Re: [libvirt PATCH 0/3] qemu: Fix default CPU for old s390 machine types

[Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>]

On Fri, Feb 7, 2020 at 9:35 AM Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx> wrote:

On Thu, Feb 6, 2020 at 11:25 AM Jiri Denemark <jdenemar@xxxxxxxxxx> wrote:

See the last patch for detailed description and
https://bugzilla.redhat.com/show_bug.cgi?id=1795651 for a discussion
about this topic.

Jiri Denemark (3):
  qemu: Pass machine type to virQEMUCapsIsCPUModeSupported
  qemuxml2*test: Add default CPU tests for s390-ccw-virtio-2.7 machines
  qemu_capabilities: Disable CPU models on old s390 machine types

Reviewed-by: Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>

I have also set up a build with the changes adding some Ubuntu machine types on top.

I eventually also want to give you a Tested-by, but those tests not be completed this week - I beg your pardon for the delay.

Tests:
- start old common type s390-ccw-virtio-2.5
- start old ubunut type s390-ccw-virtio-xenial
- migrate from old installation that was pre 2.8

Comparing:
a) libvirt 6.0 (6.0.0-0ubuntu2)
b) libvirt 6.0 + this series (6.0.0-0ubuntu3~test1)

a) failed in all cases with the expected
   qemu-system-s390x: CPU models are not available: KVM doesn't support CPU models
b) all three cases worked fine now

Special case:
If I tried to start the formerly defined "breakme" domains they got added
  <cpu mode='host-model' check='partial'/>
Therefore they now fail with:
  error: Failed to start domain breakme
  error: unsupported configuration: CPU mode 'host-model' for s390x kvm domain on s390x host is not supported by hypervisor

If I undefine, and define again fromt the template as reported in the BZ
  <domain type='kvm'>
    <name>breakme</name>
    <memory unit='KiB'>524288</memory>
    <os>
      <type arch='s390x' machine='s390-ccw-virtio-2.5'>hvm</type>
    </os>
  </domain>
I now get after define:
  <cpu mode='host-passthrough' check='none'/>
So it detected things correctly detecting the old type.

A cross check using a new type like s390-ccw-virtio-4.0 or s390-ccw-virtio-eoan worked fine and gave me the epxected
  <cpu mode='host-model' check='partial'/>

Tested-by:  Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>

 src/qemu/qemu_capabilities.c                  | 29 ++++++++++++++---
 src/qemu/qemu_capabilities.h                  |  3 +-
 src/qemu/qemu_domain.c                        |  3 +-
 src/qemu/qemu_process.c                       |  2 +-
 ...t-cpu-kvm-ccw-virtio-2.7.s390x-latest.args | 32 +++++++++++++++++++
 .../s390-default-cpu-kvm-ccw-virtio-2.7.xml   | 16 ++++++++++
 ...t-cpu-tcg-ccw-virtio-2.7.s390x-latest.args | 32 +++++++++++++++++++
 .../s390-default-cpu-tcg-ccw-virtio-2.7.xml   | 16 ++++++++++
 tests/qemuxml2argvtest.c                      |  2 ++
 ...lt-cpu-kvm-ccw-virtio-2.7.s390x-latest.xml | 24 ++++++++++++++
 ...lt-cpu-tcg-ccw-virtio-2.7.s390x-latest.xml | 26 +++++++++++++++
 tests/qemuxml2xmltest.c                       |  2 ++
 12 files changed, 180 insertions(+), 7 deletions(-)
 create mode 100644 tests/qemuxml2argvdata/s390-default-cpu-kvm-ccw-virtio-2.7.s390x-latest.args
 create mode 100644 tests/qemuxml2argvdata/s390-default-cpu-kvm-ccw-virtio-2.7.xml
 create mode 100644 tests/qemuxml2argvdata/s390-default-cpu-tcg-ccw-virtio-2.7.s390x-latest.args
 create mode 100644 tests/qemuxml2argvdata/s390-default-cpu-tcg-ccw-virtio-2.7.xml
 create mode 100644 tests/qemuxml2xmloutdata/s390-default-cpu-kvm-ccw-virtio-2.7.s390x-latest.xml
 create mode 100644 tests/qemuxml2xmloutdata/s390-default-cpu-tcg-ccw-virtio-2.7.s390x-latest.xml

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2.25.0

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Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd

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Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd