[libvirt] Transitioning from HMP to QMP for QEMU

Jan Kiszka jan.kiszka at siemens.com
Thu Dec 15 13:18:48 UTC 2011

On 2011-12-15 14:02, Stefan Hajnoczi wrote:
> What is the status of QEMU's transition from HMP to the QMP interface?
> My current understanding is that QEMU provides new HMP commands for
> humans, but HMP is being phased out as an API.  Management tools
> should rely only on QMP for new commands.  That would mean new HMP
> commands are not guaranteed to produce backwards-compatible output
> because tools are not supposed to parse the output.
> On the libvirt side, new QEMU features should only be supported via
> the json monitor in the future (i.e. human monitor patches should not
> be sent/merged)?  Existing HMP commands will still need the human
> monitor support in order to handle old QEMU versions gracefully, but
> I'm thinking about new commands only.
> Does everyone agree on this?  I think this is an important discussion
> if we want our management interface to get better and more consistent
> in the future.

To phase out the classic HMP implementation, we need an internal
HMP-over-JSON wrapper (with tab expansion etc.) so that virtual console
and gdbstub monitors continue to benefit from new commands. Those
interfaces will stay for a long time, I'm sure.


Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux

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