Quoting Michael S. Tsirkin (mst@xxxxxxxxxx): > On Mon, Sep 22, 2014 at 05:24:55PM +0200, Markus Armbruster wrote: > > "Daniel P. Berrange" <berrange@xxxxxxxxxx> writes: > > > > > On Mon, Sep 22, 2014 at 02:36:55PM +0300, Michael S. Tsirkin wrote: > > >> On Sun, Sep 21, 2014 at 03:38:59PM +0100, Alex Bligh wrote: > > >> > Add a configure option --enable-pc-1-0-qemu-kvm and the > > >> > corresponding --disable-pc-1-0-qemu-kvm, defaulting > > >> > to disabled. > > >> > > > >> > Rename machine type pc-1.0 to pc-1.0-qemu-git. > > >> > > > >> > Make pc-1.0 machine type an alias of either pc-1.0-qemu-kvm > > >> > or pc-1.0-qemu-git depending on the value of the config > > >> > option. > > >> > > > >> > Signed-off-by: Alex Bligh <alex@xxxxxxxxxxx> > > >> > > >> I have to say, this one bothers me. > > >> We end up not being able to predict what does pc-1.0 > > >> reference. > > > > > > Yeah, this is not good. Any single machine type name should have > > > fixed semantics - having two different semantics depending on build > > > options means mgmt apps can no longer simply compare the machine > > > type name to determine if it is a match with the same name on a > > > different host. > > > > You're right. However, this particular horse left the barn a long time > > ago: the pc-* machine types differ in qemu-kvm and upstream QEMU. > > > > Sure, when qemu-kvm was merged back into QEMU, its machine type variants > > were dropped. But they live on in various downstreams that just like > > QEMU had to pick between compatibility with upstream QEMU and qemu-kvm, > > but unlike QEMU picked compatibility with qemu-kvm. > > > > So this patch does *not* break any management apps by letting them "no > > longer simply compare the machine type name to determine if it is a > > match with the same name on a different host". They never could for > > these messed up machine types, at least not without knowing exactly what > > kind of QEMU runs on the hosts in question. > > > > All this patch does is adding another facet to "exactly what kind of > > QEMU". > > Right, but IMHO doing it at compile-time is wrong. > If distros want compatiblity with both sometimes, what then? > Build two binaries with different flags? > Should be a runtime option that management sets after (somehow?) > figuring out what's going on, on source. > > How does it do that? Not sure - but I'm sure destination distro has no > way to figure it out. It's not even just between distributions. Anyone who used qemu-2.0 to start a pc-1.0 machine type will have a different mt than someone who starts a vm under Ubuntu's (qemu-)kvm 1.0. Sadly. So in the packages at https://launchpad.net/~serge-hallyn/+archive/ubuntu/qemu-p-migration the default can be configured at build-time, but it can be specified on the command-line (which is then controlled by a new libvirt flag). -serge -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list