Re: [Qemu-devel] [PATCH RFC 1/1] virtio: migrate config_vector

[Michael S. Tsirkin]

On Thu, May 14, 2015 at 12:04:05PM +0200, Paolo Bonzini wrote:
> 
> 
> On 14/05/2015 11:56, Michael S. Tsirkin wrote:
> > > That's expected.  Subsections break compatibility because sometimes
> > > breaking migration is better than leaving a broken guest after migration.
> > 
> > Right, and what happens is that some devices work kind of okay without
> > config interrupts? Christian - is this why you are trying to preserve
> > the broken behaviour for cross-version migration?
> 
> If you really want that, the hook should be in the virtio device class.
> Keying on the machine type is almost never the answer, at least upstream.
> Distros can always override it if they know what they're getting into.
> 
> Paolo

I beg to disagree.  Check out PC_COMPAT_ macros.  But if you are saying
migration with virtio-ccw is just too broken ATM, so we shouldn't care
about its migration compatibility upstream, then I can buy that.

-- 
MST