On Tue, Jun 23, 2015 at 07:41:50PM +0200, Andreas Färber wrote: > Only if you use "-cpu ...,enforce", no? > > The KVM feature filtering should take care of dropping features that are > not available otherwise. > > So we seem to be getting to the interesting case of the same machine > (different from what was said previously!) but different hosts. > > The QOM property gives you insights into which feature bits are set for > the machine for the model (and for s390x I saw QMP extensions to the > same effect, I thought). That way you could discover features to > disable. However you'll only ever know which ones work once you've tried > it once, right?
On this subject, a big problem in QOM in general is that it hasn't included a distinction between object classes and object instances. So there's no way for us to introspect what a machine type provides without actually instantiating a guest with that machine type. Again allowing libvirt to control the CPU model removes this problem as libvirt will be able to determine what CPUs it can run on a given host without having to probe all the different CPU <-> machine type combinations for the QEMU on that host has. This in turn simplifies life for apps using libvirt, as they will always know that "CPUFoo-X.Y" will always mean the exact same thing on all the hosts they have no matter what QEMU version/machine is in use. Regards, Daniel -- |: 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 :|
