diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 516 |
1 files changed, 325 insertions, 191 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2d67cdfbf9c9..ef9f80b1ddde 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -400,6 +400,12 @@ arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension support + arm64.nosve [ARM64] Unconditionally disable Scalable Vector + Extension support + + arm64.nosme [ARM64] Unconditionally disable Scalable Matrix + Extension support + ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse @@ -461,6 +467,12 @@ Format: <io>,<irq>,<mode> See header of drivers/net/hamradio/baycom_ser_hdx.c. + bert_disable [ACPI] + Disable BERT OS support on buggy BIOSes. + + bgrt_disable [ACPI][X86] + 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 @@ -476,12 +488,6 @@ See Documentation/admin-guide/bootconfig.rst - bert_disable [ACPI] - Disable BERT OS support on buggy BIOSes. - - bgrt_disable [ACPI][X86] - Disable BGRT to avoid flickering OEM logo. - bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) bttv.radio= Most important insmod options are available as kernel args too. @@ -550,7 +556,7 @@ nosocket -- Disable socket memory accounting. nokmem -- Disable kernel memory accounting. - checkreqprot [SELINUX] Set initial checkreqprot flag value. + checkreqprot= [SELINUX] Set initial checkreqprot flag value. Format: { "0" | "1" } See security/selinux/Kconfig help text. 0 -- check protection applied by kernel (includes @@ -563,6 +569,25 @@ cio_ignore= [S390] See Documentation/s390/common_io.rst for details. + + clearcpuid=X[,X...] [X86] + Disable CPUID feature X for the kernel. See + arch/x86/include/asm/cpufeatures.h for the valid bit + numbers X. Note the Linux-specific bits are not necessarily + stable over kernel options, but the vendor-specific + ones should be. + X can also be a string as appearing in the flags: line + in /proc/cpuinfo which does not have the above + instability issue. However, not all features have names + in /proc/cpuinfo. + Note that using this option will taint your kernel. + Also note that user programs calling CPUID directly + or using the feature without checking anything + will still see it. This just prevents it from + being used by the kernel or shown in /proc/cpuinfo. + Also note the kernel might malfunction if you disable + some critical bits. + clk_ignore_unused [CLK] Prevents the clock framework from automatically gating @@ -631,24 +656,6 @@ Defaults to zero when built as a module and to 10 seconds when built into the kernel. - clearcpuid=X[,X...] [X86] - Disable CPUID feature X for the kernel. See - arch/x86/include/asm/cpufeatures.h for the valid bit - numbers X. Note the Linux-specific bits are not necessarily - stable over kernel options, but the vendor-specific - ones should be. - X can also be a string as appearing in the flags: line - in /proc/cpuinfo which does not have the above - instability issue. However, not all features have names - in /proc/cpuinfo. - Note that using this option will taint your kernel. - Also note that user programs calling CPUID directly - or using the feature without checking anything - will still see it. This just prevents it from - being used by the kernel or shown in /proc/cpuinfo. - Also note the kernel might malfunction if you disable - some critical bits. - cma=nn[MG]@[start[MG][-end[MG]]] [KNL,CMA] Sets the size of kernel global memory area for @@ -770,6 +777,24 @@ 0: default value, disable debugging 1: enable debugging at boot time + cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver + 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 @@ -790,9 +815,13 @@ on every CPU online, such as boot, and resume from suspend. Default: 10000 - cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver - Format: - <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] + crash_kexec_post_notifiers + Run kdump after running panic-notifiers and dumping + kmsg. This only for the users who doubt kdump always + succeeds in any situation. + Note that this also increases risks of kdump failure, + because some panic notifiers can make the crashed + kernel more unstable. crashkernel=size[KMG][@offset[KMG]] [KNL] Using kexec, Linux can switch to a 'crash kernel' @@ -956,11 +985,15 @@ [KNL] Debugging option to set a timeout in seconds for deferred probe to give up waiting on dependencies to probe. Only specific dependencies (subsystems or - drivers) that have opted in will be ignored. A timeout of 0 - will timeout at the end of initcalls. This option will also + drivers) that have opted in will be ignored. A timeout + of 0 will timeout at the end of initcalls. If the time + out hasn't expired, it'll be restarted by each + successful driver registration. This option will also dump out devices still on the deferred probe list after retrying. + delayacct [KNL] Enable per-task delay accounting + dell_smm_hwmon.ignore_dmi= [HW] Continue probing hardware even if DMI data indicates that the driver is running on unsupported @@ -1014,17 +1047,6 @@ disable= [IPV6] See Documentation/networking/ipv6.rst. - hardened_usercopy= - [KNL] Under CONFIG_HARDENED_USERCOPY, whether - hardening is enabled for this boot. Hardened - usercopy checking is used to protect the kernel - from reading or writing beyond known memory - allocation boundaries as a proactive defense - against bounds-checking flaws in the kernel's - copy_to_user()/copy_from_user() interface. - on Perform hardened usercopy checks (default). - off Disable hardened usercopy checks. - disable_radix [PPC] Disable RADIX MMU mode on POWER9 @@ -1087,7 +1109,10 @@ driver later using sysfs. driver_async_probe= [KNL] - List of driver names to be probed asynchronously. + List of driver names to be probed asynchronously. * + matches with all driver names. If * is specified, the + rest of the listed driver names are those that will NOT + match the *. Format: <driver_name1>,<driver_name2>... drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] @@ -1293,7 +1318,7 @@ Append ",keep" to not disable it when the real console takes over. - Only one of vga, efi, serial, or usb debug port can + Only one of vga, serial, or usb debug port can be used at a time. Currently only ttyS0 and ttyS1 may be specified by @@ -1308,7 +1333,7 @@ Interaction with the standard serial driver is not very good. - The VGA and EFI output is eventually overwritten by + The VGA output is eventually overwritten by the real console. The xen option can only be used in Xen domains. @@ -1327,17 +1352,6 @@ force: enforce the use of EDAC to report H/W event. default: on. - ekgdboc= [X86,KGDB] Allow early kernel console debugging - ekgdboc=kbd - - This is designed to be used in conjunction with - the boot argument: earlyprintk=vga - - This parameter works in place of the kgdboc parameter - but can only be used if the backing tty is available - very early in the boot process. For early debugging - via a serial port see kgdboc_earlycon instead. - edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} @@ -1399,6 +1413,17 @@ eisa_irq_edge= [PARISC,HW] See header of drivers/parisc/eisa.c. + ekgdboc= [X86,KGDB] Allow early kernel console debugging + Format: ekgdboc=kbd + + This is designed to be used in conjunction with + the boot argument: earlyprintk=vga + + This parameter works in place of the kgdboc parameter + but can only be used if the backing tty is available + very early in the boot process. For early debugging + via a serial port see kgdboc_earlycon instead. + elanfreq= [X86-32] See comment before function elanfreq_setup() in arch/x86/kernel/cpu/cpufreq/elanfreq.c. @@ -1420,7 +1445,7 @@ (in particular on some ATI chipsets). The kernel tries to set a reasonable default. - enforcing [SELINUX] Set initial enforcing status. + enforcing= [SELINUX] Set initial enforcing status. Format: {"0" | "1"} See security/selinux/Kconfig help text. 0 -- permissive (log only, no denials). @@ -1597,6 +1622,17 @@ Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. Default: 1024 + hardened_usercopy= + [KNL] Under CONFIG_HARDENED_USERCOPY, whether + hardening is enabled for this boot. Hardened + usercopy checking is used to protect the kernel + from reading or writing beyond known memory + allocation boundaries as a proactive defense + against bounds-checking flaws in the kernel's + copy_to_user()/copy_from_user() interface. + on Perform hardened usercopy checks (default). + off Disable hardened usercopy checks. + hardlockup_all_cpu_backtrace= [KNL] Should the hard-lockup detector generate backtraces on all cpus. @@ -1617,6 +1653,15 @@ corresponding firmware-first mode error processing logic will be disabled. + hibernate= [HIBERNATION] + noresume Don't check if there's a hibernation image + present during boot. + nocompress Don't compress/decompress hibernation images. + no Disable hibernation and resume. + protect_image Turn on image protection during restoration + (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 size of <nn>. This works even on boxes that have no highmem otherwise. This also works to reduce highmem @@ -1639,16 +1684,6 @@ hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET registers. Default set by CONFIG_HPET_MMAP_DEFAULT. - hugetlb_cma= [HW,CMA] 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) - <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] - - Reserve a CMA area of given size and allocate gigantic - hugepages using the CMA allocator. If enabled, the - boot-time allocation of gigantic hugepages is skipped. - hugepages= [HW] Number of HugeTLB pages to allocate at boot. If this follows hugepagesz (below), it specifies the number of pages of hugepagesz to be allocated. @@ -1670,17 +1705,27 @@ Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] + hugetlb_cma= [HW,CMA] 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) + <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] + + Reserve a CMA area of given size and allocate gigantic + hugepages using the CMA allocator. If enabled, the + boot-time allocation of gigantic hugepages is skipped. + hugetlb_free_vmemmap= - [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP + [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP enabled. Allows heavy hugetlb users to free up some more memory (7 * PAGE_SIZE for each 2MB hugetlb page). - Format: { on | off (default) } + Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) } - on: enable the feature - off: disable the feature + [oO][Nn]/Y/y/1: enable the feature + [oO][Ff]/N/n/0: disable the feature - Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y, + Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, the default is on. This is not compatible with memory_hotplug.memmap_on_memory. @@ -1769,26 +1814,6 @@ icn= [HW,ISDN] Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] - ide-core.nodma= [HW] (E)IDE subsystem - Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc - .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr - .cdrom .chs .ignore_cable are additional options - See Documentation/ide/ide.rst. - - ide-generic.probe-mask= [HW] (E)IDE subsystem - Format: <int> - Probe mask for legacy ISA IDE ports. Depending on - platform up to 6 ports are supported, enabled by - setting corresponding bits in the mask to 1. The - default value is 0x0, which has a special meaning. - On systems that have PCI, it triggers scanning the - PCI bus for the first and the second port, which - are then probed. On systems without PCI the value - of 0x0 enables probing the two first ports as if it - was 0x3. - - ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem - Claim all unknown PCI IDE storage controllers. idle= [X86] Format: idle=poll, idle=halt, idle=nomwait @@ -2399,8 +2424,7 @@ 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). @@ -2450,7 +2474,6 @@ protected: nVHE-based mode with support for guests whose state is kept private from the host. - Not valid if the kernel is running in EL2. Defaults to VHE/nVHE based on hardware support. Setting mode to "protected" will disable kexec and hibernation @@ -2722,8 +2745,6 @@ If there are multiple matching configurations changing the same attribute, the last one is used. - memblock=debug [KNL] Enable memblock debug messages. - load_ramdisk= [RAM] [Deprecated] lockd.nlm_grace_period=P [NFS] Assign grace period. @@ -2865,7 +2886,7 @@ different yeeloong laptops. Example: machtype=lemote-yeeloong-2f-7inch - max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater + 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 @@ -2965,6 +2986,8 @@ mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel memory. + memblock=debug [KNL] Enable memblock debug messages. + memchunk=nn[KMG] [KNL,SH] Allow user to override the default size for per-device physically contiguous DMA buffers. @@ -3085,7 +3108,7 @@ mem_encrypt=on: Activate SME mem_encrypt=off: Do not activate SME - Refer to Documentation/virt/kvm/amd-memory-encryption.rst + Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst for details on when memory encryption can be activated. mem_sleep_default= [SUSPEND] Default system suspend mode: @@ -3108,7 +3131,7 @@ mga= [HW,DRM] - min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this + min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this physical address is ignored. mini2440= [ARM,HW,KNL] @@ -3143,7 +3166,7 @@ improves system performance, but it may also expose users to several CPU vulnerabilities. Equivalent to: nopti [X86,PPC] - kpti=0 [ARM64] + if nokaslr then kpti=0 [ARM64] nospectre_v1 [X86,PPC] nobp=0 [S390] nospectre_v2 [X86,PPC,S390,ARM64] @@ -3157,6 +3180,8 @@ srbds=off [X86,INTEL] no_entry_flush [PPC] no_uaccess_flush [PPC] + mmio_stale_data=off [X86] + retbleed=off [X86] Exceptions: This does not have any effect on @@ -3178,6 +3203,8 @@ Equivalent to: l1tf=flush,nosmt [X86] mds=full,nosmt [X86] tsx_async_abort=full,nosmt [X86] + mmio_stale_data=full,nosmt [X86] + retbleed=auto,nosmt [X86] mminit_loglevel= [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this @@ -3187,6 +3214,40 @@ log everything. Information is printed at KERN_DEBUG so loglevel=8 may also need to be specified. + mmio_stale_data= + [X86,INTEL] Control mitigation for the Processor + MMIO Stale Data vulnerabilities. + + Processor MMIO Stale Data is a class of + vulnerabilities that may expose data after an MMIO + operation. Exposed data could originate or end in + the same CPU buffers as affected by MDS and TAA. + Therefore, similar to MDS and TAA, the mitigation + is to clear the affected CPU buffers. + + This parameter controls the mitigation. The + options are: + + full - Enable mitigation on vulnerable CPUs + + full,nosmt - Enable mitigation and disable SMT on + vulnerable CPUs. + + off - Unconditionally disable mitigation + + On MDS or TAA affected machines, + mmio_stale_data=off can be prevented by an active + MDS or TAA mitigation as these vulnerabilities are + mitigated with the same mechanism so in order to + disable this mitigation, you need to specify + mds=off and tsx_async_abort=off too. + + Not specifying this option is equivalent to + mmio_stale_data=full. + + For details see: + Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst + module.sig_enforce [KNL] When CONFIG_MODULE_SIG is set, this means that modules without (valid) signatures will fail to load. @@ -3233,20 +3294,6 @@ mtdparts= [MTD] See drivers/mtd/parsers/cmdlinepart.c - multitce=off [PPC] This parameter disables the use of the pSeries - firmware feature for updating multiple TCE entries - at a time. - - onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration - - Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] - - boundary - index of last SLC block on Flex-OneNAND. - The remaining blocks are configured as MLC blocks. - lock - Configure if Flex-OneNAND boundary should be locked. - Once locked, the boundary cannot be changed. - 1 indicates lock status, 0 indicates unlock status. - mtdset= [ARM] ARM/S3C2412 JIVE boot control @@ -3273,6 +3320,10 @@ Used for mtrr cleanup. It is spare mtrr entries number. Set to 2 or more if your graphical card needs more. + multitce=off [PPC] This parameter disables the use of the pSeries + firmware feature for updating multiple TCE entries + at a time. + n2= [NET] SDL Inc. RISCom/N2 synchronous serial card netdev= [NET] Network devices parameters @@ -3282,6 +3333,11 @@ This usage is only documented in each driver source file if at all. + netpoll.carrier_timeout= + [NET] Specifies amount of time (in seconds) that + netpoll should wait for a carrier. By default netpoll + waits 4 seconds. + nf_conntrack.acct= [NETFILTER] Enable connection tracking flow accounting 0 to disable accounting @@ -3432,11 +3488,6 @@ These settings can be accessed at runtime via the nmi_watchdog and hardlockup_panic sysctls. - netpoll.carrier_timeout= - [NET] Specifies amount of time (in seconds) that - netpoll should wait for a carrier. By default netpoll - waits 4 seconds. - no387 [BUGS=X86-32] Tells the kernel to use the 387 maths emulation library even if a 387 maths coprocessor is present. @@ -3491,8 +3542,6 @@ nocache [ARM] - delayacct [KNL] Enable per-task delay accounting - nodsp [SH] Disable hardware DSP at boot time. noefi Disable EFI runtime services support. @@ -3617,6 +3666,9 @@ just as if they had also been called out in the rcu_nocbs= boot parameter. + 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 @@ -3691,11 +3743,6 @@ noreplace-smp [X86-32,SMP] Don't replace SMP instructions with UP alternatives - nordrand [X86] Disable kernel use of the RDRAND and - RDSEED instructions even if they are supported - by the processor. RDRAND and RDSEED are still - available to user space applications. - noresume [SWSUSP] Disables resume and restores original swap space. @@ -3721,20 +3768,6 @@ nox2apic [X86-64,APIC] Do not enable x2APIC mode. - 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. - nps_mtm_hs_ctr= [KNL,ARC] This parameter sets the maximum duration, in cycles, each HW thread of the CTOP can run @@ -3787,6 +3820,16 @@ For example, to override I2C bus2: omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 + onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration + + Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] + + boundary - index of last SLC block on Flex-OneNAND. + The remaining blocks are configured as MLC blocks. + lock - Configure if Flex-OneNAND boundary should be locked. + 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 process, but there is a small probability of deadlocking the machine. @@ -3857,14 +3900,6 @@ panic_on_warn panic() instead of WARN(). Useful to cause kdump on a WARN(). - crash_kexec_post_notifiers - Run kdump after running panic-notifiers and dumping - kmsg. This only for the users who doubt kdump always - succeeds in any situation. - Note that this also increases risks of kdump failure, - because some panic notifiers can make the crashed - kernel more unstable. - parkbd.port= [HW] Parallel port number the keyboard adapter is connected to, default is 0. Format: <parport#> @@ -4109,6 +4144,15 @@ please report a bug. nocrs [X86] Ignore PCI host bridge windows from ACPI. If you need to use this, please report a bug. + use_e820 [X86] Use E820 reservations to exclude parts of + PCI host bridge windows. This is a workaround + for BIOS defects in host bridge _CRS methods. + If you need to use this, please report a bug to + <linux-pci@vger.kernel.org>. + no_e820 [X86] Ignore E820 reservations for PCI host + bridge windows. This is the default on modern + hardware. If you need to use this, please report + a bug to <linux-pci@vger.kernel.org>. routeirq Do IRQ routing for all PCI devices. This is normally done in pci_enable_device(), so this option is a temporary workaround @@ -4518,6 +4562,9 @@ no-callback mode from boot but the mode may be toggled at runtime via cpusets. + Note that this argument takes precedence over + the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. + rcu_nocb_poll [KNL] Rather than requiring that offloaded CPUs (specified by rcu_nocbs= above) explicitly @@ -4627,6 +4674,34 @@ 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 + otherwise be caused by callback floods through + use of the ->nocb_bypass list. However, in the + common non-flooded case, RCU queues directly to + the main ->cblist in order to avoid the extra + overhead of the ->nocb_bypass list and its lock. + But if there are too many callbacks queued during + a single jiffy, RCU pre-queues the callbacks into + 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 @@ -5156,17 +5231,32 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). - hibernate= [HIBERNATION] - noresume Don't check if there's a hibernation image - present during boot. - nocompress Don't compress/decompress hibernation images. - no Disable hibernation and resume. - protect_image Turn on image protection during restoration - (that will set all pages holding image data - during restoration read-only). - retain_initrd [RAM] Keep initrd memory after extraction + retbleed= [X86] Control mitigation of RETBleed (Arbitrary + Speculative Code Execution with Return Instructions) + vulnerability. + + 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. + + Selecting 'auto' will choose a mitigation method at run + time according to the CPU. + + Not specifying this option is equivalent to retbleed=auto. + rfkill.default_state= 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, etc. communication is blocked by default. @@ -5480,7 +5570,7 @@ 1: Fast pin select (default) 2: ATC IRMode - smt [KNL,S390] Set the maximum number of threads (logical + 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. @@ -5538,6 +5628,7 @@ eibrs - enhanced IBRS eibrs,retpoline - enhanced IBRS + Retpolines eibrs,lfence - enhanced IBRS + LFENCE + ibrs - use IBRS to protect kernel Not specifying this option is equivalent to spectre_v2=auto. @@ -5741,6 +5832,24 @@ expediting. Set to zero to disable automatic expediting. + srcutree.srcu_max_nodelay [KNL] + Specifies the number of no-delay instances + per jiffy for which the SRCU grace period + worker thread will be rescheduled with zero + delay. Beyond this limit, worker thread will + be rescheduled with a sleep delay of one jiffy. + + srcutree.srcu_max_nodelay_phase [KNL] + Specifies the per-grace-period phase, number of + non-sleeping polls of readers. Beyond this limit, + grace period worker thread will be rescheduled + with a sleep delay of one jiffy, between each + rescan of the readers, for a grace period phase. + + srcutree.srcu_retry_check_delay [KNL] + Specifies number of microseconds of non-sleeping + delay between each non-sleeping poll of readers. + srcutree.small_contention_lim [KNL] Specifies the number of update-side contention events per jiffy will be tolerated before @@ -5867,8 +5976,9 @@ This parameter controls use of the Protected Execution Facility on pSeries. - swapaccount=[0|1] - [KNL] Enable accounting of swap in memory resource + 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) @@ -5914,7 +6024,8 @@ tdfx= [HW,DRM] - test_suspend= [SUSPEND][,N] + test_suspend= [SUSPEND] + Format: { "mem" | "standby" | "freeze" }[,N] Specify "mem" (for Suspend-to-RAM) or "standby" (for standby suspend) or "freeze" (for suspend type freeze) as the system sleep state during system startup with @@ -5998,32 +6109,7 @@ This will guarantee that all the other pcrs are saved. - trace_buf_size=nn[KMG] - [FTRACE] will set tracing buffer size on each cpu. - - trace_event=[event-list] - [FTRACE] Set and start specified trace events in order - to facilitate early boot debugging. The event-list is a - comma-separated list of trace events to enable. See - also Documentation/trace/events.rst - - 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 - - For example, to enable stacktrace option (to dump the - stack trace of each event), add to the command line: - - trace_options=stacktrace - - See also Documentation/trace/ftrace.rst "trace options" - section. - - tp_printk[FTRACE] + tp_printk [FTRACE] Have the tracepoints sent to printk as well as the tracing ring buffer. This is useful for early boot up where the system hangs or reboots and does not give the @@ -6045,7 +6131,7 @@ frequency tracepoints such as irq or sched, can cause the system to live lock. - tp_printk_stop_on_boot[FTRACE] + tp_printk_stop_on_boot [FTRACE] When tp_printk (above) is set, it can cause a lot of noise on the console. It may be useful to only include the printing of events during boot up, as user space may @@ -6054,6 +6140,53 @@ This command line option will stop the printing of events to console at the late_initcall_sync() time frame. + trace_buf_size=nn[KMG] + [FTRACE] will set tracing buffer size on each cpu. + + trace_clock= [FTRACE] Set the clock used for tracing events + at boot up. + local - Use the per CPU time stamp counter + (converted into nanoseconds). Fast, but + depending on the architecture, may not be + in sync between CPUs. + global - Event time stamps are synchronize across + CPUs. May be slower than the local clock, + but better for some race conditions. + counter - Simple counting of events (1, 2, ..) + note, some counts may be skipped due to the + infrastructure grabbing the clock more than + once per event. + uptime - Use jiffies as the time stamp. + perf - Use the same clock that perf uses. + mono - Use ktime_get_mono_fast_ns() for time stamps. + mono_raw - Use ktime_get_raw_fast_ns() for time + stamps. + boot - Use ktime_get_boot_fast_ns() for time stamps. + Architectures may add more clocks. See + Documentation/trace/ftrace.rst for more details. + + trace_event=[event-list] + [FTRACE] Set and start specified trace events in order + to facilitate early boot debugging. The event-list is a + comma-separated list of trace events to enable. See + also Documentation/trace/events.rst + + 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 + + For example, to enable stacktrace option (to dump the + stack trace of each event), add to the command line: + + trace_options=stacktrace + + See also Documentation/trace/ftrace.rst "trace options" + section. + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can @@ -6405,7 +6538,7 @@ HIGHMEM regardless of setting of CONFIG_HIGHPTE. - vdso= [X86,SH] + vdso= [X86,SH,SPARC] On X86_32, this is an alias for vdso32=. Otherwise: vdso=1: enable VDSO (the default) @@ -6431,11 +6564,12 @@ video= [FB] Frame buffer configuration See Documentation/fb/modedb.rst. - video.brightness_switch_enabled= [0,1] + video.brightness_switch_enabled= [ACPI] + Format: [0|1] If set to 1, on receiving an ACPI notify event generated by hotkey, video driver will adjust brightness level and then send out the event to user space through - the allocated input device; If set to 0, video driver + the allocated input device. If set to 0, video driver will only send out the event without touching backlight brightness level. default: 1 |