| AMD64 specific boot options |
| |
| There are many others (usually documented in driver documentation), but |
| only the AMD64 specific ones are listed here. |
| |
| Machine check |
| |
| Please see Documentation/x86/x86_64/machinecheck for sysfs runtime tunables. |
| |
| mce=off |
| Disable machine check |
| mce=no_cmci |
| Disable CMCI(Corrected Machine Check Interrupt) that |
| Intel processor supports. Usually this disablement is |
| not recommended, but it might be handy if your hardware |
| is misbehaving. |
| Note that you'll get more problems without CMCI than with |
| due to the shared banks, i.e. you might get duplicated |
| error logs. |
| mce=dont_log_ce |
| Don't make logs for corrected errors. All events reported |
| as corrected are silently cleared by OS. |
| This option will be useful if you have no interest in any |
| of corrected errors. |
| mce=ignore_ce |
| Disable features for corrected errors, e.g. polling timer |
| and CMCI. All events reported as corrected are not cleared |
| by OS and remained in its error banks. |
| Usually this disablement is not recommended, however if |
| there is an agent checking/clearing corrected errors |
| (e.g. BIOS or hardware monitoring applications), conflicting |
| with OS's error handling, and you cannot deactivate the agent, |
| then this option will be a help. |
| mce=bootlog |
| Enable logging of machine checks left over from booting. |
| Disabled by default on AMD because some BIOS leave bogus ones. |
| If your BIOS doesn't do that it's a good idea to enable though |
| to make sure you log even machine check events that result |
| in a reboot. On Intel systems it is enabled by default. |
| mce=nobootlog |
| Disable boot machine check logging. |
| mce=tolerancelevel[,monarchtimeout] (number,number) |
| tolerance levels: |
| 0: always panic on uncorrected errors, log corrected errors |
| 1: panic or SIGBUS on uncorrected errors, log corrected errors |
| 2: SIGBUS or log uncorrected errors, log corrected errors |
| 3: never panic or SIGBUS, log all errors (for testing only) |
| Default is 1 |
| Can be also set using sysfs which is preferable. |
| monarchtimeout: |
| Sets the time in us to wait for other CPUs on machine checks. 0 |
| to disable. |
| |
| nomce (for compatibility with i386): same as mce=off |
| |
| Everything else is in sysfs now. |
| |
| APICs |
| |
| apic Use IO-APIC. Default |
| |
| noapic Don't use the IO-APIC. |
| |
| disableapic Don't use the local APIC |
| |
| nolapic Don't use the local APIC (alias for i386 compatibility) |
| |
| pirq=... See Documentation/x86/i386/IO-APIC.txt |
| |
| noapictimer Don't set up the APIC timer |
| |
| no_timer_check Don't check the IO-APIC timer. This can work around |
| problems with incorrect timer initialization on some boards. |
| |
| apicmaintimer Run time keeping from the local APIC timer instead |
| of using the PIT/HPET interrupt for this. This is useful |
| when the PIT/HPET interrupts are unreliable. |
| |
| noapicmaintimer Don't do time keeping using the APIC timer. |
| Useful when this option was auto selected, but doesn't work. |
| |
| apicpmtimer |
| Do APIC timer calibration using the pmtimer. Implies |
| apicmaintimer. Useful when your PIT timer is totally |
| broken. |
| |
| Early Console |
| |
| syntax: earlyprintk=vga |
| earlyprintk=serial[,ttySn[,baudrate]] |
| |
| The early console is useful when the kernel crashes before the |
| normal console is initialized. It is not enabled by |
| default because it has some cosmetic problems. |
| Append ,keep to not disable it when the real console takes over. |
| Only vga or serial at a time, not both. |
| Currently only ttyS0 and ttyS1 are supported. |
| Interaction with the standard serial driver is not very good. |
| The VGA output is eventually overwritten by the real console. |
| |
| Timing |
| |
| notsc |
| Don't use the CPU time stamp counter to read the wall time. |
| This can be used to work around timing problems on multiprocessor systems |
| with not properly synchronized CPUs. |
| |
| report_lost_ticks |
| Report when timer interrupts are lost because some code turned off |
| interrupts for too long. |
| |
| nohpet |
| Don't use the HPET timer. |
| |
| Idle loop |
| |
| idle=poll |
| Don't do power saving in the idle loop using HLT, but poll for rescheduling |
| event. This will make the CPUs eat a lot more power, but may be useful |
| to get slightly better performance in multiprocessor benchmarks. It also |
| makes some profiling using performance counters more accurate. |
| Please note that on systems with MONITOR/MWAIT support (like Intel EM64T |
| CPUs) this option has no performance advantage over the normal idle loop. |
| It may also interact badly with hyperthreading. |
| |
| Rebooting |
| |
| reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] [, [w]arm | [c]old] |
| bios Use the CPU reboot vector for warm reset |
| warm Don't set the cold reboot flag |
| cold Set the cold reboot flag |
| triple Force a triple fault (init) |
| kbd Use the keyboard controller. cold reset (default) |
| acpi Use the ACPI RESET_REG in the FADT. If ACPI is not configured or the |
| ACPI reset does not work, the reboot path attempts the reset using |
| the keyboard controller. |
| efi Use efi reset_system runtime service. If EFI is not configured or the |
| EFI reset does not work, the reboot path attempts the reset using |
| the keyboard controller. |
| |
| Using warm reset will be much faster especially on big memory |
| systems because the BIOS will not go through the memory check. |
| Disadvantage is that not all hardware will be completely reinitialized |
| on reboot so there may be boot problems on some systems. |
| |
| reboot=force |
| |
| Don't stop other CPUs on reboot. This can make reboot more reliable |
| in some cases. |
| |
| Non Executable Mappings |
| |
| noexec=on|off |
| |
| on Enable(default) |
| off Disable |
| |
| SMP |
| |
| additional_cpus=NUM Allow NUM more CPUs for hotplug |
| (defaults are specified by the BIOS, see Documentation/x86/x86_64/cpu-hotplug-spec) |
| |
| NUMA |
| |
| numa=off Only set up a single NUMA node spanning all memory. |
| |
| numa=noacpi Don't parse the SRAT table for NUMA setup |
| |
| numa=fake=CMDLINE |
| If a number, fakes CMDLINE nodes and ignores NUMA setup of the |
| actual machine. Otherwise, system memory is configured |
| depending on the sizes and coefficients listed. For example: |
| numa=fake=2*512,1024,4*256,*128 |
| gives two 512M nodes, a 1024M node, four 256M nodes, and the |
| rest split into 128M chunks. If the last character of CMDLINE |
| is a *, the remaining memory is divided up equally among its |
| coefficient: |
| numa=fake=2*512,2* |
| gives two 512M nodes and the rest split into two nodes. |
| Otherwise, the remaining system RAM is allocated to an |
| additional node. |
| |
| ACPI |
| |
| acpi=off Don't enable ACPI |
| acpi=ht Use ACPI boot table parsing, but don't enable ACPI |
| interpreter |
| acpi=force Force ACPI on (currently not needed) |
| |
| acpi=strict Disable out of spec ACPI workarounds. |
| |
| acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt. |
| |
| acpi=noirq Don't route interrupts |
| |
| PCI |
| |
| pci=off Don't use PCI |
| pci=conf1 Use conf1 access. |
| pci=conf2 Use conf2 access. |
| pci=rom Assign ROMs. |
| pci=assign-busses Assign busses |
| pci=irqmask=MASK Set PCI interrupt mask to MASK |
| pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says. |
| pci=noacpi Don't use ACPI to set up PCI interrupt routing. |
| |
| IOMMU (input/output memory management unit) |
| |
| Currently four x86-64 PCI-DMA mapping implementations exist: |
| |
| 1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all |
| (e.g. because you have < 3 GB memory). |
| Kernel boot message: "PCI-DMA: Disabling IOMMU" |
| |
| 2. <arch/x86_64/kernel/pci-gart.c>: AMD GART based hardware IOMMU. |
| Kernel boot message: "PCI-DMA: using GART IOMMU" |
| |
| 3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used |
| e.g. if there is no hardware IOMMU in the system and it is need because |
| you have >3GB memory or told the kernel to us it (iommu=soft)) |
| Kernel boot message: "PCI-DMA: Using software bounce buffering |
| for IO (SWIOTLB)" |
| |
| 4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM |
| pSeries and xSeries servers. This hardware IOMMU supports DMA address |
| mapping with memory protection, etc. |
| Kernel boot message: "PCI-DMA: Using Calgary IOMMU" |
| |
| iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>] |
| [,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge] |
| [,noaperture][,calgary] |
| |
| General iommu options: |
| off Don't initialize and use any kind of IOMMU. |
| noforce Don't force hardware IOMMU usage when it is not needed. |
| (default). |
| force Force the use of the hardware IOMMU even when it is |
| not actually needed (e.g. because < 3 GB memory). |
| soft Use software bounce buffering (SWIOTLB) (default for |
| Intel machines). This can be used to prevent the usage |
| of an available hardware IOMMU. |
| |
| iommu options only relevant to the AMD GART hardware IOMMU: |
| <size> Set the size of the remapping area in bytes. |
| allowed Overwrite iommu off workarounds for specific chipsets. |
| fullflush Flush IOMMU on each allocation (default). |
| nofullflush Don't use IOMMU fullflush. |
| leak Turn on simple iommu leak tracing (only when |
| CONFIG_IOMMU_LEAK is on). Default number of leak pages |
| is 20. |
| memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order. |
| (default: order=1, i.e. 64MB) |
| merge Do scatter-gather (SG) merging. Implies "force" |
| (experimental). |
| nomerge Don't do scatter-gather (SG) merging. |
| noaperture Ask the IOMMU not to touch the aperture for AGP. |
| forcesac Force single-address cycle (SAC) mode for masks <40bits |
| (experimental). |
| noagp Don't initialize the AGP driver and use full aperture. |
| allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB. |
| DAC is used with 32-bit PCI to push a 64-bit address in |
| two cycles. When off all DMA over >4GB is forced through |
| an IOMMU or software bounce buffering. |
| nodac Forbid DAC mode, i.e. DMA >4GB. |
| panic Always panic when IOMMU overflows. |
| calgary Use the Calgary IOMMU if it is available |
| |
| iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU |
| implementation: |
| swiotlb=<pages>[,force] |
| <pages> Prereserve that many 128K pages for the software IO |
| bounce buffering. |
| force Force all IO through the software TLB. |
| |
| Settings for the IBM Calgary hardware IOMMU currently found in IBM |
| pSeries and xSeries machines: |
| |
| calgary=[64k,128k,256k,512k,1M,2M,4M,8M] |
| calgary=[translate_empty_slots] |
| calgary=[disable=<PCI bus number>] |
| panic Always panic when IOMMU overflows |
| |
| 64k,...,8M - Set the size of each PCI slot's translation table |
| when using the Calgary IOMMU. This is the size of the translation |
| table itself in main memory. The smallest table, 64k, covers an IO |
| space of 32MB; the largest, 8MB table, can cover an IO space of |
| 4GB. Normally the kernel will make the right choice by itself. |
| |
| translate_empty_slots - Enable translation even on slots that have |
| no devices attached to them, in case a device will be hotplugged |
| in the future. |
| |
| disable=<PCI bus number> - Disable translation on a given PHB. For |
| example, the built-in graphics adapter resides on the first bridge |
| (PCI bus number 0); if translation (isolation) is enabled on this |
| bridge, X servers that access the hardware directly from user |
| space might stop working. Use this option if you have devices that |
| are accessed from userspace directly on some PCI host bridge. |
| |
| Debugging |
| |
| oops=panic 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. |
| Useful together with panic=30 to trigger a reboot. |
| |
| kstack=N Print N words from the kernel stack in oops dumps. |
| |
| pagefaulttrace Dump all page faults. Only useful for extreme debugging |
| and will create a lot of output. |
| |
| call_trace=[old|both|newfallback|new] |
| old: use old inexact backtracer |
| new: use new exact dwarf2 unwinder |
| both: print entries from both |
| newfallback: use new unwinder but fall back to old if it gets |
| stuck (default) |
| |
| Miscellaneous |
| |
| nogbpages |
| Do not use GB pages for kernel direct mappings. |
| gbpages |
| Use GB pages for kernel direct mappings. |
