On Mon, Sep 30, 2019 at 17:16:27 +0200, Paolo Bonzini wrote: > On 30/09/19 16:31, Hu, Robert wrote: > >> This might be a problem if there are plans to eventually make KVM support > >> pconfig, though. Paolo, Robert, are there plans to support pconfig in KVM in the > >> future? > > [Robert Hoo] > > Thanks Eduardo for efforts in resolving this issue, introduced from my Icelake CPU > > model patch. > > I've no idea about PCONFIG's detail and plan. Let me sync with Huang, Kai and answer > > you soon. > > It's really, really unlikely. It's possible that some future processor > overloads PCONFIG in such a way that it will become virtualizable, but > not IceLake. I guess, the likelihood of this happening would be similar to reintroducing other features, such as osxsave or ospke, right? > Would it make sense for libvirt to treat absent CPU flags as "default > off" during migration, so that it can leave out the flag in the command > line if it's off? If it's on, libvirt would pass pconfig=on as usual. > This is a variant of [2], but more generally applicable: > > > [2] However starting a domain with Icelake-Server so that it can be > > migrated or saved/restored on QEMU in 3.1.1 and 4.0.0 would be > > impossible. This can be solved by a different hack, which would drop > > pconfig=off from QEMU command line. The domain XML does not contain a complete list of all CPU features. Features which are implicitly included in a CPU model are not listed in the XML. Count in the differences in libvirt's vs QEMU's definitions of a particular CPU model and you can see feat=off cannot be mechanically dropped from the command line as the CPU model itself could turn it on by default and thus feat=off is not redundant. Jirka -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
