Re: [PATCH] qmp: Stabilize preconfig

[Paolo Bonzini <pbonzini@redhat.com>]

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El lun., 15 nov. 2021 16:40, Markus Armbruster <armbru@redhat.com> escribió:

> > Why do you care?  For another example, you can use "reboot" or
> > "systemctl isolate reboot.target" and they end up doing the same thing.
> >
> > As long as qemu_init invokes qmp_machine_set, qmp_accel_set,
> > qmp_device_add, qmp_plugin_add, qmp_cont, etc. to do its job, the
> > difference between qemu-system-* and qemu-qmp-* is a couple thousands
> > lines of boring code that all but disappears once the VM is up and
> > running.  IOW, with the right design (e.g. shortcut options for QOM
> > properties good; dozens of global variables bad), there's absolutely no
> > issue with some people using qemu-system-* and some using qemu-qmp-*.
>
> I think maintaining two binaries forever is madness.  I want the old one
> to wither away.


This seems a bit dogmatic to me. The difference between the two binaries
would be literally a single file, which basically disappears before
anything interesting happens.

Making the new binary capable of serving all use cases should not be
> hard, just work (see my design sketch).  I expect the result to serve
> *better* than the mess we have now.
>

Most of the mess is in the implementation. Not all, granted. But overall
softmmu/vl.c's ugliness is mostly due to the layers of backwards
compatibility, and that wouldn't go away very soon.

>>>> My point is that we still have quite a few commands without
> >>>> 'allow-preconfig' mostly because we are afraid of allowing them in
> >>>> preconfig state, not because of true phase dependencies.
> >>>
> >>> I think there's very few of them, if any (outside the block layer for
> >>> which patches exist), and those are due to distraction more than fear.
> >>
> >> qapi/*.json has 216 commands, of which 26 carry 'allow-preconfig'.
> >
> > Well,
> > https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg01597.html
> > alone would more than double that. :)
> >
> > Places like machine.json, machine-target.json, migration.json,
> > replay.json have a lot of commands that are, obviously, almost entirely
> > not suitable for preconfig.  I don't think there are many commands left,
> > I'd guess maybe 30 (meaning that ~60% are done).
>
> My point is that "very few" is not literally true, and I think you just
> confirmed it ;)


Ok, let me rephrase that as "most of the missing ones are block-layer
relates". ;)

Paolo

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