Ubuntu Manpage: xl.cfg - xl domain configuration file syntax

Provided by: xen-utils-common_4.17.0+24-g2f8851c37f-2_amd64

NAME

       xl.cfg - xl domain configuration file syntax

SYNOPSIS

        /etc/xen/xldomain

DESCRIPTION

       Creating a VM (a domain in Xen terminology, sometimes called a guest) with xl requires the
       provision of a domain configuration file.  Typically, these live in /etc/xen/DOMAIN.cfg,
       where DOMAIN is the name of the domain.

SYNTAX

       A domain configuration file consists of a series of options, specified by using
       "KEY=VALUE" pairs.

       Some "KEY"s are mandatory, some are general options which apply to any guest type, while
       others relate only to specific guest types (e.g. PV or HVM guests).

       A "VALUE" can be one of:

       "STRING"
           A string, surrounded by either single or double quotes. But if the STRING is part of a
           SPEC_STRING, the quotes should be omitted.

       NUMBER
           A number, in either decimal, octal (using a 0 prefix) or hexadecimal (using a "0x"
           prefix) format.

       BOOLEAN
           A "NUMBER" interpreted as "False" (0) or "True" (any other value).

       [ VALUE, VALUE, ... ]
           A list of "VALUE"s of the above types. Lists can be heterogeneous and nested.

       The semantics of each "KEY" defines which type of "VALUE" is required.

       Pairs may be separated either by a newline or a semicolon.  Both of the following are
       valid:

         name="h0"
         type="hvm"

         name="h0"; type="hvm"

OPTIONS

Mandatory Configuration Items
The following key is mandatory for any guest type.

name="NAME"
Specifies the name of the domain. Names of domains existing on a single host must be
unique.

Selecting Guest Type
type="pv"
Specifies that this is to be a PV domain, suitable for hosting Xen-aware guest
operating systems. This is the default on x86.

type="pvh"
Specifies that this is to be an PVH domain. That is a lightweight HVM-like guest
without a device model and without many of the emulated devices available to HVM
guests. Note that this mode requires a PVH aware kernel on x86. This is the default on
Arm.

type="hvm"
Specifies that this is to be an HVM domain. That is, a fully virtualised computer with
emulated BIOS, disk and network peripherals, etc.

Deprecated guest type selection

Note that the builder option is being deprecated in favor of the type option.

builder="generic"
Specifies that this is to be a PV domain, suitable for hosting Xen-aware guest
operating systems. This is the default.

builder="hvm"
Specifies that this is to be an HVM domain. That is, a fully virtualised computer
with emulated BIOS, disk and network peripherals, etc.

General Options
The following options apply to guests of any type.

CPU Allocation

pool="CPUPOOLNAME"
Put the guest's vCPUs into the named CPU pool.

vcpus=N
Start the guest with N vCPUs initially online.

maxvcpus=M
Allow the guest to bring up a maximum of M vCPUs. When starting the guest, if vcpus=N
is less than maxvcpus=M then the first N vCPUs will be created online and the
remainder will be created offline.

cpus="CPULIST"
List of host CPUs the guest is allowed to use. Default is no pinning at all (more on
this below). A "CPULIST" may be specified as follows:

"all"
To allow all the vCPUs of the guest to run on all the CPUs on the host.

"0-3,5,^1"
To allow all the vCPUs of the guest to run on CPUs 0,2,3,5. It is possible to
combine this with "all", meaning "all,^7" results in all the vCPUs of the guest
being allowed to run on all the CPUs of the host except CPU 7.

"nodes:0-3,^node:2"
To allow all the vCPUs of the guest to run on the CPUs from NUMA nodes 0,1,3 of
the host. So, if CPUs 0-3 belong to node 0, CPUs 4-7 belong to node 1, CPUs 8-11
to node 2 and CPUs 12-15 to node 3, the above would mean all the vCPUs of the
guest would be allowed to run on CPUs 0-7,12-15.

Combining this notation with the one above is possible. For instance,
"1,node:1,^6", means all the vCPUs of the guest will run on CPU 1 and on all the
CPUs of NUMA node 1, but not on CPU 6. Following the same example as above, that
would be CPUs 1,4,5,7.

Combining this with "all" is also possible, meaning "all,^node:1" results in all
the vCPUs of the guest running on all the CPUs on the host, except for the CPUs
belonging to the host NUMA node 1.

["2", "3-8,^5"]
To ask for specific vCPU mapping. That means (in this example), vCPU 0 of the
guest will run on CPU 2 of the host and vCPU 1 of the guest will run on CPUs
3,4,6,7,8 of the host (excluding CPU 5).

More complex notation can be also used, exactly as described above. So "all,^5-8",
or just "all", or "node:0,node:2,^9-11,18-20" are all legal, for each element of
the list.

If this option is not specified, no vCPU to CPU pinning is established, and the vCPUs
of the guest can run on all the CPUs of the host. If this option is specified, the
intersection of the vCPU pinning mask, provided here, and the soft affinity mask, if
provided via cpus_soft=, is utilized to compute the domain node-affinity for driving
memory allocations.

cpus_soft="CPULIST"
Exactly as cpus=, but specifies soft affinity, rather than pinning (hard affinity).
When using the credit scheduler, this means what CPUs the vCPUs of the domain prefer.

A "CPULIST" is specified exactly as for cpus=, detailed earlier in the manual.

If this option is not specified, the vCPUs of the guest will not have any preference
regarding host CPUs. If this option is specified, the intersection of the soft
affinity mask, provided here, and the vCPU pinning, if provided via cpus=, is utilized
to compute the domain node-affinity for driving memory allocations.

If this option is not specified (and cpus= is not specified either), libxl
automatically tries to place the guest on the least possible number of nodes. A
heuristic approach is used for choosing the best node (or set of nodes), with the goal
of maximizing performance for the guest and, at the same time, achieving efficient
utilization of host CPUs and memory. In that case, the soft affinity of all the vCPUs
of the domain will be set to host CPUs belonging to NUMA nodes chosen during
placement.

For more details, see xl-numa-placement(7).

CPU Scheduling

cpu_weight=WEIGHT
A domain with a weight of 512 will get twice as much CPU as a domain with a weight of
256 on a contended host. Legal weights range from 1 to 65535 and the default is 256.
Honoured by the credit and credit2 schedulers.

cap=N
The cap optionally fixes the maximum amount of CPU a domain will be able to consume,
even if the host system has idle CPU cycles. The cap is expressed as a percentage of
one physical CPU: 100 is 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc. The
default, 0, means there is no cap. Honoured by the credit and credit2 schedulers.

NOTE: Many systems have features that will scale down the computing power of a CPU
that is not 100% utilized. This can be done in the operating system, but can also
sometimes be done below the operating system, in the BIOS. If you set a cap such that
individual cores are running at less than 100%, this may have an impact on the
performance of your workload over and above the impact of the cap. For example, if
your processor runs at 2GHz, and you cap a VM at 50%, the power management system may
also reduce the clock speed to 1GHz; the effect will be that your VM gets 25% of the
available power (50% of 1GHz) rather than 50% (50% of 2GHz). If you are not getting
the performance you expect, look at performance and CPU frequency options in your
operating system and your BIOS.

Memory Allocation

memory=MBYTES
Start the guest with MBYTES megabytes of RAM.

maxmem=MBYTES
Specifies the maximum amount of memory a guest can ever see. The value of maxmem=
must be equal to or greater than that of memory=.

In combination with memory= it will start the guest "pre-ballooned", if the values of
memory= and maxmem= differ. A "pre-ballooned" HVM guest needs a balloon driver,
without a balloon driver it will crash.

NOTE: Because of the way ballooning works, the guest has to allocate memory to keep
track of maxmem pages, regardless of how much memory it actually has available to it.
A guest with maxmem=262144 and memory=8096 will report significantly less memory
available for use than a system with maxmem=8096 memory=8096 due to the memory
overhead of having to track the unused pages.

Guest Virtual NUMA Configuration

vnuma=[ VNODE_SPEC, VNODE_SPEC, ... ]
Specify virtual NUMA configuration with positional arguments. The nth VNODE_SPEC in
the list specifies the configuration of the nth virtual node.

Note that virtual NUMA is not supported for PV guests yet, because there is an issue
with the CPUID instruction handling that affects PV virtual NUMA. Furthermore, guests
with virtual NUMA cannot be saved or migrated because the migration stream does not
preserve node information.

Each VNODE_SPEC is a list, which has a form of "[VNODE_CONFIG_OPTION,
VNODE_CONFIG_OPTION, ... ]" (without the quotes).

For example, vnuma = [ ["pnode=0","size=512","vcpus=0-4","vdistances=10,20"] ] means
vnode 0 is mapped to pnode 0, has 512MB ram, has vcpus 0 to 4, the distance to itself
is 10 and the distance to vnode 1 is 20.

Each VNODE_CONFIG_OPTION is a quoted "KEY=VALUE" pair. Supported VNODE_CONFIG_OPTIONs
are (they are all mandatory at the moment):

pnode=NUMBER
Specifies which physical node this virtual node maps to.

size=MBYTES
Specifies the size of this virtual node. The sum of memory sizes of all vnodes
will become maxmem=. If maxmem= is specified separately, a check is performed to
make sure the sum of all vnode memory matches maxmem=.

vcpus="CPUSTRING"
Specifies which vCPUs belong to this node. "CPUSTRING" is a string of numerical
values separated by a comma. You can specify a range and/or a single CPU. An
example would be "vcpus=0-5,8", which means you specified vCPU 0 to vCPU 5, and
vCPU 8.

vdistances=NUMBER, NUMBER, ...
Specifies the virtual distance from this node to all nodes (including itself) with
positional arguments. For example, "vdistance=10,20" for vnode 0 means the
distance from vnode 0 to vnode 0 is 10, from vnode 0 to vnode 1 is 20. The number
of arguments supplied must match the total number of vnodes.

Normally you can use the values from xl info -n or numactl --hardware to fill the
vdistances list.

Event Actions

on_poweroff="ACTION"
Specifies what should be done with the domain if it shuts itself down. The ACTIONs
are:

destroy
destroy the domain

restart
destroy the domain and immediately create a new domain with the same configuration

rename-restart
rename the domain which terminated, and then immediately create a new domain with
the same configuration as the original

preserve
keep the domain. It can be examined, and later destroyed with xl destroy.

coredump-destroy
write a "coredump" of the domain to /var/lib/xen/dump/NAME and then destroy the
domain.

coredump-restart
write a "coredump" of the domain to /var/lib/xen/dump/NAME and then restart the
domain.

soft-reset
Reset all Xen specific interfaces for the Xen-aware HVM domain allowing it to
reestablish these interfaces and continue executing the domain. PV and non-Xen-
aware HVM guests are not supported.

The default for on_poweroff is destroy.

on_reboot="ACTION"
Action to take if the domain shuts down with a reason code requesting a reboot.
Default is restart.

on_watchdog="ACTION"
Action to take if the domain shuts down due to a Xen watchdog timeout. Default is
destroy.

on_crash="ACTION"
Action to take if the domain crashes. Default is destroy.

on_soft_reset="ACTION"
Action to take if the domain performs a 'soft reset' (e.g. does kexec). Default is
soft-reset.

Direct Kernel Boot

Direct kernel boot allows booting guests with a kernel and an initrd stored on a
filesystem available to the host physical machine, allowing command line arguments to be
passed directly. PV guest direct kernel boot is supported. HVM guest direct kernel boot is
supported with some limitations (it's supported when using qemu-xen and the default BIOS
'seabios', but not supported in case of using stubdom-dm and the old 'rombios'.)

kernel="PATHNAME"
Load the specified file as the kernel image.

ramdisk="PATHNAME"
Load the specified file as the ramdisk.

cmdline="STRING"
Append STRING to the kernel command line. (Note: the meaning of this is guest
specific). It can replace root="STRING" along with extra="STRING" and is preferred.
When cmdline="STRING" is set, root="STRING" and extra="STRING" will be ignored.

root="STRING"
Append root=STRING to the kernel command line (Note: the meaning of this is guest
specific).

extra="STRING"
Append STRING to the kernel command line. (Note: the meaning of this is guest
specific).

Non direct Kernel Boot

Non direct kernel boot allows booting guests with a firmware. This can be used by all
types of guests, although the selection of options is different depending on the guest
type.

This option provides the flexibly of letting the guest decide which kernel they want to
boot, while preventing having to poke at the guest file system form the toolstack domain.

PV guest options

firmware="pvgrub32|pvgrub64"
Boots a guest using a para-virtualized version of grub that runs inside of the guest.
The bitness of the guest needs to be know, so that the right version of pvgrub can be
selected.

Note that xl expects to find the pvgrub32.bin and pvgrub64.bin binaries in
/usr/lib/xen-4.17/boot.

HVM guest options

firmware="bios"
Boot the guest using the default BIOS firmware, which depends on the chosen device
model.

firmware="uefi"
Boot the guest using the default UEFI firmware, currently OVMF.

firmware="seabios"
Boot the guest using the SeaBIOS BIOS firmware.

firmware="rombios"
Boot the guest using the ROMBIOS BIOS firmware.

firmware="ovmf"
Boot the guest using the OVMF UEFI firmware.

firmware="PATH"
Load the specified file as firmware for the guest.

PVH guest options

Currently there's no firmware available for PVH guests, they should be booted using the
Direct Kernel Boot method or the bootloader option.

pvshim=BOOLEAN
Whether to boot this guest as a PV guest within a PVH container. Ie, the guest will
experience a PV environment, but processor hardware extensions are used to separate
its address space to mitigate the Meltdown attack (CVE-2017-5754).

Default is false.

pvshim_path="PATH"
The PV shim is a specially-built firmware-like executable constructed from the
hypervisor source tree. This option specifies to use a non-default shim. Ignored if
pvhsim is false.

pvshim_cmdline="STRING"
Command line for the shim. Default is "pv-shim console=xen,pv". Ignored if pvhsim is
false.

pvshim_extra="STRING"
Extra command line arguments for the shim. If supplied, appended to the value for
pvshim_cmdline. Default is empty. Ignored if pvhsim is false.

Other Options

uuid="UUID"
Specifies the UUID of the domain. If not specified, a fresh unique UUID will be
generated.

seclabel="LABEL"
Assign an XSM security label to this domain.

init_seclabel="LABEL"
Specify an XSM security label used for this domain temporarily during its build. The
domain's XSM label will be changed to the execution seclabel (specified by seclabel)
once the build is complete, prior to unpausing the domain. With a properly constructed
security policy (such as nomigrate_t in the example policy), this can be used to build
a domain whose memory is not accessible to the toolstack domain.

max_grant_frames=NUMBER
Specify the maximum number of grant frames the domain is allowed to have. This value
controls how many pages the domain is able to grant access to for other domains,
needed e.g. for the operation of paravirtualized devices. The default is settable via
xl.conf(5).

max_maptrack_frames=NUMBER
Specify the maximum number of grant maptrack frames the domain is allowed to have.
This value controls how many pages of foreign domains can be accessed via the grant
mechanism by this domain. The default value is settable via xl.conf(5).

max_grant_version=NUMBER
Specify the maximum grant table version the domain is allowed to use. The default
value is settable via xl.conf(5).

nomigrate=BOOLEAN
Disable migration of this domain. This enables certain other features which are
incompatible with migration. Currently this is limited to enabling the invariant TSC
feature flag in CPUID results when TSC is not emulated.

driver_domain=BOOLEAN
Specify that this domain is a driver domain. This enables certain features needed in
order to run a driver domain.

device_tree=PATH
Specify a partial device tree (compiled via the Device Tree Compiler). Everything
under the node "/passthrough" will be copied into the guest device tree. For
convenience, the node "/aliases" is also copied to allow the user to define aliases
which can be used by the guest kernel.

Given the complexity of verifying the validity of a device tree, this option should
only be used with a trusted device tree.

Note that the partial device tree should avoid using the phandle 65000 which is
reserved by the toolstack.

passthrough="STRING"
Specify whether IOMMU mappings are enabled for the domain and hence whether it will be
enabled for passthrough hardware. Valid values for this option are:

disabled
IOMMU mappings are disabled for the domain and so hardware may not be passed
through.

This option is the default if no passthrough hardware is specified in the domain's
configuration.

enabled
This option enables IOMMU mappings and selects an appropriate default operating
mode (see below for details of the operating modes). For HVM/PVH domains running
on platforms where the option is available, this is equivalent to share_pt.
Otherwise, and also for PV domains, this option is equivalent to sync_pt.

This option is the default if passthrough hardware is specified in the domain's
configuration.

sync_pt
This option means that IOMMU mappings will be synchronized with the domain's P2M
table as follows:

For a PV domain, all writable pages assigned to the domain are identity mapped by
MFN in the IOMMU page table. Thus a device driver running in the domain may
program passthrough hardware for DMA using MFN values (i.e. host/machine frame
numbers) looked up in its P2M.

For an HVM/PVH domain, all non-foreign RAM pages present in its P2M will be mapped
by GFN in the IOMMU page table. Thus a device driver running in the domain may
program passthrough hardware using GFN values (i.e. guest physical frame numbers)
without any further translation.

This option is not currently available on Arm.

share_pt
This option is unavailable for a PV domain. For an HVM/PVH domain, this option
means that the IOMMU will be programmed to directly reference the domain's P2M
table as its page table. From the point of view of a device driver running in the
domain this is functionally equivalent to sync_pt but places less load on the
hypervisor and so should generally be selected in preference. However, the
availability of this option is hardware specific. If xl info reports virt_caps
containing iommu_hap_pt_share then this option may be used.

default
The default, which chooses between disabled and enabled according to whether
passthrough devices are enabled in the config file.

xend_suspend_evtchn_compat=BOOLEAN
If this option is true the xenstore path for the domain's suspend event channel will
not be created. Instead the old xend behaviour of making the whole xenstore device
sub-tree writable by the domain will be re-instated.

The existence of the suspend event channel path can cause problems with certain PV
drivers running in the guest (e.g. old Red Hat PV drivers for Windows).

If this option is not specified then it will default to false.

vmtrace_buf_kb=KBYTES
Specifies the size of vmtrace buffer that would be allocated for each vCPU belonging
to this domain. Disabled (i.e. vmtrace_buf_kb=0) by default.

NOTE: Acceptable values are platform specific. For Intel Processor Trace, this value
must be a power of 2 between 4k and 16M.

vpmu=BOOLEAN
Currently ARM only.

Specifies whether to enable the access to PMU registers by disabling the PMU traps.

The PMU registers are not virtualized and the physical registers are directly
accessible when this parameter is enabled. There is no interrupt support and Xen will
not save/restore the register values on context switches.

vPMU, by design and purpose, exposes system level performance information to the
guest. Only to be used by sufficiently privileged domains. This feature is currently
in experimental state.

If this option is not specified then it will default to false.

Devices
The following options define the paravirtual, emulated and physical devices which the
guest will contain.

disk=[ "DISK_SPEC_STRING", "DISK_SPEC_STRING", ...]
Specifies the disks (both emulated disks and Xen virtual block devices) which are to
be provided to the guest, and what objects on the host they should map to. See
xl-disk-configuration(5) for more details.

vif=[ "NET_SPEC_STRING", "NET_SPEC_STRING", ...]
Specifies the network interfaces (both emulated network adapters, and Xen virtual
interfaces) which are to be provided to the guest. See xl-network-configuration(5)
for more details.

vtpm=[ "VTPM_SPEC_STRING", "VTPM_SPEC_STRING", ...]
Specifies the Virtual Trusted Platform module to be provided to the guest. See
xen-vtpm(7) for more details.

Each VTPM_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings from the
following list:

backend=domain-id
Specifies the backend domain name or id. This value is required! If this domain
is a guest, the backend should be set to the vTPM domain name. If this domain is a
vTPM, the backend should be set to the vTPM manager domain name.

uuid=UUID
Specifies the UUID of this vTPM device. The UUID is used to uniquely identify the
vTPM device. You can create one using the uuidgen(1) program on unix systems. If
left unspecified, a new UUID will be randomly generated every time the domain
boots. If this is a vTPM domain, you should specify a value. The value is
optional if this is a guest domain.

p9=[ "9PFS_SPEC_STRING", "9PFS_SPEC_STRING", ...]
Creates a Xen 9pfs connection to share a filesystem from the backend to the frontend.

Each 9PFS_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings, from the
following list:

tag=STRING
9pfs tag to identify the filesystem share. The tag is needed on the guest side to
mount it.

security_model="none"
Only "none" is supported today, which means that the files are stored using the
same credentials as those they have in the guest (no user ownership squash or
remap).

path=STRING
Filesystem path on the backend to export.

backend=domain-id
Specify the backend domain name or id, defaults to dom0.

pvcalls=[ "backend=domain-id", ... ]
Creates a Xen pvcalls connection to handle pvcalls requests from frontend to backend.
It can be used as an alternative networking model. For more information about the
protocol, see https://xenbits.xenproject.org/docs/unstable/misc/pvcalls.html.

vfb=[ "VFB_SPEC_STRING", "VFB_SPEC_STRING", ...]
Specifies the paravirtual framebuffer devices which should be supplied to the domain.

This option does not control the emulated graphics card presented to an HVM guest. See
Emulated VGA Graphics Device below for how to configure the emulated device. If
Emulated VGA Graphics Device options are used in a PV guest configuration, xl will
pick up vnc, vnclisten, vncpasswd, vncdisplay, vncunused, sdl, opengl and keymap to
construct the paravirtual framebuffer device for the guest.

Each VFB_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings, from the
following list:

vnc=BOOLEAN
Allow access to the display via the VNC protocol. This enables the other VNC-
related settings. Default is 1 (enabled).

vnclisten=ADDRESS[:DISPLAYNUM]
Specifies the IP address, and optionally the VNC display number, to use.

Note: if you specify the display number here, you should not use the vncdisplay
option.

vncdisplay=DISPLAYNUM
Specifies the VNC display number to use. The actual TCP port number will be
DISPLAYNUM+5900.

Note: you should not use this option if you set the DISPLAYNUM in the vnclisten
option.

vncunused=BOOLEAN
Requests that the VNC display setup searches for a free TCP port to use. The
actual display used can be accessed with xl vncviewer.

vncpasswd=PASSWORD
Specifies the password for the VNC server. If the password is set to an empty
string, authentication on the VNC server will be disabled, allowing any user to
connect.

sdl=BOOLEAN
Specifies that the display should be presented via an X window (using Simple
DirectMedia Layer). The default is 0 (not enabled).

display=DISPLAY
Specifies the X Window display that should be used when the sdl option is used.

xauthority=XAUTHORITY
Specifies the path to the X authority file that should be used to connect to the X
server when the sdl option is used.

opengl=BOOLEAN
Enable OpenGL acceleration of the SDL display. Only effects machines using
device_model_version="qemu-xen-traditional" and only if the device-model was
compiled with OpenGL support. The default is 0 (disabled).

keymap=LANG
Configure the keymap to use for the keyboard associated with this display. If the
input method does not easily support raw keycodes (e.g. this is often the case
when using VNC) then this allows us to correctly map the input keys into keycodes
seen by the guest. The specific values which are accepted are defined by the
version of the device-model which you are using. See Keymaps below or consult the
qemu(1) manpage. The default is en-us.

channel=[ "CHANNEL_SPEC_STRING", "CHANNEL_SPEC_STRING", ...]
Specifies the virtual channels to be provided to the guest. A channel is a low-
bandwidth, bidirectional byte stream, which resembles a serial link. Typical uses for
channels include transmitting VM configuration after boot and signalling to in-guest
agents. Please see xen-pv-channel(7) for more details.

Each CHANNEL_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings. Leading
and trailing whitespace is ignored in both KEY and VALUE. Neither KEY nor VALUE may
contain ',', '=' or '"'. Defined values are:

backend=domain-id
Specifies the backend domain name or id. This parameter is optional. If this
parameter is omitted then the toolstack domain will be assumed.

name=NAME
Specifies the name for this device. This parameter is mandatory! This should be a
well-known name for a specific application (e.g. guest agent) and should be used
by the frontend to connect the application to the right channel device. There is
no formal registry of channel names, so application authors are encouraged to make
their names unique by including the domain name and a version number in the string
(e.g. org.mydomain.guestagent.1).

connection=CONNECTION
Specifies how the backend will be implemented. The following options are
available:

SOCKET
The backend will bind a Unix domain socket (at the path given by path=PATH),
listen for and accept connections. The backend will proxy data between the
channel and the connected socket.

PTY The backend will create a pty and proxy data between the channel and the
master device. The command xl channel-list can be used to discover the
assigned slave device.

rdm="RDM_RESERVATION_STRING"
HVM/x86 only! Specifies information about Reserved Device Memory (RDM), which is
necessary to enable robust device passthrough. One example of RDM is reporting through
the ACPI Reserved Memory Region Reporting (RMRR) structure on the x86 platform.

RDM_RESERVATION_STRING is a comma separated list of "KEY=VALUE" settings, from the
following list:

strategy=STRING
Currently there is only one valid type, and that is "host".

host
If set to "host" it means all reserved device memory on this platform should
be checked to reserve regions in this VM's address space. This global RDM
parameter allows the user to specify reserved regions explicitly, and using
"host" includes all reserved regions reported on this platform, which is
useful when doing hotplug.

By default this isn't set so we don't check all RDMs. Instead, we just check
the RDM specific to a given device if we're assigning this kind of a device.

Note: this option is not recommended unless you can make sure that no
conflicts exist.

For example, you're trying to set "memory = 2800" to allocate memory to one
given VM but the platform owns two RDM regions like:

Device A [sbdf_A]: RMRR region_A: base_addr ac6d3000 end_address ac6e6fff

Device B [sbdf_B]: RMRR region_B: base_addr ad800000 end_address afffffff

In this conflict case,

#1. If strategy is set to "host", for example:

rdm = "strategy=host,policy=strict" or rdm = "strategy=host,policy=relaxed"

it means all conflicts will be handled according to the policy introduced by
policy as described below.

#2. If strategy is not set at all, but

pci = [ 'sbdf_A, rdm_policy=xxxxx' ]

it means only one conflict of region_A will be handled according to the policy
introduced by rdm_policy=STRING as described inside pci options.

policy=STRING
Specifies how to deal with conflicts when reserving already reserved device memory
in the guest address space.

strict
Specifies that in case of an unresolved conflict the VM can't be created, or
the associated device can't be attached in the case of hotplug.

relaxed
Specifies that in case of an unresolved conflict the VM is allowed to be
created but may cause the VM to crash if a pass-through device accesses RDM.
For example, the Windows IGD GFX driver always accesses RDM regions so it
leads to a VM crash.

Note: this may be overridden by the rdm_policy option in the pci device
configuration.

usbctrl=[ "USBCTRL_SPEC_STRING", "USBCTRL_SPEC_STRING", ...]
Specifies the USB controllers created for this guest.

Each USBCTRL_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings, from the
following list:

type=TYPE
Specifies the usb controller type.

pv Specifies a kernel based PVUSB backend.

qusb
Specifies a QEMU based PVUSB backend.

devicemodel
Specifies a USB controller emulated by QEMU. It will show up as a PCI-device
in the guest.

auto
Determines whether a kernel based backend is installed. If this is the case,
pv is used, otherwise qusb will be used. For HVM domains devicemodel will be
selected.

This option is the default.

version=VERSION
Specifies the usb controller version. Possible values include 1 (USB1.1), 2
(USB2.0) and 3 (USB3.0). Default is 2 (USB2.0). Value 3 (USB3.0) is available
for the devicemodel type only.

ports=PORTS
Specifies the total number of ports of the usb controller. The maximum number is
31. The default is 8. With the type devicemodel the number of ports is more
limited: a USB1.1 controller always has 2 ports, a USB2.0 controller always has 6
ports and a USB3.0 controller can have up to 15 ports.

USB controller ids start from 0. In line with the USB specification, however,
ports on a controller start from 1.

EXAMPLE

usbctrl=["version=1,ports=4", "version=2,ports=8"]

The first controller is USB1.1 and has:

controller id = 0, and ports 1,2,3,4.

The second controller is USB2.0 and has:

controller id = 1, and ports 1,2,3,4,5,6,7,8.

usbdev=[ "USBDEV_SPEC_STRING", "USBDEV_SPEC_STRING", ...]
Specifies the USB devices to be attached to the guest at boot.

Each USBDEV_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings, from the
following list:

type=hostdev
Specifies USB device type. Currently only "hostdev" is supported.

hostbus=busnum
Specifies busnum of the USB device from the host perspective.

hostaddr=devnum
Specifies devnum of the USB device from the host perspective.

controller=CONTROLLER
Specifies the USB controller id, to which controller the USB device is attached.

If no controller is specified, an available controller:port combination will be
used. If there are no available controller:port combinations, a new controller
will be created.

port=PORT
Specifies the USB port to which the USB device is attached. The port option is
valid only when the controller option is specified.

pci=[ "PCI_SPEC_STRING", "PCI_SPEC_STRING", ...]
Specifies the host PCI devices to passthrough to this guest. See
xl-pci-configuration(5) for more details.

pci_permissive=BOOLEAN
Changes the default value of permissive for all PCI devices passed through to this VM.
See permissive above.

pci_msitranslate=BOOLEAN
Changes the default value of msitranslate for all PCI devices passed through to this
VM. See msitranslate above.

pci_seize=BOOLEAN
Changes the default value of seize for all PCI devices passed through to this VM. See
seize above.

pci_power_mgmt=BOOLEAN
(HVM only) Changes the default value of power_mgmt for all PCI devices passed through
to this VM. See power_mgmt above.

gfx_passthru=BOOLEAN|"STRING"
Enable graphics device PCI passthrough. This option makes an assigned PCI graphics
card become the primary graphics card in the VM. The QEMU emulated graphics adapter is
disabled and the VNC console for the VM will not have any graphics output. All
graphics output, including boot time QEMU BIOS messages from the VM, will go to the
physical outputs of the passed through physical graphics card.

The graphics card PCI device to pass through is chosen with the pci option, in exactly
the same way a normal Xen PCI device passthrough/assignment is done. Note that
gfx_passthru does not do any kind of sharing of the GPU, so you can assign the GPU to
only one single VM at a time.

gfx_passthru also enables various legacy VGA memory ranges, BARs, MMIOs, and ioports
to be passed through to the VM, since those are required for correct operation of
things like VGA BIOS, text mode, VBE, etc.

Enabling the gfx_passthru option also copies the physical graphics card video BIOS to
the guest memory, and executes the VBIOS in the guest to initialize the graphics card.

Most graphics adapters require vendor specific tweaks for properly working graphics
passthrough. See the XenVGAPassthroughTestedAdapters
<https://wiki.xenproject.org/wiki/XenVGAPassthroughTestedAdapters> wiki page for
graphics cards currently supported by gfx_passthru.

gfx_passthru is currently supported both with the qemu-xen-traditional device-model
and upstream qemu-xen device-model.

When given as a boolean the gfx_passthru option either disables graphics card
passthrough or enables autodetection.

When given as a string the gfx_passthru option describes the type of device to enable.
Note that this behavior is only supported with the upstream qemu-xen device-model.
With qemu-xen-traditional IGD (Intel Graphics Device) is always assumed and options
other than autodetect or explicit IGD will result in an error.

Currently, valid values for the option are:

0 Disables graphics device PCI passthrough.

1, "default"
Enables graphics device PCI passthrough and autodetects the type of device which
is being used.

"igd"
Enables graphics device PCI passthrough but forcing the type of device to Intel
Graphics Device.

Note that some graphics cards (AMD/ATI cards, for example) do not necessarily require
the gfx_passthru option, so you can use the normal Xen PCI passthrough to assign the
graphics card as a secondary graphics card to the VM. The QEMU-emulated graphics card
remains the primary graphics card, and VNC output is available from the QEMU-emulated
primary adapter.

More information about the Xen gfx_passthru feature is available on the
XenVGAPassthrough <https://wiki.xenproject.org/wiki/XenVGAPassthrough> wiki page.

rdm_mem_boundary=MBYTES
Number of megabytes to set for a boundary when checking for RDM conflicts.

When RDM conflicts with RAM, RDM is probably scattered over the whole RAM space.
Having multiple RDM entries would worsen this and lead to a complicated memory layout.
Here we're trying to figure out a simple solution to avoid breaking the existing
layout. When a conflict occurs,

#1. Above a predefined boundary
- move lowmem_end below the reserved region to solve the conflict;

#2. Below a predefined boundary
- Check if the policy is strict or relaxed.
A "strict" policy leads to a fail in libxl.
Note that when both policies are specified on a given region,
"strict" is always preferred.
The "relaxed" policy issues a warning message and also masks this
entry INVALID to indicate we shouldn't expose this entry to
hvmloader.

The default value is 2048.

dtdev=[ "DTDEV_PATH", "DTDEV_PATH", ...]
Specifies the host device tree nodes to passt hrough to this guest. Each DTDEV_PATH is
an absolute path in the device tree.

ioports=[ "IOPORT_RANGE", "IOPORT_RANGE", ...]
Allow the guest to access specific legacy I/O ports. Each IOPORT_RANGE is given in
hexadecimal format and may either be a range, e.g. "2f8-2ff" (inclusive), or a single
I/O port, e.g. "2f8".

It is recommended to only use this option for trusted VMs under administrator's
control.

iomem=[ "IOMEM_START,NUM_PAGES[@GFN]", "IOMEM_START,NUM_PAGES[@GFN]", ...]
Allow auto-translated domains to access specific hardware I/O memory pages.

IOMEM_START is a physical page number. NUM_PAGES is the number of pages, beginning
with START_PAGE, to allow access to. GFN specifies the guest frame number where the
mapping will start in the guest's address space. If GFN is not specified, the mapping
will be performed using IOMEM_START as a start in the guest's address space, therefore
performing a 1:1 mapping by default. All of these values must be given in hexadecimal
format.

Note that the IOMMU won't be updated with the mappings specified with this option.
This option therefore should not be used to pass through any IOMMU-protected devices.

It is recommended to only use this option for trusted VMs under administrator's
control.

irqs=[ NUMBER, NUMBER, ...]
Allow a guest to access specific physical IRQs.

It is recommended to only use this option for trusted VMs under administrator's
control.

If vuart console is enabled then irq 32 is reserved for it. See "vuart="uart"" to know
how to enable vuart console.

max_event_channels=N
Limit the guest to using at most N event channels (PV interrupts). Guests use
hypervisor resources for each event channel they use.

The default of 1023 should be sufficient for typical guests. The maximum value
depends on what the guest supports. Guests supporting the FIFO-based event channel
ABI support up to 131,071 event channels. Other guests are limited to 4095 (64-bit
x86 and ARM) or 1023 (32-bit x86).

vdispl=[ "VDISPL_SPEC_STRING", "VDISPL_SPEC_STRING", ...]
Specifies the virtual display devices to be provided to the guest.

Each VDISPL_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings, from the
following list:

"backend=DOMAIN"
Specifies the backend domain name or id. If not specified Domain-0 is used.

"be-alloc=BOOLEAN"
Indicates if backend can be a buffer provider/allocator for this domain. See
display protocol for details.

"connectors=CONNECTORS"
Specifies virtual connectors for the device in following format
<id>:<W>x<H>;<id>:<W>x<H>... where:

"id"
String connector unique id. Space, comma symbols are not allowed.

"W" Connector width in pixels.

"H" Connector height in pixels.

EXAMPLE

connectors=id0:1920x1080;id1:800x600;id2:640x480

dm_restrict=BOOLEAN
Restrict the device model after startup, to limit the consequencese of security
vulnerabilities in qemu.

See docs/features/qemu-depriv.pandoc for more information on Linux and QEMU version
requirements, device model user setup, and current limitations.

This feature is a technology preview. See SUPPORT.md for a security support
statement.

device_model_user=USERNAME
When running dm_restrict, run the device model as this user.

NOTE: Each domain MUST have a SEPARATE username.

See docs/features/qemu-depriv.pandoc for more information.

vsnd=[ VCARD_SPEC, VCARD_SPEC, ... ]
Specifies the virtual sound cards to be provided to the guest. Each VCARD_SPEC is a
list, which has a form of "[VSND_ITEM_SPEC, VSND_ITEM_SPEC, ... ]" (without the
quotes). The virtual sound card has hierarchical structure. Every card has a set of
PCM devices and streams, each could be individually configured.

VSND_ITEM_SPEC describes individual item parameters. VSND_ITEM_SPEC is a string of
comma separated item parameters headed by item identifier. Each item parameter is
"KEY=VALUE" pair:

"identifier, param = value, ...".

Identifier shall be one of following values: "CARD", "PCM", "STREAM". The child item
treated as belonging to the previously defined parent item.

All parameters are optional.

There are group of parameters which are common for all items. This group can be
defined at higher level of the hierarchy and be fully or partially re-used by the
underlying layers. These parameters are:

* number of channels (min/max)

* supported sample rates

* supported sample formats

E.g. one can define these values for the whole card, device or stream. Every
underlying layer in turn can re-define some or all of them to better fit its needs.
For example, card may define number of channels to be in [1; 8] range, and some
particular stream may be limited to [1; 2] only. The rule is that the underlying
layer must be a subset of the upper layer range.

COMMON parameters:

sample-rates=RATES
List of integer values separated by semicolon: sample-rates=8000;22050;44100

sample-formats=FORMATS
List of string values separated by semicolon: sample-formats=s16_le;s8;u32_be

Supported formats: s8, u8, s16_le, s16_be, u16_le, u16_be, s24_le, s24_be,
u24_le, u24_be, s32_le, s32_be, u32_le, u32_be, float_le, float_be,
float64_le, float64_be, iec958_subframe_le, iec958_subframe_be, mu_law, a_law,
ima_adpcm, mpeg, gsm

channels-min=NUMBER
The minimum amount of channels.

channels-max=NUMBER
The maximum amount of channels.

buffer-size=NUMBER
The maximum size in octets of the buffer to allocate per stream.

CARD specification:

backend=domain-id
Specify the backend domain name or id, defaults to dom0.

short-name=STRING
Short name of the virtual sound card.

long-name=STRING
Long name of the virtual sound card.

PCM specification:

name=STRING
Name of the PCM sound device within the virtual sound card.

STREAM specification:

unique-id=STRING
Unique stream identifier.

type=TYPE
Stream type: "p" - playback stream, "c" - capture stream.

EXAMPLE:

vsnd = [
['CARD, short-name=Main, sample-formats=s16_le;s8;u32_be',
'PCM, name=Main',
'STREAM, id=0, type=p',
'STREAM, id=1, type=c, channels-max=2'
],
['CARD, short-name=Second',
'PCM, name=Second, buffer-size=1024',
'STREAM, id=2, type=p',
'STREAM, id=3, type=c'
]
]

vkb=[ "VKB_SPEC_STRING", "VKB_SPEC_STRING", ...]
Specifies the virtual keyboard device to be provided to the guest.

Each VKB_SPEC_STRING is a comma-separated list of "KEY=VALUE" settings from the
following list:

unique-id=STRING
Specifies the unique input device id.

backend=domain-id
Specifies the backend domain name or id.

backend-type=type
Specifies the backend type: qemu - for QEMU backend or linux - for Linux PV
domain.

feature-disable-keyboard=BOOLEAN
Indicates if keyboard device is disabled.

feature-disable-pointer=BOOLEAN
Indicates if pointer device is disabled.

feature-abs-pointer=BOOLEAN
Indicates if pointer device can return absolute coordinates.

feature-raw-pointer=BOOLEAN
Indicates if pointer device can return raw (unscaled) absolute coordinates.

feature-multi-touch=BOOLEAN
Indicates if input device supports multi touch.

multi-touch-width=MULTI_TOUCH_WIDTH
Set maximum width for multi touch device.

multi-touch-height=MULTI_TOUCH_HEIGHT
Set maximum height for multi touch device.

multi-touch-num-contacts=MULTI_TOUCH_NUM_CONTACTS
Set maximum contacts number for multi touch device.

width=WIDTH
Set maximum width for pointer device.

height=HEIGHT
Set maximum height for pointer device.

tee="STRING"
Arm only. Set TEE type for the guest. TEE is a Trusted Execution Environment --
separate secure OS found on some platforms. STRING can be one of the:

none
"Don't allow the guest to use TEE if present on the platform. This is the default
value.

optee
Allow a guest to access the host OP-TEE OS. Xen will mediate the access to OP-TEE
and the resource isolation will be provided directly by OP-TEE. OP-TEE itself may
limit the number of guests that can concurrently use it. This requires a
virtualization-aware OP-TEE for this to work.

You can refer to OP-TEE documentation
<https://optee.readthedocs.io/en/latest/architecture/virtualization.html> for more
information about how to enable and configure virtualization support in OP-TEE.

This feature is a technology preview.

Paravirtualised (PV) Guest Specific Options
The following options apply only to Paravirtual (PV) guests.

bootloader="PROGRAM"
Run "PROGRAM" to find the kernel image and ramdisk to use. Normally "PROGRAM" would
be "pygrub", which is an emulation of grub/grub2/syslinux. Either kernel or bootloader
must be specified for PV guests.

bootloader_args=[ "ARG", "ARG", ...]
Append ARGs to the arguments to the bootloader program. Alternatively if the argument
is a simple string then it will be split into words at whitespace (this second option
is deprecated).

e820_host=BOOLEAN
Selects whether to expose the host e820 (memory map) to the guest via the virtual
e820. When this option is false (0) the guest pseudo-physical address space consists
of a single contiguous RAM region. When this option is specified the virtual e820
instead reflects the host e820 and contains the same PCI holes. The total amount of
RAM represented by the memory map is always the same, this option configures only how
it is laid out.

Exposing the host e820 to the guest gives the guest kernel the opportunity to set
aside the required part of its pseudo-physical address space in order to provide
address space to map passedthrough PCI devices. It is guest Operating System dependent
whether this option is required, specifically it is required when using a mainline
Linux ("pvops") kernel. This option defaults to true (1) if any PCI passthrough
devices are configured and false (0) otherwise. If you do not configure any
passthrough devices at domain creation time but expect to hotplug devices later then
you should set this option. Conversely if your particular guest kernel does not
require this behaviour then it is safe to allow this to be enabled but you may wish to
disable it anyway.

Fully-virtualised (HVM) Guest Specific Options
The following options apply only to Fully-virtualised (HVM) guests.

Boot Device

boot="STRING"
Specifies the emulated virtual device to boot from.

Possible values are:

c Hard disk.

d CD-ROM.

n Network / PXE.

Note: multiple options can be given and will be attempted in the order they are given,
e.g. to boot from CD-ROM but fall back to the hard disk you can specify it as dc.

The default is cd, meaning try booting from the hard disk first, but fall back to the
CD-ROM.

Emulated disk controller type

hdtype=STRING
Specifies the hard disk type.

Possible values are:

ide If thise mode is specified xl adds an emulated IDE controller, which is suitable
even for older operation systems.

ahci
If this mode is specified, xl adds an ich9 disk controller in AHCI mode and uses
it with upstream QEMU to emulate disks instead of IDE. It decreases boot time but
may not be supported by default in older operating systems, e.g. Windows XP.

The default is ide.

Paging

The following options control the mechanisms used to virtualise guest memory. The
defaults are selected to give the best results for the common cases so you should normally
leave these options unspecified.

hap=BOOLEAN
Turns "hardware assisted paging" (the use of the hardware nested page table feature)
on or off. This feature is called EPT (Extended Page Tables) by Intel and NPT (Nested
Page Tables) or RVI (Rapid Virtualisation Indexing) by AMD. If turned off, Xen will
run the guest in "shadow page table" mode where the guest's page table updates and/or
TLB flushes etc. will be emulated. Use of HAP is the default when available.

oos=BOOLEAN
Turns "out of sync pagetables" on or off. When running in shadow page table mode, the
guest's page table updates may be deferred as specified in the Intel/AMD architecture
manuals. However, this may expose unexpected bugs in the guest, or find bugs in Xen,
so it is possible to disable this feature. Use of out of sync page tables, when Xen
thinks it appropriate, is the default.

shadow_memory=MBYTES
Number of megabytes to set aside for shadowing guest pagetable pages (effectively
acting as a cache of translated pages) or to use for HAP state. By default this is 1MB
per guest vCPU plus 8KB per MB of guest RAM. You should not normally need to adjust
this value. However, if you are not using hardware assisted paging (i.e. you are using
shadow mode) and your guest workload consists of a very large number of similar
processes then increasing this value may improve performance.

Processor and Platform Features

The following options allow various processor and platform level features to be hidden or
exposed from the guest's point of view. This can be useful when running older guest
Operating Systems which may misbehave when faced with more modern features. In general,
you should accept the defaults for these options wherever possible.

bios="STRING"
Select the virtual firmware that is exposed to the guest. By default, a guess is made
based on the device model, but sometimes it may be useful to request a different one,
like UEFI.

rombios
Loads ROMBIOS, a 16-bit x86 compatible BIOS. This is used by default when
device_model_version=qemu-xen-traditional. This is the only BIOS option supported
when device_model_version=qemu-xen-traditional. This is the BIOS used by all
previous Xen versions.

seabios
Loads SeaBIOS, a 16-bit x86 compatible BIOS. This is used by default with
device_model_version=qemu-xen.

ovmf
Loads OVMF, a standard UEFI firmware by Tianocore project. Requires
device_model_version=qemu-xen.

bios_path_override="PATH"
Override the path to the blob to be used as BIOS. The blob provided here MUST be
consistent with the bios= which you have specified. You should not normally need to
specify this option.

This option does not have any effect if using bios="rombios" or
device_model_version="qemu-xen-traditional".

pae=BOOLEAN
Hide or expose the IA32 Physical Address Extensions. These extensions make it possible
for a 32 bit guest Operating System to access more than 4GB of RAM. Enabling PAE also
enabled other features such as NX. PAE is required if you wish to run a 64-bit guest
Operating System. In general, you should leave this enabled and allow the guest
Operating System to choose whether or not to use PAE. (X86 only)

acpi=BOOLEAN
Expose ACPI (Advanced Configuration and Power Interface) tables from the virtual
firmware to the guest Operating System. ACPI is required by most modern guest
Operating Systems. This option is enabled by default and usually you should omit it.
However, it may be necessary to disable ACPI for compatibility with some guest
Operating Systems. This option is true for x86 while it's false for ARM by default.

acpi_s3=BOOLEAN
Include the S3 (suspend-to-ram) power state in the virtual firmware ACPI table. True
(1) by default.

acpi_s4=BOOLEAN
Include S4 (suspend-to-disk) power state in the virtual firmware ACPI table. True (1)
by default.

acpi_laptop_slate=BOOLEAN
Include the Windows laptop/slate mode switch device in the virtual firmware ACPI
table. False (0) by default.

apic=BOOLEAN
(x86 only) Include information regarding APIC (Advanced Programmable Interrupt
Controller) in the firmware/BIOS tables on a single processor guest. This causes the
MP (multiprocessor) and PIR (PCI Interrupt Routing) tables to be exported by the
virtual firmware. This option has no effect on a guest with multiple virtual CPUs as
they must always include these tables. This option is enabled by default and you
should usually omit it but it may be necessary to disable these firmware tables when
using certain older guest Operating Systems. These tables have been superseded by
newer constructs within the ACPI tables.

nx=BOOLEAN
(x86 only) Hides or exposes the No-eXecute capability. This allows a guest Operating
System to map pages in such a way that they cannot be executed which can enhance
security. This options requires that PAE also be enabled.

hpet=BOOLEAN
(x86 only) Enables or disables HPET (High Precision Event Timer). This option is
enabled by default and you should usually omit it. It may be necessary to disable the
HPET in order to improve compatibility with guest Operating Systems.

altp2m="MODE"
(x86 only) Specifies the access mode to the alternate-p2m capability. Alternate-p2m
allows a guest to manage multiple p2m guest physical "memory views" (as opposed to a
single p2m). You may want this option if you want to access-control/isolate access to
specific guest physical memory pages accessed by the guest, e.g. for domain memory
introspection or for isolation/access-control of memory between components within a
single guest domain. This option is disabled by default.

The valid values are as follows:

disabled
Altp2m is disabled for the domain (default).

mixed
The mixed mode allows access to the altp2m interface for both in-guest and
external tools as well.

external
Enables access to the alternate-p2m capability by external privileged tools.

limited
Enables limited access to the alternate-p2m capability, ie. giving the guest
access only to enable/disable the VMFUNC and #VE features.

altp2mhvm=BOOLEAN
Enables or disables HVM guest access to alternate-p2m capability. Alternate-p2m
allows a guest to manage multiple p2m guest physical "memory views" (as opposed to a
single p2m). This option is disabled by default and is available only to HVM domains.
You may want this option if you want to access-control/isolate access to specific
guest physical memory pages accessed by the guest, e.g. for HVM domain memory
introspection or for isolation/access-control of memory between components within a
single guest HVM domain. This option is deprecated, use the option "altp2m" instead.

Note: While the option "altp2mhvm" is deprecated, legacy applications for x86 systems
will continue to work using it.

nestedhvm=BOOLEAN
Enable or disables guest access to hardware virtualisation features, e.g. it allows a
guest Operating System to also function as a hypervisor. You may want this option if
you want to run another hypervisor (including another copy of Xen) within a Xen guest
or to support a guest Operating System which uses hardware virtualisation extensions
(e.g. Windows XP compatibility mode on more modern Windows OS). This option is
disabled by default.

cpuid="LIBXL_STRING" or cpuid=[ "XEND_STRING", "XEND_STRING" ]
Configure the value returned when a guest executes the CPUID instruction. Two
versions of config syntax are recognized: libxl and xend.

Both formats use a common notation for specifying a single feature bit. Possible
values are:
'1' -> force the corresponding bit to 1
'0' -> force to 0
'x' -> Get a safe value (pass through and mask with the default policy)
'k' -> pass through the host bit value (at boot only - value preserved on migrate)
's' -> legacy alias for 'k'

Libxl format:

The libxl format is a single string, starting with the word "host", and followed
by a comma separated list of key=value pairs. A few keys take a numerical value,
all others take a single character which describes what to do with the feature
bit. e.g.:

cpuid="host,tm=0,sse3=0"

List of keys taking a value:

apicidsize brandid clflush family localapicid maxleaf maxhvleaf model nc
proccount procpkg stepping

List of keys taking a character:

3dnow 3dnowext 3dnowprefetch abm acpi adx aes altmovcr8 apic arat avx avx2
avx512-4fmaps avx512-4vnniw avx512bw avx512cd avx512dq avx512er avx512f
avx512ifma avx512pf avx512vbmi avx512vl bmi1 bmi2 clflushopt clfsh clwb cmov
cmplegacy cmpxchg16 cmpxchg8 cmt cntxid dca de ds dscpl dtes64 erms est
extapic f16c ffxsr fma fma4 fpu fsgsbase fxsr hle htt hypervisor ia64 ibs
invpcid invtsc lahfsahf lm lwp mca mce misalignsse mmx mmxext monitor movbe
mpx msr mtrr nodeid nx ospke osvw osxsave pae page1gb pat pbe pcid pclmulqdq
pdcm perfctr_core perfctr_nb pge pku popcnt pse pse36 psn rdrand rdseed rdtscp
rtm sha skinit smap smep smx ss sse sse2 sse3 sse4.1 sse4.2 sse4_1 sse4_2
sse4a ssse3 svm svm_decode svm_lbrv svm_npt svm_nrips svm_pausefilt
svm_tscrate svm_vmcbclean syscall sysenter tbm tm tm2 topoext tsc tsc-deadline
tsc_adjust umip vme vmx wdt x2apic xop xsave xtpr

Xend format:

Xend format consists of an array of one or more strings of the form
"leaf:reg=bitstring,...". e.g. (matching the libxl example above):

cpuid=["1:ecx=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx0,edx=xx0xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
...]

"leaf" is an integer, either decimal or hex with a "0x" prefix. e.g. to specify
something in the AMD feature leaves, use "0x80000001:ecx=...".

Some leaves have subleaves which can be specified as "leaf,subleaf". e.g. for the
Intel structured feature leaf, use "7,0:ebx=..."

The bitstring represents all bits in the register, its length must be 32 chars.
Each successive character represent a lesser-significant bit.

Note: when specifying cpuid for hypervisor leaves (0x4000xxxx major group) only the
lowest 8 bits of leaf's 0x4000xx00 EAX register are processed, the rest are ignored
(these 8 bits signify maximum number of hypervisor leaves).

More info about the CPUID instruction can be found in the processor manuals, and on
Wikipedia: <https://en.wikipedia.org/wiki/CPUID>

acpi_firmware="STRING"
Specifies a path to a file that contains extra ACPI firmware tables to pass into a
guest. The file can contain several tables in their binary AML form concatenated
together. Each table self describes its length so no additional information is needed.
These tables will be added to the ACPI table set in the guest. Note that existing
tables cannot be overridden by this feature. For example, this cannot be used to
override tables like DSDT, FADT, etc.

smbios_firmware="STRING"
Specifies a path to a file that contains extra SMBIOS firmware structures to pass into
a guest. The file can contain a set of DMTF predefined structures which will override
the internal defaults. Not all predefined structures can be overridden, only the
following types: 0, 1, 2, 3, 11, 22, 39. The file can also contain any number of
vendor defined SMBIOS structures (type 128 - 255). Since SMBIOS structures do not
present their overall size, each entry in the file must be preceded by a 32b integer
indicating the size of the following structure.

ms_vm_genid="OPTION"
Provide a VM generation ID to the guest.

The VM generation ID is a 128-bit random number that a guest may use to determine if
the guest has been restored from an earlier snapshot or cloned.

This is required for Microsoft Windows Server 2012 (and later) domain controllers.

Valid options are:

generate
Generate a random VM generation ID every time the domain is created or restored.

none
Do not provide a VM generation ID.

See also "Virtual Machine Generation ID" by Microsoft:
<https://docs.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-machine-generation-identifier>

Guest Virtual Time Controls

tsc_mode="MODE"
(x86 only) Specifies how the TSC (Time Stamp Counter) should be provided to the guest.
Specifying this option as a number is deprecated.

Options are:

default
Guest rdtsc/p is executed natively when monotonicity can be guaranteed and
emulated otherwise (with frequency scaled if necessary).

If a HVM container in default TSC mode is created on a host that provides constant
host TSC, its guest TSC frequency will be the same as the host. If it is later
migrated to another host that provide constant host TSC and supports Intel VMX TSC
scaling/AMD SVM TSC ratio, its guest TSC frequency will be the same before and
after migration, and guest rdtsc/p will be executed natively after migration as
well

always_emulate
Guest rdtsc/p is always emulated and the virtual TSC will appear to increment
(kernel and user) at a fixed 1GHz rate, regardless of the pCPU HZ rate or power
state. Although there is an overhead associated with emulation, this will NOT
affect underlying CPU performance.

native
Guest rdtsc/p is always executed natively (no monotonicity/frequency guarantees).
Guest rdtsc/p is emulated at native frequency if unsupported by h/w, else executed
natively.

native_paravirt
This mode has been removed.

Please see xen-tscmode(7) for more information on this option.

localtime=BOOLEAN
Set the real time clock to local time or to UTC. False (0) by default, i.e. set to
UTC.

rtc_timeoffset=SECONDS
Set the real time clock offset in seconds. No offset (0) by default.

vpt_align=BOOLEAN
Specifies that periodic Virtual Platform Timers should be aligned to reduce guest
interrupts. Enabling this option can reduce power consumption, especially when a guest
uses a high timer interrupt frequency (HZ) values. The default is true (1).

timer_mode="MODE"
Specifies the mode for Virtual Timers. The valid values are as follows:

delay_for_missed_ticks
Delay for missed ticks. Do not advance a vCPU's time beyond the correct delivery
time for interrupts that have been missed due to preemption. Deliver missed
interrupts when the vCPU is rescheduled and advance the vCPU's virtual time
stepwise for each one.

no_delay_for_missed_ticks
No delay for missed ticks. As above, missed interrupts are delivered, but guest
time always tracks wallclock (i.e., real) time while doing so. This is the
default.

no_missed_ticks_pending
No missed interrupts are held pending. Instead, to ensure ticks are delivered at
some non-zero rate, if we detect missed ticks then the internal tick alarm is not
disabled if the vCPU is preempted during the next tick period.

one_missed_tick_pending
One missed tick pending. Missed interrupts are collapsed together and delivered as
one 'late tick'. Guest time always tracks wallclock (i.e., real) time.

Memory layout

mmio_hole=MBYTES
Specifies the size the MMIO hole below 4GiB will be. Only valid for
device_model_version="qemu-xen".

Cannot be smaller than 256. Cannot be larger than 3840.

Known good large value is 3072.

Support for Paravirtualisation of HVM Guests

The following options allow Paravirtualised features (such as devices) to be exposed to
the guest Operating System in an HVM guest. Utilising these features requires specific
guest support but when available they will result in improved performance.

xen_platform_pci=BOOLEAN
Enable or disable the Xen platform PCI device. The presence of this virtual device
enables a guest Operating System (subject to the availability of suitable drivers) to
make use of paravirtualisation features such as disk and network devices etc. Enabling
these drivers improves performance and is strongly recommended when available. PV
drivers are available for various Operating Systems including HVM Linux (out-of-the-
box) and Microsoft Windows <https://xenproject.org/windows-pv-drivers/>.

Setting xen_platform_pci=0 with the default device_model "qemu-xen" requires at least
QEMU 1.6.

viridian=[ "GROUP", "GROUP", ...] or viridian=BOOLEAN
The groups of Microsoft Hyper-V (AKA viridian) compatible enlightenments exposed to
the guest. The following groups of enlightenments may be specified:

base
This group incorporates the Hypercall MSRs, Virtual processor index MSR, and APIC
access MSRs. These enlightenments can improve performance of Windows Vista and
Windows Server 2008 onwards and setting this option for such guests is strongly
recommended. This group is also a pre-requisite for all others. If it is disabled
then it is an error to attempt to enable any other group.

freq
This group incorporates the TSC and APIC frequency MSRs. These enlightenments can
improve performance of Windows 7 and Windows Server 2008 R2 onwards.

time_ref_count
This group incorporates Partition Time Reference Counter MSR. This enlightenment
can improve performance of Windows 8 and Windows Server 2012 onwards.

reference_tsc
This set incorporates the Partition Reference TSC MSR. This enlightenment can
improve performance of Windows 7 and Windows Server 2008 R2 onwards.

hcall_remote_tlb_flush
This set incorporates use of hypercalls for remote TLB flushing. This
enlightenment may improve performance of Windows guests running on hosts with
higher levels of (physical) CPU contention.

apic_assist
This set incorporates use of the APIC assist page to avoid EOI of the local APIC.
This enlightenment may improve performance of guests that make use of per-vCPU
event channel upcall vectors. Note that this enlightenment will have no effect if
the guest is using APICv posted interrupts.

crash_ctl
This group incorporates the crash control MSRs. These enlightenments allow Windows
to write crash information such that it can be logged by Xen.

stimer
This set incorporates the SynIC and synthetic timer MSRs. Windows will use
synthetic timers in preference to emulated HPET for a source of ticks and hence
enabling this group will ensure that ticks will be consistent with use of an
enlightened time source (time_ref_count or reference_tsc).

hcall_ipi
This set incorporates use of a hypercall for interprocessor interrupts. This
enlightenment may improve performance of Windows guests with multiple virtual
CPUs.

ex_processor_masks
This set enables new hypercall variants taking a variably-sized sparse Virtual
Processor Set as an argument, rather than a simple 64-bit mask. Hence this
enlightenment must be specified for guests with more than 64 vCPUs if
hcall_remote_tlb_flush and/or hcall_ipi are also specified.

no_vp_limit
This group when set indicates to a guest that the hypervisor does not explicitly
have any limits on the number of Virtual processors a guest is allowed to bring
up. It is strongly recommended to keep this enabled for guests with more than 64
vCPUs.

cpu_hotplug
This set enables dynamic changes to Virtual processor states in Windows guests
effectively allowing vCPU hotplug.

defaults
This is a special value that enables the default set of groups, which is currently
the base, freq, time_ref_count, apic_assist, crash_ctl, stimer, no_vp_limit and
cpu_hotplug groups.

all This is a special value that enables all available groups.

Groups can be disabled by prefixing the name with '!'. So, for example, to enable all
groups except freq, specify:

viridian=[ "all", "!freq" ]

For details of the enlightenments see the latest version of Microsoft's Hypervisor
Top-Level Functional Specification.

The enlightenments should be harmless for other versions of Windows (although they
will not give any benefit) and the majority of other non-Windows OSes. However it is
known that they are incompatible with some other Operating Systems and in some
circumstance can prevent Xen's own paravirtualisation interfaces for HVM guests from
being used.

The viridian option can be specified as a boolean. A value of true (1) is equivalent
to the list [ "defaults" ], and a value of false (0) is equivalent to an empty list.

Emulated VGA Graphics Device

The following options control the features of the emulated graphics device. Many of these
options behave similarly to the equivalent key in the VFB_SPEC_STRING for configuring
virtual frame buffer devices (see above).

videoram=MBYTES
Sets the amount of RAM which the emulated video card will contain, which in turn
limits the resolutions and bit depths which will be available.

When using the qemu-xen-traditional device-model, the default as well as minimum
amount of video RAM for stdvga is 8 MB, which is sufficient for e.g. 1600x1200 at
32bpp. For the upstream qemu-xen device-model, the default and minimum is 16 MB.

When using the emulated Cirrus graphics card (vga="cirrus") and the qemu-xen-
traditional device-model, the amount of video RAM is fixed at 4 MB, which is
sufficient for 1024x768 at 32 bpp. For the upstream qemu-xen device-model, the default
and minimum is 8 MB.

For QXL vga, both the default and minimal are 128MB. If videoram is set less than
128MB, an error will be triggered.

stdvga=BOOLEAN
Specifies a standard VGA card with VBE (VESA BIOS Extensions) as the emulated graphics
device. If your guest supports VBE 2.0 or later (e.g. Windows XP onwards) then you
should enable this. stdvga supports more video ram and bigger resolutions than
Cirrus. The default is false (0) which means to emulate a Cirrus Logic GD5446 VGA
card. This option is deprecated, use vga="stdvga" instead.

vga="STRING"
Selects the emulated video card. Options are: none, stdvga, cirrus and qxl. The
default is cirrus.

In general, QXL should work with the Spice remote display protocol for acceleration,
and a QXL driver is necessary in the guest in that case. QXL can also work with the
VNC protocol, but it will be like a standard VGA card without acceleration.

vnc=BOOLEAN
Allow access to the display via the VNC protocol. This enables the other VNC-related
settings. The default is (1) enabled.

vnclisten="ADDRESS[:DISPLAYNUM]"
Specifies the IP address and, optionally, the VNC display number to use.

vncdisplay=DISPLAYNUM
Specifies the VNC display number to use. The actual TCP port number will be
DISPLAYNUM+5900.

vncunused=BOOLEAN
Requests that the VNC display setup searches for a free TCP port to use. The actual
display used can be accessed with xl vncviewer.

vncpasswd="PASSWORD"
Specifies the password for the VNC server. If the password is set to an empty string,
authentication on the VNC server will be disabled allowing any user to connect.

keymap="LANG"
Configure the keymap to use for the keyboard associated with this display. If the
input method does not easily support raw keycodes (e.g. this is often the case when
using VNC) then this allows us to correctly map the input keys into keycodes seen by
the guest. The specific values which are accepted are defined by the version of the
device-model which you are using. See Keymaps below or consult the qemu(1) manpage.
The default is en-us.

sdl=BOOLEAN
Specifies that the display should be presented via an X window (using Simple
DirectMedia Layer). The default is (0) not enabled.

opengl=BOOLEAN
Enable OpenGL acceleration of the SDL display. Only effects machines using
device_model_version="qemu-xen-traditional" and only if the device-model was compiled
with OpenGL support. Default is (0) false.

nographic=BOOLEAN
Enable or disable the virtual graphics device. The default is to provide a VGA
graphics device but this option can be used to disable it.

Spice Graphics Support

The following options control the features of SPICE.

spice=BOOLEAN
Allow access to the display via the SPICE protocol. This enables the other SPICE-
related settings.

spicehost="ADDRESS"
Specifies the interface address to listen on if given, otherwise any interface.

spiceport=NUMBER
Specifies the port to listen on by the SPICE server if SPICE is enabled.

spicetls_port=NUMBER
Specifies the secure port to listen on by the SPICE server if SPICE is enabled. At
least one of spiceport or spicetls_port must be given if SPICE is enabled.

Note: the options depending on spicetls_port have not been supported.

spicedisable_ticketing=BOOLEAN
Enable clients to connect without specifying a password. When disabled, spicepasswd
must be set. The default is (0) false.

spicepasswd="PASSWORD"
Specify the password which is used by clients for establishing a connection.

spiceagent_mouse=BOOLEAN
Whether SPICE agent is used for client mouse mode. The default is (1) true.

spicevdagent=BOOLEAN
Enables the SPICE vdagent. The SPICE vdagent is an optional component for enhancing
user experience and performing guest-oriented management tasks. Its features include:
client mouse mode (no need to grab the mouse by the client, no mouse lag), automatic
adjustment of screen resolution, copy and paste (text and image) between the client
and the guest. It also requires the vdagent service installed on the guest OS to work.
The default is (0) disabled.

spice_clipboard_sharing=BOOLEAN
Enables SPICE clipboard sharing (copy/paste). It requires that spicevdagent is
enabled. The default is (0) false.

spiceusbredirection=NUMBER
Enables SPICE USB redirection. Creates a NUMBER of USB redirection channels for
redirecting up to 4 USB devices from the SPICE client to the guest's QEMU. It
requires an USB controller and, if not defined, it will automatically add an USB2.0
controller. The default is (0) disabled.

spice_image_compression="COMPRESSION"
Specifies what image compression is to be used by SPICE (if given), otherwise the QEMU
default will be used. Please see the documentation of your QEMU version for more
details.

Available options are: auto_glz, auto_lz, quic, glz, lz, off.

spice_streaming_video="VIDEO"
Specifies what streaming video setting is to be used by SPICE (if given), otherwise
the QEMU default will be used.

Available options are: filter, all, off.

Miscellaneous Emulated Hardware

serial=[ "DEVICE", "DEVICE", ...]
Redirect virtual serial ports to DEVICEs. Please see the -serial option in the qemu(1)
manpage for details of the valid DEVICE options. Default is vc when in graphical mode
and stdio if nographic=1 is used.

The form serial=DEVICE is also accepted for backwards compatibility.

soundhw="DEVICE"
Select the virtual sound card to expose to the guest. The valid devices are hda, ac97,
es1370, adlib, cs4231a, gus, sb16 if there are available with the device model QEMU.
The default is not to export any sound device.

vkb_device=BOOLEAN
Specifies that the HVM guest gets a vkdb. The default is true (1).

usb=BOOLEAN
Enables or disables an emulated USB bus in the guest.

usbversion=NUMBER
Specifies the type of an emulated USB bus in the guest, values 1 for USB1.1, 2 for
USB2.0 and 3 for USB3.0. It is available only with an upstream QEMU. Due to
implementation limitations this is not compatible with the usb and usbdevice
parameters. Default is (0) no USB controller defined.

usbdevice=[ "DEVICE", "DEVICE", ...]
Adds DEVICEs to the emulated USB bus. The USB bus must also be enabled using usb=1.
The most common use for this option is usbdevice=['tablet'] which adds a pointer
device using absolute coordinates. Such devices function better than relative
coordinate devices (such as a standard mouse) since many methods of exporting guest
graphics (such as VNC) work better in this mode. Note that this is independent of the
actual pointer device you are using on the host/client side.

Host devices can also be passed through in this way, by specifying host:USBID, where
USBID is of the form xxxx:yyyy. The USBID can typically be found by using lsusb(1) or
usb-devices(1).

If you wish to use the "host:bus.addr" format, remove any leading '0' from the bus and
addr. For example, for the USB device on bus 008 dev 002, you should write "host:8.2".

The form usbdevice=DEVICE is also accepted for backwards compatibility.

More valid options can be found in the "usbdevice" section of the QEMU documentation.

vendor_device="VENDOR_DEVICE"
Selects which variant of the QEMU xen-pvdevice should be used for this guest. Valid
values are:

none
The xen-pvdevice should be omitted. This is the default.

xenserver
The xenserver variant of the xen-pvdevice (device-id=C000) will be specified,
enabling the use of XenServer PV drivers in the guest.

This parameter only takes effect when device_model_version=qemu-xen. See
xen-pci-device-reservations(7) for more information.

PVH Guest Specific Options
nestedhvm=BOOLEAN
Enable or disables guest access to hardware virtualisation features, e.g. it allows a
guest Operating System to also function as a hypervisor. You may want this option if
you want to run another hypervisor (including another copy of Xen) within a Xen guest
or to support a guest Operating System which uses hardware virtualisation extensions
(e.g. Windows XP compatibility mode on more modern Windows OS).

This option is disabled by default.

timer_mode="MODE"
Specifies the mode for Virtual Timers. The valid values are as follows:

no_delay_for_missed_ticks
No delay for missed ticks. As above, missed interrupts are delivered, but guest
time always tracks wallclock (i.e., real) time while doing so. This is the
default.

one_missed_tick_pending
One missed tick pending. Missed interrupts are collapsed together and delivered as
one 'late tick'. Guest time always tracks wallclock (i.e., real) time.

Paging

On Arm, this field is used to determine the size of the guest P2M pages pool, and the
default value is the same as x86 HAP mode, plus 512KB to cover the extended regions.
Users should adjust this value if bigger P2M pool size is needed.

Device-Model Options
The following options control the selection of the device-model. This is the component
which provides emulation of the virtual devices to an HVM guest. For a PV guest a device-
model is sometimes used to provide backends for certain PV devices (most usually a virtual
framebuffer device).

device_model_version="DEVICE-MODEL"
Selects which variant of the device-model should be used for this guest.

Valid values are:

qemu-xen
Use the device-model merged into the upstream QEMU project. This device-model is
the default for Linux dom0.

qemu-xen-traditional
Use the device-model based upon the historical Xen fork of QEMU. This device-
model is still the default for NetBSD dom0.

It is recommended to accept the default value for new guests. If you have existing
guests then, depending on the nature of the guest Operating System, you may wish to
force them to use the device model which they were installed with.

device_model_override="PATH"
Override the path to the binary to be used as the device-model running in toolstack
domain. The binary provided here MUST be consistent with the device_model_version
which you have specified. You should not normally need to specify this option.

stubdomain_kernel="PATH"
Override the path to the kernel image used as device-model stubdomain. The binary
provided here MUST be consistent with the device_model_version which you have
specified. In case of qemu-xen-traditional it is expected to be MiniOS-based
stubdomain image, in case of qemu-xen it is expected to be Linux-based stubdomain
kernel.

stubdomain_cmdline="STRING"
Set the device-model stubdomain kernel command line to STRING.

stubdomain_ramdisk="PATH"
Override the path to the ramdisk image used as device-model stubdomain. The binary
provided here is to be used by a kernel pointed by stubdomain_kernel. It is known to
be used only by Linux-based stubdomain kernel.

stubdomain_memory=MBYTES
Start the stubdomain with MBYTES megabytes of RAM. Default is 128.

device_model_stubdomain_override=BOOLEAN
Override the use of stubdomain based device-model. Normally this will be
automatically selected based upon the other features and options you have selected.

device_model_stubdomain_seclabel="LABEL"
Assign an XSM security label to the device-model stubdomain.

device_model_args=[ "ARG", "ARG", ...]
Pass additional arbitrary options on the device-model command line. Each element in
the list is passed as an option to the device-model.

device_model_args_pv=[ "ARG", "ARG", ...]
Pass additional arbitrary options on the device-model command line for a PV device
model only. Each element in the list is passed as an option to the device-model.

device_model_args_hvm=[ "ARG", "ARG", ...]
Pass additional arbitrary options on the device-model command line for an HVM device
model only. Each element in the list is passed as an option to the device-model.

Keymaps
The keymaps available are defined by the device-model which you are using. Commonly this
includes:

ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr

The default is en-us.

See qemu(1) for more information.

Architecture Specific options
ARM

gic_version="vN"
Version of the GIC emulated for the guest.

Currently, the following versions are supported:

v2 Emulate a GICv2

v3 Emulate a GICv3. Note that the emulated GIC does not support the GICv2
compatibility mode.

default
Emulate the same version as the native GIC hardware used by the host where the
domain was created.

This requires hardware compatibility with the requested version, either natively or
via hardware backwards compatibility support.

vuart="uart"
To enable vuart console, user must specify the following option in the VM config file:

vuart = "sbsa_uart"

Currently, only the "sbsa_uart" model is supported for ARM.

x86

mca_caps=[ "CAP", "CAP", ... ]
(HVM only) Enable MCA capabilities besides default ones enabled by Xen hypervisor for
the HVM domain. "CAP" can be one in the following list:

"lmce"
Intel local MCE

default
No MCA capabilities in above list are enabled.

msr_relaxed=BOOLEAN
The "msr_relaxed" boolean is an interim option, and defaults to false.

In Xen 4.15, the default behaviour for unhandled MSRs has been changed, to avoid
leaking host data into guests, and to avoid breaking guest logic which uses #GP
probing to identify the availability of MSRs.

However, this new stricter behaviour has the possibility to break guests, and a more
4.14-like behaviour can be selected by setting this option.

If using this option is necessary to fix an issue, please report a bug.

FILES

       /etc/xen/NAME.cfg /var/lib/xen/dump/NAME

BUGS

       This document may contain items which require further documentation. Patches to improve
       incomplete items (or any other item) are gratefully received on the
       xen-devel@lists.xenproject.org mailing list. Please see
       <https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches> for information on how
       to submit a patch to Xen.

NAME

SYNOPSIS

DESCRIPTION

SYNTAX

OPTIONS

SEE ALSO

FILES

BUGS