Re: [PATCH v3 3/3] qemu: process: disable deprecated features for s390 models by default

On 5/26/25 14:40, Peter Krempa via Devel wrote: > On Thu, May 22, 2025 at 02:03:16 -0400, Collin Walling wrote: > > To ease the user with defining a guest with a migratable CPU model, > > disclaimer: I'm not an expert on: > - libvirt's cpu driver > - s390x cpu etc. > > > let's disable the deprecated features from the get-go. If these > > features are still desired, they may be reenabled via the > > deprecated_features='on' attribute. > > I'd expect that anything that happens with cpu model (as it has guest > visible implications [2]) would happen also in XML ... > > > Some existing tests utilize this updated behavior, so update the CPU > > features on the corresponding args files. > > > > Signed-off-by: Collin Walling <walling(a)linux.ibm.com&gt; > > --- > > src/qemu/qemu_process.c | 11 +++++++++++ > > .../default-video-type-s390x.s390x-latest.args | 2 +- > > ...hostdev-vfio-zpci-ccw-memballoon.s390x-latest.args | 2 +- > > .../launch-security-s390-pv.s390x-latest.args | 2 +- > > ...0-default-cpu-kvm-ccw-virtio-4.2.s390x-latest.args | 2 +- > > .../s390-defaultconsole.s390x-latest.args | 2 +- > > ... which doesn't seem to be the case as just the .args files changed. Do the mocked tests perform a cpu model expansion which is done when starting a domain? I tested Collins changes and when dumping the active domain xml the expanded CPU model and also deprecated_features='off' is included if deprecated_features was not already included in the persisted domain xml. > > So won't this actually break the guest ABI? I think Daniel's old email can shed some light on that question. https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/message/M... My understanding is that guest ABI does not include guaranties how a CPU model is expanded and therefore this change does not break the guest ABI.