On Tue, Aug 25, 2015 at 05:21:16PM +0100, Daniel P. Berrange wrote: > On Mon, Aug 24, 2015 at 11:54:48AM +0200, Markus Armbruster wrote: > > John Snow <js...@redhat.com> writes: > > > > > On 08/19/2015 02:55 AM, Dr. David Alan Gilbert wrote: > > >> * Eduardo Habkost (ehabk...@redhat.com) wrote: > > >>> Migration with q35 was not possible before commit > > >>> 04329029a8c539eb5f75dcb6d8b016f0c53a031a, because q35 unconditionally > > >>> creates > > >>> an ich9-ahci device, that was marked as unmigratable. So all q35 > > >>> machines > > >>> before pc-q35-2.4 were unmigratable, and there's no point in keeping > > >>> compatibility code for them. > > >>> > > >>> Remove all old pc-q35 machine classes and keep only pc-q35-2.4. > > >> > > >> But doesn't that mean that anyone who has a machine configured with one > > >> of those machine types will suddenly find it wont start? > > >> > > >> Dave > > >> > > > > > > To some extent, all versions of this board prior to 2.4 should be > > > considered unsupported and we should discourage their use anyway. > > > > > > If you really want, I suppose we could just alias them to 2.4 ... > > > > I'd very much prefer an honest "won't start" over a silent change of the > > machine type. > > > > If we really want to bend over backwards for existing uses of these > > machine types, we could make them error out with "use pc-q35-2.5 > > instead". Since I don't think they exist outside testing, I wouldn't > > bother. > > Agreed, we should be reporting a hard error for any machine types we > have deleted. Or if we care about smooth upgrade path then we shouldn't > be deleting them in the first place. Silently changing the user's > requested machine type into a different machine type is violating > the semantics of stable machine types. > > Regards, > Daniel
The reason we are deleting them is because changes in behaviour are not user visible implementation details, and live migration is unsupported. In other words 2.4 is identical to <2.3 in all respect except live migration, which didn't work in <2.3 and works in 2.4, that's why aliasing them is fine. But if people really want "2.3 = 2.4 that does not migrate" we could do that with very little code, too. > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
