Re: [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause" src logic

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

* Peter Xu (peterx@redhat.com) wrote:
> On Thu, Nov 30, 2017 at 10:49:45AM +0000, Dr. David Alan Gilbert wrote:
> > * Peter Xu (peterx@redhat.com) wrote:
> > > Now when network down for postcopy, the source side will not fail the
> > > migration. Instead we convert the status into this new paused state, and
> > > we will try to wait for a rescue in the future.
> > > 
> > > If a recovery is detected, migration_thread() will reset its local
> > > variables to prepare for that.
> > > 
> > > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > 
> > That's still OK; you might want to consider reusing the 'pause_sem' that I
> > added to MigrationStatus for the other pause case.
> 
> Yes I can.  I am just a bit worried about how these two different
> features cross-affect each other.  Say, what if something tries to
> execute "migrate-continue" during a postcopy network failure?  IMHO it
> should not be allowed, but we don't yet have a protection so far.
> 
> So I would prefer to still separate these two semaphores.

Yes, that's fair enough; the semantics might be different enough that
they don't quite fit - but worth keeping in mind.

> Though I found that I can move init/destroy of the two new semaphores
> (postcopy_pause_sem, postcopy_pause_rp_sem) into object init/destroy
> just like what we did for pause_sem, which seems to be cleaner.  I
> hope I can still keep your r-b if I do that small change.  Thanks,

Yes, I think that's OK.

Dave

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