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

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Just a heads up.
After installing libvirt rpms of this branch all my existing kvm s390 domains ended up with

  <cpu mode='custom' match='exact' check='none'>
    <model fallback='forbid'>qemu</model>
  </cpu>

Newly defined domains without specified cpu do so as well.


On 11/14/19 4:44 PM, 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(-)



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Mit freundlichen Grüßen/Kind regards
   Boris Fiuczynski

IBM Deutschland Research & Development GmbH
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