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Re: [Qemu-devel] [PATCH v5] i386: Introduce ARAT CPU feature


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH v5] i386: Introduce ARAT CPU feature
Date: Mon, 08 Jun 2015 17:40:06 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0


On 07/06/2015 11:15, Jan Kiszka wrote:
> From: Jan Kiszka <address@hidden>
> 
> ARAT signals that the APIC timer does not stop in power saving states.
> As our APICs are emulated, it's fine to expose this feature to guests,
> at least when asking for KVM host features or with CPU types that
> include the flag. The exact model number that introduced the feature is
> not known, but reports can be found that it's at least available since
> Sandy Bridge.
> 
> Signed-off-by: Jan Kiszka <address@hidden>
> ---
> 
> Changes in v5:
>  - rebased over master
> 
>  include/hw/i386/pc.h |  7 ++++++-
>  target-i386/cpu.c    | 33 ++++++++++++++++++++++++++++++++-
>  target-i386/cpu.h    |  3 +++
>  target-i386/kvm.c    |  2 ++
>  4 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index bec6de1..3b0b30f 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -294,7 +294,12 @@ int e820_get_num_entries(void);
>  bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
>  
>  #define PC_COMPAT_2_3 \
> -        HW_COMPAT_2_3
> +        HW_COMPAT_2_3 \
> +        {\
> +            .driver   = TYPE_X86_CPU,\
> +            .property = "arat",\
> +            .value    = "off",\
> +        },
>  
>  #define PC_COMPAT_2_2 \
>          PC_COMPAT_2_3 \
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 99ad551..b5b9fc2 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -284,6 +284,17 @@ static const char *cpuid_xsave_feature_name[] = {
>      NULL, NULL, NULL, NULL,
>  };
>  
> +static const char *cpuid_6_feature_name[] = {
> +    NULL, NULL, "arat", NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +    NULL, NULL, NULL, NULL,
> +};
> +
>  #define I486_FEATURES (CPUID_FP87 | CPUID_VME | CPUID_PSE)
>  #define PENTIUM_FEATURES (I486_FEATURES | CPUID_DE | CPUID_TSC | \
>            CPUID_MSR | CPUID_MCE | CPUID_CX8 | CPUID_MMX | CPUID_APIC)
> @@ -339,6 +350,7 @@ static const char *cpuid_xsave_feature_name[] = {
>            CPUID_7_0_EBX_ERMS, CPUID_7_0_EBX_INVPCID, CPUID_7_0_EBX_RTM,
>            CPUID_7_0_EBX_RDSEED */
>  #define TCG_APM_FEATURES 0
> +#define TCG_6_EAX_FEATURES CPUID_6_EAX_ARAT
>  
>  
>  typedef struct FeatureWordInfo {
> @@ -408,6 +420,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] 
> = {
>          .cpuid_reg = R_EAX,
>          .tcg_features = 0,
>      },
> +    [FEAT_6_EAX] = {
> +        .feat_names = cpuid_6_feature_name,
> +        .cpuid_eax = 6, .cpuid_reg = R_EAX,
> +        .tcg_features = TCG_6_EAX_FEATURES,
> +    },
>  };
>  
>  typedef struct X86RegisterInfo32 {
> @@ -1001,6 +1018,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_EXT2_LM | CPUID_EXT2_SYSCALL | CPUID_EXT2_NX,
>          .features[FEAT_8000_0001_ECX] =
>              CPUID_EXT3_LAHF_LM,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Westmere E56xx/L56xx/X56xx (Nehalem-C)",
>      },
> @@ -1030,6 +1049,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_EXT3_LAHF_LM,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Xeon E312xx (Sandy Bridge)",
>      },
> @@ -1062,6 +1083,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_EXT3_LAHF_LM,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Xeon E3-12xx v2 (Ivy Bridge)",
>      },
> @@ -1096,6 +1119,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_7_0_EBX_BMI2 | CPUID_7_0_EBX_ERMS | CPUID_7_0_EBX_INVPCID,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Core Processor (Haswell, no TSX)",
>      },    {
> @@ -1130,6 +1155,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_7_0_EBX_RTM,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Core Processor (Haswell)",
>      },
> @@ -1166,6 +1193,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_7_0_EBX_SMAP,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Core Processor (Broadwell, no TSX)",
>      },
> @@ -1202,6 +1231,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_7_0_EBX_SMAP,
>          .features[FEAT_XSAVE] =
>              CPUID_XSAVE_XSAVEOPT,
> +        .features[FEAT_6_EAX] =
> +            CPUID_6_EAX_ARAT,
>          .xlevel = 0x8000000A,
>          .model_id = "Intel Core Processor (Broadwell)",
>      },
> @@ -2358,7 +2389,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>          break;
>      case 6:
>          /* Thermal and Power Leaf */
> -        *eax = 0;
> +        *eax = env->features[FEAT_6_EAX];
>          *ebx = 0;
>          *ecx = 0;
>          *edx = 0;
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index 26182bd..074a9c9 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -412,6 +412,7 @@ typedef enum FeatureWord {
>      FEAT_KVM,           /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
>      FEAT_SVM,           /* CPUID[8000_000A].EDX */
>      FEAT_XSAVE,         /* CPUID[EAX=0xd,ECX=1].EAX */
> +    FEAT_6_EAX,         /* CPUID[6].EAX */
>      FEATURE_WORDS,
>  } FeatureWord;
>  
> @@ -577,6 +578,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_XSAVE_XGETBV1    (1U << 2)
>  #define CPUID_XSAVE_XSAVES     (1U << 3)
>  
> +#define CPUID_6_EAX_ARAT       (1U << 2)
> +
>  /* CPUID[0x80000007].EDX flags: */
>  #define CPUID_APM_INVTSC       (1U << 8)
>  
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index ca2da84..d7bd205 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -233,6 +233,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, 
> uint32_t function,
>          if (!kvm_irqchip_in_kernel()) {
>              ret &= ~CPUID_EXT_X2APIC;
>          }
> +    } else if (function == 6 && reg == R_EAX) {
> +        ret |= CPUID_6_EAX_ARAT; /* safe to allow because of emulated APIC */
>      } else if (function == 0x80000001 && reg == R_EDX) {
>          /* On Intel, kvm returns cpuid according to the Intel spec,
>           * so add missing bits according to the AMD spec:
> 

Acked-by: Paolo Bonzini <address@hidden>

Paolo



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