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