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

[Michael S. Tsirkin]

On Tue, Dec 14, 2010 at 04:59:55PM +0100, Paolo Bonzini wrote:
> On 12/14/2010 04:41 PM, Alex Williamson wrote:
> >>  Maybe in this particular case the advantage is minimal.
> >>  But it seems easier to stick to a rule of no more version
> >>  bumps than argue about each case.
> >
> >Do we have such a rule?  If we have a subsection who's needed function
> >is return 1, I think that's a good indication that it's not appropriate
> >for a subsection and the end result is equivalent to bumping the main
> >driver vmstate version.  It's convoluted to try to hide a one-way
> >upgrade in a subsection.  Thanks,
> 
> 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?

>  In this case it's either
> no-bump-and-live-with-the-consequences, or changing the version id.
> 
> Paolo

This was discussed to death already.  version ids have the problem
that they don't play nicely with downstreams.

-- 
MST