MonitorProtocol
QEMU Monitor Protocol
The QEMU Monitor Protocol (QMP) allows applications to communicate with QEMU's Monitor.
QMP is JSON-based, its main features are:
- Lightweight, text-based, easy to parse data format
- Asynchronous events support
The README file explains how to use it and its full specification can be found here.
General Status
A preview version of QMP is available in QEMU version 0.12.
However, QMP is still under development being considered unstable and incomplete. For more information about converted handlers, please check #Conversion Status.
Examples
In the following examples, 'C' stands for 'Client' and 'S' stands for 'Server'.
Server Greeting
S: {"QMP": {"capabilities": []}}
Query version
C: { "execute": "query-version" }
S: {"return": {"qemu": "0.11.50", "package": ""}}
Eject a device
C: { "execute": "eject", "arguments": { "device": "ide1-cd0" } }
S: {"return": {}}
Development
Primary contact is Luiz Capitulino, but all QMP-related discussions happen on the qemu-devel mailing list.
Next features, hot fixes and other patches are stored in the QMP unstable repository:
http://repo.or.cz/w/qemu/qmp-unstable.git
NOTE: all branches in this repository are constantly rebased (master inclusive).
TODO
- Convert all remaining commands
- High-level protocol documentation
- High-level internal documentation
- Improve internal API, currently it's too low-level
- Better QObjects and QMP debug support
- Array-based Monitor's command table
- Libqmp
Conversion Status
UPDATED: 2009-12-16
| Command | Info | |
| Handlers | 62 | 36 |
| Converted | 19 | 15 |
| Percentage | 30% | 41% |
The following tables have a per-function status. There is one table for command handlers and another one for info handlers.
Status can be:
- merged: already merged upstream
- converted: converted but not merged yet
- partial: merged, but error handling is incomplete
NOTE: Handlers used by Libvirt are marked with yellow.
Command handlers
| Handler name | Status | Version | Comments |
| do_acl_add() | |||
| do_acl_policy() | |||
| do_acl_remove() | |||
| do_acl_reset() | |||
| do_acl_show() | |||
| do_balloon() | merged | 0.12 | |
| do_block_set_passwd() | merged | 0.12 | |
| do_boot_set() | |||
| do_change() | merged | 0.12 | |
| do_closefd() | merged | 0.12 | |
| do_commit() | |||
| do_cont() | merged | 0.12 | |
| do_cpu_set() | merged | 0.12.50 | |
| do_delvm() | |||
| do_device_add() | |||
| do_device_del() | |||
| do_eject() | merged | 0.12 | |
| do_gdbserver() | |||
| do_getfd() | merged | 0.12 | |
| do_help_cmd() | |||
| do_info() | merged | 0.12 | as 'query-' commands |
| do_inject_mce() | |||
| do_inject_nmi() | |||
| do_ioport_read() | |||
| do_ioport_write() | |||
| do_loadvm() | |||
| do_log() | |||
| do_logfile() | |||
| do_memory_dump() | |||
| do_memory_save() | merged | 0.12.50 | |
| do_migrate() | partial | 0.12 | |
| do_migrate_cancel() | merged | 0.12 | |
| do_migrate_set_downtime() | merged | 0.12.50 | |
| do_migrate_set_speed() | merged | 0.12.50 | |
| do_mouse_button() | |||
| do_mouse_move() | |||
| do_mouse_set() | |||
| do_pci_device_hot_remove() | partial | 0.12 | legacy, use device_del instead |
| do_physical_memory_dump() | |||
| do_physical_memory_save() | merged | 0.12.50 | |
| do_print() | |||
| do_quit() | merged | 0.12 | |
| do_savevm() | |||
| do_screen_dump() | |||
| do_sendkey() | |||
| do_set_link() | |||
| do_singlestep() | |||
| do_stop() | merged | 0.12 | |
| do_stop_capture() | |||
| do_sum() | |||
| do_system_powerdown() | merged | 0.12 | |
| do_system_reset() | merged | 0.12 | |
| do_usb_add() | legacy, use device_add instead | ||
| do_usb_del() | legacy, use device_del instead | ||
| do_watchdog_action() | |||
| do_wav_capture() | |||
| drive_hot_add() | |||
| net_host_device_add() | consider do_netdev_add() instead | ||
| net_host_device_remove() | consider do_netdev_del() instead | ||
| net_slirp_hostfwd_add() | |||
| net_slirp_hostfwd_remove() | |||
| pci_device_hot_add() | partial | 0.12 | legacy, use device_add instead |
| do_chardev_add() | to be created | ||
| do_chardev_del() | to be created | ||
| do_blockdev_add() | to be created | ||
| do_blockdev_del() | to be created | ||
| do_netdev_add() | to be created | ||
| do_netdev_del() | to be created |
Info handlers
| Handler name | Status | Version | Comments |
| bdrv_info() | merged | 0.12 | |
| bdrv_info_stats() | merged | 0.12 | |
| do_info_balloon() | merged | 0.12 | |
| do_info_capture() | |||
| do_info_cpus() | merged | 0.12 | |
| do_info_cpu_stats() | |||
| do_info_history() | |||
| do_info_hpet() | merged | 0.12 | |
| do_info_jit() | |||
| do_info_kvm() | merged | 0.12 | |
| do_info_mice() | merged | 0.12 | |
| do_info_migrate() | merged | 0.12 | |
| do_info_name() | merged | 0.12 | |
| do_info_network() | |||
| do_info_numa() | |||
| do_info_profile() | |||
| do_info_qdm() | |||
| do_info_qtree() | |||
| do_info_registers() | |||
| do_info_roms() | |||
| do_info_snapshots() | |||
| do_info_status() | merged | 0.12 | |
| do_info_usernet() | |||
| do_info_uuid() | merged | 0.12 | |
| do_info_version() | merged | 0.12 | |
| do_info_vnc() | merged | 0.12 | |
| irq_info() | |||
| mem_info() | |||
| pci_info() | |||
| pcmcia_info() | |||
| pic_info() | |||
| qemu_chr_info() | merged | 0.12 | |
| tlb_info() | |||
| usb_host_info() | |||
| usb_info() |
Testing
Unfortunately, there is no automated tool to test QMP correctness yet. Probably, the right thing to do is to integrate with kvm-autotest but we still have to think how this should be done.
Meanwhile, QMP testing is a low-level procedure which requires knowledge about the protocol and its implementation, so the first thing to do is to read the README and spec files.
This section describes two ways of testing QMP:
- By hand (difficult, only worth it if you're chasing a specific bug)
- Using qmp-shell script (automates part of the job)
TODO: libvirt should be far easier, describe it!
By hand
1. Start QMP on a TCP socket, so that telnet can be used
qemu [...] -qmp tcp:localhost:4444,server
2. Now, run telnet
telnet localhost 4444
3. You should see the following prompt
{"QMP": {"capabilities": []}}
4. Now you can issue commands. To get a list of QMP supported commands, run query-commands
{ "execute": "query-commands" }
NOTE: all "info" commands are available under QMP as "query-", for example "info vnc" is "query-vnc".
The output of query-commands is a JSON array of objects, each with a 'name' key, which has the name of the supported command. QMP doesn't have user documentation yet, this means that, to find out which arguments a command accepts or what's its output, you will have to either check the qemu-monitor.hx file and/or the function which implements the command.
Yes, it's that low-level.
qmp-shell script
This script is available under the QMP directory in QEMU's source-tree. It automates a bit the testing work, as it can construct commands.
1. Start QMP on a unix socket, like:
qemu [...] -qmp unix:./qmp-sock,server
2. Run the script
qmp-shell ./qmp-sock
3. You should get the following prompt
(QEMU)
4. Now you can run commands. For example, let's change the VNC password:
(QEMU) change device=vnc target=password arg='1234'
So, it's needed to name the arguments and the script is not very smart. Again, to find out what arguments a command accepts, you have to either check the qemu-monitor.hx file and/or the function which implements the command.
Have fun!
History
This was the fourth proposal for a Monitor protocol, past discussions can be found in the following links: