On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
> to determine if they run on dedicated vCPUs, allowing optimizations such
> as usage of qspinlocks.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> v1 -> v2:
> * add a new feature word
>
> target/i386/cpu.c | 14 ++++++++++++++
> target/i386/cpu.h | 3 +++
> target/i386/kvm.c | 4 ++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index d70954b..e2974ad 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
> .tcg_features = TCG_KVM_FEATURES,
> },
> + [FEAT_KVM_HINTS] = {
> + .feat_names = {
> + "hint-dedicated", NULL, NULL, NULL,
I suggest naming it "kvm-hint-dedicated", to indicate it's
KVM-specific.
If there are no objections, I can rename it while applying.
With the rename:
Reviewed-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> + 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,
> + },
> + .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
> + .tcg_features = TCG_KVM_FEATURES,
> + },
> [FEAT_HYPERV_EAX] = {
> .feat_names = {
> NULL /* hv_msr_vp_runtime_access */, NULL /* hv_msr_time_refcount_access */,
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index f91e37d..9f73692 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -475,6 +475,7 @@ typedef enum FeatureWord {
> FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
> FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
> FEAT_KVM, /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
> + FEAT_KVM_HINTS, /* CPUID[4000_0001].EDX */
> FEAT_HYPERV_EAX, /* CPUID[4000_0003].EAX */
> FEAT_HYPERV_EBX, /* CPUID[4000_0003].EBX */
> FEAT_HYPERV_EDX, /* CPUID[4000_0003].EDX */
> @@ -670,6 +671,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
> #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
> #define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Speculation Control */
>
> +#define KVM_HINTS_DEDICATED (1U << 0)
> +
> #define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
>
> #define CPUID_XSAVE_XSAVEOPT (1U << 0)
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index ad4b159..44ee524 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -383,6 +383,9 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
> if (!kvm_irqchip_in_kernel()) {
> ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
> }
> + } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
> + ret |= KVM_HINTS_DEDICATED;
> + found = 1;
> }
>
> /* fallback for older kernels */
> @@ -801,6 +804,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
> c = &cpuid_data.entries[cpuid_i++];
> c->function = KVM_CPUID_FEATURES | kvm_base;
> c->eax = env->features[FEAT_KVM];
> + c->edx = env->features[FEAT_KVM_HINTS];
> }
>
> cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
> --
> 2.7.4
>
--
Eduardo
