From: Wanpeng Li <[email protected]> If host CPUs are dedicated to a VM, we can avoid VM exits on HLT. This patch adds the per-VM non-HLT-exiting capability.
Cc: Paolo Bonzini <[email protected]> Cc: Radim Krčmář <[email protected]> Cc: Jan H. Schönherr <[email protected]> Signed-off-by: Wanpeng Li <[email protected]> --- Documentation/virtual/kvm/api.txt | 3 ++- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 5 +++++ arch/x86/kvm/svm.c | 4 +++- arch/x86/kvm/vmx.c | 24 ++++++++++++++++++++++++ arch/x86/kvm/x86.c | 3 +++ arch/x86/kvm/x86.h | 9 ++++++++- 7 files changed, 46 insertions(+), 3 deletions(-) diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 76e5a15..b46494d 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -4367,10 +4367,11 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid exits Valid exits in args[0] are #define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0) +#define KVM_X86_DISABLE_EXITS_HLT (1 << 1) Enabling this capability on a VM provides userspace with a way to no longer intercepts some instructions for improved latency in some -workloads. +workloads. Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits. 8. Other capabilities. ---------------------- diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index e107171..1a79065 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -812,6 +812,7 @@ struct kvm_arch { gpa_t wall_clock; bool mwait_in_guest; + bool hlt_in_guest; bool ept_identity_pagetable_done; gpa_t ept_identity_map_addr; diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index e2d3050..82055b9 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -135,6 +135,11 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) return -EINVAL; } + best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0); + if (kvm_hlt_in_guest(vcpu->kvm) && best && + (best->eax & (1 << KVM_FEATURE_PV_UNHALT))) + best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT); + /* Update physical-address width */ vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); kvm_mmu_reset_context(vcpu); diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 321b3fd..0b2e7af 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1372,7 +1372,6 @@ static void init_vmcb(struct vcpu_svm *svm) set_intercept(svm, INTERCEPT_RDPMC); set_intercept(svm, INTERCEPT_CPUID); set_intercept(svm, INTERCEPT_INVD); - set_intercept(svm, INTERCEPT_HLT); set_intercept(svm, INTERCEPT_INVLPG); set_intercept(svm, INTERCEPT_INVLPGA); set_intercept(svm, INTERCEPT_IOIO_PROT); @@ -1395,6 +1394,9 @@ static void init_vmcb(struct vcpu_svm *svm) set_intercept(svm, INTERCEPT_MWAIT); } + if (!kvm_hlt_in_guest(svm->vcpu.kvm)) + set_intercept(svm, INTERCEPT_HLT); + control->iopm_base_pa = __sme_set(iopm_base); control->msrpm_base_pa = __sme_set(__pa(svm->msrpm)); control->int_ctl = V_INTR_MASKING_MASK; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 2302ae2..fa0c5e1 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2543,6 +2543,19 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit return 0; } +static void vmx_clear_hlt(struct kvm_vcpu *vcpu) +{ + /* + * Ensure that we clear the HLT state in the VMCS. We don't need to + * explicitly skip the instruction because if the HLT state is set, + * then the instruction is already executing and RIP has already been + * advanced. + */ + if (kvm_hlt_in_guest(vcpu->kvm) && + vmcs_read32(GUEST_ACTIVITY_STATE) == GUEST_ACTIVITY_HLT) + vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE); +} + static void vmx_queue_exception(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); @@ -2573,6 +2586,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu) intr_info |= INTR_TYPE_HARD_EXCEPTION; vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info); + + vmx_clear_hlt(vcpu); } static bool vmx_rdtscp_supported(void) @@ -5532,6 +5547,8 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx) if (kvm_mwait_in_guest(vmx->vcpu.kvm)) exec_control &= ~(CPU_BASED_MWAIT_EXITING | CPU_BASED_MONITOR_EXITING); + if (kvm_hlt_in_guest(vmx->vcpu.kvm)) + exec_control &= ~CPU_BASED_HLT_EXITING; return exec_control; } @@ -5893,6 +5910,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) update_exception_bitmap(vcpu); vpid_sync_context(vmx->vpid); + if (init_event) + vmx_clear_hlt(vcpu); } /* @@ -5963,6 +5982,8 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu) } else intr |= INTR_TYPE_EXT_INTR; vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr); + + vmx_clear_hlt(vcpu); } static void vmx_inject_nmi(struct kvm_vcpu *vcpu) @@ -5993,6 +6014,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu) vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR); + + vmx_clear_hlt(vcpu); } static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu) @@ -12314,6 +12337,7 @@ static int vmx_pre_enter_smm(struct kvm_vcpu *vcpu, char *smstate) vmx->nested.smm.vmxon = vmx->nested.vmxon; vmx->nested.vmxon = false; + vmx_clear_hlt(vcpu); return 0; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5fae476..73255e6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2874,6 +2874,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_CLOCK_TSC_STABLE; break; case KVM_CAP_X86_DISABLE_EXITS: + r |= KVM_X86_DISABLE_EXITS_HTL; if(kvm_can_mwait_in_guest()) r |= KVM_X86_DISABLE_EXITS_MWAIT; break; @@ -4228,6 +4229,8 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && kvm_can_mwait_in_guest()) kvm->arch.mwait_in_guest = true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_HTL) + kvm->arch.hlt_in_guest = true; r = 0; break; default: diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index cd1215e..d4ddb00 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -263,11 +263,18 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec) }) #define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0) -#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT) +#define KVM_X86_DISABLE_EXITS_HTL (1 << 1) +#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \ + KVM_X86_DISABLE_EXITS_HTL) static inline bool kvm_mwait_in_guest(struct kvm *kvm) { return kvm->arch.mwait_in_guest; } +static inline bool kvm_hlt_in_guest(struct kvm *kvm) +{ + return kvm->arch.hlt_in_guest; +} + #endif -- 2.7.4
