On Fri, Mar 16, 2018 at 07:36:42AM -0700, Wanpeng Li wrote:
> From: Wanpeng Li <wanpen...@tencent.com>
>
> 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 <pbonz...@redhat.com>
> Cc: Radim Krčmář <rkrc...@redhat.com>
> Cc: Eduardo Habkost <ehabk...@redhat.com>
> Signed-off-by: Wanpeng Li <wanpen...@tencent.com>
> ---
> linux-headers/linux/kvm.h | 6 +++++-
> target/i386/kvm.c | 12 ++++++++++++
> 2 files changed, 17 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/kvm.c b/target/i386/kvm.c
> index d23fff1..95ed9eb 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -999,6 +999,18 @@ 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 (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);
Why not a bit per capability?
I can see how someone might want to disable mwait exists
but not the rest of them.
> --
> 2.7.4
