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xl(1) Xen xl(1)

NAME
xl - Xen management tool, based on libxenlight

SYNOPSIS
xl subcommand [args]

DESCRIPTION
The xl program is the new tool for managing Xen guest domains. The program
can be used to create, pause, and shutdown domains. It can also be used to
list current domains, enable or pin VCPUs, and attach or detach virtual
block devices.

The basic structure of every xl command is almost always:

xl subcommand [OPTIONS] domain-id

Where subcommand is one of the subcommands listed below, domain-id is the
numeric domain id, or the domain name (which will be internally translated
to domain id), and OPTIONS are subcommand specific options. There are a
few exceptions to this rule in the cases where the subcommand in question
acts on all domains, the entire machine, or directly on the Xen hypervisor.
Those exceptions will be clear for each of those subcommands.

NOTES
start the script /etc/init.d/xencommons at boot time
Most xl operations rely upon xenstored and xenconsoled: make sure you
start the script /etc/init.d/xencommons at boot time to initialize all
the daemons needed by xl.

setup a xenbr0 bridge in dom0
In the most common network configuration, you need to setup a bridge in
dom0 named xenbr0 in order to have a working network in the guest do-
mains. Please refer to the documentation of your Linux distribution to
know how to setup the bridge.

autoballoon
If you specify the amount of memory dom0 has, passing dom0_mem to Xen,
it is highly recommended to disable autoballoon. Edit /etc/xen/xl.conf
and set it to 0.

run xl as root
Most xl commands require root privileges to run due to the communica-
tions channels used to talk to the hypervisor. Running as non root
will return an error.

GLOBAL OPTIONS
Some global options are always available:

-v Verbose.

-N Dry run: do not actually execute the command.

-f Force execution: xl will refuse to run some commands if it detects that
xend is also running, this option will force the execution of those
commands, even though it is unsafe.

-t Always use carriage-return-based overwriting for displaying progress
messages without scrolling the screen. Without -t, this is done only
if stderr is a tty.

-T Include timestamps and pid of the xl process in output.

DOMAIN SUBCOMMANDS
The following subcommands manipulate domains directly. As stated previ-
ously, most commands take domain-id as the first parameter.

button-press domain-id button
This command is deprecated. Please use "xl trigger" instead.

Indicate an ACPI button press to the domain, where button can be
'power' or 'sleep'. This command is only available for HVM domains.

create [configfile] [OPTIONS]
The create subcommand takes a config file as its first argument: see
xl.cfg(5) for full details of the file format and possible options. If
configfile is missing xl creates the domain assuming the default values
for every option.

configfile has to be an absolute path to a file.

Create will return as soon as the domain is started. This does not
mean the guest OS in the domain has actually booted, or is available
for input.

If the -F option is specified, create will start the domain and not re-
turn until its death.

OPTIONS

-q, --quiet
No console output.

-f=FILE, --defconfig=FILE
Use the given configuration file.

-p Leave the domain paused after it is created.

-F Run in foreground until death of the domain.

-V, --vncviewer
Attach to domain's VNC server, forking a vncviewer process.

-A, --vncviewer-autopass
Pass the VNC password to vncviewer via stdin.

-c Attach console to the domain as soon as it has started. This is
useful for determining issues with crashing domains and just as a
general convenience since you often want to watch the domain boot.

key=value
It is possible to pass key=value pairs on the command line to pro-
vide options as if they were written in the configuration file;
these override whatever is in the configfile.

NB: Many config options require characters such as quotes or brack-
ets which are interpreted by the shell (and often discarded) before
being passed to xl, resulting in xl being unable to parse the value
correctly. A simple work-around is to put all extra options within
a single set of quotes, separated by semicolons. (See below for an
example.)

EXAMPLES

with extra parameters
xl create hvm.cfg 'cpus="0-3"; pci=["01:05.1","01:05.2"]'

This creates a domain with the file hvm.cfg, but additionally pins
it to cpus 0-3, and passes through two PCI devices.

config-update domain-id [configfile] [OPTIONS]
Update the saved configuration for a running domain. This has no imme-
diate effect but will be applied when the guest is next restarted. This
command is useful to ensure that runtime modifications made to the
guest will be preserved when the guest is restarted.

Since Xen 4.5 xl has improved capabilities to handle dynamic domain
configuration changes and will preserve any changes made at runtime
when necessary. Therefore it should not normally be necessary to use
this command any more.

configfile has to be an absolute path to a file.

OPTIONS

-f=FILE, --defconfig=FILE
Use the given configuration file.

key=value
It is possible to pass key=value pairs on the command line to pro-
vide options as if they were written in the configuration file;
these override whatever is in the configfile. Please see the note
under create on handling special characters when passing key=value
pairs on the command line.

console [OPTIONS] domain-id
Attach to the console of a domain specified by domain-id. If you've
set up your domains to have a traditional login console this will look
much like a normal text login screen.

Use the escape character key combination (default Ctrl+]) to detach
from the domain console.

OPTIONS

-t [pv|serial]
Connect to a PV console or connect to an emulated serial console.
PV consoles are the only consoles available for PV domains while
HVM domains can have both. If this option is not specified it de-
faults to emulated serial for HVM guests and PV console for PV
guests.

-n NUM
Connect to console number NUM. Console numbers start from 0.

-e escapechar
Customize the escape sequence used to detach from the domain con-
sole to escapechar. If not specified, the value "^]" is used.

destroy [OPTIONS] domain-id
Immediately terminate the domain specified by domain-id. This doesn't
give the domain OS any chance to react, and is the equivalent of rip-
ping the power cord out on a physical machine. In most cases you will
want to use the shutdown command instead.

OPTIONS

-f Allow domain 0 to be destroyed. Because a domain cannot destroy
itself, this is only possible when using a disaggregated toolstack,
and is most useful when using a hardware domain separated from do-
main 0.

domid domain-name
Converts a domain name to a domain id.

domname domain-id
Converts a domain id to a domain name.

rename domain-id new-name
Change the domain name of a domain specified by domain-id to new-name.

dump-core domain-id [filename]
Dumps the virtual machine's memory for the specified domain to the
filename specified, without pausing the domain. The dump file will be
written to a distribution specific directory for dump files, for exam-
ple: /var/lib/xen/dump/dump.

help [--long]
Displays the short help message (i.e. common commands) by default.

If the --long option is specified, it displays the complete set of xl
subcommands, grouped by function.

list [OPTIONS] [domain-id ...]
Displays information about one or more domains. If no domains are
specified it displays information about all domains.

OPTIONS

-l, --long
The output for xl list is not the table view shown below, but in-
stead presents the data as a JSON data structure.

-Z, --context
Also displays the security labels.

-v, --verbose
Also displays the domain UUIDs, the shutdown reason and security
labels.

-c, --cpupool
Also displays the cpupool the domain belongs to.

-n, --numa
Also displays the domain NUMA node affinity.

EXAMPLE

An example format for the list is as follows:

Name ID Mem VCPUs State Time(s)
Domain-0 0 750 4 r----- 11794.3
win 1 1019 1 r----- 0.3
linux 2 2048 2 r----- 5624.2

Name is the name of the domain. ID the numeric domain id. Mem is the
desired amount of memory to allocate to the domain (although it may not
be the currently allocated amount). VCPUs is the number of virtual
CPUs allocated to the domain. State is the run state (see below).
Time is the total run time of the domain as accounted for by Xen.

STATES

The State field lists 6 states for a Xen domain, and which ones the
current domain is in.

r - running
The domain is currently running on a CPU.

b - blocked
The domain is blocked, and not running or runnable. This can be
because the domain is waiting on IO (a traditional wait state) or
has gone to sleep because there was nothing else for it to do.

p - paused
The domain has been paused, usually occurring through the adminis-
trator running xl pause. When in a paused state the domain will
still consume allocated resources (like memory), but will not be
eligible for scheduling by the Xen hypervisor.

s - shutdown
The guest OS has shut down (SCHEDOP_shutdown has been called) but
the domain is not dying yet.

c - crashed
The domain has crashed, which is always a violent ending. Usually
this state only occurs if the domain has been configured not to
restart on a crash. See xl.cfg(5) for more info.

d - dying
The domain is in the process of dying, but hasn't completely shut
down or crashed.

NOTES

The Time column is deceptive. Virtual IO (network and block de-
vices) used by the domains requires coordination by Domain0, which
means that Domain0 is actually charged for much of the time that a
DomainU is doing IO. Use of this time value to determine relative
utilizations by domains is thus very unreliable, as a high IO work-
load may show as less utilized than a high CPU workload. Consider
yourself warned.

mem-set domain-id mem
Set the target for the domain's balloon driver.

The default unit is kiB. Add 't' for TiB, 'g' for GiB, 'm' for MiB,
'k' for kiB, and 'b' for bytes (e.g., `2048m` for 2048 MiB).

This must be less than the initial maxmem parameter in the domain's
configuration.

Note that this operation requests the guest operating system's balloon
driver to reach the target amount of memory. The guest may fail to
reach that amount of memory for any number of reasons, including:

* The guest doesn't have a balloon driver installed

* The guest's balloon driver is buggy

* The guest's balloon driver cannot create free guest memory due to
guest memory pressure

* The guest's balloon driver cannot allocate memory from Xen because
of hypervisor memory pressure

* The guest administrator has disabled the balloon driver

Warning: There is no good way to know in advance how small of a mem-set
will make a domain unstable and cause it to crash. Be very careful
when using this command on running domains.

mem-max domain-id mem
Specify the limit Xen will place on the amount of memory a guest may
allocate.

The default unit is kiB. Add 't' for TiB, 'g' for GiB, 'm' for MiB,
'k' for kiB, and 'b' for bytes (e.g., `2048m` for 2048 MiB).

mem can't be set lower than the current memory target for domain-id.
It is allowed to be higher than the configured maximum memory size of
the domain (maxmem parameter in the domain's configuration).

Setting the maximum memory size above the configured maximum memory
size will require special guest support (memory hotplug) in order to be
usable by the guest.

The domain will not receive any signal regarding the changed memory
limit.

migrate [OPTIONS] domain-id host
Migrate a domain to another host machine. By default xl relies on ssh
as a transport mechanism between the two hosts.

OPTIONS

-s sshcommand
Use <sshcommand> instead of ssh. String will be passed to sh. If
empty, run <host> instead of ssh <host> xl migrate-receive [-d -e].

-e On the new <host>, do not wait in the background for the death of
the domain. See the corresponding option of the create subcommand.

-C config
Send the specified <config> file instead of the file used on cre-
ation of the domain.

--debug
Display huge (!) amount of debug information during the migration
process.

-p Leave the domain on the receive side paused after migration.

-D Preserve the domain-id in the domain coniguration that is trans-
ferred such that it will be identical on the destination host, un-
less that configuration is overridden using the -C option. Note
that it is not possible to use this option for a 'localhost' migra-
tion.

remus [OPTIONS] domain-id host
Enable Remus HA or COLO HA for domain. By default xl relies on ssh as a
transport mechanism between the two hosts.

NOTES

Remus support in xl is still in experimental (proof-of-concept)
phase. Disk replication support is limited to DRBD disks.

COLO support in xl is still in experimental (proof-of-concept)
phase. All options are subject to change in the future.

COLO disk configuration looks like:

disk = ['...,colo,colo-host=xxx,colo-port=xxx,colo-export=xxx,active-disk=xxx,hidden-disk=xxx...']

The supported options are:

colo-host : Secondary host's ip address.
colo-port : Secondary host's port, we will run a nbd server on the
secondary host, and the nbd server will listen on this port.
colo-export : Nbd server's disk export name of the secondary host.
active-disk : Secondary's guest write will be buffered to this disk,
and it's used by the secondary.
hidden-disk : Primary's modified contents will be buffered in this
disk, and it's used by the secondary.

COLO network configuration looks like:

vif = [ '...,forwarddev=xxx,...']

The supported options are:

forwarddev : Forward devices for the primary and the secondary, they
are directly connected.

OPTIONS

-i MS
Checkpoint domain memory every MS milliseconds (default 200ms).

-u Disable memory checkpoint compression.

-s sshcommand
Use <sshcommand> instead of ssh. String will be passed to sh. If
empty, run <host> instead of ssh <host> xl migrate-receive -r [-e].

-e On the new <host>, do not wait in the background for the death of
the domain. See the corresponding option of the create subcommand.

-N netbufscript
Use <netbufscript> to setup network buffering instead of the de-
fault script (/etc/xen/scripts/remus-netbuf-setup).

-F Run Remus in unsafe mode. Use this option with caution as failover
may not work as intended.

-b Replicate memory checkpoints to /dev/null (blackhole). Generally
useful for debugging. Requires enabling unsafe mode.

-n Disable network output buffering. Requires enabling unsafe mode.

-d Disable disk replication. Requires enabling unsafe mode.

-c Enable COLO HA. This conflicts with -i and -b, and memory check-
point compression must be disabled.

-p Use userspace COLO Proxy. This option must be used in conjunction
with -c.

pause domain-id
Pause a domain. When in a paused state the domain will still consume
allocated resources (such as memory), but will not be eligible for
scheduling by the Xen hypervisor.

reboot [OPTIONS] domain-id
Reboot a domain. This acts just as if the domain had the reboot com-
mand run from the console. The command returns as soon as it has exe-
cuted the reboot action, which may be significantly earlier than when
the domain actually reboots.

For HVM domains this requires PV drivers to be installed in your guest
OS. If PV drivers are not present but you have configured the guest OS
to behave appropriately you may be able to use the -F option to trigger
a reset button press.

The behavior of what happens to a domain when it reboots is set by the
on_reboot parameter of the domain configuration file when the domain
was created.

OPTIONS

-F If the guest does not support PV reboot control then fallback to
sending an ACPI power event (equivalent to the reset option to
trigger).

You should ensure that the guest is configured to behave as ex-
pected in response to this event.

restore [OPTIONS] [configfile] checkpointfile
Build a domain from an xl save state file. See save for more info.

OPTIONS

-p Do not unpause the domain after restoring it.

-e Do not wait in the background for the death of the domain on the
new host. See the corresponding option of the create subcommand.

-d Enable debug messages.

-V, --vncviewer
Attach to the domain's VNC server, forking a vncviewer process.

-A, --vncviewer-autopass
Pass the VNC password to vncviewer via stdin.

resume domain-id
Resume a domain, after having been suspended.

save [OPTIONS] domain-id checkpointfile [configfile]
Saves a running domain to a state file so that it can be restored
later. Once saved, the domain will no longer be running on the system,
unless the -c or -p options are used. xl restore restores from this
checkpoint file. Passing a config file argument allows the user to
manually select the VM config file used to create the domain.

-c Leave the domain running after creating the snapshot.

-p Leave the domain paused after creating the snapshot.

-D Preserve the domain-id in the domain coniguration that is embedded
in the state file such that it will be identical when the domain is
restored, unless that configuration is overridden. (See the restore
operation above).

sharing [domain-id]
Display the number of shared pages for a specified domain. If no domain
is specified it displays information about all domains.

shutdown [OPTIONS] -a|domain-id
Gracefully shuts down a domain. This coordinates with the domain OS to
perform graceful shutdown, so there is no guarantee that it will suc-
ceed, and may take a variable length of time depending on what services
must be shut down in the domain.

The command returns immediately after signaling the domain unless the
-w flag is used.

The behavior of what happens to a domain when it reboots is set by the
on_shutdown parameter of the domain configuration file when the domain
was created.

OPTIONS

-a, --all
Shutdown all guest domains. Often used when doing a complete shut-
down of a Xen system.

-w, --wait
Wait for the domain to complete shutdown before returning. If
given once, the wait is for domain shutdown or domain death. If
given multiple times, the wait is for domain death only.

-F If the guest does not support PV shutdown control then fallback to
sending an ACPI power event (equivalent to the power option to
trigger).

You should ensure that the guest is configured to behave as ex-
pected in response to this event.

suspend domain-id
Suspend a domain. This is a cooperative operation where the domain
must respond to the xenstore trigger. When in a suspended state the
domain still consumes allocated resources (such as memory), but is not
eligible for scheduling by the Xen hypervisor. It is in a shutdown
state, but not dying.

sysrq domain-id letter
Send a <Magic System Request> to the domain, each type of request is
represented by a different letter. It can be used to send SysRq re-
quests to Linux guests, see sysrq.txt in your Linux Kernel sources for
more information. It requires PV drivers to be installed in your guest
OS.

trigger domain-id nmi|reset|init|power|sleep|s3resume [VCPU]
Send a trigger to a domain, where the trigger can be: nmi, reset, init,
power or sleep. Optionally a specific vcpu number can be passed as an
argument. This command is only available for HVM domains.

unpause domain-id
Moves a domain out of the paused state. This will allow a previously
paused domain to now be eligible for scheduling by the Xen hypervisor.

vcpu-set domain-id vcpu-count
Enables the vcpu-count virtual CPUs for the domain in question. Like
mem-set, this command can only allocate up to the maximum virtual CPU
count configured at boot for the domain.

If the vcpu-count is smaller than the current number of active VCPUs,
the highest number VCPUs will be hotplug removed. This may be impor-
tant for pinning purposes.

Attempting to set the VCPUs to a number larger than the initially con-
figured VCPU count is an error. Trying to set VCPUs to < 1 will be
quietly ignored.

Some guests may need to actually bring the newly added CPU online after
vcpu-set, go to SEE ALSO section for information.

vcpu-list [domain-id]
Lists VCPU information for a specific domain. If no domain is speci-
fied, VCPU information for all domains will be provided.

vcpu-pin [-f|--force] domain-id vcpu cpus hard cpus soft
Set hard and soft affinity for a vcpu of <domain-id>. Normally VCPUs
can float between available CPUs whenever Xen deems a different run
state is appropriate.

Hard affinity can be used to restrict this, by ensuring certain VCPUs
can only run on certain physical CPUs. Soft affinity specifies a pre-
ferred set of CPUs. Soft affinity needs special support in the sched-
uler, which is only provided in credit1.

The keyword all can be used to apply the hard and soft affinity masks
to all the VCPUs in the domain. The symbol '-' can be used to leave ei-
ther hard or soft affinity alone.

For example:

xl vcpu-pin 0 3 - 6-9

will set soft affinity for vCPU 3 of domain 0 to pCPUs 6,7,8 and 9,
leaving its hard affinity untouched. On the other hand:

xl vcpu-pin 0 3 3,4 6-9

will set both hard and soft affinity, the former to pCPUs 3 and 4, the
latter to pCPUs 6,7,8, and 9.

Specifying -f or --force will remove a temporary pinning done by the
operating system (normally this should be done by the operating sys-
tem). In case a temporary pinning is active for a vcpu the affinity of
this vcpu can't be changed without this option.

vm-list
Prints information about guests. This list excludes information about
service or auxiliary domains such as dom0 and stubdoms.

EXAMPLE

An example format for the list is as follows:

UUID ID name
59e1cf6c-6ab9-4879-90e7-adc8d1c63bf5 2 win
50bc8f75-81d0-4d53-b2e6-95cb44e2682e 3 linux

vncviewer [OPTIONS] domain-id
Attach to the domain's VNC server, forking a vncviewer process.

OPTIONS

--autopass
Pass the VNC password to vncviewer via stdin.

XEN HOST SUBCOMMANDS
debug-keys keys
Send debug keys to Xen. It is the same as pressing the Xen "conswitch"
(Ctrl-A by default) three times and then pressing "keys".

set-parameters params
Set hypervisor parameters as specified in params. This allows for some
boot parameters of the hypervisor to be modified in the running sys-
tems.

dmesg [OPTIONS]
Reads the Xen message buffer, similar to dmesg on a Linux system. The
buffer contains informational, warning, and error messages created dur-
ing Xen's boot process. If you are having problems with Xen, this is
one of the first places to look as part of problem determination.

OPTIONS

-c, --clear
Clears Xen's message buffer.

info [OPTIONS]
Print information about the Xen host in name : value format. When re-
porting a Xen bug, please provide this information as part of the bug
report. See https://wiki.xenproject.org/wiki/Report-
ing_Bugs_against_Xen_Project on how to report Xen bugs.

Sample output looks as follows:

host : scarlett
release : 3.1.0-rc4+
version : #1001 SMP Wed Oct 19 11:09:54 UTC 2011
machine : x86_64
nr_cpus : 4
nr_nodes : 1
cores_per_socket : 4
threads_per_core : 1
cpu_mhz : 2266
hw_caps : bfebfbff:28100800:00000000:00003b40:009ce3bd:00000000:00000001:00000000
virt_caps : hvm hvm_directio
total_memory : 6141
free_memory : 4274
free_cpus : 0
outstanding_claims : 0
xen_major : 4
xen_minor : 2
xen_extra : -unstable
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler : credit
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset : Wed Nov 02 17:09:09 2011 +0000 24066:54a5e994a241
xen_commandline : com1=115200,8n1 guest_loglvl=all dom0_mem=750M console=com1
cc_compiler : gcc version 4.4.5 (Debian 4.4.5-8)
cc_compile_by : sstabellini
cc_compile_domain : uk.xensource.com
cc_compile_date : Tue Nov 8 12:03:05 UTC 2011
xend_config_format : 4

FIELDS

Not all fields will be explained here, but some of the less obvious
ones deserve explanation:

hw_caps
A vector showing what hardware capabilities are supported by your
processor. This is equivalent to, though more cryptic, the flags
field in /proc/cpuinfo on a normal Linux machine: they both derive
from the feature bits returned by the cpuid command on x86 plat-
forms.

free_memory
Available memory (in MB) not allocated to Xen, or any other do-
mains, or claimed for domains.

outstanding_claims
When a claim call is done (see xl.conf(5)) a reservation for a spe-
cific amount of pages is set and also a global value is incre-
mented. This global value (outstanding_claims) is then reduced as
the domain's memory is populated and eventually reaches zero. Most
of the time the value will be zero, but if you are launching multi-
ple guests, and claim_mode is enabled, this value can increase/de-
crease. Note that the value also affects the free_memory - as it
will reflect the free memory in the hypervisor minus the outstand-
ing pages claimed for guests. See xl info claims parameter for de-
tailed listing.

xen_caps
The Xen version and architecture. Architecture values can be one
of: x86_32, x86_32p (i.e. PAE enabled), x86_64, ia64.

xen_changeset
The Xen mercurial changeset id. Very useful for determining ex-
actly what version of code your Xen system was built from.

OPTIONS

-n, --numa
List host NUMA topology information

-x, --xenstore
Show Xenstore features available.

top Executes the xentop(1) command, which provides real time monitoring of
domains. Xentop has a curses interface, and is reasonably self ex-
planatory.

uptime
Prints the current uptime of the domains running.

claims
Prints information about outstanding claims by the guests. This pro-
vides the outstanding claims and currently populated memory count for
the guests. These values added up reflect the global outstanding claim
value, which is provided via the info argument, outstanding_claims
value. The Mem column has the cumulative value of outstanding claims
and the total amount of memory that has been right now allocated to the
guest.

EXAMPLE

An example format for the list is as follows:

Name ID Mem VCPUs State Time(s) Claimed
Domain-0 0 2047 4 r----- 19.7 0
OL5 2 2048 1 --p--- 0.0 847
OL6 3 1024 4 r----- 5.9 0
Windows_XP 4 2047 1 --p--- 0.0 1989

In which it can be seen that the OL5 guest still has 847MB of claimed
memory (out of the total 2048MB where 1191MB has been allocated to the
guest).

SCHEDULER SUBCOMMANDS
Xen ships with a number of domain schedulers, which can be set at boot time
with the sched= parameter on the Xen command line. By default credit is
used for scheduling.

sched-credit [OPTIONS]
Set or get credit (aka credit1) scheduler parameters. The credit
scheduler is a proportional fair share CPU scheduler built from the
ground up to be work conserving on SMP hosts.

Each domain (including Domain0) is assigned a weight and a cap.

OPTIONS

-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or
retrieved. Mandatory for modifying scheduler parameters.

-w WEIGHT, --weight=WEIGHT
A domain with a weight of 512 will get twice as much CPU as a do-
main with a weight of 256 on a contended host. Legal weights range
from 1 to 65535 and the default is 256.

-c CAP, --cap=CAP
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 in percentage of one physical CPU: 100 is 1 physi-
cal CPU, 50 is half a CPU, 400 is 4 CPUs, etc. The default, 0,
means there is no upper cap.

NB: Many systems have features that will scale down the computing
power of a cpu that is not 100% utilized. This can be in the oper-
ating system, but can also sometimes be below the operating system
in the BIOS. If you set a cap such that individual cores are run-
ning 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 ef-
fect 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 cpufreq options in
your operating system and your BIOS.

-p CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.

-s, --schedparam
Specify to list or set pool-wide scheduler parameters.

-t TSLICE, --tslice_ms=TSLICE
Timeslice tells the scheduler how long to allow VMs to run before
pre-empting. The default is 30ms. Valid ranges are 1ms to 1000ms.
The length of the timeslice (in ms) must be higher than the length
of the ratelimit (see below).

-r RLIMIT, --ratelimit_us=RLIMIT
Ratelimit attempts to limit the number of schedules per second. It
sets a minimum amount of time (in microseconds) a VM must run be-
fore we will allow a higher-priority VM to pre-empt it. The de-
fault value is 1000 microseconds (1ms). Valid range is 100 to
500000 (500ms). The ratelimit length must be lower than the times-
lice length.

-m DELAY, --migration_delay_us=DELAY
Migration delay specifies for how long a vCPU, after it stopped
running should be considered "cache-hot". Basically, if less than
DELAY us passed since when the vCPU was executing on a CPU, it is
likely that most of the vCPU's working set is still in the CPU's
cache, and therefore the vCPU is not migrated.

Default is 0. Maximum is 100 ms. This can be effective at prevent-
ing vCPUs to bounce among CPUs too quickly, but, at the same time,
the scheduler stops being fully work-conserving.

COMBINATION

The following is the effect of combining the above options:

<nothing> : List all domain params and sched params from
all pools
-d [domid] : List domain params for domain [domid]
-d [domid] [params] : Set domain params for domain [domid]
-p [pool] : list all domains and sched params for [pool]
-s : List sched params for poolid 0
-s [params] : Set sched params for poolid 0
-p [pool] -s : List sched params for [pool]
-p [pool] -s [params] : Set sched params for [pool]
-p [pool] -d... : Illegal

sched-credit2 [OPTIONS]
Set or get credit2 scheduler parameters. The credit2 scheduler is a
proportional fair share CPU scheduler built from the ground up to be
work conserving on SMP hosts.

Each domain (including Domain0) is assigned a weight.

OPTIONS

-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or
retrieved. Mandatory for modifying scheduler parameters.

-w WEIGHT, --weight=WEIGHT
A domain with a weight of 512 will get twice as much CPU as a do-
main with a weight of 256 on a contended host. Legal weights range
from 1 to 65535 and the default is 256.

-p CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.

-s, --schedparam
Specify to list or set pool-wide scheduler parameters.

-r RLIMIT, --ratelimit_us=RLIMIT
Attempts to limit the rate of context switching. It is basically
the same as --ratelimit_us in sched-credit

sched-rtds [OPTIONS]
Set or get rtds (Real Time Deferrable Server) scheduler parameters.
This rt scheduler applies Preemptive Global Earliest Deadline First
real-time scheduling algorithm to schedule VCPUs in the system. Each
VCPU has a dedicated period, budget and extratime. While scheduled, a
VCPU burns its budget. A VCPU has its budget replenished at the begin-
ning of each period; Unused budget is discarded at the end of each pe-
riod. A VCPU with extratime set gets extra time from the unreserved
system resource.

OPTIONS

-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or
retrieved. Mandatory for modifying scheduler parameters.

-v VCPUID/all, --vcpuid=VCPUID/all
Specify vcpu for which scheduler parameters are to be modified or
retrieved.

-p PERIOD, --period=PERIOD
Period of time, in microseconds, over which to replenish the bud-
get.

-b BUDGET, --budget=BUDGET
Amount of time, in microseconds, that the VCPU will be allowed to
run every period.

-e Extratime, --extratime=Extratime
Binary flag to decide if the VCPU will be allowed to get extra time
from the unreserved system resource.

-c CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.

EXAMPLE

1) Use -v all to see the budget and period of all the VCPUs of all
the domains:

xl sched-rtds -v all
Cpupool Pool-0: sched=RTDS
Name ID VCPU Period Budget Extratime
Domain-0 0 0 10000 4000 yes
vm1 2 0 300 150 yes
vm1 2 1 400 200 yes
vm1 2 2 10000 4000 yes
vm1 2 3 1000 500 yes
vm2 4 0 10000 4000 yes
vm2 4 1 10000 4000 yes

Without any arguments, it will output the default scheduling para-
meters for each domain:

xl sched-rtds
Cpupool Pool-0: sched=RTDS
Name ID Period Budget Extratime
Domain-0 0 10000 4000 yes
vm1 2 10000 4000 yes
vm2 4 10000 4000 yes

2) Use, for instance, -d vm1, -v all to see the budget and period
of all VCPUs of a specific domain (vm1):

xl sched-rtds -d vm1 -v all
Name ID VCPU Period Budget Extratime
vm1 2 0 300 150 yes
vm1 2 1 400 200 yes
vm1 2 2 10000 4000 yes
vm1 2 3 1000 500 yes

To see the parameters of a subset of the VCPUs of a domain, use:

xl sched-rtds -d vm1 -v 0 -v 3
Name ID VCPU Period Budget Extratime
vm1 2 0 300 150 yes
vm1 2 3 1000 500 yes

If no -v is specified, the default scheduling parameters for the
domain are shown:

xl sched-rtds -d vm1
Name ID Period Budget Extratime
vm1 2 10000 4000 yes

3) Users can set the budget and period of multiple VCPUs of a spe-
cific domain with only one command, e.g., "xl sched-rtds -d vm1 -v
0 -p 100 -b 50 -e 1 -v 3 -p 300 -b 150 -e 0".

To change the parameters of all the VCPUs of a domain, use -v all,
e.g., "xl sched-rtds -d vm1 -v all -p 500 -b 250 -e 1".

CPUPOOLS COMMANDS
Xen can group the physical cpus of a server in cpu-pools. Each physical CPU
is assigned at most to one cpu-pool. Domains are each restricted to a sin-
gle cpu-pool. Scheduling does not cross cpu-pool boundaries, so each
cpu-pool has its own scheduler. Physical cpus and domains can be moved
from one cpu-pool to another only by an explicit command. Cpu-pools can be
specified either by name or by id.

cpupool-create [OPTIONS] [configfile] [variable=value ...]
Create a cpu pool based an config from a configfile or command-line pa-
rameters. Variable settings from the configfile may be altered by
specifying new or additional assignments on the command line.

See the xlcpupool.cfg(5) manpage for more information.

OPTIONS

-f=FILE, --defconfig=FILE
Use the given configuration file.

cpupool-list [OPTIONS] [cpu-pool]
List CPU pools on the host.

OPTIONS

-c, --cpus
If this option is specified, xl prints a list of CPUs used by
cpu-pool.

cpupool-destroy cpu-pool
Deactivates a cpu pool. This is possible only if no domain is active
in the cpu-pool.

cpupool-rename cpu-pool <newname>
Renames a cpu-pool to newname.

cpupool-cpu-add cpu-pool cpus|node:nodes
Adds one or more CPUs or NUMA nodes to cpu-pool. CPUs and NUMA nodes
can be specified as single CPU/node IDs or as ranges.

For example:

(a) xl cpupool-cpu-add mypool 4
(b) xl cpupool-cpu-add mypool 1,5,10-16,^13
(c) xl cpupool-cpu-add mypool node:0,nodes:2-3,^10-12,8

means adding CPU 4 to mypool, in (a); adding CPUs 1,5,10,11,12,14,15
and 16, in (b); and adding all the CPUs of NUMA nodes 0, 2 and 3, plus
CPU 8, but keeping out CPUs 10,11,12, in (c).

All the specified CPUs that can be added to the cpupool will be added
to it. If some CPU can't (e.g., because they're already part of another
cpupool), an error is reported about each one of them.

cpupool-cpu-remove cpu-pool cpus|node:nodes
Removes one or more CPUs or NUMA nodes from cpu-pool. CPUs and NUMA
nodes can be specified as single CPU/node IDs or as ranges, using the
exact same syntax as in cpupool-cpu-add above.

cpupool-migrate domain-id cpu-pool
Moves a domain specified by domain-id or domain-name into a cpu-pool.
Domain-0 can't be moved to another cpu-pool.

cpupool-numa-split
Splits up the machine into one cpu-pool per numa node.

VIRTUAL DEVICE COMMANDS
Most virtual devices can be added and removed while guests are running, as-
suming that the necessary support exists in the guest OS. The effect to
the guest OS is much the same as any hotplug event.

BLOCK DEVICES
block-attach domain-id disc-spec-component(s) ...
Create a new virtual block device and attach it to the specified do-
main. A disc specification is in the same format used for the disk
variable in the domain config file. See xl-disk-configuration(5). This
will trigger a hotplug event for the guest.

Note that only PV block devices are supported by block-attach. Re-
quests to attach emulated devices (eg, vdev=hdc) will result in only
the PV view being available to the guest.

block-detach [OPTIONS] domain-id devid
Detach a domain's virtual block device. devid may be the symbolic name
or the numeric device id given to the device by domain 0. You will
need to run xl block-list to determine that number.

Detaching the device requires the cooperation of the domain. If the
domain fails to release the device (perhaps because the domain is hung
or is still using the device), the detach will fail.

OPTIONS

--force
If this parameter is specified the device will be forcefully de-
tached, which may cause IO errors in the domain and possibly a
guest crash

block-list domain-id
List virtual block devices for a domain.

cd-insert domain-id virtualdevice target
Insert a cdrom into a guest domain's existing virtual cd drive. The
virtual drive must already exist but can be empty. How the device
should be presented to the guest domain is specified by the virtualde-
vice parameter; for example "hdc". Parameter target is the target path
in the backend domain (usually domain 0) to be exported; can be a block
device or a file etc. See target in xl-disk-configuration(5).

Only works with HVM domains.

cd-eject domain-id virtualdevice
Eject a cdrom from a guest domain's virtual cd drive, specified by vir-
tualdevice. Only works with HVM domains.

NETWORK DEVICES
network-attach domain-id network-device
Creates a new network device in the domain specified by domain-id.
network-device describes the device to attach, using the same format as
the vif string in the domain config file. See xl.cfg(5) and xl-net-
work-configuration(5) for more information.

Note that only attaching PV network interfaces is supported.

network-detach domain-id devid|mac
Removes the network device from the domain specified by domain-id. de-
vid is the virtual interface device number within the domain (i.e. the
3 in vif22.3). Alternatively, the mac address can be used to select the
virtual interface to detach.

network-list domain-id
List virtual network interfaces for a domain.

CHANNEL DEVICES
channel-list domain-id
List virtual channel interfaces for a domain.

VIRTUAL TRUSTED PLATFORM MODULE (vTPM) DEVICES
vtpm-attach domain-id vtpm-device
Creates a new vtpm (virtual Trusted Platform Module) device in the do-
main specified by domain-id. vtpm-device describes the device to at-
tach, using the same format as the vtpm string in the domain config
file. See xl.cfg(5) for more information.

vtpm-detach domain-id devid|uuid
Removes the vtpm device from the domain specified by domain-id. devid
is the numeric device id given to the virtual Trusted Platform Module
device. You will need to run xl vtpm-list to determine that number. Al-
ternatively, the uuid of the vtpm can be used to select the virtual de-
vice to detach.

vtpm-list domain-id
List virtual Trusted Platform Modules for a domain.

VDISPL DEVICES
vdispl-attach domain-id vdispl-device
Creates a new vdispl device in the domain specified by domain-id.
vdispl-device describes the device to attach, using the same format as
the vdispl string in the domain config file. See xl.cfg(5) for more in-
formation.

NOTES

As in vdispl-device string semicolon is used then put quotes or es-
caping when using from the shell.

EXAMPLE

xl vdispl-attach DomU connec-
tors='id0:1920x1080;id1:800x600;id2:640x480'

xl vdispl-attach DomU connec-
tors=id0:1920x1080\;id1:800x600\;id2:640x480

vdispl-detach domain-id dev-id
Removes the vdispl device specified by dev-id from the domain specified
by domain-id.

vdispl-list domain-id
List virtual displays for a domain.

VSND DEVICES
vsnd-attach domain-id vsnd-item vsnd-item ...
Creates a new vsnd device in the domain specified by domain-id.
vsnd-item's describe the vsnd device to attach, using the same format
as the VSND_ITEM_SPEC string in the domain config file. See xl.cfg(5)
for more information.

EXAMPLE

xl vsnd-attach DomU 'CARD, short-name=Main, sample-for-
mats=s16_le;s8;u32_be' 'PCM, name=Main' 'STREAM, id=0, type=p'
'STREAM, id=1, type=c, channels-max=2'

vsnd-detach domain-id dev-id
Removes the vsnd device specified by dev-id from the domain specified
by domain-id.

vsnd-list domain-id
List vsnd devices for a domain.

KEYBOARD DEVICES
vkb-attach domain-id vkb-device
Creates a new keyboard device in the domain specified by domain-id.
vkb-device describes the device to attach, using the same format as the
VKB_SPEC_STRING string in the domain config file. See xl.cfg(5) for
more information.

vkb-detach domain-id devid
Removes the keyboard device from the domain specified by domain-id.
devid is the virtual interface device number within the domain

vkb-list domain-id
List virtual network interfaces for a domain.

PCI PASS-THROUGH
pci-assignable-list [-n]
List all the BDF of assignable PCI devices. See xl-pci-configuration(5)
for more information. If the -n option is specified then any name sup-
plied when the device was made assignable will also be displayed.

These are devices in the system which are configured to be available
for passthrough and are bound to a suitable PCI backend driver in do-
main 0 rather than a real driver.

pci-assignable-add [-n NAME] BDF
Make the device at BDF assignable to guests. See xl-pci-configura-
tion(5) for more information. If the -n option is supplied then the as-
signable device entry will the named with the given NAME.

This will bind the device to the pciback driver and assign it to the
"quarantine domain". If it is already bound to a driver, it will first
be unbound, and the original driver stored so that it can be re-bound
to the same driver later if desired. If the device is already bound,
it will assign it to the quarantine domain and return success.

CAUTION: This will make the device unusable by Domain 0 until it is re-
turned with pci-assignable-remove. Care should therefore be taken not
to do this on a device critical to domain 0's operation, such as stor-
age controllers, network interfaces, or GPUs that are currently being
used.

pci-assignable-remove [-r] BDF|NAME
Make a device non-assignable to guests. The device may be identified
either by its BDF or the NAME supplied when the device was made assign-
able. See xl-pci-configuration(5) for more information.

This will at least unbind the device from pciback, and re-assign it
from the "quarantine domain" back to domain 0. If the -r option is
specified, it will also attempt to re-bind the device to its original
driver, making it usable by Domain 0 again. If the device is not bound
to pciback, it will return success.

Note that this functionality will work even for devices which were not
made assignable by pci-assignable-add. This can be used to allow dom0
to access devices which were automatically quarantined by Xen after do-
main destruction as a result of Xen's iommu=quarantine command-line de-
fault.

As always, this should only be done if you trust the guest, or are con-
fident that the particular device you're re-assigning to dom0 will can-
cel all in-flight DMA on FLR.

pci-attach domain-id PCI_SPEC_STRING
Hot-plug a new pass-through pci device to the specified domain. See
xl-pci-configuration(5) for more information.

pci-detach [OPTIONS] domain-id PCI_SPEC_STRING
Hot-unplug a pci device that was previously passed through to a domain.
See xl-pci-configuration(5) for more information.

OPTIONS

-f If this parameter is specified, xl is going to forcefully remove
the device even without guest domain's collaboration.

pci-list domain-id
List the BDF of pci devices passed through to a domain.

USB PASS-THROUGH
usbctrl-attach domain-id usbctrl-device
Create a new USB controller in the domain specified by domain-id, usbc-
trl-device describes the device to attach, using form "KEY=VALUE
KEY=VALUE ..." where KEY=VALUE has the same meaning as the usbctrl de-
scription in the domain config file. See xl.cfg(5) for more informa-
tion.

usbctrl-detach domain-id devid
Destroy a USB controller from the specified domain. devid is devid of
the USB controller.

usbdev-attach domain-id usbdev-device
Hot-plug a new pass-through USB device to the domain specified by do-
main-id, usbdev-device describes the device to attach, using form
"KEY=VALUE KEY=VALUE ..." where KEY=VALUE has the same meaning as the
usbdev description in the domain config file. See xl.cfg(5) for more
information.

usbdev-detach domain-id controller=devid port=number
Hot-unplug a previously assigned USB device from a domain. con-
troller=devid and port=number is USB controller:port in the guest do-
main the USB device is attached to.

usb-list domain-id
List pass-through usb devices for a domain.

DEVICE-MODEL CONTROL
qemu-monitor-command domain-id command
Issue a monitor command to the device model of the domain specified by
domain-id. command can be any valid command qemu understands. This can
be e.g. used to add non-standard devices or devices with non-standard
parameters to a domain. The output of the command is printed to stdout.

Warning: This qemu monitor access is provided for convenience when de-
bugging, troubleshooting, and experimenting. Its use is not supported
by the Xen Project.

Specifically, not all information displayed by the qemu monitor will
necessarily be accurate or complete, because in a Xen system qemu does
not have a complete view of the guest.

Furthermore, modifying the guest's setup via the qemu monitor may con-
flict with the Xen toolstack's assumptions. Resulting problems may in-
clude, but are not limited to: guest crashes; toolstack error messages;
inability to migrate the guest; and security vulnerabilities which are
not covered by the Xen Project security response policy.

EXAMPLE

Obtain information of USB devices connected as such via the device
model (only!) to a domain:

xl qemu-monitor-command vm1 'info usb'
Device 0.2, Port 5, Speed 480 Mb/s, Product Mass Storage

FLASK
FLASK is a security framework that defines a mandatory access control pol-
icy providing fine-grained controls over Xen domains, allowing the policy
writer to define what interactions between domains, devices, and the hyper-
visor are permitted. Some example of what you can do using XSM/FLASK:
- Prevent two domains from communicating via event channels or grants
- Control which domains can use device passthrough (and which devices)
- Restrict or audit operations performed by privileged domains
- Prevent a privileged domain from arbitrarily mapping pages from other
domains.

You can find more details on how to use FLASK and an example security pol-
icy here: <https://xenbits.xenproject.org/docs/unstable/misc/xsm-flask.txt>

getenforce
Determine if the FLASK security module is loaded and enforcing its pol-
icy.

setenforce 1|0|Enforcing|Permissive
Enable or disable enforcing of the FLASK access controls. The default
is permissive, but this can be changed to enforcing by specifying
"flask=enforcing" or "flask=late" on the hypervisor's command line.

loadpolicy policy-file
Load FLASK policy from the given policy file. The initial policy is
provided to the hypervisor as a multiboot module; this command allows
runtime updates to the policy. Loading new security policy will reset
runtime changes to device labels.

PLATFORM SHARED RESOURCE MONITORING/CONTROL
Intel Haswell and later server platforms offer shared resource monitoring
and control technologies. The availability of these technologies and the
hardware capabilities can be shown with psr-hwinfo.

See <https://xenbits.xenproject.org/docs/unstable/misc/xl-psr.html> for
more information.

psr-hwinfo [OPTIONS]
Show Platform Shared Resource (PSR) hardware information.

OPTIONS

-m, --cmt
Show Cache Monitoring Technology (CMT) hardware information.

-a, --cat
Show Cache Allocation Technology (CAT) hardware information.

CACHE MONITORING TECHNOLOGY
Intel Haswell and later server platforms offer monitoring capability in
each logical processor to measure specific platform shared resource metric,
for example, L3 cache occupancy. In the Xen implementation, the monitoring
granularity is domain level. To monitor a specific domain, just attach the
domain id with the monitoring service. When the domain doesn't need to be
monitored any more, detach the domain id from the monitoring service.

Intel Broadwell and later server platforms also offer total/local memory
bandwidth monitoring. Xen supports per-domain monitoring for these two ad-
ditional monitoring types. Both memory bandwidth monitoring and L3 cache
occupancy monitoring share the same set of underlying monitoring service.
Once a domain is attached to the monitoring service, monitoring data can be
shown for any of these monitoring types.

There is no cache monitoring and memory bandwidth monitoring on L2 cache so
far.

psr-cmt-attach domain-id
attach: Attach the platform shared resource monitoring service to a do-
main.

psr-cmt-detach domain-id
detach: Detach the platform shared resource monitoring service from a
domain.

psr-cmt-show psr-monitor-type [domain-id]
Show monitoring data for a certain domain or all domains. Current sup-
ported monitor types are:
- "cache-occupancy": showing the L3 cache occupancy(KB).
- "total-mem-bandwidth": showing the total memory bandwidth(KB/s).
- "local-mem-bandwidth": showing the local memory bandwidth(KB/s).

CACHE ALLOCATION TECHNOLOGY
Intel Broadwell and later server platforms offer capabilities to configure
and make use of the Cache Allocation Technology (CAT) mechanisms, which en-
able more cache resources (i.e. L3/L2 cache) to be made available for high
priority applications. In the Xen implementation, CAT is used to control
cache allocation on VM basis. To enforce cache on a specific domain, just
set capacity bitmasks (CBM) for the domain.

Intel Broadwell and later server platforms also offer Code/Data Prioritiza-
tion (CDP) for cache allocations, which support specifying code or data
cache for applications. CDP is used on a per VM basis in the Xen implemen-
tation. To specify code or data CBM for the domain, CDP feature must be en-
abled and CBM type options need to be specified when setting CBM, and the
type options (code and data) are mutually exclusive. There is no CDP sup-
port on L2 so far.

psr-cat-set [OPTIONS] domain-id cbm
Set cache capacity bitmasks(CBM) for a domain. For how to specify cbm
please refer to <https://xenbits.xenproject.org/docs/unsta-
ble/misc/xl-psr.html>.

OPTIONS

-s SOCKET, --socket=SOCKET
Specify the socket to process, otherwise all sockets are processed.

-l LEVEL, --level=LEVEL
Specify the cache level to process, otherwise the last level cache
(L3) is processed.

-c, --code
Set code CBM when CDP is enabled.

-d, --data
Set data CBM when CDP is enabled.

psr-cat-show [OPTIONS] [domain-id]
Show CAT settings for a certain domain or all domains.

OPTIONS

-l LEVEL, --level=LEVEL
Specify the cache level to process, otherwise the last level cache
(L3) is processed.

Memory Bandwidth Allocation
Intel Skylake and later server platforms offer capabilities to configure
and make use of the Memory Bandwidth Allocation (MBA) mechanisms, which
provides OS/VMMs the ability to slow misbehaving apps/VMs by using a
credit-based throttling mechanism. In the Xen implementation, MBA is used
to control memory bandwidth on VM basis. To enforce bandwidth on a specific
domain, just set throttling value (THRTL) for the domain.

psr-mba-set [OPTIONS] domain-id thrtl
Set throttling value (THRTL) for a domain. For how to specify thrtl
please refer to <https://xenbits.xenproject.org/docs/unsta-
ble/misc/xl-psr.html>.

OPTIONS

-s SOCKET, --socket=SOCKET
Specify the socket to process, otherwise all sockets are processed.

psr-mba-show [domain-id]
Show MBA settings for a certain domain or all domains. For linear mode,
it shows the decimal value. For non-linear mode, it shows hexadecimal
value.

IGNORED FOR COMPATIBILITY WITH XM
xl is mostly command-line compatible with the old xm utility used with the
old Python xend. For compatibility, the following options are ignored:

xl migrate --live

ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of xl:

LIBXL_BOOTLOADER_RESTRICT
Equivalent to xl.cfg(5) bootloader_restrict option. Provided for com-
patibility reasons. Having this variable set is equivalent to enabling
the option, even if the value is 0.

If set takes precedence over xl.cfg(5) and xl.conf(5) bootloader_re-
strict options.

LIBXL_BOOTLOADER_USER
Equivalent to xl.cfg(5) bootloader_user option. Provided for compati-
bility reasons.

If set takes precedence over xl.cfg(5) bootloader_user option.

LIBXL_BOOTLOADER_TIMEOUT
Timeout in seconds for bootloader execution when running in restricted
mode. Otherwise the build time default in LIBXL_BOOTLOADER_TIMEOUT
will be used.

If defined the value must be an unsigned integer between 0 and INT_MAX,
otherwise behavior is undefined. Setting to 0 disables the timeout.