Re: [Qemu-devel] [PATCH v4 27/33] target-i386: Register X86CPU "feat-kvmclock" feature

[Michael S. Tsirkin]

On Thu, Aug 14, 2014 at 04:25:56PM -0300, Eduardo Habkost wrote:
> The "kvmclock" feature is special because it affects two bits in the KVM
> CPUID leaf, so it has to be handled differently from the other feature
> properties that will be added.
> 
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
>  target-i386/cpu.c | 61 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index b005b0d..0eb401b 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -2774,6 +2774,61 @@ uint32_t x86_cpu_apic_id_from_index(unsigned int 
> cpu_index)
>      }
>  }
>  
> +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.
> + */
> +static void x86_cpu_register_feature_prop(X86CPU *cpu,
> +                                          const char *prop_name,
> +                                          FeatureWord w,
> +                                          uint32_t mask)
> +{
> +    FeatureProperty *fp;
> +    fp = g_new0(FeatureProperty, 1);
> +    fp->word = w;
> +    fp->mask = mask;
> +    object_property_add(OBJECT(cpu), prop_name, "bool",
> +                        x86_cpu_set_feature_prop,
> +                        x86_cpu_get_feature_prop,
> +                        NULL, fp, &error_abort);
> +}
> +

This looks similar to what what DEFINE_PROP_BIT does.
Can't this be reused in some way?


>  static void x86_cpu_initfn(Object *obj)
>  {
>      CPUState *cs = CPU(obj);
> @@ -2819,6 +2874,12 @@ static void x86_cpu_initfn(Object *obj)
>                          x86_cpu_get_feature_words,
>                          NULL, NULL, (void *)cpu->filtered_features, NULL);
>  
> +    /* "feat-kvmclock" will affect both kvmclock feature bits */
> +    x86_cpu_register_feature_prop(cpu, "feat-kvmclock", FEAT_KVM,
> +                                  (1UL << KVM_FEATURE_CLOCKSOURCE) |
> +                                  (1UL << KVM_FEATURE_CLOCKSOURCE2));
> +
> +
>      cpu->hyperv_spinlock_attempts = HYPERV_SPINLOCK_NEVER_RETRY;
>      env->cpuid_apic_id = x86_cpu_apic_id_from_index(cs->cpu_index);
>  
> -- 
> 1.9.3