Re: [RFC PATCH] qapi: Make CpuModelExpansionInfo::deprecated-props optional and generic

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 7/5/25 16:41, Markus Armbruster wrote:
> Cc: author and reviewer of the @deprecated-props feature
> 
> Philippe Mathieu-Daudé <philmd@linaro.org> writes:
> 
>> 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 541f93eeb78..3b109b4af87 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'] } },
>>     'if': { 'any': [ 'TARGET_S390X',
>>                      'TARGET_I386',
>>                      'TARGET_ARM',
> 
> 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 also happy to implement as "present but empty".