Archipelago » qemu

QMP is JSON[1] based and currently has the following features:

- Asynchronous messages support (ie. events)

- Capabilities Negotiation

For detailed information on QMP's usage, please, refer to the following files:

o qmp-commands.txt  QMP supported commands (auto-generated at build-time)

o qmp-shell  A shell

o vm-info    Show some information about the Virtual Machine

IMPORTANT: It's strongly recommended to read the 'Stability Considerations'

section in the qmp-commands.txt file before making any serious use of QMP.

To enable QMP, you need a QEMU monitor instance in "control mode". There are

two ways of doing this.

The simplest one is using the '-qmp' command-line option. The following

example makes QMP available on localhost port 4444:

  $ qemu [...] -qmp tcp:localhost:4444,server

However, in order to have more complex combinations, like multiple monitors,

the '-mon' command-line option should be used along with the '-chardev' one.

For instance, the following example creates one user monitor on stdio and one

QMP monitor on localhost port 4444.

   $ qemu [...] -chardev stdio,id=mon0 -mon chardev=mon0,mode=readline \

                -chardev socket,id=mon1,host=localhost,port=4444,server \

                -mon chardev=mon1,mode=control

Please, refer to QEMU's manpage for more information.

To manually test QMP one can connect with telnet and issue commands by hand:

{"QMP": {"version": {"qemu": {"micro": 50, "minor": 13, "major": 0}, "package": ""}, "capabilities": []}}

{"return": {"qemu": {"micro": 50, "minor": 13, "major": 0}, "package": ""}}

Development Process

-------------------

When changing QMP's interface (by adding new commands, events or modifying

existing ones) it's mandatory to update the relevant documentation, which is

one (or more) of the files listed in the 'Introduction' section*.

Also, it's strongly recommended to send the documentation patch first, before

doing any code change. This is so because:

  1. Avoids the code dictating the interface

  2. Review can improve your interface.  Letting that happen before

     you implement it can save you work.

* The qmp-commands.txt file is generated from the qemu-monitor.hx one, which

  is the file that should be edited.

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