Re: [Qemu-devel] [PATCH v2 7/9] i386: Make unversioned CPU models be aliases

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jul 02, 2019 at 10:45:25AM +0100, Daniel P. Berrangé wrote:
> On Thu, Jun 27, 2019 at 09:28:42PM -0300, Eduardo Habkost wrote:
> > This will make unversioned CPU models behavior depend on the
> > machine type:
> > 
> > * "pc-*-4.0" and older will not report them as aliases.
> >   This is done to keep compatibility with older QEMU versions
> >   after management software starts translating aliases.
> > 
> > * "pc-*-4.1" will translate unversioned CPU models to -v1.
> >   This is done to keep compatibility with existing management
> >   software, that still relies on CPU model runnability promises.
> > 
> > * "none" will translate unversioned CPU models to their latest
> >   version.  This is planned become the default in future machine
> >   types (probably in pc-*-4.3).
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > Patch v1 was "[PATCH 4/6] i386: Infrastructure for versioned CPU
> > models", and was split into multiple patches.
> > 
> > Changes v1 -> v2:
> > * Make version numbers simple integers, completely independent
> >   from machine type versions
> > * New X86CPUVersion typedef
> > * New CPU_VERSION_* defines to make X86CPUModel::version
> >   semantics clearer
> > ---
> >  include/hw/i386/pc.h                       |   3 +
> >  target/i386/cpu.h                          |  12 ++
> >  hw/i386/pc.c                               |   3 +
> >  hw/i386/pc_piix.c                          |   4 +
> >  hw/i386/pc_q35.c                           |   4 +
> >  target/i386/cpu.c                          |  52 ++++++++-
> >  tests/acceptance/x86_cpu_model_versions.py | 126 +++++++++++++++++++++
> >  7 files changed, 203 insertions(+), 1 deletion(-)



> > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > index 57232aed6b..397e1fdd2f 100644
> > --- a/hw/i386/pc_q35.c
> > +++ b/hw/i386/pc_q35.c
> > @@ -367,8 +367,10 @@ static void pc_q35_machine_options(MachineClass *m)
> >  
> >  static void pc_q35_4_1_machine_options(MachineClass *m)
> >  {
> > +    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> >      pc_q35_machine_options(m);
> >      m->alias = "q35";
> > +    pcmc->default_cpu_version = 1;
> 
> How will this work in future if we need to introduce a v2 of some,
> but not all CPU models, and then further a v3 of some others.
> 
> Can we select Haswell-v1,  Skylake-Server-v2, CascadeLake-v3
> as defaults in some way ?

Answered in reply to a later patch so

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|