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Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 569 |
1 files changed, 439 insertions, 130 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..068ccc29b48d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -13,7 +13,7 @@ For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" are available - See also Documentation/power/runtime_pm.txt, pci=noacpi + See also Documentation/power/runtime_pm.rst, pci=noacpi acpi_apic_instance= [ACPI, IOAPIC] Format: <int> @@ -53,7 +53,7 @@ ACPI_DEBUG_PRINT statements, e.g., ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... The debug_level mask defaults to "info". See - Documentation/acpi/debug.txt for more information about + Documentation/firmware-guide/acpi/debug.rst for more information about debug layers and levels. Enable processor driver info messages: @@ -223,7 +223,7 @@ acpi_sleep= [HW,ACPI] Sleep options Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering, nonvs, sci_force_enable, nobl } - See Documentation/power/video.txt for information on + See Documentation/power/video.rst for information on s3_bios and s3_mode. s3_beep is for debugging; it makes the PC's speaker beep as soon as the kernel's real-mode entry point is called. @@ -430,15 +430,13 @@ blkdevparts= Manual partition parsing of block device(s) for embedded devices based on command line input. - See Documentation/block/cmdline-partition.txt + 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). Format: integer - bootmem_debug [KNL] Enable bootmem allocator debug messages. - bert_disable [ACPI] Disable BERT OS support on buggy BIOSes. @@ -478,7 +476,7 @@ others). ccw_timeout_log [S390] - See Documentation/s390/CommonIO for details. + See Documentation/s390/common_io.rst for details. cgroup_disable= [KNL] Disable a particular controller Format: {name of the controller(s) to disable} @@ -516,7 +514,7 @@ /selinux/checkreqprot. cio_ignore= [S390] - See Documentation/s390/CommonIO for details. + See Documentation/s390/common_io.rst for details. clk_ignore_unused [CLK] Prevents the clock framework from automatically gating @@ -704,15 +702,18 @@ 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. Check - Documentation/kdump/kdump.txt for further details. + 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. + See Documentation/admin-guide/kdump/kdump.rst for further details. crashkernel=range1:size1[,range2:size2,...][@offset] [KNL] Same as above, but depends on the memory in the running system. The syntax of range is start-[end] where start and end are both a memory unit (amount[KMG]). See also - Documentation/kdump/kdump.txt for an example. + Documentation/admin-guide/kdump/kdump.rst for an example. crashkernel=size[KMG],high [KNL, x86_64] range could be above 4G. Allow kernel @@ -802,12 +803,12 @@ tracking down these problems. debug_pagealloc= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this - parameter enables the feature at boot time. In - default, it is disabled. We can avoid allocating huge - chunk of memory for debug pagealloc if we don't enable - it at boot time and the system will work mostly same - with the kernel built without CONFIG_DEBUG_PAGEALLOC. + [KNL] 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. + Note: to get most of debug_pagealloc error reports, it's + useful to also enable the page_owner functionality. on: enable the feature debugpat [X86] Enable PAT debugging @@ -859,6 +860,10 @@ disable_radix [PPC] Disable RADIX MMU mode on POWER9 + 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 @@ -929,7 +934,7 @@ 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/EDID/HOWTO.txt. An EDID + available in Documentation/driver-api/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 @@ -960,7 +965,7 @@ for details. nompx [X86] Disables Intel Memory Protection Extensions. - See Documentation/x86/intel_mpx.txt for more + See Documentation/x86/intel_mpx.rst for more information about the feature. nopku [X86] Disable Memory Protection Keys CPU feature found @@ -976,12 +981,10 @@ earlycon= [KNL] Output early console device and options. - [ARM64] The early console is determined by the - stdout-path property in device tree's chosen node, - or determined by the ACPI SPCR table. - - [X86] When used with no options the early console is - determined by the ACPI SPCR table. + When used with no options, the early console is + determined by stdout-path property in device tree's + chosen node or the ACPI SPCR table if supported by + the platform. cdns,<addr>[,options] Start an early, polled-mode console on a Cadence @@ -1043,6 +1046,10 @@ specified address. The serial port must already be setup and configured. Options are not yet supported. + sbi + Use RISC-V SBI (Supervisor Binary Interface) for early + console. + smh Use ARM semihosting calls for early console. s3c2410,<addr> @@ -1089,6 +1096,12 @@ the framebuffer, pass the 'ram' option so that it is mapped with the correct attributes. + linflex,<addr> + Use early console provided by Freescale LinFlex UART + serial driver for NXP S32V234 SoCs. A valid base + address must be provided, and the serial port must + already be setup and configured. + earlyprintk= [X86,SH,ARM,M68k,S390] earlyprintk=vga earlyprintk=sclp @@ -1151,7 +1164,8 @@ Format: {"off" | "on" | "skip[mbr]"} efi= [EFI] - Format: { "old_map", "nochunk", "noruntime", "debug" } + Format: { "old_map", "nochunk", "noruntime", "debug", + "nosoftreserve" } old_map [X86-64]: switch to the old ioremap-based EFI runtime services mapping. 32-bit still uses this one by default. @@ -1160,6 +1174,12 @@ firmware implementations. noruntime : disable EFI runtime services support debug: enable misc debug output + nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) + attribute may cause the kernel to reserve the + memory range for a memory mapping driver to + claim. Specify efi=nosoftreserve to disable this + reservation and treat the memory by its base type + (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). efi_no_storage_paranoia [EFI; X86] Using this parameter you can use more than 50% of @@ -1172,21 +1192,27 @@ updating original EFI memory map. Region of memory which aa attribute is added to is from ss to ss+nn. + If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) attribute is added to range 0x100000000-0x180000000 and 0x10a0000000-0x1120000000. + If efi_fake_mem=8G@9G:0x40000 is specified, the + EFI_MEMORY_SP(0x40000) attribute is added to + range 0x240000000-0x43fffffff. + Using this parameter you can do debugging of EFI memmap - related feature. For example, you can do debugging of + related features. For example, you can do debugging of Address Range Mirroring feature even if your box - doesn't support it. + doesn't support it, or mark specific memory as + "soft reserved". efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT that is to be dynamically loaded by Linux. If there are multiple variables with the same name but with different vendor GUIDs, all of them will be loaded. See - Documentation/acpi/ssdt-overlays.txt for details. + Documentation/admin-guide/acpi/ssdt-overlays.rst for details. eisa_irq_edge= [PARISC,HW] @@ -1196,17 +1222,11 @@ See comment before function elanfreq_setup() in arch/x86/kernel/cpu/cpufreq/elanfreq.c. - elevator= [IOSCHED] - Format: { "mq-deadline" | "kyber" | "bfq" } - See Documentation/block/deadline-iosched.txt, - Documentation/block/kyber-iosched.txt and - Documentation/block/bfq-iosched.txt for details. - elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] 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/kdump/kdump.txt for details. + See Documentation/admin-guide/kdump/kdump.rst for details. enable_mtrr_cleanup [X86] The kernel tries to adjust MTRR layout from continuous @@ -1248,7 +1268,7 @@ See also Documentation/fault-injection/. floppy= [HW] - See Documentation/blockdev/floppy.txt. + See Documentation/admin-guide/blockdev/floppy.rst. force_pal_cache_flush [IA-64] Avoid check_sal_cache_flush which may hang on @@ -1385,9 +1405,6 @@ Valid parameters: "on", "off" Default: "on" - hisax= [HW,ISDN] - See Documentation/isdn/README.HiSax. - hlt [BUGS=ARM,SH] hpet= [X86-32,HPET] option to control HPET usage @@ -1504,7 +1521,7 @@ 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.txt. + See Documentation/ide/ide.rst. ide-generic.probe-mask= [HW] (E)IDE subsystem Format: <int> @@ -1585,7 +1602,7 @@ Format: { "off" | "enforce" | "fix" | "log" } default: "enforce" - ima_appraise_tcb [IMA] + ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. The builtin appraise policy appraises all files owned by uid=0. @@ -1612,8 +1629,7 @@ uid=0. The "appraise_tcb" policy appraises the integrity of - all files owned by root. (This is the equivalent - of ima_appraise_tcb.) + all files owned by root. The "secure_boot" policy appraises the integrity of files (eg. kexec kernel image, kernel modules, @@ -1671,6 +1687,15 @@ initrd= [BOOT] Specify the location of the initial ramdisk + init_on_alloc= [MM] 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. + Format: 0 | 1 + Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. + init_pkru= [x86] Specify the default memory protection keys rights register contents for all processes. 0x55555554 by default (disallow access to all but pkey 0). Can @@ -1726,6 +1751,11 @@ Note that using this option lowers the security provided by tboot because it makes the system vulnerable to DMA attacks. + nobounce [Default off] + Disable bounce buffer for unstrusted devices such as + the Thunderbolt devices. This will treat the untrusted + devices as the trusted ones, hence might expose security + risks of DMA attacks. intel_idle.max_cstate= [KNL,HW,ACPI,X86] 0 disables intel_idle and fall back on acpi_idle. @@ -1805,7 +1835,7 @@ synchronously. iommu.passthrough= - [ARM64] Configure DMA to bypass the IOMMU by default. + [ARM64, X86] Configure DMA to bypass the IOMMU by default. Format: { "0" | "1" } 0 - Use IOMMU translation for DMA. 1 - Bypass the IOMMU for DMA. @@ -1828,6 +1858,9 @@ ip= [IP_PNP] See Documentation/filesystems/nfs/nfsroot.txt. + ipcmni_extend [KNL] 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. @@ -2002,6 +2035,19 @@ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, the default is off. + kprobe_event=[probe-list] + [FTRACE] Add kprobe events and enable at boot time. + The probe-list is a semicolon delimited list of probe + definitions. Each definition is same as kprobe_events + interface, but the parameters are comma delimited. + For example, to add a kprobe event on vfs_read with + arg1 and arg2, add to the command line; + + kprobe_event=p,vfs_read,$arg1,$arg2 + + See also Documentation/trace/kprobetrace.rst "Kernel + Boot Parameter" section. + kpti= [ARM64] Control page table isolation of user and kernel address spaces. Default: enabled on cores which need mitigation. @@ -2018,6 +2064,25 @@ KVM MMU at runtime. Default is 0 (off) + kvm.nx_huge_pages= + [KVM] Controls the software workaround for the + X86_BUG_ITLB_MULTIHIT bug. + force : Always deploy workaround. + off : Never deploy workaround. + auto : Deploy workaround based on the presence of + X86_BUG_ITLB_MULTIHIT. + + Default is 'auto'. + + If the software workaround is enabled for the host, + guests do need not to enable it for nested guests. + + kvm.nx_huge_pages_recovery_ratio= + [KVM] Controls how many 4KiB pages are periodically zapped + back to huge pages. 0 disables the recovery, otherwise if + the value is N KVM will zap 1/Nth of the 4KiB pages every + minute. The default is 60. + kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. Default is 1 (enabled) @@ -2141,7 +2206,7 @@ Default is 'flush'. - For details see: Documentation/admin-guide/l1tf.rst + For details see: Documentation/admin-guide/hw-vuln/l1tf.rst l2cr= [PPC] @@ -2225,7 +2290,7 @@ memblock=debug [KNL] Enable memblock debug messages. load_ramdisk= [RAM] List of ramdisks to load from floppy - See Documentation/blockdev/ramdisk.txt. + See Documentation/admin-guide/blockdev/ramdisk.rst. lockd.nlm_grace_period=P [NFS] Assign grace period. Format: <integer> @@ -2239,6 +2304,15 @@ lockd.nlm_udpport=M [NFS] Assign UDP port. Format: <integer> + lockdown= [SECURITY] + { integrity | confidentiality } + Enable the kernel lockdown feature. If set to + integrity, kernel features that allow userland to + modify the running kernel are disabled. If set to + confidentiality, kernel features that allow userland + to extract confidential information from the kernel + are also disabled. + locktorture.nreaders_stress= [KNL] Set the number of locking read-acquisition kthreads. Defaults to being automatically set based on the @@ -2351,7 +2425,7 @@ machvec= [IA-64] Force the use of a particular machine-vector (machvec) in a generic kernel. - Example: machvec=hpzx1_swiotlb + Example: machvec=hpzx1 machtype= [Loongson] Share the same kernel image file between different yeeloong laptop. @@ -2378,7 +2452,7 @@ mce [X86-32] Machine Check Exception - mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt + mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst md= [HW] RAID subsystems devices and level See Documentation/admin-guide/md.rst. @@ -2387,6 +2461,38 @@ Format: <first>,<last> Specifies range of consoles to be captured by the MDA. + mds= [X86,INTEL] + Control mitigation for the Micro-architectural Data + Sampling (MDS) vulnerability. + + Certain CPUs are vulnerable to an exploit against CPU + internal buffers which can forward information to a + disclosure gadget under certain conditions. + + In vulnerable processors, the speculatively + forwarded data can be used in a cache side channel + attack, to access data to which the attacker does + not have direct access. + + This parameter controls the MDS mitigation. The + options are: + + full - Enable MDS mitigation on vulnerable CPUs + full,nosmt - Enable MDS mitigation and disable + SMT on vulnerable CPUs + off - Unconditionally disable MDS mitigation + + On TAA-affected machines, mds=off can be prevented by + an active TAA mitigation as both vulnerabilities are + mitigated with the same mechanism so in order to disable + this mitigation, you need to specify tsx_async_abort=off + too. + + Not specifying this option is equivalent to + mds=full. + + For details see: Documentation/admin-guide/hw-vuln/mds.rst + mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory Amount of memory to be used when the kernel is not able to see the whole system memory or for test. @@ -2408,7 +2514,7 @@ set according to the CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config option. - See Documentation/memory-hotplug.txt. + See Documentation/admin-guide/mm/memory-hotplug.rst. memmap=exactmap [KNL,X86] Enable setting of an exact E820 memory map, as specified by the user. @@ -2497,7 +2603,7 @@ mem_encrypt=on: Activate SME mem_encrypt=off: Do not activate SME - Refer to Documentation/x86/amd-memory-encryption.txt + Refer to Documentation/virt/kvm/amd-memory-encryption.rst for details on when memory encryption can be activated. mem_sleep_default= [SUSPEND] Default system suspend mode: @@ -2544,6 +2650,50 @@ in the "bleeding edge" mini2440 support kernel at http://repo.or.cz/w/linux-2.6/mini2440.git + mitigations= + [X86,PPC,S390,ARM64] 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. + + off + Disable all optional CPU mitigations. This + improves system performance, but it may also + expose users to several CPU vulnerabilities. + Equivalent to: nopti [X86,PPC] + 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] + l1tf=off [X86] + mds=off [X86] + tsx_async_abort=off [X86] + kvm.nx_huge_pages=off [X86] + + Exceptions: + This does not have any effect on + kvm.nx_huge_pages when + kvm.nx_huge_pages=force. + + auto (default) + Mitigate all CPU vulnerabilities, but leave SMT + enabled, even if it's vulnerable. This is for + users who don't want to be surprised by SMT + getting disabled across kernel upgrades, or who + have other ways of avoiding SMT-based attacks. + Equivalent to: (default behavior) + + auto,nosmt + Mitigate all CPU vulnerabilities, disabling SMT + if needed. This is for users who always want to + be fully mitigated, even if it means losing SMT. + Equivalent to: l1tf=flush,nosmt [X86] + mds=full,nosmt [X86] + tsx_async_abort=full,nosmt [X86] + mminit_loglevel= [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this parameter allows control of the logging verbosity for @@ -2769,8 +2919,9 @@ 0 - turn hardlockup detector in nmi_watchdog off 1 - turn hardlockup detector in nmi_watchdog on When panic is specified, panic when an NMI watchdog - timeout occurs (or 'nopanic' to override the opposite - default). To disable both hard and soft lockup detectors, + timeout occurs (or 'nopanic' to not panic on an NMI + watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) + To disable both hard and soft lockup detectors, please see 'nowatchdog'. This is useful when you use a panic=... timeout and need the box quickly up again. @@ -2805,6 +2956,17 @@ /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. @@ -2839,11 +3001,11 @@ noexec=on: enable non-executable mappings (default) noexec=off: disable non-executable mappings - nosmap [X86] + nosmap [X86,PPC] Disable SMAP (Supervisor Mode Access Prevention) even if it is supported by processor. - nosmep [X86] + nosmep [X86,PPC] Disable SMEP (Supervisor Mode Execution Prevention) even if it is supported by processor. @@ -2860,7 +3022,7 @@ register save and restore. The kernel will only save legacy floating-point registers on task switch. - nohugeiomap [KNL,x86] Disable kernel huge I/O mappings. + nohugeiomap [KNL,x86,PPC] Disable kernel huge I/O mappings. nosmt [KNL,S390] Disable symmetric multithreading (SMT). Equivalent to smt=1. @@ -2869,14 +3031,14 @@ nosmt=force: Force disable SMT, cannot be undone via the sysfs control file. - nospectre_v1 [PPC] Disable mitigations for Spectre Variant 1 (bounds - check bypass). With this option data leaks are possible - in the system. + 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] Disable all mitigations for the Spectre variant 2 - (indirect branch prediction) vulnerability. System may - allow data leaks with this option, which is equivalent - to spectre_v2=off. + 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 @@ -2963,9 +3125,9 @@ [X86,PV_OPS] Disable paravirtualized VMware scheduler clock and use the default one. - no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting. - steal time is computed, but won't influence scheduler - behaviour + no-steal-acc [X86,KVM,ARM64] Disable paravirtualized steal time + accounting. steal time is computed, but won't + influence scheduler behaviour nolapic [X86-32,APIC] Do not enable or use the local APIC. @@ -3072,7 +3234,13 @@ numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 'node', 'default' can be specified This can be set from sysctl after boot. - See Documentation/sysctl/vm.txt for details. + See Documentation/admin-guide/sysctl/vm.rst for details. + + of_devlink [OF, KNL] Create device links between consumer and + supplier devices by scanning the devictree to infer the + consumer/supplier relationships. A consumer device + will not be probed until all the supplier devices have + probed successfully. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. See Documentation/debugging-via-ohci1394.txt for more @@ -3110,6 +3278,16 @@ This will also cause panics on machine check exceptions. Useful together with panic=30 to trigger a reboot. + page_alloc.shuffle= + [KNL] Boolean flag to control whether the page allocator + should randomize its free lists. The randomization may + be automatically enabled if the kernel detects it is + running on a platform with a direct-mapped memory-side + cache, and this parameter can be used to + override/disable that behavior. The state of the flag + can be read from sysfs at: + /sys/module/page_alloc/parameters/shuffle. + page_owner= [KNL] Boot-time page_owner enabling option. Storage of the information about who allocated each page is disabled in default. With this switch, @@ -3135,6 +3313,7 @@ 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 panic_on_warn panic() instead of WARN(). Useful to cause kdump on a WARN(). @@ -3185,7 +3364,7 @@ pcd. [PARIDE] See header of drivers/block/paride/pcd.c. - See also Documentation/blockdev/paride.txt. + See also Documentation/admin-guide/blockdev/paride.rst. pci=option[,option...] [PCI] various PCI subsystem options. @@ -3345,12 +3524,13 @@ specify the device is described above. If <order of align> is not specified, PAGE_SIZE is used as alignment. - PCI-PCI bridge can be specified, if resource + A PCI-PCI bridge can be specified if resource windows need to be expanded. To specify the alignment for several instances of a device, the PCI vendor, device, subvendor, and subdevice may be - specified, e.g., 4096@pci:8086:9c22:103c:198f + 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). bios: Use BIOS/firmware settings. This is the @@ -3394,6 +3574,8 @@ bridges without forcing it upstream. Note: this removes isolation between devices and may put more devices in an IOMMU group. + force_floating [S390] Force usage of floating interrupts. + nomio [S390] Do not use MIO instructions. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power Management. @@ -3427,7 +3609,7 @@ needed on a platform with proper driver support. pd. [PARIDE] - See Documentation/blockdev/paride.txt. + See Documentation/admin-guide/blockdev/paride.rst. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at boot time. @@ -3442,13 +3624,13 @@ and performance comparison. pf. [PARIDE] - See Documentation/blockdev/paride.txt. + See Documentation/admin-guide/blockdev/paride.rst. pg. [PARIDE] - See Documentation/blockdev/paride.txt. + See Documentation/admin-guide/blockdev/paride.rst. pirq= [SMP,APIC] Manual mp-table setup - See Documentation/x86/i386/IO-APIC.txt. + See Documentation/x86/i386/IO-APIC.rst. plip= [PPT,NET] Parallel port network link Format: { parport<nr> | timid | 0 } @@ -3557,7 +3739,7 @@ prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk before loading. - See Documentation/blockdev/ramdisk.txt. + See Documentation/admin-guide/blockdev/ramdisk.rst. psi= [KNL] Enable or disable pressure stall information tracking. @@ -3579,7 +3761,7 @@ pstore.backend= Specify the name of the pstore backend to use pt. [PARIDE] - See Documentation/blockdev/paride.txt. + See Documentation/admin-guide/blockdev/paride.rst. pti= [X86_64] Control Page Table Isolation of user and kernel address spaces. Disabling this feature @@ -3608,7 +3790,7 @@ See Documentation/admin-guide/md.rst. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes - See Documentation/blockdev/ramdisk.txt. + See Documentation/admin-guide/blockdev/ramdisk.rst. random.trust_cpu={on,off} [KNL] Enable or disable trusting the use of the @@ -3623,7 +3805,9 @@ see CONFIG_RAS_CEC help text. rcu_nocbs= [KNL] - The argument is a cpu list, as described above. + The argument is a cpu list, as described above, + except that the string "all" can be used to + specify every CPU on the system. In kernels built with CONFIG_RCU_NOCB_CPU=y, set the specified list of CPUs to be no-callback CPUs. @@ -3670,6 +3854,12 @@ 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. + rcutree.rcu_fanout_exact= [KNL] Disable autobalancing of the rcu_node combining tree. This is used by rcutorture, and might @@ -3720,12 +3910,13 @@ RCU_BOOST is not set, valid values are 0-99 and the default is zero (non-realtime operation). - rcutree.rcu_nocb_leader_stride= [KNL] - Set the number of NOCB kthread groups, which - defaults to the square root of the number of - CPUs. Larger numbers reduces the wakeup overhead - on the per-CPU grace-period kthreads, but increases - that same overhead on each group's leader. + 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 @@ -3930,6 +4121,10 @@ rcutorture.verbose= [KNL] Enable additional printk() statements. + rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] + Dump ftrace buffer after reporting RCU CPU + stall warning. + rcupdate.rcu_cpu_stall_suppress= [KNL] Suppress RCU CPU stall warning messages. @@ -3973,6 +4168,13 @@ Run specified binary instead of /init from the ramdisk, used for early userspace startup. See initrd. + rdrand= [X86] + force - Override the decision by the kernel to hide the + advertisement of RDRAND support (this affects + certain AMD processors because of buggy BIOS + support, specifically around the suspend/resume + path). + rdt= [HW,X86,RDT] Turn on/off individual RDT features. List is: cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, @@ -3986,7 +4188,9 @@ [[,]s[mp]#### \ [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ [[,]f[orce] - Where reboot_mode is one of warm (soft) or cold (hard) or gpio, + Where reboot_mode is one of warm (soft) or cold (hard) or gpio + (prefix with 'panic_' to set mode for panic + reboot only), reboot_type is one of bios, acpi, kbd, triple, efi, or pci, reboot_force is either force or not specified, reboot_cpu is s[mp]#### with #### being the processor @@ -3994,7 +4198,7 @@ relax_domain_level= [KNL, SMP] Set scheduler's default relax_domain_level. - See Documentation/cgroup-v1/cpusets.txt. + See Documentation/admin-guide/cgroup-v1/cpusets.rst. reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory Format: <base1>,<size1>[,<base2>,<size2>,...] @@ -4024,7 +4228,7 @@ Specify the offset from the beginning of the partition given by "resume=" at which the swap header is located, in <PAGE_SIZE> units (needed only for swap files). - See Documentation/power/swsusp-and-swap-files.txt + See Documentation/power/swsusp-and-swap-files.rst resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to read the resume files @@ -4252,7 +4456,7 @@ Format: <integer> sonypi.*= [HW] Sony Programmable I/O Control Device driver - See Documentation/laptops/sonypi.txt + See Documentation/admin-guide/laptops/sonypi.rst spectre_v2= [X86] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. @@ -4501,10 +4705,15 @@ /sys/power/pm_test). Only available when CONFIG_PM_DEBUG is set. Default value is 5. + svm= [PPC] + Format: { on | off | y | n | 1 | 0 } + This parameter controls use of the Protected + Execution Facility on pSeries. + swapaccount=[0|1] [KNL] Enable accounting of swap in memory resource controller if no parameter or 1 is given or disable - it if 0 is given (See Documentation/cgroup-v1/memory.txt) + it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) swiotlb= [ARM,IA-64,PPC,MIPS,X86] Format: { <int> | force | noforce } @@ -4579,27 +4788,6 @@ Force threading of all interrupt handlers except those marked explicitly IRQF_NO_THREAD. - tmem [KNL,XEN] - Enable the Transcendent memory driver if built-in. - - tmem.cleancache=0|1 [KNL, XEN] - Default is on (1). Disable the usage of the cleancache - API to send anonymous pages to the hypervisor. - - tmem.frontswap=0|1 [KNL, XEN] - Default is on (1). Disable the usage of the frontswap - API to send swap pages to the hypervisor. If disabled - the selfballooning and selfshrinking are force disabled. - - tmem.selfballooning=0|1 [KNL, XEN] - Default is on (1). Disable the driving of swap pages - to the hypervisor. - - tmem.selfshrinking=0|1 [KNL, XEN] - Default is on (1). Partial swapoff that immediately - transfers pages from Xen hypervisor back to the - kernel based on different criteria. - topology= [S390] Format: {off | on} Specify if the kernel should make use of the cpu @@ -4703,6 +4891,80 @@ [x86] unstable: mark the TSC clocksource as unstable, this marks the TSC unconditionally unstable at bootup and avoids any further wobbles once the TSC watchdog notices. + [x86] nowatchdog: disable clocksource watchdog. Used + in situations with strict latency requirements (where + interruptions from clocksource watchdog are not + acceptable). + + tsx= [X86] Control Transactional Synchronization + Extensions (TSX) feature in Intel processors that + support TSX control. + + This parameter controls the TSX feature. The options are: + + on - Enable TSX on the system. Although there are + mitigations for all known security vulnerabilities, + TSX has been known to be an accelerator for + several previous speculation-related CVEs, and + so there may be unknown security risks associated + with leaving it enabled. + + off - Disable TSX on the system. (Note that this + option takes effect only on newer CPUs which are + not vulnerable to MDS, i.e., have + MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get + the new IA32_TSX_CTRL MSR through a microcode + update. This new MSR allows for the reliable + deactivation of the TSX functionality.) + + auto - Disable TSX if X86_BUG_TAA is present, + otherwise enable TSX on the system. + + Not specifying this option is equivalent to tsx=off. + + See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst + for more details. + + tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async + Abort (TAA) vulnerability. + + Similar to Micro-architectural Data Sampling (MDS) + certain CPUs that support Transactional + Synchronization Extensions (TSX) are vulnerable to an + exploit against CPU internal buffers which can forward + information to a disclosure gadget under certain + conditions. + + In vulnerable processors, the speculatively forwarded + data can be used in a cache side channel attack, to + access data to which the attacker does not have direct + access. + + This parameter controls the TAA mitigation. The + options are: + + full - Enable TAA mitigation on vulnerable CPUs + if TSX is enabled. + + full,nosmt - Enable TAA mitigation and disable SMT on + vulnerable CPUs. If TSX is disabled, SMT + is not disabled because CPU is not + vulnerable to cross-thread TAA attacks. + off - Unconditionally disable TAA mitigation + + On MDS-affected machines, tsx_async_abort=off can be + prevented by an active MDS mitigation as both vulnerabilities + are mitigated with the same mechanism so in order to disable + this mitigation, you need to specify mds=off too. + + Not specifying this option is equivalent to + tsx_async_abort=full. On CPUs which are MDS affected + and deploy MDS mitigation, TAA mitigation is not + required and doesn't provide any additional + mitigation. + + For details see: + Documentation/admin-guide/hw-vuln/tsx_async_abort.rst turbografx.map[2|3]= [HW,JOY] TurboGraFX parallel port interface @@ -4854,13 +5116,13 @@ Flags is a set of characters, each corresponding to a common usb-storage quirk flag as follows: a = SANE_SENSE (collect more than 18 bytes - of sense data); + of sense data, not on uas); b = BAD_SENSE (don't collect more than 18 - bytes of sense data); + bytes of sense data, not on uas); c = FIX_CAPACITY (decrease the reported device capacity by one sector); d = NO_READ_DISC_INFO (don't use - READ_DISC_INFO command); + READ_DISC_INFO command, not on uas); e = NO_READ_CAPACITY_16 (don't use READ_CAPACITY_16 command); f = NO_REPORT_OPCODES (don't use report opcodes @@ -4875,17 +5137,18 @@ j = NO_REPORT_LUNS (don't use report luns command, uas only); l = NOT_LOCKABLE (don't try to lock and - unlock ejectable media); + unlock ejectable media, not on uas); m = MAX_SECTORS_64 (don't transfer more - than 64 sectors = 32 KB at a time); + than 64 sectors = 32 KB at a time, + not on uas); n = INITIAL_READ10 (force a retry of the - initial READ(10) command); + initial READ(10) command, not on uas); o = CAPACITY_OK (accept the capacity - reported by the device); + reported by the device, not on uas); p = WRITE_CACHE (the device cache is ON - by default); + by default, not on uas); r = IGNORE_RESIDUE (the device reports - bogus residue values); + bogus residue values, not on uas); s = SINGLE_LUN (the device has only one Logical Unit); t = NO_ATA_1X (don't allow ATA(12) and ATA(16) @@ -4894,7 +5157,8 @@ w = NO_WP_DETECT (don't test whether the medium is write-protected). y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE - even if the device claims no cache) + even if the device claims no cache, + not on uas) Example: quirks=0419:aaf5:rl,0421:0433:rc user_debug= [KNL,ARM] @@ -4938,7 +5202,7 @@ vector=percpu: enable percpu vector domain video= [FB] Frame buffer configuration - See Documentation/fb/modedb.txt. + See Documentation/fb/modedb.rst. video.brightness_switch_enabled= [0,1] If set to 1, on receiving an ACPI notify event @@ -4966,8 +5230,8 @@ Can be used multiple times for multiple devices. vga= [BOOT,X86-32] Select a particular video mode - See Documentation/x86/boot.txt and - Documentation/svga.txt. + See Documentation/x86/boot.rst and + Documentation/admin-guide/svga.rst. Use vga=ask for menu. This is actually a boot loader parameter; the value is passed to the kernel using a special protocol. @@ -5012,13 +5276,12 @@ targets for exploits that can control RIP. emulate [default] Vsyscalls turn into traps and are - emulated reasonably safely. + emulated reasonably safely. The vsyscall + page is readable. - native Vsyscalls are native syscall instructions. - This is a little bit faster than trapping - and makes a few dynamic recompilers work - better than they would in emulation mode. - It also makes exploits much easier to write. + xonly Vsyscalls turn into traps and are + emulated reasonably safely. The vsyscall + page is not readable. none Vsyscalls don't work at all. This makes them quite hard to use for exploits but @@ -5074,7 +5337,7 @@ Default: 3 = cyan. watchdog timers [HW,WDT] For information on watchdog timers, - see Documentation/watchdog/watchdog-parameters.txt + see Documentation/watchdog/watchdog-parameters.rst or other driver-specific files in the Documentation/watchdog/ directory. @@ -5159,6 +5422,10 @@ the unplug protocol never -- do not unplug even if version check succeeds + xen_legacy_crash [X86,XEN] + Crash from Xen panic notifier, without executing late + panic() code such as dumping handler. + xen_nopvspin [X86,XEN] Disables the ticketlock slowpath using Xen PV optimizations. @@ -5166,6 +5433,8 @@ xen_nopv [X86] Disables the PV optimizations forcing the HVM guest to run as generic HVM guest with no PV drivers. + This option is obsoleted by the "nopv" option, which + has equivalent effect for XEN platform. xen_scrub_pages= [XEN] Boolean option to control scrubbing pages before giving them back @@ -5173,11 +5442,51 @@ 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] + 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 + improve timer resolution at the expense of processing + more timer interrupts. + + 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. + xirc2ps_cs= [NET,PCMCIA] Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] + xive= [PPC] + By default on POWER9 and above, the kernel will + natively use the XIVE interrupt controller. This option + allows the fallback firmware mode to be used: + + off Fallback to firmware control of XIVE interrupt + controller on both pseries and powernv + platforms. Only useful on POWER9 and above. + xhci-hcd.quirks [USB,KNL] A hex value specifying bitmask with supplemental xhci host controller quirks. Meaning of each bit can be consulted in header drivers/usb/host/xhci.h. + + xmon [PPC] + Format: { early | on | rw | ro | off } + Controls if xmon debugger is enabled. Default is off. + Passing only "xmon" is equivalent to "xmon=early". + early Call xmon as early as possible on boot; xmon + debugger is called from setup_arch(). + on xmon debugger hooks will be installed so xmon + is only called on a kernel crash. Default mode, + i.e. either "ro" or "rw" mode, is controlled + with CONFIG_XMON_DEFAULT_RO_MODE. + rw xmon debugger hooks will be installed so xmon + is called only on a kernel crash, mode is write, + meaning SPR registers, memory and, other data + can be written using xmon commands. + ro same as "rw" option above but SPR registers, + memory, and other data can't be written using + xmon commands. + off xmon is disabled. |