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

Provided by: xen-utils-common_4.11.3+24-g14b62ab3e5-1ubuntu2.3_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.

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.

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-4.11/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).

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.

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.xen.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. Each PCI_SPEC_STRING has the form of
[DDDD:]BB:DD.F[@VSLOT],KEY=VALUE,KEY=VALUE,... where:

[DDDD:]BB:DD.F
Identifies the PCI device from the host perspective in the domain (DDDD), Bus (BB), Device (DD)
and Function (F) syntax. This is the same scheme as used in the output of lspci(1) for the device
in question.

Note: by default lspci(1) will omit the domain (DDDD) if it is zero and it is optional here also.
You may specify the function (F) as * to indicate all functions.

@VSLOT
Specifies the virtual slot where the guest will see this device. This is equivalent to the DD
which the guest sees. In a guest DDDD and BB are "0000:00".

permissive=BOOLEAN
By default pciback only allows PV guests to write "known safe" values into PCI configuration
space, likewise QEMU (both qemu-xen and qemu-xen-traditional) imposes the same constraint on HVM
guests. However, many devices require writes to other areas of the configuration space in order
to operate properly. This option tells the backend (pciback or QEMU) to allow all writes to the
PCI configuration space of this device by this domain.

This option should be enabled with caution: it gives the guest much more control over the device,
which may have security or stability implications. It is recommended to only enable this option
for trusted VMs under administrator's control.

msitranslate=BOOLEAN
Specifies that MSI-INTx translation should be turned on for the PCI device. When enabled, MSI-
INTx translation will always enable MSI on the PCI device regardless of whether the guest uses
INTx or MSI. Some device drivers, such as NVIDIA's, detect an inconsistency and do not function
when this option is enabled. Therefore the default is false (0).

seize=BOOLEAN
Tells xl to automatically attempt to re-assign a device to pciback if it is not already assigned.

WARNING: If you set this option, xl will gladly re-assign a critical system device, such as a
network or a disk controller being used by dom0 without confirmation. Please use with care.

power_mgmt=BOOLEAN
(HVM only) Specifies that the VM should be able to program the D0-D3hot power management states
for the PCI device. The default is false (0).

rdm_policy=STRING
(HVM/x86 only) This is the same as the policy setting inside the rdm option but just specific to
a given device. The default is "relaxed".

Note: this would override global rdm option.

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 <http://wiki.xen.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
<http://wiki.xen.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 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.

With this feature enabled, a compromise of the device model, via such a vulnerability, will not
provide a privilege escalation attack on the whole system.

This feature is a technology preview. There are some significant limitations:

• This is not likely to work at all for PV guests nor guests using qdisk backends for their block
devices.

• You must have a new enough qemu. In particular, if your qemu does not have the commit xen:
restrict: use xentoolcore_restrict_all the restriction request will be silently ineffective!

• The mechanisms used are not effective against denial of service problems. A compromised qemu can
probably still impair or perhaps even prevent the proper functioning of the whole system, (at the
very least, but not limited to, through resource exhaustion).

• It is not known whether the protection is effective when a domain is migrated.

• Some domain management functions do not work. For example, cdrom insert will fail.

• You should say "vga="none"". Domains with stdvga graphics cards to not work. Domains with
cirrus vga may seem to work.

• You must create user(s) for qemu to run as.

Ideally, set aside a range of 32752 uids (from N to N+32751) and create a user whose name is xen-
qemuuser-range-base and whose uid is N and whose gid is a plain unprivileged gid. libxl will use
one such user for each domid.

Alternatively, either create xen-qemuuser-domid$domid for every $domid from 1 to 32751 inclusive,
or xen-qemuuser-shared (in which case different guests will not be protected against each other).

• There are no countermeasures taken against reuse of the same unix user (uid) for subsequent
domains, even if the xen-qemuuser-domid$domid users are created. So a past domain with the same
domid may be able to interferer with future domains. Possibly, even after a reboot.

• A compromised qemu will be able to read world-readable files in the dom0 operating system.

• Because of these limitations, this functionality, while it may enhance your security, should not
be relied on. Any further limitations discovered in the current version will not be handled via
the Xen Project Security Process.

• In the future as we enhance this feature to improve the security, we may break backward
compatibility.

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.

The libxl syntax is a comma separated list of key=value pairs, preceded by the word "host". A few
keys take a numerical value, all others take a single character which describes what to do with the
feature bit.

Possible values for a single feature bit:
'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
's' -> as 'k' but preserve across save/restore and migration (not implemented)

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).

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

The xend syntax is a list of values in the form of 'leafnum:register=bitstring,register=bitstring'
"leafnum" is the requested function,
"register" is the response register to modify
"bitstring" represents all bits in the register, its length must be 32 chars.
Each successive character represent a lesser-significant bit, possible values
are listed above in the libxl section.

Example to hide two features from the guest: 'tm', which is bit #29 in EDX, and 'pni' (SSE3), which
is bit #0 in ECX:

xend: [ "1:ecx=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx0,edx=xx0xxxxxxxxxxxxxxxxxxxxxxxxxxxxx" ]

libxl: "host,tm=0,sse3=0"

More info about the CPUID instruction can be found in the processor manuals, and on Wikipedia:
<http://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:
<http://www.microsoft.com/en-us/download/details.aspx?id=30707>

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
Same as native, except Xen manages the TSC_AUX register so the guest can determine when a
restore/migration has occurred and assumes guest obtains/uses a pvclock-like mechanism to adjust
for monotonicity and frequency changes.

If a HVM container in native_paravirt TSC mode can execute both guest rdtsc and guest rdtscp
natively, then the guest TSC frequency will be determined in a similar way to that of default TSC
mode.

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 <http://wiki.xen.org/wiki/XenLinuxPVonHVMdrivers> and Microsoft Windows
<http://wiki.xen.org/wiki/XenWindowsGplPv>.

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.

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

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 nographics=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 defined by the device
model configuration, please see the qemu(1) manpage for details. The default is not to export any
sound device.

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

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. 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.

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.

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.xen.org  mailing  list.  Please  see
       <http://wiki.xen.org/wiki/SubmittingXenPatches> for information on how to submit a patch to Xen.

4.11.4-pre                                         2022-08-22                                          xl.cfg(5)

NAME

SYNOPSIS

DESCRIPTION

SYNTAX

OPTIONS

SEE ALSO

FILES

BUGS