Re: [PATCH v3 1/1] os-posix: asynchronous teardown for shutdown on Linux

[Christian Borntraeger]

Am 11.08.22 um 14:27 schrieb Daniel P. Berrangé:
[...]
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -4743,6 +4743,23 @@ HXCOMM Internal use
> >   DEF("qtest", HAS_ARG, QEMU_OPTION_qtest, "", QEMU_ARCH_ALL)
> >   DEF("qtest-log", HAS_ARG, QEMU_OPTION_qtest_log, "", QEMU_ARCH_ALL)
> >   
> > +#ifdef __linux__
> > +DEF("async-teardown", 0, QEMU_OPTION_asyncteardown,
> > +    "-async-teardown enable asynchronous teardown\n",
> > +    QEMU_ARCH_ALL)
> > +#endif
> > +SRST
> > +``-async-teardown``
> > +    Enable asynchronous teardown. A new teardown process will be
> > +    created at startup, using clone. The teardown process will share
> > +    the address space of the main qemu process, and wait for the main
> > +    process to terminate. At that point, the teardown process will
> > +    also exit. This allows qemu to terminate quickly if the guest was
> > +    huge, leaving the teardown of the address space to the teardown
> > +    process. Since the teardown process shares the same cgroups as the
> > +    main qemu process, accounting is performed correctly.
> > +ERST
> > +
> >   DEF("msg", HAS_ARG, QEMU_OPTION_msg,
> >       "-msg [timestamp[=on|off]][,guest-name=[on|off]]\n"
> >       "                control error message format\n"
>
> It occurrs to me that we've got a general goal of getting away from
> adding new top level command line arguments. Most of the time there's
> an obvious existing place to put them, but I'm really not sure
> where this particular  option would fit ?
>
> it isn't tied to any aspect of the VM backend configuration nor
> hardware frontends.
>
> The closest match is the lifecycle action option (-no-shutdown)
> which were merged into a -action arg, but even that's a bit of a
> stretch.
>
> Markus/Paolo:  do you have suggestions ?

Also extending this to libvirt, would it make sense to add this to the event 
list
<on_poweroff>
<on_reboot>
<on_crash>
<on_lockfailure>

as
<on_teardown> with async/sync

This might give an indication where to put it in qemu.