On Tue, Apr 17, 2018 at 01:24:15AM -0700, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> This patch adds support for KVM_CAP_X86_DISABLE_EXITS. Provides userspace with
> per-VM capability(KVM_CAP_X86_DISABLE_EXITS) to not intercept MWAIT/HLT/PAUSE
> in order that to improve latency in some workloads.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
>
> linux-headers/linux/kvm.h | 6 +++++-
> target/i386/cpu.h | 2 ++
> target/i386/kvm.c | 16 ++++++++++++++++
> 3 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index a167be8..857df15 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -925,7 +925,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_S390_GS 140
> #define KVM_CAP_S390_AIS 141
> #define KVM_CAP_SPAPR_TCE_VFIO 142
> -#define KVM_CAP_X86_GUEST_MWAIT 143
> +#define KVM_CAP_X86_DISABLE_EXITS 143
> #define KVM_CAP_ARM_USER_IRQ 144
> #define KVM_CAP_S390_CMMA_MIGRATION 145
> #define KVM_CAP_PPC_FWNMI 146
> @@ -1508,6 +1508,10 @@ struct kvm_assigned_msix_entry {
> #define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
> #define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
>
> +#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
> +#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
> +#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
> +
> /* Available with KVM_CAP_ARM_USER_IRQ */
>
> /* Bits for run->s.regs.device_irq_level */
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 1b219fa..965de1b 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -685,6 +685,8 @@ 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_PV_UNHALT (1U << 7)
> +
Why don't we use KVM_FEATURE_PV_UNHALT from kvm_para.h?
> #define KVM_HINTS_DEDICATED (1U << 0)
>
BTW I wonder whether we should switch to a value from
kvm_para.h? I'll send a version to do it, pls take a look.
> #define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 6c49954..3e99830 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1029,6 +1029,22 @@ int kvm_arch_init_vcpu(CPUState *cs)
> }
> }
>
> + if (env->features[FEAT_KVM_HINTS] & KVM_HINTS_DEDICATED) {
> + int disable_exits = kvm_check_extension(cs->kvm_state, KVM_CAP_X86_DISABLE_EXITS);
> +
> + if (disable_exits) {
> + disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
> + KVM_X86_DISABLE_EXITS_HLT |
> + KVM_X86_DISABLE_EXITS_PAUSE);
> + if (env->user_features[FEAT_KVM] & KVM_PV_UNHALT) {
> + disable_exits &= ~KVM_X86_DISABLE_EXITS_HLT;
> + }
> + }
> + if (kvm_vm_enable_cap(cs->kvm_state, KVM_CAP_X86_DISABLE_EXITS, 0, disable_exits)) {
> + error_report("kvm: DISABLE EXITS not supported");
> + }
> + }
> +
> qemu_add_vm_change_state_handler(cpu_update_state, env);
>
> c = cpuid_find_entry(&cpuid_data.cpuid, 1, 0);
> --
> 2.7.4
