Re: [PATCH 08/17] s390x/cpumodel: Fix UI to CPU features pcc-cmac-{aes,eaes}-256

[Christian Borntraeger]

On 28.04.20 19:13, David Hildenbrand wrote:
> On 28.04.20 18:34, Markus Armbruster wrote:
>> Both s390_features[S390_FEAT_PCC_CMAC_AES_256].name and
>> s390_features[S390_FEAT_PCC_CMAC_EAES_256].name is
>> "pcc-cmac-eaes-256".  The former is obviously a pasto.
>>
>> Impact:
>>
>> * s390_feat_bitmap_to_ascii() misidentifies S390_FEAT_PCC_CMAC_AES_256
>>   as "pcc-cmac-eaes-256".  Affects QMP commands query-cpu-definitions,
>>   query-cpu-model-expansion, query-cpu-model-baseline,
>>   query-cpu-model-comparison, and the error message when
>>   s390_realize_cpu_model() fails in check_compatibility().
>>
>> * s390_realize_cpu_model() misidentifies it in check_consistency()
>>   warnings.
>>
>> * s390_cpu_list() likewise.  Affects -cpu help.
>>
>> * s390_cpu_model_register_props() creates CPU property
>>   "pcc-cmac-eaes-256" twice.  The second one fails, but the error is
>>   ignored (a later commit will change that).  Results in a single
>>   property "pcc-cmac-eaes-256" with the description for
>>   S390_FEAT_PCC_CMAC_AES_256, and no property for
>>   S390_FEAT_PCC_CMAC_EAES_256.  CPU properties are visible in CLI -cpu
>>   and -device, QMP & HMP device_add, QMP device-list-properties, and
>>   QOM introspection.
>>
>> Fix by deleting the wayward 'e'.
> 
> Very nice catch - thanks!
> 
> While this sounds very bad, it's luckily not that bad in practice
> (currently).
> 
> The feature (or rather, both features) is part of the feature group
> "msa4". As long as we have all sub-features part of that group (which is
> usually the case), we will always indicate "msa4" to the user, instead
> of all the separate sub-features. So, expansion, baseline, comparison
> will usually only work with "msa4".
> 
> (in addition, current KVM is not capable of actually masking off these
> sub-features, so it will still, always see the feature, even if not
> explicitly specified via "-cpu X,pcc-cmac-aes-256=on)
> 
> I think we should do stable backports.

makes sense, but I would like to do some testing upfront (old QEMU <-> new QEMU