diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 117 |
1 files changed, 97 insertions, 20 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index f5a27f067db9..b7ccaa2ea867 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -724,6 +724,12 @@ hvc<n> Use the hypervisor console device <n>. This is for both Xen and PowerPC hypervisors. + { null | "" } + Use to disable console output, i.e., to have kernel + console messages discarded. + This must be the only console= parameter used on the + kernel command line. + If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instance console=brl,ttyS0 @@ -944,6 +950,30 @@ dump out devices still on the deferred probe list after retrying. + dell_smm_hwmon.ignore_dmi= + [HW] Continue probing hardware even if DMI data + indicates that the driver is running on unsupported + hardware. + + dell_smm_hwmon.force= + [HW] Activate driver even if SMM BIOS signature does + not match list of supported models and enable otherwise + blacklisted features. + + dell_smm_hwmon.power_status= + [HW] Report power status in /proc/i8k + (disabled by default). + + dell_smm_hwmon.restricted= + [HW] Allow controlling fans only if SYS_ADMIN + capability is set. + + dell_smm_hwmon.fan_mult= + [HW] Factor to multiply fan speed with. + + dell_smm_hwmon.fan_max= + [HW] Maximum configurable fan speed. + dfltcc= [HW,S390] Format: { on | off | def_only | inf_only | always } on: s390 zlib hardware support for compression on @@ -1435,6 +1465,14 @@ as early as possible in order to facilitate early boot debugging. + ftrace_boot_snapshot + [FTRACE] On boot up, a snapshot will be taken of the + ftrace ring buffer that can be read at: + /sys/kernel/tracing/snapshot. + This is useful if you need tracing information from kernel + boot up that is likely to be overridden by user space + start up functionality. + ftrace_dump_on_oops[=orig_cpu] [FTRACE] will dump the trace buffers on oops. If no parameter is passed, ftrace will dump @@ -1625,7 +1663,7 @@ [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP enabled. Allows heavy hugetlb users to free up some more - memory (6 * PAGE_SIZE for each 2MB hugetlb page). + memory (7 * PAGE_SIZE for each 2MB hugetlb page). Format: { on | off (default) } on: enable the feature @@ -1703,17 +1741,6 @@ i810= [HW,DRM] - i8k.ignore_dmi [HW] Continue probing hardware even if DMI data - indicates that the driver is running on unsupported - hardware. - i8k.force [HW] Activate i8k driver even if SMM BIOS signature - does not match list of supported models. - i8k.power_status - [HW] Report power status in /proc/i8k - (disabled by default) - i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN - capability is set. - i915.invert_brightness= [DRM] Invert the sense of the variable that is used to set the brightness of the panel backlight. Normally a @@ -2339,13 +2366,35 @@ kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. Default is 0 (don't ignore, but inject #GP) + kvm.eager_page_split= + [KVM,X86] Controls whether or not KVM will try to + proactively split all huge pages during dirty logging. + Eager page splitting reduces interruptions to vCPU + execution by eliminating the write-protection faults + and MMU lock contention that would otherwise be + required to split huge pages lazily. + + VM workloads that rarely perform writes or that write + only to a small region of VM memory may benefit from + disabling eager page splitting to allow huge pages to + still be used for reads. + + The behavior of eager page splitting depends on whether + KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If + disabled, all huge pages in a memslot will be eagerly + split when dirty logging is enabled on that memslot. If + enabled, eager page splitting will be performed during + 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. + + Default is Y (on). + kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. Default is false (don't support). - kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit - KVM MMU at runtime. - Default is 0 (off) - kvm.nx_huge_pages= [KVM] Controls the software workaround for the X86_BUG_ITLB_MULTIHIT bug. @@ -2827,6 +2876,9 @@ For details see: Documentation/admin-guide/hw-vuln/mds.rst + mem=nn[KMG] [HEXAGON] 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: @@ -2834,6 +2886,13 @@ 2 when the kernel is not able to see the whole system memory; 3 memory that lies after 'mem=' boundary is excluded from the hypervisor, then assigned to KVM guests. + 4 to limit the memory available for kdump kernel. + + [ARC,MICROBLAZE] - the limit applies only to low memory, + high memory is not affected. + + [ARM64] - only limits memory covered by the linear + mapping. The NOMAP regions are not affected. [X86] Work as limiting max address. Use together with memmap= to avoid physical address space collisions. @@ -2844,6 +2903,14 @@ in above case 3, memory may need be hot added after boot if system memory of hypervisor is not sufficient. + mem=nn[KMG]@ss[KMG] + [ARM,MIPS] - 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 + multiple mem= parameters on the command line. + mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel memory. @@ -3485,8 +3552,7 @@ difficult since unequal pointers can no longer be compared. However, if this command-line option is specified, then all normal pointers will have their true - value printed. Pointers printed via %pK may still be - hashed. This option should only be specified when + value printed. This option should only be specified when debugging the kernel. Please do not use on production kernels. @@ -3726,6 +3792,11 @@ 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() Format: <hex>[,nousertaint] @@ -4504,6 +4575,8 @@ (the least-favored priority). Otherwise, when RCU_BOOST is not set, valid values are 0-99 and the default is zero (non-realtime operation). + When RCU_NOCB_CPU is set, also adjust the + priority of NOCB callback kthreads. rcutree.rcu_nocb_gp_stride= [KNL] Set the number of NOCB callback kthreads in @@ -5361,8 +5434,12 @@ Specific mitigations can also be selected manually: retpoline - replace indirect branches - retpoline,generic - google's original retpoline - retpoline,amd - AMD-specific minimal thunk + 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 Not specifying this option is equivalent to spectre_v2=auto. |