Re: [Qemu-devel] [RFC 2/2 v2] target-i386: Add "x-allow-emulation" X86CPU property

[Alexander Graf]

On 05.06.14 21:57, Eduardo Habkost wrote:
> The new option will allow slow emulated features (the ones returned by
> GET_EMULATED_CPUID) to be enabled. We don't want to allow them to be
> enabled by accident, so they will be enabled only if emulation is
> explicitly allowed by the user.
>
> Use "x-" prefix on the property name, to document that it is not
> supposed to be supported forever, and intended for developers who want
> to test GET_EMULATED_CPUID.
>
> Signed-off-by: Eduardo Habkost <address@hidden>

ack if you do s/emulation/experimental/g throughout the patch :).


Alex

> ---
> Changes v1 -> v2:
>   * Rename property to x-allow-emulation
> ---
>   target-i386/cpu-qom.h |  3 +++
>   target-i386/cpu.c     | 18 ++++++++++++++----
>   2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
> index 385b81f..831f7bf 100644
> --- a/target-i386/cpu-qom.h
> +++ b/target-i386/cpu-qom.h
> @@ -74,6 +74,8 @@ typedef struct X86CPUClass {
>    * @migratable: If set, only migratable flags will be accepted when "enforce"
>    * mode is used, and only migratable flags will be included in the "host"
>    * CPU model.
> + * @allow_emulation: If set, accelerator-specific code will allow emulated
> + * features to be enabled.
>    *
>    * An x86 CPU.
>    */
> @@ -91,6 +93,7 @@ typedef struct X86CPU {
>       bool check_cpuid;
>       bool enforce_cpuid;
>       bool migratable;
> +    bool allow_emulation;
>   
>       /* if true the CPUID code directly forward host cache leaves to the guest */
>       bool cache_info_passthrough;
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 1395473..cf6ab59 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1280,7 +1280,8 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void 
> *data)
>   }
>   
>   static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
> -                                                   bool migratable_only);
> +                                                   bool migratable_only,
> +                                                   bool allow_emulation);
>   
>   static void host_x86_cpu_initfn(Object *obj)
>   {
> @@ -1297,7 +1298,8 @@ static void host_x86_cpu_initfn(Object *obj)
>   
>       for (w = 0; w < FEATURE_WORDS; w++) {
>           env->features[w] =
> -            x86_cpu_get_supported_feature_word(w, cpu->migratable);
> +            x86_cpu_get_supported_feature_word(w, cpu->migratable,
> +                                                  cpu->allow_emulation);
>       }
>       object_property_set_bool(OBJECT(cpu), true, "pmu", &error_abort);
>   }
> @@ -1887,7 +1889,8 @@ CpuDefinitionInfoList *arch_query_cpu_definitions(Error 
> **errp)
>   }
>   
>   static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
> -                                                   bool migratable_only)
> +                                                   bool migratable_only,
> +                                                   bool allow_emulation)
>   {
>       FeatureWordInfo *wi = &feature_word_info[w];
>       uint32_t r;
> @@ -1896,6 +1899,11 @@ static uint32_t 
> x86_cpu_get_supported_feature_word(FeatureWord w,
>           r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax,
>                                                       wi->cpuid_ecx,
>                                                       wi->cpuid_reg);
> +        if (allow_emulation) {
> +            r |= kvm_arch_get_emulated_cpuid(kvm_state,  wi->cpuid_eax,
> +                                                         wi->cpuid_ecx,
> +                                                         wi->cpuid_reg);
> +        }
>       } else if (tcg_enabled()) {
>           r = wi->tcg_features;
>       } else {
> @@ -1920,7 +1928,8 @@ static int x86_cpu_filter_features(X86CPU *cpu)
>   
>       for (w = 0; w < FEATURE_WORDS; w++) {
>           uint32_t host_feat =
> -            x86_cpu_get_supported_feature_word(w, cpu->migratable);
> +            x86_cpu_get_supported_feature_word(w, cpu->migratable,
> +                                                  cpu->allow_emulation);
>           uint32_t requested_features = env->features[w];
>           env->features[w] &= host_feat;
>           cpu->filtered_features[w] = requested_features & ~env->features[w];
> @@ -2854,6 +2863,7 @@ static Property x86_cpu_properties[] = {
>       DEFINE_PROP_BOOL("hv-time", X86CPU, hyperv_time, false),
>       DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, false),
>       DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
> +    DEFINE_PROP_BOOL("x-allow-emulation", X86CPU, allow_emulation, true),
>       DEFINE_PROP_END_OF_LIST()
>   };
>