Re: [PATCH] qmp: Stabilize preconfig

[Markus Armbruster]

Paolo Bonzini <pbonzini@redhat.com> writes:

>> On 11/3/21 09:02, Markus Armbruster wrote:
>>> I wonder whether we really have to step through three states
>>>
>>>           x-exit-preconfig  cont
>>>      preconfig ---> pre run ---> run
>>>
>>> and not two
>>>
>>>              cont
>>>      pre run ---> run
>
> Devices would be hotplugged between x-exit-preconfig and cont, and

Cold plugged!

> part of the machine until x-exit-preconfig; so there is a need for
> something like x-exit-preconfig.

Can you briefly explain why device_add doesn't work before
x-exit-preconfig and does after?

> In my prototype of a QMP-only binary, the idea would be that there
> wouldn't be a single x-exit-preconfig command, but "cont", 
> "migrate-incoming", "finish-machine-init" (the stable replacement for
> x-exit-preconfig) and "loadvm" would all complete the configuration of 
> the machine.  "finish-machine-init" would do nothing else, the others
> would continue with whatever they were supposed to do.
>
>>> Which of the queries you need work only between x-exit-preconfig and -S?
>> Well before x-exit-preconfig, QMP only permits a very small number
>> of commands - QEMU has loosened that up a bit, but I don't think anyone
>> has checked whether there's enough to cover libvirt's current usage yet.
>
> Indeed I looked at the commands that operate on the backends, but not
> that much at query commands.
>
> Paolo