[libvirt] [PATCH 00/22] qemu: Store default CPU in domain XML

[Jiri Denemark]

On Mon, Oct 07, 2019 at 17:24:11 +0200, Andrea Bolognani wrote:
> On Thu, 2019-10-03 at 16:00 +0200, Jiri Denemark wrote:
> > When starting a domain without a CPU model specified in the domain XML,
> > QEMU will choose a default one. Which is fine unless the domain gets
> > migrated to another host because libvirt doesn't perform any CPU ABI
> > checks and the virtual CPU provided by QEMU on the destination host can
> > differ from the one on the source host.
> > 
> > With QEMU 4.2.0 we can probe for the default CPU model used by QEMU for
> > a particular machine type and store it in the domain XML. This way the
> > chosen CPU model is more visible to users and libvirt will make sure
> > the guest will see the exact same CPU after migration.
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1598151
> > https://bugzilla.redhat.com/show_bug.cgi?id=1598162
> 
> Unfortunately this will break all ppc64 guests that have been defined
> without specifying a CPU model, because it will result in something
> like
> 
>   <cpu mode='custom' match='exact' check='partial'>
>     <model fallback='allow'>power8</model>
>   </cpu>
> 
> being added to the domain XML, which in turn at runtime will cause
> 
>   error: internal error: Unknown CPU model power8

This should be fixed by an old forgotten series "Fix ppc64 CPU
configuration for QEMU 2.11+". I'll send a rebased version of that
series and once approved, I will base a v2 of this series on top.

Thanks for checking the behaviour on a different architecture.

Jirka