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QEMU Monitor Protocol |
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===================== |
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Introduction |
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------------- |
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The QEMU Monitor Protocol (QMP) allows applications to communicate with |
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QEMU's Monitor. |
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|
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QMP is JSON[1] based and currently has the following features: |
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- Lightweight, text-based, easy to parse data format |
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- Asynchronous messages support (ie. events) |
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- Capabilities Negotiation |
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For detailed information on QMP's usage, please, refer to the following files: |
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|
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o qmp-spec.txt QEMU Monitor Protocol current specification |
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o qmp-commands.txt QMP supported commands (auto-generated at build-time) |
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o qmp-events.txt List of available asynchronous events |
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There is also a simple Python script called 'qmp-shell' available. |
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IMPORTANT: It's strongly recommended to read the 'Stability Considerations' |
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section in the qmp-commands.txt file before making any serious use of QMP. |
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[1] http://www.json.org |
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|
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Usage |
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----- |
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To enable QMP, you need a QEMU monitor instance in "control mode". There are |
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two ways of doing this. |
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|
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The simplest one is using the '-qmp' command-line option. The following |
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example makes QMP available on localhost port 4444: |
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$ qemu [...] -qmp tcp:localhost:4444,server |
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However, in order to have more complex combinations, like multiple monitors, |
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the '-mon' command-line option should be used along with the '-chardev' one. |
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For instance, the following example creates one user monitor on stdio and one |
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QMP monitor on localhost port 4444. |
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$ qemu [...] -chardev stdio,id=mon0 -mon chardev=mon0,mode=readline \ |
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-chardev socket,id=mon1,host=localhost,port=4444,server \ |
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-mon chardev=mon1,mode=control |
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Please, refer to QEMU's manpage for more information. |
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Simple Testing |
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-------------- |
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|
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To manually test QMP one can connect with telnet and issue commands by hand: |
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|
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$ telnet localhost 4444 |
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Trying 127.0.0.1... |
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Connected to localhost. |
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Escape character is '^]'. |
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{"QMP": {"version": {"qemu": {"micro": 50, "minor": 13, "major": 0}, "package": ""}, "capabilities": []}} |
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{ "execute": "qmp_capabilities" } |
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{"return": {}} |
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{ "execute": "query-version" } |
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{"return": {"qemu": {"micro": 50, "minor": 13, "major": 0}, "package": ""}} |
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Development Process |
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------------------- |
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When changing QMP's interface (by adding new commands, events or modifying |
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existing ones) it's mandatory to update the relevant documentation, which is |
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one (or more) of the files listed in the 'Introduction' section*. |
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Also, it's strongly recommended to send the documentation patch first, before |
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doing any code change. This is so because: |
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1. Avoids the code dictating the interface |
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2. Review can improve your interface. Letting that happen before |
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you implement it can save you work. |
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* The qmp-commands.txt file is generated from the qmp-commands.hx one, which |
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is the file that should be edited. |
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Homepage |
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-------- |
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|
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http://wiki.qemu.org/QMP |