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. I'll defer to Jiri on how we'd actually go about making that work in libvirt from a code POV. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|