MonitorProtocol
QEMU Monitor Protocol
The QEMU Monitor Protocol (QMP) is a JSON-based protocol which allows applications to communicate with QEMU's Monitor.
QMP's main features are:
- Lightweight, text-based, easy to parse data format
- Asynchronous messages support (ie. events)
- Capabilities Negotiation
- Stable API (starting with QEMU version 0.13)
The README file has a simple introduction and the full specification is recommended for application writers.
General Status
A preview version of QMP is available in QEMU version 0.12. This means that QMP is still under development and there will be incompatible changes between QEMU 0.12 and QEMU 0.13.
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": { "version": { "qemu": "0.12.50", "package": "" }, "capabilities": [] } }
Query version
C: { "execute": "query-version" }
S: { "return": { "qemu": "0.12.50", "package": ""} }
Eject a device
C: { "execute": "eject", "arguments": { "device": "ide1-cd0" } }
S: {"return": {}}
Development
Main developers are Luiz Capitulino and Markus Armbruster, 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
High Priority
- do_device_add()/do_device_del() conversions (markus)
- do_netdev_add()/do_netdev_del() conversions (markus)
- do_blockdev_add()/do_blockdev_del() conversions (markus)
- Events Grouping (luiz)
- Make qmp-shell work again (luiz)
- Self-description & High-level protocol documentation
- High-level internal documentation
- Better QObjects and QMP debug support
Normal Priority
- Convert all remaining commands to the QObject API
- Improve internal API, currently it's too low-level
- Array-based Monitor's command table
- Libqmp
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 three ways of testing QMP:
- By hand (difficult, only worth it if you're chasing a specific bug)
- qmp-shell script (automates part of the job)
- Libvirt integration (assumes familiarity with libvirt)
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": {"version": {"qemu": "0.12.50", "package": ""}, "capabilities": []}}
4. Now you can issue commands. For example, to get a list of QMP supported commands, run query-commands
{ "execute": "query-commands" }
NOTE (1): all "info" commands are available under QMP as "query-", for example "info vnc" is "query-vnc".
NOTE (2): 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.
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'
NOTE: 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.
Libvirt
Libvirt already has QMP support, but it's currently disable. This test procedure explains how to enable it and put libvirt to run on top of QMP.
1. Install yajl-devel (If you're running Fedora 12 or above just do 'yum install yajl-devel')
2. From a fresh checkout of libvirt master branch run the following:
./autogen.sh --system --enable-compile-warnings=error
NOTE (1): The '--system' flag is a shortcut for compiling with the --prefix and other directories matching a system RPM build.
NOTE (2): Make sure the final summary of autogen.sh tells you that it found the yajl library
3. To enable QMP support, edit src/qemu/qemu_conf.c and find:
#if 0
if (version >= 13000)
flags |= QEMUD_CMD_FLAG_MONITOR_JSON;
#endif
Change to '#if 1', and change the version to 12000 so it detects your GIT build of QEMU
4. Run 'make' to build. There is no need to 'make install' anything especially since that would overwrite your RPM based install
5. As root simply stop the current daemon & start the one you built
/etc/init.d/libvirtd stop $HOME/your/git/checkout/of/libvirt/daemon/libvirtd
6. As root you can use the newly built virsh too
cd $HOME/your/git/checkout/of/libvirt/src ./virsh <BLAH>
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
- partial: merged, but error handling is incomplete
NOTE: Handlers used by Libvirt are marked with yellow. Handlers it is expected to use are marked khaki
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_cpu_set_nr() | qemu-kvm only | ||
| do_delvm() | |||
| do_device_add() | merged | 0.12.50 | |
| do_device_del() | merged | 0.12.50 | |
| 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_netdev_add() | merged | 0.12.50 | |
| do_netdev_del() | merged | 0.12.50 | |
| 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() | legacy, use blockdev_add, device_add instead | ||
| 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, blockdev_add instead |
| do_blockdev_add() | to be created | ||
| do_blockdev_del() | to be created | ||
| do_chardev_add() | to be created | ||
| do_chardev_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_commands() | merged | 0.12 | |
| do_info_cpu_stats() | |||
| do_info_cpus() | merged | 0.12 | |
| 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() | Being worked on in SoC | ||
| do_info_numa() | |||
| do_info_profile() | |||
| do_info_qdm() | |||
| do_info_qtree() | |||
| do_info_registers() | |||
| do_info_roms() | |||
| do_info_snapshots() | lacks parent info, libvirt wants it | ||
| 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 | |
| do_pci_info() | merged | 0.12.50 | libvirt uses this, but only with pre-0.12.x QEMU |
| irq_info() | |||
| mem_info() | |||
| pcmcia_info() | |||
| pic_info() | |||
| qemu_chr_info() | merged | 0.12 | |
| tlb_info() | |||
| usb_host_info() | |||
| usb_info() |
History
This was the fourth proposal for a Monitor protocol, past discussions can be found in the following links: