xen/docs/misc/xen-command-line.markdown

Xen Hypervisor Command Line Options

This document is still a work in progress. There are currently some command line options listed twice, and they are defined in separate arch trees, and some options are currently separate from their legacy versions. Please remove this notice when complete.

This document coveres the command line options which the Xen Hypervisor.

Types of parameter

Most parameters take the form option=value. Different options on the command line should be space delimited.

Boolean (<boolean>)

All boolean option may be explicitly enabled using a value of

yes, on, true, enable or 1

They may be explicitly disabled using a value of

no, off, false, disable or 0

In addition, a boolean option may be enabled by simply stating its name, and may be disabled by prefixing its name with no-.

####Examples

Enable noreboot mode

noreboot=true

Disable x2apic support (if present)

x2apic=off

Enable synchronous console mode

sync_console

Integer (<integer>)

An integer parameter will default to decimal and may be prefixed with a - for negative numbers. Alternativly, a hexidecimal number may be used by prefixing the number with 0x, or an octal number may be used if a leading 0 is present.

Size (<size>)

A size parameter may be any integer, with a size suffix

• G or g: Giga (2^30)
• M or m: Mega (2^20)
• K or k: Kilo (2^10)
• B or b: Bytes

Without a size suffix, the default will be kilo.

String

Many parameters are more complicated and require more intricate configuration. The detailed description of each individual paramter specify which values are valid.

List

Some options take a comma separated list of values.

Combination

Some parameters act as combinations of the above, most commonly a mix of Boolean and String. These are noted in the relevant sections.

Parameter details

acpi

= force | ht | noirq | <boolean>

String, or Boolean to disable.

The acpi option is used to control a set of four related boolean flags; acpi_force, acpi_ht, acpi_noirq and acpi_disabled.

By default, Xen will scan the DMI data and blacklist certain systems which are known to have broken ACPI setups. Providing acpi=force will cause Xen to ignore the blacklist and attempt to use all ACPI features.

Using acpi=ht causes Xen to parse the ACPI tables enough to enumerate all CPUs, but will not use other ACPI features. This is not common, and only has an effect if your system is blacklisted.

The acpi=noirq option causes Xen to not parse the ACPI MADT table looking for IO-APIC entries. This is also not common, and any system which requries this option to function should be blacklisted. Additionally, this will not prevent Xen from finding IO-APIC entries from the MP tables.

Finally, any of the boolean false options can be used to disable ACPI usage entirely.

Because responsiblity for ACPI processing is shared between Xen and the domain 0 kernel this option is automatically propagated to the domain 0 command line

acpi_apic_instance

= <integer>

Specify which ACPI MADT table to parse for APIC information, if more than one is present.

acpi_pstate_strict

acpi_skip_timer_override

Instruct Xen to ignore timer-interrupt override.

Because responsiblity for ACPI processing is shared between Xen and the domain 0 kernel this option is automatically propagated to the domain 0 command line

acpi_sleep

additional_cpus

allowsuperpage

apic

= summit | bigsmp | default

Override Xen's logic for choosing the APIC driver. By default, if there are more than 8 CPUs, Xen will switch to bigsmp over default.

apic_verbosity

= verbose | debug

Increase the verbosity of the APIC code from the default value.

ats

availmem

badpage

= List of [ <integer> | <integer>-<integer> ]

Specify that certain pages, or certain ranges of pages contain bad bytes and should not be used. For example, if your memory tester says that byte 0x12345678 is bad, you would place badpage=0x12345 on Xen's command line.

bootscrub

cachesize

clocksource

com1,com2

= <baud>[/<clock_hz>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]] | pci | amt ]

Both option com1 and com2 follow the same format.

• <baud> may be either an integer baud rate, or the string auto if the bootloader or other earlier firmware has already set it up.

• Optionally, a clock speed measured in hz can be specified.

• DPS represents the number of data bits, the parity, and the number of stop bits.

  D is an integer between 5 and 8 for the number of data bits.

  P is a single character representing the type of parity:

  • n No
  • o Odd
  • e Even
  • m Mark
  • s Space

  S is an integer 1 or 2 for the number of stop bits.

• <io-base> is an integer which specifies the IO base port for UART registers.

• <irq> is the IRQ number to use, or 0 to use the UART in poll mode only.

• <port-bdf> is the PCI location of the UART, in <bus>:<device>.<function> notation.

• <bridge-bdf> is the PCI bridge behind which is the UART, in <bus>:<device>.<function> notation.

• pci indicates that Xen should scan the PCI bus for the UART, avoiding Intel AMT devices.

• amt indicated that Xen should scan the PCI bus for the UART, including Intel AMT devices if presetn.

A typical setup for most situations might be com1=115200,8n1

conring_size

= <size>

Default: conring_size=16k

Specify the size of the console ring buffer.

console

= List of [ vga | com1[H,L] | com2[H,L] | none ]

Default: console=com1,vga

Specify which console(s) Xen should use.

vga indicates that Xen should try and use the vga graphics adapter.

com1 and com2 indicates that Xen should use serial ports 1 and 2 respectivly. Optionally, these arguments may be followed by an H or L. H indicates that transmitted characters will have their MSB set, while recieved characters must have their MSB set. L indicates the converse; transmitted and recieved characters will have their MSB cleared. This allows a single port to be shared by two subsystems (e.g. console and debugger).

none indicates that Xen should not use a console. This option only makes sense on its own.

console_timestamps

= <boolean>

Default: false

Flag to indicate whether include a timestamp with each console line.

console_to_ring

= <boolean>

Default: false

Flag to indicate whether all guest console output should be copied into the console ring buffer.

conswitch

= <switch char>[,x]

Default conswitch=a

Specify which character should be used to switch serial input between Xen and dom0. The required sequence is CTRL-<switch char> three times.

The optional trailing x indicates that Xen should not automatically switch the console input to dom0 during boot. Any other value, including omission, causes Xen to automatically switch to the dom0 console during dom0 boot.

contig_mem

cpu_type

cpufreq

cpuid_mask_cpu

cpuid_mask_ecx

cpuid_mask_edx

cpuid_mask_ext_ecx

cpuid_mask_ext_edx

cpuid_mask_xsave_eax

cpuidle

cpuinfo

crashinfo_maxaddr

= <size>

Default: 4G

Specify the maximum address to allocate certain strucutres, if used in combination with the low_crashinfo command line option.

crashkernel

credit2_balance_over

credit2_balance_under

credit2_load_window_shift

debug_stack_lines

debug_stack_lines

debugtrace

dma_bits

= <integer>

Specify the bit width of the DMA heap.

dom0_ioports_disable

dom0_max_vcpus

= <integer>

Specifiy the maximum number of vcpus to give to dom0. This defaults to the number of pcpus on the host.

dom0_mem (ia64)

= <size>

Specify the total size for dom0.

dom0_mem (x86)

= List of ( min:<size> | max:<size> | <size> )

Set the amount of memory for the initial domain (dom0). If a size is positive, it represents an absolute value. If a size is negative, the size specified is subtracted from the total available memory.

• min:<size> specifies the minimum amount of memory allocated to dom0.
• max:<size> specifies the maximum amount of memory allocated to dom0.
• <size> specified the exact amount of memory allocated to dom0.

max:<size> also sets the maximum reservation (the maximum amount of memory dom0 can balloon up to). If this is omitted then the maximum reservation is unlimited.

For example, to set dom0's memory to 512 MB but no more than 1 GB use dom0_mem=512M,max:1G.

dom0_shadow

dom0_vcpus_pin

= <boolean>

Default: false

Pin dom0 vcpus to their respective pcpus

dom0_vhpt_size_log2

dom_rid_bits

e820-mtrr-clip

e820-verbose

edd (x86)

= off | on | skipmbr

Control retrieval of Extended Disc Data (EDD) from the BIOS during boot.

edid (x86)

= no | force

Either force retrieval of monitor EDID information via VESA DDC, or disable it (edid=no). This option should not normally be required except for debugging purposes.

efi_print

extra_guest_irqs

= <number>

Increase the number of PIRQs available for the guest. The default is 32.

flask_enabled

flask_enforcing

font

gdb

gnttab_max_nr_frames

guest_loglvl

= <level>[/<rate-limited level>] where level is none | error | warning | info | debug | all

Default: guest_loglvl=none/warning

Set the logging level for Xen guests. Any log message with equal more more importance will be printed.

The optional <rate-limited level> options instructs which severities should be rate limited.

hap_1gb

hap_2mb

hpetbroadcast

hvm_debug

hvm_port80

idle_latency_factor

ioapic_ack

iommu

iommu_inclusive_mapping

irq_ratelimit

irq_vector_map

lapic

Force the use of use of the local APIC on a uniprocessor system, even if left disabled by the BIOS. This option will accept any value at all.

lapic_timer_c2_ok

ler

loglvl

= <level>[/<rate-limited level>] where level is none | error | warning | info | debug | all

Default: loglvl=warning

Set the logging level for Xen. Any log message with equal more more importance will be printed.

The optional <rate-limited level> options instructs which severities should be rate limited.

low_crashinfo

= none | min | all

Default: none if not specified at all, or to min if low\_crashinfo is present without qualification.

This option is only useful for hosts with a 32bit dom0 kernel, wishing to use kexec functionality in the case of a crash. It represents which data structures should be deliberatly allocated in low memory, so the crash kernel may find find them. Should be used in combination with crashinfo_maxaddr.

max_cstate

max_gsi_irqs

maxcpus

maxcpus

mce

mce_fb

mce_verbosity

mem

= <size>

Specifies the maximum address of physical RAM. Any RAM beyond this limit is ignored by Xen.

mmcfg

nmi

= ignore | dom0 | fatal

Default: nmi=fatal

Specify what Xen should do in the event of an NMI parity or I/O error. ignore discards the error; dom0 causes Xen to report the error to dom0, while 'fatal' causes Xen to print diagnostics and then hang.

noapic

Instruct Xen to ignore any IOAPICs that are present in the system, and instead continue to use the legacy PIC. This is not recommended with pvops type kernels.

Because responsiblity for APIC setup is shared between Xen and the domain 0 kernel this option is automatically propagated to the domain 0 command line.

nofxsr

noirqbalance

= <boolean>

Disable software IRQ balancing and affinity. This can be used on systems such as Dell 1850/2850 that have workarounds in hardware for IRQ routing issues.

nolapic

Ignore the local APIC on a uniprocessor system, even if enabled by the BIOS. This option will accept value.

no-real-mode (x86)

Do not execute real-mode bootstrap code when booting Xen. This option should not be used except for debugging. It will effectively disable the vga option, which relies on real mode to set the video mode.

noreboot

= <boolean>

Do not automatically reboot after an error. This is useful for catching debug output. Defaults to automatically reboot after 5 seconds.

noserialnumber

nosmp

= <boolean>

Disable SMP support. No secondary processors will be booted. Defaults to booting secondary processors.

nr_irqs

numa

pervcpu_vhpt

ple_gap

ple_window

reboot

sched

= credit | credit2 | sedf | arinc653

Default: sched=credit

Choose the default scheduler.

sched_credit2_migrate_resist

sched_credit_default_yield

sched_credit_tslice_ms

sched_ratelimit_us

sched_smt_power_savings

serial_tx_buffer

= <size>

Set the serial tramsit buffer size. Defaults to 16kB.

smep

snb_igd_quirk

sync_console

= <boolean>

Default: false

Flag to force synchronous console output. Useful for debugging, but not suitable for production environments due to incurred overhead.

tboot

tbuf_size

= <integer>

Specify the per-cpu trace buffer size in pages.

tdt

tevt_mask

tickle_one_idle_cpu

timer_slop

tmem

tmem_compress

tmem_dedup

tmem_lock

tmem_shared_auth

tmem_tze

tsc

ucode

unrestricted_guest

vcpu_migration_delay

vesa-map

vesa-mtrr

vesa-ram

vga

= ( ask | current | text-80x<rows> | gfx-<width>x<height>x<depth> | mode-<mode> )[,keep]

ask causes Xen to display a menu of available modes and request the user to choose one of them.

current causes Xen to use the graphics adapter in its current state, without further setup.

text-80x<rows> instructs Xen to set up text mode. Valid values for <rows> are 25, 28, 30, 34, 43, 50, 80

gfx-<width>x<height>x<depth> instructs Xen to set up graphics mode with the specified width, height and depth.

mode-<mode> instructs Xen to use a specific mode, as shown with the ask option. (N.B menu modes are displayed in hex, so <mode> should be a hexidecimal number)

The optional keep parameter causes Xen to continue using the vga console even after dom0 has been started. The default behaviour is to relinquish control to dom0.

vpid

vpmu

vti_vhpt_size

vti_vtlb_size

watchdog

= <boolean>

Default: false

Run an NMI watchdog on each processor. If a processor is stuck for longer than the watchdog_timeout, a panic occurs.

watchdog_timeout

= <integer>

Default: 5

Set the NMI watchdog timeout in seconds. Specifying 0 will turn off the watchdog.

x2apic

x2apic_phys

xencons

xencons_poll

xsave