[Qemu-devel] Re: [PATCH] rtl8139: IO memory is not part of vmstate

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Dec 15, 2010 at 06:12:25PM +0100, Paolo Bonzini wrote:
> On 12/15/2010 11:00 AM, Michael S. Tsirkin wrote:
> >>Indeed, subsections are for data that is rarely needed so that
> >>there's some chance (sometimes ~100%) of migration working
> >>seemlessly.
> >
> >If a subsection arrives that qemu does
> >not know about, won't migratin fail?
> 
> Yes, that's why rarely needed => some high chance of migration
> working (though no certainty).
> 
> >>In this case it's either
> >>no-bump-and-live-with-the-consequences, or changing the version id.
> >
> >This was discussed to death already.  version ids have the problem
> >that they don't play nicely with downstreams.
> 
> Downstream version bumps don't play nicely with upstream, so
> downstream does have a reason for always-necessary subsections.  But
> upstream can bump the version id as much as they care.
> 
> Paolo

This assuming upstream developers do not care about downstreams.
To give a chance for downstream to cherry-pick changes, upstream
should use subsections instead of version ids too.

-- 
MST