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

> On Wed, Jun 22, 2016 at 09:34:49 +0200, David Hildenbrand wrote: > > I think the coffee didn't do its work already :) . I wanted to write that we can > > _with_ this additional query. Meaning the involved overhead would be ok - in my > > opinion for s390x. > > > > What we could do to avoid one compare operation would be: > > > > a) Expand the host model > > b) Expand the target model (because on s390x we could have migration unsafe > > model) > > c) Work with the runnability information returned via query-cpu-definitions > > > > But as we have to do b) either way on s390x, we can directly do a compare > > operation. (which makes implementation a lot simpler, because libvirt then > > doesn't have to deal with any feature/model names). > > But why do you even need to do any comparison? Isn't it possible to let > QEMU do it when a domain starts? The thing is we should avoid doing > completely different things on each architecture. > Sure, QEMU will of course double check when starting the guest! So trying to start and failing is of course an option! So no check is needed if that is acceptable.