Re: [Qemu-devel] [PATCH v6 3/3] target-i386: Return runnability information on query-cpu-definitions

[Igor Mammedov <imammedo@redhat.com>]

On Fri,  7 Oct 2016 17:29:02 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> Fill the "unavailable-features" field on the x86 implementation
> of query-cpu-definitions.
> 
> Cc: Jiri Denemark <jdenemar@redhat.com>
> Cc: libvir-list@redhat.com
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
> Changes v5 -> v6:
> * Call x86_cpu_filter_features(), now that x86_cpu_load_features()
>   won't run it automatically
> 
> Changes v4 -> v5:
> * (none)
> 
> Changes v3 -> v4:
> * Handle missing XSAVE components cleanly, but looking up
>   the original feature that required it
> * Use x86_cpu_load_features() function
> 
> Changes v2 -> v3:
> * Create a x86_cpu_feature_name() function, to
>   isolate the code that returns the property name
> 
> Changes v1 -> v2:
> * Updated to the new schema: no @runnable field, and
>   always report @unavailable-features as present
> ---
>  target-i386/cpu.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 76 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 23cc19b..63330ce 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1945,6 +1945,27 @@ static inline void feat2prop(char *s)
>      }
>  }
>  
> +/* Return the feature property name for a feature flag bit */
> +static const char *x86_cpu_feature_name(FeatureWord w, int bitnr)
> +{
> +    /* XSAVE components are automatically enabled by other features,
> +     * so return the original feature name instead
> +     */
> +    if (w == FEAT_XSAVE_COMP_LO || w == FEAT_XSAVE_COMP_HI) {
> +        int comp = (w == FEAT_XSAVE_COMP_HI) ? bitnr + 32 : bitnr;
> +
> +        if (comp < ARRAY_SIZE(x86_ext_save_areas) &&
> +            x86_ext_save_areas[comp].bits) {
> +            w = x86_ext_save_areas[comp].feature;
> +            bitnr = ctz32(x86_ext_save_areas[comp].bits);
> +        }
> +    }
> +
> +    assert(bitnr < 32);
> +    assert(w < FEATURE_WORDS);
> +    return feature_word_info[w].feat_names[bitnr];
> +}
> +
>  /* Compatibily hack to maintain legacy +-feat semantic,
>   * where +-feat overwrites any feature set by
>   * feat=on|feat even if the later is parsed after +-feat
> @@ -2030,6 +2051,59 @@ static void x86_cpu_parse_featurestr(const char *typename, char *features,
>      }
>  }
>  
> +static void x86_cpu_load_features(X86CPU *cpu, Error **errp);
> +static int x86_cpu_filter_features(X86CPU *cpu);
> +
> +/* Check for missing features that may prevent the CPU class from
> + * running using the current machine and accelerator.
> + */
> +static void x86_cpu_class_check_missing_features(X86CPUClass *xcc,
> +                                                 strList **missing_feats)
> +{
> +    X86CPU *xc;
> +    FeatureWord w;
> +    Error *err = NULL;
> +    strList **next = missing_feats;
> +
> +    if (xcc->kvm_required && !kvm_enabled()) {
> +        strList *new = g_new0(strList, 1);
> +        new->value = g_strdup("kvm");;
> +        *missing_feats = new;
> +        return;
> +    }
> +
> +    xc = X86_CPU(object_new(object_class_get_name(OBJECT_CLASS(xcc))));
> +
> +    x86_cpu_load_features(xc, &err);
> +    if (err) {
> +        /* Errors at x86_cpu_load_features should never happen,
> +         * but in case it does, just report the model as not
> +         * runnable at all using the "type" property.
> +         */
> +        strList *new = g_new0(strList, 1);
> +        new->value = g_strdup("type");
> +        *next = new;
> +        next = &new->next;
> +    }
> +
> +    x86_cpu_filter_features(xc);
> +
> +    for (w = 0; w < FEATURE_WORDS; w++) {
> +        uint32_t filtered = xc->filtered_features[w];
> +        int i;
> +        for (i = 0; i < 32; i++) {
> +            if (filtered & (1UL << i)) {
> +                strList *new = g_new0(strList, 1);
> +                new->value = g_strdup(x86_cpu_feature_name(w, i));
> +                *next = new;
> +                next = &new->next;
> +            }
> +        }
> +    }
> +
> +    object_unref(OBJECT(xc));
> +}
> +
>  /* Print all cpuid feature names in featureset
>   */
>  static void listflags(FILE *f, fprintf_function print, const char **featureset)
> @@ -2122,6 +2196,8 @@ static void x86_cpu_definition_entry(gpointer data, gpointer user_data)
>  
>      info = g_malloc0(sizeof(*info));
>      info->name = x86_cpu_class_get_model_name(cc);
> +    x86_cpu_class_check_missing_features(cc, &info->unavailable_features);
> +    info->has_unavailable_features = true;
>  
>      entry = g_malloc0(sizeof(*entry));
>      entry->value = info;