Re: [Qemu-devel] [PATCH v2] make windows notice media change

[Paul Brook <paul@codesourcery.com>]

> >>> Why shouldn't we support loading version 2 snapshots? Afterall that's
> >>> why we had the versioning in the first place.
> >>
> >> No it's not. Versioning was introduced to *prevent* loading old
> >> snapshots and crashing or ending up with inconsistent guest state. I'm
> >> still unconvinced that anything other than very short term backward
> >> compatibility is worthwhile or even viable.
> >
> > I see it as a way to migrate a running guest to newer QEMU version,
> > possibly even with live migration. In fact I used it quite often back in
> > the day when snapshots were not part of qcow2 yet and when kqemu was
> > still in its heydays.
>
> BTW, why would there be the version parameter in the first place if it
> wasn't supposed to load older versions?!

Like I already said: it's there to prevent an old version being loaded 
accidentally. Without this an incompatible change will  result in anything 
from a crash to corrupt/inconsistent guest state. Versioning allows us to 
reject the snapshot and fail safely.

Paul