[Qemu-devel] Re: Live migration protocol, device features, ABIs and other beasts

[Michael S. Tsirkin]

On Wed, Nov 25, 2009 at 10:30:47AM +0100, Juan Quintela wrote:
> "Michael S. Tsirkin" <address@hidden> wrote:
> > On Tue, Nov 24, 2009 at 03:21:34PM +0100, Juan Quintela wrote:
> 
> > A device already supports load for a range
> > of versions between X and Y. We want to support
> > saving to a range of versions.
> >
> > Which versions to use is a separate decision
> > which should be taken on run time, not
> > at startup time.
> 
> Not in the general case.

If that means "not in all cases", I agree.
But it seems pretty common for bugfixes.

> Think that v8 brings featureX to one device.  If you _know_ that you don't
> want to use feature X, startup time is the proper place.  Important
> thing is not the savevm format (we can do any change here), what we
> really need is that the guest still runs on the destination, and for
> that you can't change the hardware too much.
> 
> Later, Juan.

I think it's clear: if you change guest visible properties
these are features that might belong in machine description.
If not - they don't belong in machine description.

-- 
MST