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".
--
Eduardo