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Re: [libvirt] [Qemu-devel] Transitioning from HMP to QMP for QEMU



On 12/15/2011 11:33 AM, Kevin Wolf wrote:
Am 15.12.2011 14:18, schrieb Jan Kiszka:
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.

I think we're not talking about dropping HMP here, only about how long
to support it as a stable API for management tools. I believe that we
have been in a transitional phase for long enough now that we can start
changing the output format of HMP commands without considering it an API
breakage.

Yes, I've got the same impression. But while we are at it, forgive my naiveness, but wouldn't be worthwhile to consider dropping the human monitor in the long run?


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