[libvirt] [PATCH 0/4] qemu: Use host-model CPU on s390 by default

[Collin Walling]

On 11/14/19 10:44 AM, Jiri Denemark wrote:
> On s390 machines host-passthrough and host-model CPUs result in the same
> guest ABI (with QEMU new enough to be able to tell us what "host" CPU is
> expanded to, which was implemented around 2.9.0). So instead of using
> host-passthrough CPU when there's no CPU specified in a domain XML we
> can safely use host-model and benefit from CPU compatibility checks
> during migration, snapshot restore and similar operations.
> 
> 
> This series applies on top of "qemu: Store default CPU in domain XML"
> which is already acked, but it's waiting for a QEMU patch to be applied
> to 4.2.0.
> 
> You can fetch both series at once using
> 
>     git fetch https://gitlab.com/jirkade/libvirt cpu-default-type
> 
> Jiri Denemark (4):
>   cpu_conf: Fix default value for CPU match attribute
>   cpu_conf: Don't format empty model for host-model CPUs
>   cpu_s390: Don't check match attribute for host-model CPUs
>   qemu: Use host-model CPU on s390 by default
> 
>  src/conf/cpu_conf.c                           | 25 ++++----------
>  src/conf/cpu_conf.h                           |  2 +-
>  src/cpu/cpu_s390.c                            | 18 +++++-----
>  src/qemu/qemu_domain.c                        | 33 ++++++++++++-------
>  .../ppc64-host+guest-compat-none.xml          |  4 +--
>  ...t-cpu-kvm-ccw-virtio-4.2.s390x-latest.args |  4 ++-
>  .../cpu-check-default-partial.xml             |  4 +--
>  .../cpu-host-model-features.xml               |  1 -
>  ...lt-cpu-kvm-ccw-virtio-4.2.s390x-latest.xml |  2 +-
>  9 files changed, 45 insertions(+), 48 deletions(-)
> 

Guest defined as expected. Once I start a guest, a dumpxml showed
the model name and associated features as expected. Was able to 
successfully migrate the guest as well.

Much preferred over the old default host-passthrough way.

Built libvirt using the repo and branch you provided
Built QEMU using master 4.1.92 (v4.2.0-rc2-27-g65e05c82bd)
 - guest used machine s390-ccw-virtio-4.2
Migrated between a weird mixed environment I'm chaotically working with :)

Perhaps the testing was a bit over-extensive, but it's good to make sure.

Tested-by: Collin Walling <walling at linux.ibm.com>

-- 
Respectfully,
- Collin Walling