/mm/slub.rst. + (slub_min_objects legacy name also accepted for now) - slub_min_order= [MM, SLUB] + slab_min_order= [MM] Determines the minimum page order for slabs. Must be - lower than slub_max_order. - For more information see Documentation/vm/slub.rst. + lower or equal to slab_max_order. For more information see + Documentation/mm/slub.rst. + (slub_min_order legacy name also accepted for now) - slub_merge [MM, SLUB] - Same with slab_merge. + slab_nomerge [MM] + Disable merging of slabs with similar size. May be + necessary if there is some reason to distinguish + allocs to different slabs, especially in hardened + environments where the risk of heap overflows and + layout control by attackers can usually be + frustrated by disabling merging. This will reduce + most of the exposure of a heap attack to a single + cache (risks via metadata attacks are mostly + unchanged). Debug options disable merging on their + own. + For more information see Documentation/mm/slub.rst. + (slub_nomerge legacy name also accepted for now) - slub_nomerge [MM, SLUB] - Same with slab_nomerge. This is supported for legacy. - See slab_nomerge for more information. + slram= [HW,MTD] smart2= [HW] Format: <io1>[,<io2>[,...,<io8>]] @@ -5560,6 +6020,13 @@ This feature may be more efficiently disabled using the csdlock_debug- kernel parameter. + smp.panic_on_ipistall= [KNL] + If a csd_lock_timeout extends for more than + the specified number of milliseconds, panic the + system. By default, let CSD-lock acquisition + take as long as they take. Specifying 300,000 + for this value provides a 5-minute timeout. + smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port smsc-ircc2.ircc_sir= [HW] SIR base I/O port @@ -5571,10 +6038,10 @@ 1: Fast pin select (default) 2: ATC IRMode - smt= [KNL,S390] Set the maximum number of threads (logical - CPUs) to use per physical CPU on systems capable of - symmetric multithreading (SMT). Will be capped to the - actual hardware limit. + smt= [KNL,MIPS,S390,EARLY] Set the maximum number of threads + (logical CPUs) to use per physical CPU on systems + capable of symmetric multithreading (SMT). Will + be capped to the actual hardware limit. Format: <integer> Default: -1 (no limit) @@ -5596,7 +6063,7 @@ sonypi.*= [HW] Sony Programmable I/O Control Device driver See Documentation/admin-guide/laptops/sonypi.rst - spectre_v2= [X86] Control mitigation of Spectre variant 2 + spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. The default operation protects the kernel from user space attacks. @@ -5611,8 +6078,8 @@ Selecting 'on' will, and 'auto' may, choose a mitigation method at run time according to the CPU, the available microcode, the setting of the - CONFIG_RETPOLINE configuration option, and the - compiler with which the kernel was built. + CONFIG_MITIGATION_RETPOLINE configuration option, + and the compiler with which the kernel was built. Selecting 'on' will also enable the mitigation against user space to user space task attacks. @@ -5626,9 +6093,9 @@ retpoline,generic - Retpolines retpoline,lfence - LFENCE; indirect branch retpoline,amd - alias for retpoline,lfence - eibrs - enhanced IBRS - eibrs,retpoline - enhanced IBRS + Retpolines - eibrs,lfence - enhanced IBRS + LFENCE + eibrs - Enhanced/Auto IBRS + eibrs,retpoline - Enhanced/Auto IBRS + Retpolines + eibrs,lfence - Enhanced/Auto IBRS + LFENCE ibrs - use IBRS to protect kernel Not specifying this option is equivalent to @@ -5675,8 +6142,19 @@ Not specifying this option is equivalent to spectre_v2_user=auto. + spec_rstack_overflow= + [X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs + + off - Disable mitigation + microcode - Enable microcode mitigation only + safe-ret - Enable sw-only safe RET mitigation (default) + ibpb - Enable mitigation by issuing IBPB on + kernel entry + ibpb-vmexit - Issue IBPB only on VMEXIT + (cloud-specific mitigation) + spec_store_bypass_disable= - [HW] Control Speculative Store Bypass (SSB) Disable mitigation + [HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation (Speculative Store Bypass vulnerability) Certain CPUs are vulnerable to an exploit against a @@ -5772,7 +6250,7 @@ #DB exception for bus lock is triggered only when CPL > 0. - srbds= [X86,INTEL] + srbds= [X86,INTEL,EARLY] Control the Special Register Buffer Data Sampling (SRBDS) mitigation. @@ -5859,7 +6337,7 @@ srcutree.convert_to_big must have the 0x10 bit set for contention-based conversions to occur. - ssbd= [ARM64,HW] + ssbd= [ARM64,HW,EARLY] Speculative Store Bypass Disable control On CPUs that are vulnerable to the Speculative @@ -5883,7 +6361,7 @@ growing up) the main stack are reserved for no other mapping. Default value is 256 pages. - stack_depot_disable= [KNL] + stack_depot_disable= [KNL,EARLY] Setting this to true through kernel command line will disable the stack depot thereby saving the static memory consumed by the stack hash table. By default this is set @@ -5922,6 +6400,16 @@ be used to filter out binaries which have not yet been made aware of AT_MINSIGSTKSZ. + stress_hpt [PPC,EARLY] + Limits the number of kernel HPT entries in the hash + page table to increase the rate of hash page table + faults on kernel addresses. + + stress_slb [PPC,EARLY] + Limits the number of kernel SLB entries, and flushes + them frequently to increase the rate of SLB faults + on kernel addresses. + sunrpc.min_resvport= sunrpc.max_resvport= [NFS,SUNRPC] @@ -5977,20 +6465,17 @@ This parameter controls use of the Protected Execution Facility on pSeries. - swapaccount= [KNL] - Format: [0|1] - Enable accounting of swap in memory resource - controller if no parameter or 1 is given or disable - it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) - - swiotlb= [ARM,IA-64,PPC,MIPS,X86] - Format: { <int> | force | noforce } + swiotlb= [ARM,IA-64,PPC,MIPS,X86,EARLY] + Format: { <int> [,<int>] | force | noforce } <int> -- Number of I/O TLB slabs + <int> -- Second integer after comma. Number of swiotlb + areas with their own lock. Will be rounded up + to a power of 2. force -- force using of bounce buffers even if they wouldn't be automatically used by the kernel noforce -- Never use bounce buffers (for debugging) - switches= [HW,M68k] + switches= [HW,M68k,EARLY] sysctl.*= [KNL] Set a sysctl parameter, right before loading the init @@ -6001,15 +6486,6 @@ later by a loaded module cannot be set this way. Example: sysctl.vm.swappiness=40 - sysfs.deprecated=0|1 [KNL] - Enable/disable old style sysfs layout for old udev - on older distributions. When this option is enabled - very new udev will not work anymore. When this option - is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) - in older udev will not work anymore. - Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in - the kernel configuration. - sysrq_always_enabled [KNL] Ignore sysrq setting - this boot parameter will @@ -6045,10 +6521,6 @@ -1: disable all critical trip points in all thermal zones <degrees C>: override all critical trip points - thermal.nocrt= [HW,ACPI] - Set to disable actions on ACPI thermal zone - critical and hot trip points. - thermal.off= [HW,ACPI] 1: disable ACPI thermal control @@ -6062,11 +6534,11 @@ <deci-seconds>: poll all this frequency 0: no polling (default) - threadirqs [KNL] + threadirqs [KNL,EARLY] Force threading of all interrupt handlers except those marked explicitly IRQF_NO_THREAD. - topology= [S390] + topology= [S390,EARLY] Format: {off | on} Specify if the kernel should make use of the cpu topology information if the hardware supports this. @@ -6110,6 +6582,13 @@ This will guarantee that all the other pcrs are saved. + tpm_tis.interrupts= [HW,TPM] + Enable interrupts for the MMIO based physical layer + for the FIFO interface. By default it is set to false + (0). For more information about TPM hardware interfaces + defined by Trusted Computing Group (TCG) see + https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/ + tp_printk [FTRACE] Have the tracepoints sent to printk as well as the tracing ring buffer. This is useful for early boot up @@ -6172,13 +6651,33 @@ comma-separated list of trace events to enable. See also Documentation/trace/events.rst + trace_instance=[instance-info] + [FTRACE] Create a ring buffer instance early in boot up. + This will be listed in: + + /sys/kernel/tracing/instances + + Events can be enabled at the time the instance is created + via: + + trace_instance=<name>,<system1>:<event1>,<system2>:<event2> + + Note, the "<system*>:" portion is optional if the event is + unique. + + trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall + + will enable the "sched_switch" event (note, the "sched:" is optional, and + the same thing would happen if it was left off). The irq_handler_entry + event, and all events under the "initcall" system. + trace_options=[option-list] [FTRACE] Enable or disable tracer options at boot. The option-list is a comma delimited list of options that can be enabled or disabled just as if you were to echo the option name into - /sys/kernel/debug/tracing/trace_options + /sys/kernel/tracing/trace_options For example, to enable stacktrace option (to dump the stack trace of each event), add to the command line: @@ -6188,11 +6687,30 @@ See also Documentation/trace/ftrace.rst "trace options" section. + trace_trigger=[trigger-list] + [FTRACE] Add a event trigger on specific events. + Set a trigger on top of a specific event, with an optional + filter. + + The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..." + Where more than one trigger may be specified that are comma deliminated. + + For example: + + trace_trigger="sched_switch.stacktrace if prev_state == 2" + + The above will enable the "stacktrace" trigger on the "sched_switch" + event but only trigger it if the "prev_state" of the "sched_switch" + event is "2" (TASK_UNINTERUPTIBLE). + + See also "Event triggers" in Documentation/trace/events.rst + + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can be enabled again by echoing '1' into the "tracing_on" - file located in /sys/kernel/debug/tracing/ + file located in /sys/kernel/tracing/ This option is useful, as it disables the trace before the WARNING dump is called, which prevents the trace to @@ -6250,8 +6768,18 @@ in situations with strict latency requirements (where interruptions from clocksource watchdog are not acceptable). - - tsc_early_khz= [X86] Skip early TSC calibration and use the given + [x86] recalibrate: force recalibration against a HW timer + (HPET or PM timer) on systems whose TSC frequency was + obtained from HW or FW using either an MSR or CPUID(0x15). + Warn if the difference is more than 500 ppm. + [x86] watchdog: Use TSC as the watchdog clocksource with + which to check other HW timers (HPET or PM timer), but + only on systems where TSC has been deemed trustworthy. + This will be suppressed by an earlier tsc=nowatchdog and + can be overridden by a later tsc=nowatchdog. A console + message will flag any such suppression or overriding. + + tsc_early_khz= [X86,EARLY] Skip early TSC calibration and use the given value instead. Useful when the early TSC frequency discovery procedure is not reliable, such as on overclocked systems with CPUID.16h support and partial CPUID.15h support. @@ -6286,7 +6814,7 @@ See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst for more details. - tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async + tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async Abort (TAA) vulnerability. Similar to Micro-architectural Data Sampling (MDS) @@ -6352,9 +6880,15 @@ unknown_nmi_panic [X86] Cause panic on unknown NMI. + unwind_debug [X86-64,EARLY] + Enable unwinder debug output. This can be + useful for debugging certain unwinder error + conditions, including corrupt stacks and + bad/missing unwinder metadata. + usbcore.authorized_default= [USB] Default USB device authorization: - (default -1 = authorized except for wireless USB, + (default -1 = authorized (same as 1), 0 = not authorized, 1 = authorized, 2 = authorized if device connected to internal port) @@ -6452,6 +6986,9 @@ pause after every control message); o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra delay after resetting its port); + p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT + (Reduce timeout of the SET_ADDRESS + request from 5000 ms to 500 ms); Example: quirks=0781:5580:bk,0a5c:5834:gij usbhid.mousepoll= @@ -6533,7 +7070,7 @@ Example: user_debug=31 userpte= - [X86] Flags controlling user PTE allocations. + [X86,EARLY] Flags controlling user PTE allocations. nohigh = do not allocate PTE pages in HIGHMEM regardless of setting @@ -6562,7 +7099,7 @@ vector= [IA-64,SMP] vector=percpu: enable percpu vector domain - video= [FB] Frame buffer configuration + video= [FB,EARLY] Frame buffer configuration See Documentation/fb/modedb.rst. video.brightness_switch_enabled= [ACPI] @@ -6592,7 +7129,7 @@ Can be used multiple times for multiple devices. vga= [BOOT,X86-32] Select a particular video mode - See Documentation/x86/boot.rst and + See Documentation/arch/x86/boot.rst and Documentation/admin-guide/svga.rst. Use vga=ask for menu. This is actually a boot loader parameter; the value is @@ -6610,13 +7147,13 @@ P Enable page structure init time poisoning - Disable all of the above options - vmalloc=nn[KMG] [KNL,BOOT] 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. + 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. - vmcp_cma=nn[MG] [KNL,S390] + vmcp_cma=nn[MG] [KNL,S390,EARLY] Sets the memory size reserved for contiguous memory allocations for the vmcp device driver. @@ -6629,7 +7166,7 @@ vmpoff= [KNL,S390] Perform z/VM CP command after power off. Format: <command> - vsyscall= [X86-64] + vsyscall= [X86-64,EARLY] Controls the behavior of vsyscalls (i.e. calls to fixed addresses of 0xffffffffff600x00 from legacy code). Most statically-linked binaries and older @@ -6637,11 +7174,11 @@ functions are at fixed addresses, they make nice targets for exploits that can control RIP. - emulate [default] Vsyscalls turn into traps and are - emulated reasonably safely. The vsyscall - page is readable. + emulate Vsyscalls turn into traps and are emulated + reasonably safely. The vsyscall page is + readable. - xonly Vsyscalls turn into traps and are + xonly [default] Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall page is not readable. @@ -6711,6 +7248,13 @@ disables both lockup detectors. Default is 10 seconds. + workqueue.unbound_cpus= + [KNL,SMP] Specify to constrain one or some CPUs + to use in unbound workqueues. + Format: <cpu-list> + By default, all online CPUs are available for + unbound workqueues. + workqueue.watchdog_thresh= If CONFIG_WQ_WATCHDOG is configured, workqueue can warn stall conditions and dump internal state to @@ -6720,14 +7264,26 @@ it can be updated at runtime by writing to the corresponding sysfs file. - workqueue.disable_numa - By default, all work items queued to unbound - workqueues are affine to the NUMA nodes they're - issued on, which results in better behavior in - general. If NUMA affinity needs to be disabled for - whatever reason, this option can be used. Note - that this also can be controlled per-workqueue for - workqueues visible under /sys/bus/workqueue/. + workqueue.cpu_intensive_thresh_us= + Per-cpu work items which run for longer than this + threshold are automatically considered CPU intensive + and excluded from concurrency management to prevent + them from noticeably delaying other per-cpu work + items. Default is 10000 (10ms). + + If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel + will report the work functions which violate this + threshold repeatedly. They are likely good + candidates for using WQ_UNBOUND workqueues instead. + + workqueue.cpu_intensive_warning_thresh=<uint> + If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel + will report the work functions which violate the + intensive_threshold_us repeatedly. In order to prevent + spurious warnings, start printing only after a work + function has violated this threshold number of times. + + The default is 4 times. 0 disables the warning. workqueue.power_efficient Per-cpu workqueues are generally preferred because @@ -6744,6 +7300,18 @@ The default value of this parameter is determined by the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. + workqueue.default_affinity_scope= + Select the default affinity scope to use for unbound + workqueues. Can be one of "cpu", "smt", "cache", + "numa" and "system". Default is "cache". For more + information, see the Affinity Scopes section in + Documentation/core-api/workqueue.rst. + + 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. + workqueue.debug_force_rr_cpu Workqueue used to implicitly guarantee that work items queued without explicit CPU specified are put @@ -6755,7 +7323,13 @@ When enabled, memory and cache locality will be impacted. - x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of + writecombine= [LOONGARCH,EARLY] Control the MAT (Memory Access + Type) of ioremap_wc(). + + on - Enable writecombine, use WUC for ioremap_wc() + off - Disable writecombine, use SUC for ioremap_wc() + + x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of default x2apic cluster mode on platforms supporting x2apic. @@ -6766,7 +7340,7 @@ save/restore/migration must be enabled to handle larger domains. - xen_emul_unplug= [HW,X86,XEN] + xen_emul_unplug= [HW,X86,XEN,EARLY] Unplug Xen emulated devices Format: [unplug0,][unplug1] ide-disks -- unplug primary master IDE devices @@ -6778,11 +7352,17 @@ the unplug protocol never -- do not unplug even if version check succeeds - xen_legacy_crash [X86,XEN] + xen_legacy_crash [X86,XEN,EARLY] Crash from Xen panic notifier, without executing late panic() code such as dumping handler. - xen_nopvspin [X86,XEN] + 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. @@ -6794,7 +7374,7 @@ has equivalent effect for XEN platform. xen_no_vector_callback - [KNL,X86,XEN] Disable the vector callback for Xen + [KNL,X86,XEN,EARLY] Disable the vector callback for Xen event channel interrupts. xen_scrub_pages= [XEN] @@ -6803,7 +7383,7 @@ with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. - xen_timer_slop= [X86-64,XEN] + xen_timer_slop= [X86-64,XEN,EARLY] Set the timer slop (in nanoseconds) for the virtual Xen timers (default is 100000). This adjusts the minimum delta of virtualized Xen timers, where lower values @@ -6832,16 +7412,6 @@ fairer and the number of possible event channels is much higher. Default is on (use fifo events). - nopv= [X86,XEN,KVM,HYPER_V,VMWARE] - Disables the PV optimizations forcing the guest to run - as generic guest with no PV drivers. Currently support - XEN HVM, KVM, HYPER_V and VMWARE guest. - - nopvspin [X86,XEN,KVM] - Disables the qspinlock slow path using PV optimizations - which allow the hypervisor to 'idle' the guest on lock - contention. - xirc2ps_cs= [NET,PCMCIA] Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] @@ -6866,7 +7436,7 @@ host controller quirks. Meaning of each bit can be consulted in header drivers/usb/host/xhci.h. - xmon [PPC] + xmon [PPC,EARLY] Format: { early | on | rw | ro | off } Controls if xmon debugger is enabled. Default is off. Passing only "xmon" is equivalent to "xmon=early". @@ -6884,3 +7454,4 @@ memory, and other data can't be written using xmon commands. off xmon is disabled. + |