Re: [Qemu-devel] [RFC 07/20] target-i386: convert cpuid features into properties

[Eduardo Habkost]

On Fri, Aug 10, 2012 at 01:22:23PM +0200, Igor Mammedov wrote:
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
>  target-i386/cpu.c | 103 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 103 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index a47cc12..4b22598 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -605,6 +605,103 @@ static int check_features_against_host(x86_def_t 
> *guest_def)
>      return rv;
>  }
>  
> +static bool is_feature_set(const char *name, const uint32_t featbitmap,
> +                                  const char **featureset)
> +{
> +    uint32_t mask;
> +
> +    for (mask = 1; mask; mask <<= 1) {
> +        if (featureset[ffs(mask) - 1] &&
> +            !altcmp(name, NULL, featureset[ffs(mask) - 1])) {
> +            break;
> +    }

Wrong indentation.

> +    }
> +    if (featbitmap & mask) {
> +        return true;
> +    }
> +    return false;

Isn't it simpler to write this as:

    int bit;

    for (bit = 0; bit < 32; bit++) {
        if (featureset[bit] && !altcmp(name, NULL, featureset[bit])) {
            if (featbitmap & (1 << bit)) {
                return true;
        }
    }
    return false;

?

> +}
> +
> +static void x86_cpuid_get_feature(Object *obj, Visitor *v, void *opaque,
> +                                         const char *name, Error **errp)
> +{
> +    X86CPU *cpu = X86_CPU(obj);
> +    CPUX86State *env = &cpu->env;
> +    bool value = true;
> +
> +    if (!is_feature_set(name, env->cpuid_features, feature_name) &&
> +       !is_feature_set(name, env->cpuid_ext_features, ext_feature_name) &&
> +       !is_feature_set(name, env->cpuid_ext2_features, ext2_feature_name) &&
> +       !is_feature_set(name, env->cpuid_ext3_features, ext3_feature_name) &&
> +       !is_feature_set(name, env->cpuid_kvm_features, kvm_feature_name) &&
> +       !is_feature_set(name, env->cpuid_svm_features, svm_feature_name)) {
> +        value = false;
> +    }
> +
> +    visit_type_bool(v, &value, name, errp);
> +}
> +
> +static void x86_cpuid_set_feature(Object *obj, Visitor *v, void *opaque,
> +                                         const char *name, Error **errp)
> +{
> +    X86CPU *cpu = X86_CPU(obj);
> +    CPUX86State *env = &cpu->env;
> +    uint32_t mask = 0;
> +    uint32_t *dst_features;
> +    bool value;
> +
> +    visit_type_bool(v, &value, name, errp);
> +    if (error_is_set(errp)) {
> +        return;
> +    }
> +
> +    if (lookup_feature(&mask, name, NULL, feature_name)) {
> +        dst_features = &env->cpuid_features;
> +    } else if (lookup_feature(&mask, name, NULL, ext_feature_name)) {
> +        dst_features = &env->cpuid_ext_features;
> +    } else if (lookup_feature(&mask, name, NULL, ext2_feature_name)) {
> +        dst_features = &env->cpuid_ext2_features;
> +    } else if (lookup_feature(&mask, name, NULL, ext3_feature_name)) {
> +        dst_features = &env->cpuid_ext3_features;
> +    } else if (lookup_feature(&mask, name, NULL, kvm_feature_name)) {
> +        dst_features = &env->cpuid_kvm_features;
> +    } else if (lookup_feature(&mask, name, NULL, svm_feature_name)) {
> +        dst_features = &env->cpuid_svm_features;
> +    } else {
> +        error_set(errp, QERR_PROPERTY_NOT_FOUND, "", name);
> +        return;
> +    }
> +
> +    if (value) {
> +        *dst_features |= mask;
> +    } else {
> +        *dst_features &= ~mask;
> +    }
> +}
> +
> +static void x86_register_cpuid_properties(Object *obj, const char 
> **featureset)
> +{
> +    uint32_t mask;
> +
> +    for (mask = 1; mask; mask <<= 1) {
> +        if (featureset[ffs(mask) - 1]) {
> +            char *feature_name, *save_ptr;
> +            char buf[32];
> +            if (strlen(featureset[ffs(mask) - 1]) > sizeof(buf) - 1) {
> +                abort();
> +            }
> +            pstrcpy(buf, sizeof(buf), featureset[ffs(mask) - 1]);
> +            feature_name = strtok_r(buf, "|", &save_ptr);
> +            while (feature_name) {
> +                object_property_add(obj, feature_name, "bool",
> +                                x86_cpuid_get_feature,
> +                                x86_cpuid_set_feature, NULL, NULL, NULL);
> +                feature_name = strtok_r(NULL, "|", &save_ptr);
> +            }
> +        }
> +    }

Same case as above: why the mask/ffs tricks when you could just use
"for (bit = 0; bit < 32; bit++)" and use "bit" instead of
"ffs(mask) - 1"?

> +}
> +
>  static void x86_cpuid_version_get_family(Object *obj, Visitor *v, void 
> *opaque,
>                                           const char *name, Error **errp)
>  {
> @@ -1801,6 +1898,12 @@ static void x86_cpu_initfn(Object *obj)
>      object_property_add(obj, "tsc-frequency", "int",
>                          x86_cpuid_get_tsc_freq,
>                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
> +    x86_register_cpuid_properties(obj, feature_name);
> +    x86_register_cpuid_properties(obj, ext_feature_name);
> +    x86_register_cpuid_properties(obj, ext2_feature_name);
> +    x86_register_cpuid_properties(obj, ext3_feature_name);
> +    x86_register_cpuid_properties(obj, kvm_feature_name);
> +    x86_register_cpuid_properties(obj, svm_feature_name);
>  
>      env->cpuid_apic_id = env->cpu_index;
>  
> -- 
> 1.7.11.2
> 

-- 
Eduardo