Re: [Qemu-devel] [PATCH f0r 2.11] runstate/migrate: Two more transitions

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Xu (peterx@redhat.com) wrote:
> On Fri, Aug 04, 2017 at 06:50:11PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > There's a race if someone does a 'stop' near the end of migrate;
> > the migration process goes through two runstates:
> >     'finish migrate'
> >     'postmigrate'
> > 
> > If the user issues a 'stop' between the two we end up with invalid
> > state transitions.
> > Add the transitions as valid.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  vl.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/vl.c b/vl.c
> > index 99fcfa0442..bacb03f49d 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -621,6 +621,7 @@ static const RunStateTransition runstate_transitions_def[] = {
> >  
> >      { RUN_STATE_PAUSED, RUN_STATE_RUNNING },
> >      { RUN_STATE_PAUSED, RUN_STATE_FINISH_MIGRATE },
> > +    { RUN_STATE_PAUSED, RUN_STATE_POSTMIGRATE },
> >      { RUN_STATE_PAUSED, RUN_STATE_PRELAUNCH },
> >      { RUN_STATE_PAUSED, RUN_STATE_COLO},
> >  
> > @@ -633,6 +634,7 @@ static const RunStateTransition runstate_transitions_def[] = {
> >      { RUN_STATE_PRELAUNCH, RUN_STATE_INMIGRATE },
> >  
> >      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_RUNNING },
> > +    { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PAUSED },
> >      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_POSTMIGRATE },
> >      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_PRELAUNCH },
> >      { RUN_STATE_FINISH_MIGRATE, RUN_STATE_COLO},
> 
> Do we need this as well?
> 
>     { RUN_STATE_POSTMIGRATE, RUN_STATE_PAUSED },

Apparently not:

(qemu) migrate "exec:cat > /dev/null"
(qemu) infomigrate
unknown command: 'infomigrate'
(qemu) info status
VM status: paused (postmigrate)
(qemu) stop
(qemu) info status
VM status: paused (postmigrate)
(qemu)


so doing a stop at that point doesn't seem to cause any problem.

Dave

> -- 
> Peter Xu
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK