Re: [Qemu-devel] [PATCH] Change virtio-console to PCI_CLASS_SERIAL_OTHER

[Daniel P. Berrange]

On Thu, May 28, 2009 at 01:53:49PM +0100, Paul Brook wrote:
> On Wednesday 27 May 2009, Mark McLoughlin wrote:
> > On Wed, 2009-05-27 at 09:21 -0500, Anthony Liguori wrote:
> > > We need a mechanism to toggle this for both this and virtio-blk.  The
> > > reason a toggle is needed is so that 0.11 can create the same device
> > > model as 0.10.
> >
> > Okay, so the scenario is:
> >
> >   - 0.10 guest running on source machine
> >
> >   - migrate to dest machine running 0.11
> >
> >   - the device model cannot change or the guest OS will get confused
> 
> IMHO think the only sane response is "don't do that". Trying to support 
> migration between different qemu versions just isn't worth the pain.

I think that further more, we shouldn't make a change like altering
the PCI device class in the stable branch, only in the unstable 
branch. If we restrict the stable branch to bug fixes, then it ought
to be (more?) practical to support save under 0.10 and restore under
0.11, without needing to support the hard problem of save under 0.10
and restore under 1.00 (or whatever next major release branch is)

Regards,
Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
|: http://libvirt.org  -o-  http://virt-manager.org  -o-  http://ovirt.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505  -o-  F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|