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AMD64 specific boot options

There are many others (usually documented in driver documentation), but

only the AMD64 specific ones are listed here.

Machine check

(see the Opteron BIOS&Kernel manual for more details on the banks etc.)

   mce=off disable machine check

   mce=nok8 disable k8 specific features

   mce=disable disable bank NUMBER

   mce=enable enable bank number

   mce=device   Enable more machine check options in Northbridge.

                Can be useful for device driver debugging.

   mce=NUMBER mcheck timer interval number seconds.

   Can be also comma separated in a single mce=

   nomce (for compatibility with i386): same as mce=off

APICs

   nolocalapic   Don't use a local or IO-APIC. This should only

                 be needed if you have a buggy BIOS. The newer

                 kernels already turn it off by default if the

                 BIOS didn't enable the local APIC, so it will

                 be hopefully not needed.

                 Note this code path is not very well tested, you are on

                 your own.

   apic          Use IO-APIC. Default

   noapic        Don't use the IO-APIC.

                 Also only lightly tested.

   pirq=...      See Documentation/i386/IO-APIC.txt

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. Only useful with a SMP kernel

  report_lost_ticks

  Report when timer interrupts are lost because some code turned off

  interrupts for too long.

  nmi_watchdog=NUMBER

  NUMBER can be:

  1 use the IO-APIC timer for the NMI watchdog

  2 use the local APIC for the NMI watchdog using a performance counter. Note

  This will use one performance counter and the local APIC's performance

  counter vector.

Idle loop

  idle=poll

  Don't do power saving in the idle loop using HLT, but poll for rescheduling

  events. This will make the CPUs burn 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.

Rebooting

   reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]

   bios   Use the CPU reboto vector for warm reset

   warm   Don't set the cold reboot flag

   cold   Set the cold reboto flag

   triple Force a triple fault (init)

   kbd    Use the keyboard controller. cold reset (default)

   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.

Non Executable Mappings

  noexec=on|off

  on      Enable

  off     Disable

  noforce (default) Don't enable by default for heap/stack/data,

          but allow PROT_EXEC to be effective

  noexec32=opt{,opt}

  Control the no exec default for 32bit processes.

  Requires noexec=on or noexec=noforce to be effective.

  Valid options:

     all,on    Heap,stack,data is non executable.

     off       (default) Heap,stack,data is executable

     stack     Stack is non executable, heap/data is.

     force     Don't imply PROT_EXEC for PROT_READ

     compat    (default) Imply PROT_EXEC for PROT_READ

SMP

  nosmp Only use a single CPU

  maxcpus=NUMBER only use upto NUMBER CPUs

  cpumask=MASK   only use cpus with bits set in mask

NUMA

  numa=off      Only set up a single NUMA node spanning all memory.

ACPI

  acpi=off      Don't enable ACPI

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.

IOMMU

  iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]]

   size  set size of iommu (in bytes)

   noagp don't initialize the AGP driver and use full aperture.

   off   don't use the IOMMU

   leak  turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on)

   memaper[=order] allocate an own aperture over RAM with size 32MB^order.

   noforce don't force IOMMU usage. Default.

   force  Force IOMMU for all devices.