Re: [PATCH v5 5/5] qemu: add default_cpu_deprecated_features configuration option

On Sun, Jun 29, 2025 at 11:19:30PM -0400, Collin Walling wrote: > From: Boris Fiuczynski <fiuczy(a)linux.ibm.com&gt; > > Allow to define the default for deprecated_features when the attribute > is not set in the cpu defintion of a domain XML. If these features are > still desired, they may be reenabled via the deprecated_features='on' > attribute. > > Some existing tests utilize this updated behavior, so update the CPU > features on the corresponding args files. > > Signed-off-by: Boris Fiuczynski <fiuczy(a)linux.ibm.com&gt; > Signed-off-by: Collin Walling <walling(a)linux.ibm.com&gt; > --- > src/qemu/libvirtd_qemu.aug | 3 ++ > src/qemu/qemu.conf.in | 14 ++++++++ > src/qemu/qemu_conf.c | 33 +++++++++++++++++++ > src/qemu/qemu_conf.h | 12 +++++++ > src/qemu/qemu_process.c | 26 ++++++++++++++- > src/qemu/test_libvirtd_qemu.aug.in | 1 + > ...deprecated-features-none.s390x-latest.args | 2 +- > ...default-video-type-s390x.s390x-latest.args | 2 +- > ...vfio-zpci-ccw-memballoon.s390x-latest.args | 2 +- > .../launch-security-s390-pv.s390x-latest.args | 2 +- > ...t-cpu-kvm-ccw-virtio-4.2.s390x-latest.args | 2 +- > .../s390-defaultconsole.s390x-latest.args | 2 +- > .../s390-panic.s390x-latest.args | 2 +- > 13 files changed, 95 insertions(+), 8 deletions(-) > > diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug > index e1e479d72c..2b674d258d 100644 > --- a/src/qemu/libvirtd_qemu.aug > +++ b/src/qemu/libvirtd_qemu.aug > @@ -160,6 +160,8 @@ module Libvirtd_qemu = > > let filesystem_entry = str_array_entry "shared_filesystems" > > + let default_cpu_deprecated_features = str_entry "default_cpu_deprecated_features" > + > (* Entries that used to exist in the config which are now > * deleted. We keep on parsing them so we don't break > * ability to parse old configs after upgrade > @@ -192,6 +194,7 @@ module Libvirtd_qemu = > | capability_filters_entry > | storage_entry > | filesystem_entry > + | default_cpu_deprecated_features > | obsolete_entry > > let comment = [ label "#comment" . del /#[ \t]*/ "# " . store /([^ \t\n][^\n]*)?/ . del /\n/ "\n" ] > diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in > index 221bfa8095..368d929f78 100644 > --- a/src/qemu/qemu.conf.in > +++ b/src/qemu/qemu.conf.in > @@ -1100,3 +1100,17 @@ > # "/path/to/nvram", > # "/path/to/swtpm" > #] > + > +# If QEMU provides a list of deprecated CPU features it is possible to use > +# this list for removal of deprecated CPU features during CPU model expansion. > +# The deprecated_features XML attribute on the XML CPU element in the domain > +# XML can be used to turn deprecated CPU features 'off' or 'on'. Using the > +# option default_cpu_deprecated_features allows to define the default behavior > +# when the attribute deprecated_features is not provided in the domain XML. > +# > +# Possible options are: > +# "off" - (default) deprecated features are removed during CPU model expansion > +# "on" - deprecated features remain required in the expanded CPU model > +# "none" - no deprecated_features attribute is added to expanded CPU model > +# > +#default_cpu_deprecated_features = "off" Having a host level config parameter change the guest ABI seems like a bad idea to me. IMHO mgmt apps should be updated to use the XML to request deprecated features are turned off by default. With regards, Daniel