Re: [Qemu-devel] [PATCH 3/6] target-i386: Register QOM properties for feature flags

[Paolo Bonzini <pbonzini@redhat.com>]

On 07/04/2015 22:46, Eduardo Habkost wrote:
> This uses the feature name arrays to register "feat-*" QOM properties
> for feature flags. This simply adds the properties so they can be
> configured using -global, but doesn't change x86_cpu_parse_featurestr()
> to use them yet.

Out of curiosity, why the prefix?  (Also, perhaps a prefix such as
"cpuid-*" would be better since the property often only affects the
cpuid leaves, rather than the availability of the feature itself).

Paolo

> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  target-i386/cpu.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 98 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 099ed03..f29e55e 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -2883,12 +2883,103 @@ out:
>      }
>  }
>  
> +typedef struct FeatureProperty {
> +    FeatureWord word;
> +    uint32_t mask;
> +} FeatureProperty;
> +
> +
> +static void x86_cpu_get_feature_prop(Object *obj,
> +                                     struct Visitor *v,
> +                                     void *opaque,
> +                                     const char *name,
> +                                     Error **errp)
> +{
> +    X86CPU *cpu = X86_CPU(obj);
> +    CPUX86State *env = &cpu->env;
> +    FeatureProperty *fp = opaque;
> +    bool value = (env->features[fp->word] & fp->mask) == fp->mask;
> +    visit_type_bool(v, &value, name, errp);
> +}
> +
> +static void x86_cpu_set_feature_prop(Object *obj,
> +                                     struct Visitor *v,
> +                                     void *opaque,
> +                                     const char *name,
> +                                     Error **errp)
> +{
> +    X86CPU *cpu = X86_CPU(obj);
> +    CPUX86State *env = &cpu->env;
> +    FeatureProperty *fp = opaque;
> +    bool value;
> +    visit_type_bool(v, &value, name, errp);
> +    if (value) {
> +        env->features[fp->word] |= fp->mask;
> +    } else {
> +        env->features[fp->word] &= ~fp->mask;
> +    }
> +}
> +
> +/* Register a boolean feature-bits property.
> + * If mask has multiple bits, all must be set for the property to return true.
> + * The same property name can be registered multiple times to make it affect
> + * multiple bits in the same FeatureWord.
> + */
> +static void x86_cpu_register_feature_prop(X86CPU *cpu,
> +                                          const char *prop_name,
> +                                          FeatureWord w,
> +                                          uint32_t mask)
> +{
> +    FeatureProperty *fp;
> +    ObjectProperty *op;
> +    op = object_property_find(OBJECT(cpu), prop_name, NULL);
> +    if (op) {
> +        fp = op->opaque;
> +        assert(fp->word == w);
> +        fp->mask |= mask;
> +    } else {
> +        fp = g_new0(FeatureProperty, 1);
> +        fp->word = w;
> +        fp->mask = mask;
> +        object_property_add(OBJECT(cpu), prop_name, "bool",
> +                            x86_cpu_get_feature_prop,
> +                            x86_cpu_set_feature_prop,
> +                            NULL, fp, &error_abort);
> +    }
> +}
> +
> +static void x86_cpu_register_feature_bit_props(X86CPU *cpu,
> +                                               FeatureWord w,
> +                                               int bit)
> +{
> +    int i;
> +    char **names;
> +    FeatureWordInfo *fi = &feature_word_info[w];
> +
> +    if (!fi->feat_names) {
> +        return;
> +    }
> +    if (!fi->feat_names[bit]) {
> +        return;
> +    }
> +
> +    names = g_strsplit(fi->feat_names[bit], "|", 0);
> +    for (i = 0; names[i]; i++) {
> +        char *feat_name = names[i];
> +        char *prop_name = g_strdup_printf("feat-%s", feat_name);
> +        x86_cpu_register_feature_prop(cpu, prop_name, w, (1UL << bit));
> +        g_free(prop_name);
> +    }
> +    g_strfreev(names);
> +}
> +
>  static void x86_cpu_initfn(Object *obj)
>  {
>      CPUState *cs = CPU(obj);
>      X86CPU *cpu = X86_CPU(obj);
>      X86CPUClass *xcc = X86_CPU_GET_CLASS(obj);
>      CPUX86State *env = &cpu->env;
> +    FeatureWord w;
>      static int inited;
>  
>      cs->env_ptr = env;
> @@ -2935,6 +3026,13 @@ static void x86_cpu_initfn(Object *obj)
>      cpu->apic_id = -1;
>  #endif
>  
> +    for (w = 0; w < FEATURE_WORDS; w++) {
> +        int bit;
> +        for (bit = 0; bit < 32; bit++) {
> +            x86_cpu_register_feature_bit_props(cpu, w, bit);
> +        }
> +    }
> +
>      x86_cpu_load_def(cpu, xcc->cpu_def, &error_abort);
>  
>      /* init various static tables used in TCG mode */
>