path: root/docs/qmp-commands.txt

                        QMP Supported Commands
                        ----------------------

This document describes all commands currently supported by QMP.

Most of the time their usage is exactly the same as in the user Monitor, this
means that any other document which also describe commands (the manpage,
QEMU's manual, etc) can and should be consulted.

QMP has two types of commands: regular and query commands. Regular commands
usually change the Virtual Machine's state someway, while query commands just
return information. The sections below are divided accordingly.

It's important to observe that all communication examples are formatted in
a reader-friendly way, so that they're easier to understand. However, in real
protocol usage, they're emitted as a single line.

Also, the following notation is used to denote data flow:

-> data issued by the Client
<- Server data response

Please, refer to the QMP specification (docs/qmp-spec.txt) for detailed
information on the Server command and response formats.

NOTE: This document is temporary and will be replaced soon.

1. Stability Considerations
===========================

The current QMP command set (described in this file) may be useful for a
number of use cases, however it's limited and several commands have bad
defined semantics, specially with regard to command completion.

These problems are going to be solved incrementally in the next QEMU releases
and we're going to establish a deprecation policy for badly defined commands.

If you're planning to adopt QMP, please observe the following:

    1. The deprecation policy will take effect and be documented soon, please
       check the documentation of each used command as soon as a new release of
       QEMU is available

    2. DO NOT rely on anything which is not explicit documented

    3. Errors, in special, are not documented. Applications should NOT check
       for specific errors classes or data (it's strongly recommended to only
       check for the "error" key)

2. Regular Commands
===================

Server's responses in the examples below are always a success response, please
refer to the QMP specification for more details on error responses.

device_add
----------

Add a device.

Arguments:

- "driver": the name of the new device's driver (json-string)
- "bus": the device's parent bus (device tree path, json-string, optional)
- "id": the device's ID, must be unique (json-string)
- device properties

Example:

-> { "execute": "device_add", "arguments": { "driver": "e1000", "id": "net1" } }
<- { "return": {} }

Notes:

(1) For detailed information about this command, please refer to the
    'docs/qdev-device-use.txt' file.

(2) It's possible to list device properties by running QEMU with the
    "-device DEVICE,\?" command-line argument, where DEVICE is the device's name

cpu
---

Set the default CPU.

Arguments:

- "index": the CPU's index (json-int)

Example:

-> { "execute": "cpu", "arguments": { "index": 0 } }
<- { "return": {} }

Note: CPUs' indexes are obtained with the 'query-cpus' command.

xen-load-devices-state
----------------------

Load the state of all devices from file. The RAM and the block devices
of the VM are not loaded by this command.

Arguments:

- "filename": the file to load the state of the devices from as binary
data. See xen-save-devices-state.txt for a description of the binary
format.

Example:

-> { "execute": "xen-load-devices-state",
     "arguments": { "filename": "/tmp/resume" } }
<- { "return": {} }

migrate-set-cache-size
----------------------

Set cache size to be used by XBZRLE migration, the cache size will be rounded
down to the nearest power of 2

Arguments:

- "value": cache size in bytes (json-int)

Example:

-> { "execute": "migrate-set-cache-size", "arguments": { "value": 536870912 } }
<- { "return": {} }

x-colo-lost-heartbeat
--------------------

Tell COLO that heartbeat is lost, a failover or takeover is needed.

Example:

-> { "execute": "x-colo-lost-heartbeat" }
<- { "return": {} }

query-dump
----------

Query background dump status.

Arguments: None.

Example:

-> { "execute": "query-dump" }
<- { "return": { "status": "active", "completed": 1024000,
                 "total": 2048000 } }

blockdev-mirror
------------

Start mirroring a block device's writes to another block device. target
specifies the target of mirror operation.

Arguments:

- "job-id": Identifier for the newly-created block job. If omitted,
            the device name will be used. (json-string, optional)
- "device": The device name or node-name of a root node whose writes should be
            mirrored (json-string)
- "target": device name to mirror to (json-string)
- "replaces": the block driver node name to replace when finished
              (json-string, optional)
- "speed": maximum speed of the streaming job, in bytes per second
  (json-int)
- "granularity": granularity of the dirty bitmap, in bytes (json-int, optional)
- "buf_size": maximum amount of data in flight from source to target, in bytes
  (json-int, default 10M)
- "sync": what parts of the disk image should be copied to the destination;
  possibilities include "full" for all the disk, "top" for only the sectors
  allocated in the topmost image, or "none" to only replicate new I/O
  (MirrorSyncMode).
- "on-source-error": the action to take on an error on the source
  (BlockdevOnError, default 'report')
- "on-target-error": the action to take on an error on the target
  (BlockdevOnError, default 'report')

The default value of the granularity is the image cluster size clamped
between 4096 and 65536, if the image format defines one.  If the format
does not define a cluster size, the default value of the granularity
is 65536.

Example:

-> { "execute": "blockdev-mirror", "arguments": { "device": "ide-hd0",
                                                  "target": "target0",
                                                  "sync": "full" } }
<- { "return": {} }

qmp_capabilities
----------------

Enable QMP capabilities.

Arguments: None.

Example:

-> { "execute": "qmp_capabilities" }
<- { "return": {} }

Note: This command must be issued before issuing any other command.

3. Query Commands
=================


query-qmp-schema
----------------

Return the QMP wire schema.  The returned value is a json-array of
named schema entities.  Entities are commands, events and various
types.  See docs/qapi-code-gen.txt for information on their structure
and intended use.

x-blockdev-change
-----------------

Dynamically reconfigure the block driver state graph. It can be used
to add, remove, insert or replace a graph node. Currently only the
Quorum driver implements this feature to add or remove its child. This
is useful to fix a broken quorum child.

If @node is specified, it will be inserted under @parent. @child
may not be specified in this case. If both @parent and @child are
specified but @node is not, @child will be detached from @parent.

Arguments:
- "parent": the id or name of the parent node (json-string)
- "child": the name of a child under the given parent node (json-string, optional)
- "node": the name of the node that will be added (json-string, optional)

Note: this command is experimental, and not a stable API. It doesn't
support all kinds of operations, all kinds of children, nor all block
drivers.

Warning: The data in a new quorum child MUST be consistent with that of
the rest of the array.

Example:

Add a new node to a quorum
-> { "execute": "blockdev-add",
     "arguments": { "driver": "raw",
                    "node-name": "new_node",
                    "file": { "driver": "file",
                              "filename": "test.raw" } } }
<- { "return": {} }
-> { "execute": "x-blockdev-change",
     "arguments": { "parent": "disk1",
                    "node": "new_node" } }
<- { "return": {} }

Delete a quorum's node
-> { "execute": "x-blockdev-change",
     "arguments": { "parent": "disk1",
                    "child": "children.1" } }
<- { "return": {} }

trace-event-set-state
---------------------

Set the state of events.

Arguments:

- "name": Event name pattern (json-string).
- "enable": Whether to enable or disable the event (json-bool).
- "ignore-unavailable": Whether to ignore errors for events that cannot be
  changed (json-bool, optional).
- "vcpu": The vCPU to act upon, all vCPUs by default (json-int, optional).

An event's state is modified if:
- its name matches the "name" pattern, and
- if "vcpu" is given, the event has the "vcpu" property.

Therefore, if "vcpu" is given, the operation will only match per-vCPU events,
setting their state on the specified vCPU. Special case: if "name" is an exact
match, "vcpu" is given and the event does not have the "vcpu" property, an error
is returned.

Example:

-> { "execute": "trace-event-set-state", "arguments": { "name": "qemu_memalign", "enable": "true" } }
<- { "return": {} }

query-gic-capabilities
---------------

Return a list of GICCapability objects, describing supported GIC
(Generic Interrupt Controller) versions.

Arguments: None

Example:

-> { "execute": "query-gic-capabilities" }
<- { "return": [{ "version": 2, "emulated": true, "kernel": false },
                { "version": 3, "emulated": false, "kernel": true } ] }

Show existing/possible CPUs
---------------------------

Arguments: None.

Example for pseries machine type started with
-smp 2,cores=2,maxcpus=4 -cpu POWER8:

-> { "execute": "query-hotpluggable-cpus" }
<- {"return": [
     { "props": { "core-id": 8 }, "type": "POWER8-spapr-cpu-core",
       "vcpus-count": 1 },
     { "props": { "core-id": 0 }, "type": "POWER8-spapr-cpu-core",
       "vcpus-count": 1, "qom-path": "/machine/unattached/device[0]"}
   ]}'

Example for pc machine type started with
-smp 1,maxcpus=2:
    -> { "execute": "query-hotpluggable-cpus" }
    <- {"return": [
         {
            "type": "qemu64-x86_64-cpu", "vcpus-count": 1,
            "props": {"core-id": 0, "socket-id": 1, "thread-id": 0}
         },
         {
            "qom-path": "/machine/unattached/device[0]",
            "type": "qemu64-x86_64-cpu", "vcpus-count": 1,
            "props": {"core-id": 0, "socket-id": 0, "thread-id": 0}
         }
       ]}