Re: [PATCH 08/10] qapi: Make CpuModelExpansionInfo::deprecated-props optional and generic

[Daniel P . Berrangé]

On Tue, May 13, 2025 at 02:38:40PM +0200, Markus Armbruster wrote:
> Copying my review from the initial posting:
> 
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > From: Philippe Mathieu-Daudé <philmd@linaro.org>
> >
> > We'd like to have some unified QAPI schema. Having a structure field
> > conditional to a target being built in is not very practical.
> >
> > While @deprecated-props is only used by s390x target, it is generic
> > enough and could be used by other targets (assuming we expand
> > CpuModelExpansionType enum values).
> >
> > Let's always include this field, regardless of the target, but
> > make it optional.
> >
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > ---
> >  qapi/machine-target.json | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> > index 541f93eeb7..3b109b4af8 100644
> > --- a/qapi/machine-target.json
> > +++ b/qapi/machine-target.json
> > @@ -244,19 +244,18 @@
> >  #
> >  # @model: the expanded CpuModelInfo.
> >  #
> > -# @deprecated-props: a list of properties that are flagged as
> > +# @deprecated-props: an optional list of properties that are flagged as
> >  #     deprecated by the CPU vendor.  The list depends on the
> >  #     CpuModelExpansionType: "static" properties are a subset of the
> >  #     enabled-properties for the expanded model; "full" properties are
> >  #     a set of properties that are deprecated across all models for
> > -#     the architecture.  (since: 9.1).
> > +#     the architecture.  (since: 10.1 -- since 9.1 on s390x --).
> >  #
> >  # Since: 2.8
> >  ##
> >  { 'struct': 'CpuModelExpansionInfo',
> >    'data': { 'model': 'CpuModelInfo',
> > -            'deprecated-props' : { 'type': ['str'],
> > -                                   'if': 'TARGET_S390X' } },
> > +            '*deprecated-props' : { 'type': ['str'] } },
> 
> Make this
> 
>                '*deprecated-props' : ['str'] },
> 
> please.
> 
> When I see "optional array", I wonder about the difference between
> "absent" and "present and empty".  The doc comment doesn't quite explain
> it.  I figure "present and empty" means empty, while "absent" means we
> don't know / not implemented.
> 
> Is the difference useful?

I'm doubtful that the difference is useful.

With regards,
Daniel
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