| kernel-parameters.txt (6f5bf947bab06f37ff931c359fd5770c4d9cbf87) | kernel-parameters.txt (e34e0131fea1b0f63c2105a1958c94af2ee90f4d) |
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| 1 accept_memory= [MM] 2 Format: { eager | lazy } 3 default: lazy 4 By default, unaccepted memory is accepted lazily to 5 avoid prolonged boot times. The lazy option will add 6 some runtime overhead until all memory is eventually 7 accepted. In most cases the overhead is negligible. 8 For some workloads or for debugging purposes --- 1393 unchanged lines hidden (view full) --- 1402 earlyprintk= [X86,SH,ARM,M68k,S390,UM,EARLY] 1403 earlyprintk=vga 1404 earlyprintk=sclp 1405 earlyprintk=xen 1406 earlyprintk=serial[,ttySn[,baudrate]] 1407 earlyprintk=serial[,0x...[,baudrate]] 1408 earlyprintk=ttySn[,baudrate] 1409 earlyprintk=dbgp[debugController#] | 1 accept_memory= [MM] 2 Format: { eager | lazy } 3 default: lazy 4 By default, unaccepted memory is accepted lazily to 5 avoid prolonged boot times. The lazy option will add 6 some runtime overhead until all memory is eventually 7 accepted. In most cases the overhead is negligible. 8 For some workloads or for debugging purposes --- 1393 unchanged lines hidden (view full) --- 1402 earlyprintk= [X86,SH,ARM,M68k,S390,UM,EARLY] 1403 earlyprintk=vga 1404 earlyprintk=sclp 1405 earlyprintk=xen 1406 earlyprintk=serial[,ttySn[,baudrate]] 1407 earlyprintk=serial[,0x...[,baudrate]] 1408 earlyprintk=ttySn[,baudrate] 1409 earlyprintk=dbgp[debugController#] |
| 1410 earlyprintk=mmio32,membase[,{nocfg|baudrate}] | |
| 1411 earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}] 1412 earlyprintk=xdbc[xhciController#] 1413 earlyprintk=bios | 1410 earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}] 1411 earlyprintk=xdbc[xhciController#] 1412 earlyprintk=bios |
| 1413 earlyprintk=mmio,membase[,{nocfg|baudrate}] |
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| 1414 1415 earlyprintk is useful when the kernel crashes before 1416 the normal console is initialized. It is not enabled by 1417 default because it has some cosmetic problems. 1418 | 1414 1415 earlyprintk is useful when the kernel crashes before 1416 the normal console is initialized. It is not enabled by 1417 default because it has some cosmetic problems. 1418 |
| 1419 Only 32-bit memory addresses are supported for "mmio" 1420 and "pciserial" devices. 1421 |
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| 1419 Use "nocfg" to skip UART configuration, assume 1420 BIOS/firmware has configured UART correctly. 1421 1422 Append ",keep" to not disable it when the real console 1423 takes over. 1424 1425 Only one of vga, serial, or usb debug port can 1426 be used at a time. --- 770 unchanged lines hidden (view full) --- 2197 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 2198 Format: <bufsize> 2199 Set hashing buffer size. Default: 4k. 2200 2201 ahash performance varies for different chunk sizes on 2202 different crypto accelerators. This option can be used 2203 to achieve best performance for particular HW. 2204 | 1422 Use "nocfg" to skip UART configuration, assume 1423 BIOS/firmware has configured UART correctly. 1424 1425 Append ",keep" to not disable it when the real console 1426 takes over. 1427 1428 Only one of vga, serial, or usb debug port can 1429 be used at a time. --- 770 unchanged lines hidden (view full) --- 2200 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size 2201 Format: <bufsize> 2202 Set hashing buffer size. Default: 4k. 2203 2204 ahash performance varies for different chunk sizes on 2205 different crypto accelerators. This option can be used 2206 to achieve best performance for particular HW. 2207 |
| 2205 indirect_target_selection= [X86,Intel] Mitigation control for Indirect 2206 Target Selection(ITS) bug in Intel CPUs. Updated 2207 microcode is also required for a fix in IBPB. 2208 2209 on: Enable mitigation (default). 2210 off: Disable mitigation. 2211 force: Force the ITS bug and deploy default 2212 mitigation. 2213 vmexit: Only deploy mitigation if CPU is affected by 2214 guest/host isolation part of ITS. 2215 stuff: Deploy RSB-fill mitigation when retpoline is 2216 also deployed. Otherwise, deploy the default 2217 mitigation. 2218 2219 For details see: 2220 Documentation/admin-guide/hw-vuln/indirect-target-selection.rst 2221 | |
| 2222 init= [KNL] 2223 Format: <full_path> 2224 Run specified binary instead of /sbin/init as init 2225 process. 2226 2227 initcall_debug [KNL] Trace initcalls as they are executed. Useful 2228 for working out where the kernel is dying during 2229 startup. --- 1475 unchanged lines hidden (view full) --- 3705 kernel was built with CPU_MITIGATIONS=y. 3706 3707 off 3708 Disable all optional CPU mitigations. This 3709 improves system performance, but it may also 3710 expose users to several CPU vulnerabilities. 3711 Equivalent to: if nokaslr then kpti=0 [ARM64] 3712 gather_data_sampling=off [X86] | 2208 init= [KNL] 2209 Format: <full_path> 2210 Run specified binary instead of /sbin/init as init 2211 process. 2212 2213 initcall_debug [KNL] Trace initcalls as they are executed. Useful 2214 for working out where the kernel is dying during 2215 startup. --- 1475 unchanged lines hidden (view full) --- 3691 kernel was built with CPU_MITIGATIONS=y. 3692 3693 off 3694 Disable all optional CPU mitigations. This 3695 improves system performance, but it may also 3696 expose users to several CPU vulnerabilities. 3697 Equivalent to: if nokaslr then kpti=0 [ARM64] 3698 gather_data_sampling=off [X86] |
| 3713 indirect_target_selection=off [X86] | |
| 3714 kvm.nx_huge_pages=off [X86] 3715 l1tf=off [X86] 3716 mds=off [X86] 3717 mmio_stale_data=off [X86] 3718 no_entry_flush [PPC] 3719 no_uaccess_flush [PPC] 3720 nobp=0 [S390] 3721 nopti [X86,PPC] --- 553 unchanged lines hidden (view full) --- 4275 4276 nosmep [PPC64s,EARLY] 4277 Disable SMEP (Supervisor Mode Execution Prevention) 4278 even if it is supported by processor. 4279 4280 nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel, 4281 and disable the IO APIC. legacy for "maxcpus=0". 4282 | 3699 kvm.nx_huge_pages=off [X86] 3700 l1tf=off [X86] 3701 mds=off [X86] 3702 mmio_stale_data=off [X86] 3703 no_entry_flush [PPC] 3704 no_uaccess_flush [PPC] 3705 nobp=0 [S390] 3706 nopti [X86,PPC] --- 553 unchanged lines hidden (view full) --- 4260 4261 nosmep [PPC64s,EARLY] 4262 Disable SMEP (Supervisor Mode Execution Prevention) 4263 even if it is supported by processor. 4264 4265 nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel, 4266 and disable the IO APIC. legacy for "maxcpus=0". 4267 |
| 4283 nosmt [KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT). | 4268 nosmt [KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT). |
| 4284 Equivalent to smt=1. 4285 | 4269 Equivalent to smt=1. 4270 |
| 4286 [KNL,X86,PPC,S390] Disable symmetric multithreading (SMT). | 4271 [KNL,X86,PPC] Disable symmetric multithreading (SMT). |
| 4287 nosmt=force: Force disable SMT, cannot be undone 4288 via the sysfs control file. 4289 4290 nosoftlockup [KNL] Disable the soft-lockup detector. 4291 4292 nospec_store_bypass_disable 4293 [HW,EARLY] Disable all mitigations for the Speculative 4294 Store Bypass vulnerability --- 1995 unchanged lines hidden (view full) --- 6290 to show up before attempting to mount the root 6291 filesystem. 6292 6293 rproc_mem=nn[KMG][@address] 6294 [KNL,ARM,CMA] Remoteproc physical memory block. 6295 Memory area to be used by remote processor image, 6296 managed by CMA. 6297 | 4272 nosmt=force: Force disable SMT, cannot be undone 4273 via the sysfs control file. 4274 4275 nosoftlockup [KNL] Disable the soft-lockup detector. 4276 4277 nospec_store_bypass_disable 4278 [HW,EARLY] Disable all mitigations for the Speculative 4279 Store Bypass vulnerability --- 1995 unchanged lines hidden (view full) --- 6275 to show up before attempting to mount the root 6276 filesystem. 6277 6278 rproc_mem=nn[KMG][@address] 6279 [KNL,ARM,CMA] Remoteproc physical memory block. 6280 Memory area to be used by remote processor image, 6281 managed by CMA. 6282 |
| 6283 rt_group_sched= [KNL] Enable or disable SCHED_RR/FIFO group scheduling 6284 when CONFIG_RT_GROUP_SCHED=y. Defaults to 6285 !CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED. 6286 Format: <bool> 6287 |
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| 6298 rw [KNL] Mount root device read-write on boot 6299 6300 S [KNL] Run init in single mode 6301 6302 s390_iommu= [HW,S390] 6303 Set s390 IOTLB flushing mode 6304 strict 6305 With strict flushing every unmap operation will result --- 992 unchanged lines hidden (view full) --- 7298 reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq 7299 7300 Note, saving the trace buffer across reboots does require that the system 7301 is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION 7302 can force a memory reset on boot which will clear any trace that was stored. 7303 This is just one of many ways that can clear memory. Make sure your system 7304 keeps the content of memory across reboots before relying on this option. 7305 | 6288 rw [KNL] Mount root device read-write on boot 6289 6290 S [KNL] Run init in single mode 6291 6292 s390_iommu= [HW,S390] 6293 Set s390 IOTLB flushing mode 6294 strict 6295 With strict flushing every unmap operation will result --- 992 unchanged lines hidden (view full) --- 7288 reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq 7289 7290 Note, saving the trace buffer across reboots does require that the system 7291 is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION 7292 can force a memory reset on boot which will clear any trace that was stored. 7293 This is just one of many ways that can clear memory. Make sure your system 7294 keeps the content of memory across reboots before relying on this option. 7295 |
| 7306 NB: Both the mapped address and size must be page aligned for the architecture. 7307 | |
| 7308 See also Documentation/trace/debugging.rst 7309 7310 7311 trace_options=[option-list] 7312 [FTRACE] Enable or disable tracer options at boot. 7313 The option-list is a comma delimited list of options 7314 that can be enabled or disabled just as if you were 7315 to echo the option name into --- 229 unchanged lines hidden (view full) --- 7545 uhci-hcd.ignore_oc= 7546 [USB] Ignore overcurrent events (default N). 7547 Some badly-designed motherboards generate lots of 7548 bogus events, for ports that aren't wired to 7549 anything. Set this parameter to avoid log spamming. 7550 Note that genuine overcurrent events won't be 7551 reported either. 7552 | 7296 See also Documentation/trace/debugging.rst 7297 7298 7299 trace_options=[option-list] 7300 [FTRACE] Enable or disable tracer options at boot. 7301 The option-list is a comma delimited list of options 7302 that can be enabled or disabled just as if you were 7303 to echo the option name into --- 229 unchanged lines hidden (view full) --- 7533 uhci-hcd.ignore_oc= 7534 [USB] Ignore overcurrent events (default N). 7535 Some badly-designed motherboards generate lots of 7536 bogus events, for ports that aren't wired to 7537 anything. Set this parameter to avoid log spamming. 7538 Note that genuine overcurrent events won't be 7539 reported either. 7540 |
| 7553 unaligned_scalar_speed= 7554 [RISCV] 7555 Format: {slow | fast | unsupported} 7556 Allow skipping scalar unaligned access speed tests. This 7557 is useful for testing alternative code paths and to skip 7558 the tests in environments where they run too slowly. All 7559 CPUs must have the same scalar unaligned access speed. 7560 7561 unaligned_vector_speed= 7562 [RISCV] 7563 Format: {slow | fast | unsupported} 7564 Allow skipping vector unaligned access speed tests. This 7565 is useful for testing alternative code paths and to skip 7566 the tests in environments where they run too slowly. All 7567 CPUs must have the same vector unaligned access speed. 7568 | |
| 7569 unknown_nmi_panic 7570 [X86] Cause panic on unknown NMI. 7571 7572 unwind_debug [X86-64,EARLY] 7573 Enable unwinder debug output. This can be 7574 useful for debugging certain unwinder error 7575 conditions, including corrupt stacks and 7576 bad/missing unwinder metadata. --- 573 unchanged lines hidden --- | 7541 unknown_nmi_panic 7542 [X86] Cause panic on unknown NMI. 7543 7544 unwind_debug [X86-64,EARLY] 7545 Enable unwinder debug output. This can be 7546 useful for debugging certain unwinder error 7547 conditions, including corrupt stacks and 7548 bad/missing unwinder metadata. --- 573 unchanged lines hidden --- |