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

[Paolo Bonzini]

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