Re: [libvirt] [RFC 00/28] s390x CPU models: exposing features

On Tue, Jun 21, 2016 at 11:09:49PM +0200, Jiri Denemark wrote: [...] > > 1) "query-cpu-model-expansion model=host" vs "query-host-cpu": > > > > I still don't think we want to set in stone that "the result the > > guest sees when using -cpu host" is always the same as "what the > > host supports running". > > > > For example: let's assume a given architecture have two features > > (A and B) that are both supported by the host but can never be > > enabled together. For actual "-cpu host" usage, QEMU would have > > to choose between enabling A and B. For querying host > > capabilities, we still want to let management software know that > > either A or B are supported. > > What libvirt is really interested in is the guest CPU which would be > used with -cpu host. This is actually what I thought query-host-cpu was > all about. Perhaps because there's no difference for x86. In that case, I think it makes sense to just extend query-cpu-definitions or use "query-cpu-model-expansion model=host" instead of a query-host-cpu command. Probably query-cpu-model-expansion is better than just extending query-cpu-definitions, because it would allow the expansion of extra CPU options, like "host,migratable=off".