On Fri, Sep 27, 2019 at 10:09:05AM +0100, Daniel P. Berrangé wrote: > On Thu, Sep 26, 2019 at 09:42:20PM -0300, Eduardo Habkost wrote: > > (CCing libvir-list) > > > > On Thu, Sep 26, 2019 at 11:58:30PM +0200, Paolo Bonzini wrote: > > > Is this really needed? QEMU's value of pconfig=on vs. off should be > > > provided by QMP CPU model queries, if a property is not available then > > > Libvirt should not try to set it to off. > > > > > > > Libvirt can easily work around it for new VMs, and it should. > > > > The issue are VMs that were created with QEMU 3.1.0. QEMU 3.1.0 > > was telling libvirt "Icelake-Server can't be used unless > > pconfig=off is used", and libvirt was adding pconfig=off to the > > domain XML as expected. > > > > It would be wrong for libvirt to remove a device option when > > migrating an existing VM to another QEMU version. We can change > > the rules (and document that), but do we want to? > > IIUC currently any existing VMs with Icelake-Server will *not* have > pconfig present, since libvirt is going to set pconfig=off > > QEMU has now dropped pconfig CPUID entirely. If libvirt were to stop > setting pconfig=off, then there is NO guest ABI change, so we'd be > safe in that sense. This is correct. Only pconfig=off worked, and no accelerator ever supported pconfig=on. -- Eduardo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
