Re: [PATCH v1] target/s390x: move @deprecated-props to CpuModelExpansion Info

[Markus Armbruster <armbru@redhat.com>]

Collin Walling <walling@linux.ibm.com> writes:

> The @deprecated-props array did not make any sense to be a member of the
> CpuModelInfo struct, since this field would only be populated by a
> query-cpu-model-expansion response and ignored otherwise.

Doesn't query-cpu-model-baseline also return it in its response?  It
seems to assume the "static" expansion type.

>                                                           Move this
> field to the CpuModelExpansionInfo struct where is makes more sense.
>
> References:
>  - https://lists.gnu.org/archive/html/qemu-devel/2024-07/msg05996.html
>  - commit eed0e8ffa38f0695c0519508f6e4f5a3297cbd67
>
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> ---
>
> @David, the previous commit header did not align with the changes made
> here, so I tagged this as a "v1" but added the previous conversation as
> a reference.  I hope this is appropriate?
>
> ---
>  qapi/machine-target.json         | 18 ++++++++++--------
>  target/s390x/cpu_models_sysemu.c | 31 ++++++++++++++++++++-----------
>  2 files changed, 30 insertions(+), 19 deletions(-)
>
> diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> index a552e2b0ce..09dec2b9bb 100644
> --- a/qapi/machine-target.json
> +++ b/qapi/machine-target.json
> @@ -20,17 +20,11 @@
>  #
>  # @props: a dictionary of QOM properties to be applied
>  #
> -# @deprecated-props: a list of properties that are flagged as deprecated
> -#     by the CPU vendor.  These properties are either a subset of the
> -#     properties enabled on the CPU model, or a set of properties
> -#     deprecated across all models for the architecture.
> -#
>  # Since: 2.8
>  ##
>  { 'struct': 'CpuModelInfo',
>    'data': { 'name': 'str',
> -            '*props': 'any',
> -            '*deprecated-props': ['str'] } }
> +            '*props': 'any' } }
>  
>  ##
>  # @CpuModelExpansionType:
> @@ -248,10 +242,18 @@
>  #
>  # @model: the expanded CpuModelInfo.
>  #
> +# @deprecated-props: a 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).
> +#
>  # Since: 2.8
>  ##
>  { 'struct': 'CpuModelExpansionInfo',
> -  'data': { 'model': 'CpuModelInfo' },
> +  'data': { 'model': 'CpuModelInfo',
> +            '*deprecated-props': ['str'] },
>    'if': { 'any': [ 'TARGET_S390X',
>                     'TARGET_I386',
>                     'TARGET_ARM',

This solves several interface problems:

1. Removes inappropriate @deprecated-props argument of
   query-cpu-model-comparison, query-cpu-model-expansion,
   query-cpu-model-baseline.

2. Removes @deprecated-props return of query-cpu-model-baseline.

3. Properly documents how @deprecated-props depends on the expansion
   type.

Remaining problem:

4. Only S390 implements this.

Suggest to capture 1-3 more clearly in the commit message, perhaps like
this:

    CpuModelInfo is used both as command argument and in command
    returns.

    Its @deprecated-props array does not make any sense in arguments,
    and is silently ignored.  We actually want it only as return value
    of query-cpu-model-expansion.

    Move it from CpuModelInfo to CpuModelExpansionType, and document
    its dependence on expansion type propetly.

The simplest way to address 4 is to tack 'if': 'TARGET_S390X' to
@deprecated-props.

I recommend to make @deprecated-props mandatory rather than optional
then.

> diff --git a/target/s390x/cpu_models_sysemu.c b/target/s390x/cpu_models_sysemu.c
> index 94dd798b4c..44e7587acb 100644
> --- a/target/s390x/cpu_models_sysemu.c
> +++ b/target/s390x/cpu_models_sysemu.c
> @@ -174,15 +174,11 @@ static void cpu_info_from_model(CpuModelInfo *info, const S390CPUModel *model,
>                                  bool delta_changes)
>  {
>      QDict *qdict = qdict_new();
> -    S390FeatBitmap bitmap, deprecated;
> +    S390FeatBitmap bitmap;
>  
>      /* always fallback to the static base model */
>      info->name = g_strdup_printf("%s-base", model->def->name);
>  
> -    /* features flagged as deprecated */
> -    bitmap_zero(deprecated, S390_FEAT_MAX);
> -    s390_get_deprecated_features(deprecated);
> -
>      if (delta_changes) {
>          /* features deleted from the base feature set */
>          bitmap_andnot(bitmap, model->def->base_feat, model->features,
> @@ -197,9 +193,6 @@ static void cpu_info_from_model(CpuModelInfo *info, const S390CPUModel *model,
>          if (!bitmap_empty(bitmap, S390_FEAT_MAX)) {
>              s390_feat_bitmap_to_ascii(bitmap, qdict, qdict_add_enabled_feat);
>          }
> -
> -        /* deprecated features that are a subset of the model's enabled features */
> -        bitmap_and(deprecated, deprecated, model->features, S390_FEAT_MAX);
>      } else {
>          /* expand all features */
>          s390_feat_bitmap_to_ascii(model->features, qdict,
> @@ -213,9 +206,6 @@ static void cpu_info_from_model(CpuModelInfo *info, const S390CPUModel *model,
>      } else {
>          info->props = QOBJECT(qdict);
>      }
> -
> -    s390_feat_bitmap_to_ascii(deprecated, &info->deprecated_props, list_add_feat);
> -    info->has_deprecated_props = !!info->deprecated_props;
>  }
>  
>  CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
> @@ -226,6 +216,7 @@ CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
>      CpuModelExpansionInfo *expansion_info = NULL;
>      S390CPUModel s390_model;
>      bool delta_changes = false;
> +    S390FeatBitmap deprecated_feats;
>  
>      /* convert it to our internal representation */
>      cpu_model_from_info(&s390_model, model, "model", &err);
> @@ -245,6 +236,24 @@ CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
>      expansion_info = g_new0(CpuModelExpansionInfo, 1);
>      expansion_info->model = g_malloc0(sizeof(*expansion_info->model));
>      cpu_info_from_model(expansion_info->model, &s390_model, delta_changes);
> +
> +    /* populated list of deprecated features */
> +    bitmap_zero(deprecated_feats, S390_FEAT_MAX);
> +    s390_get_deprecated_features(deprecated_feats);
> +
> +    if (delta_changes) {
> +        /*
> +         * Only populate deprecated features that are a
> +         * subset of the features enabled on the CPU model.
> +         */
> +        bitmap_and(deprecated_feats, deprecated_feats,
> +                   s390_model.features, S390_FEAT_MAX);
> +    }
> +
> +    s390_feat_bitmap_to_ascii(deprecated_feats,
> +                              &expansion_info->deprecated_props, list_add_feat);
> +    expansion_info->has_deprecated_props = !!expansion_info->deprecated_props;
> +
>      return expansion_info;
>  }

Implementation looks good to me.