KVM: X86: Provide a capability to disable HLT intercepts
If host CPUs are dedicated to a VM, we can avoid VM exits on HLT. This patch adds the per-VM capability to disable them. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Jan H. Schönherr <jschoenh@amazon.de> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -4367,6 +4367,7 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid exits
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Valid bits in args[0] are
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#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
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#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
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Enabling this capability on a VM provides userspace with a way to no
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longer intercept some instructions for improved latency in some
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@ -4375,6 +4376,7 @@ physical CPUs. More bits can be added in the future; userspace can
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just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable
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all such vmexits.
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Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
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8. Other capabilities.
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----------------------
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@ -812,6 +812,7 @@ struct kvm_arch {
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gpa_t wall_clock;
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bool mwait_in_guest;
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bool hlt_in_guest;
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bool ept_identity_pagetable_done;
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gpa_t ept_identity_map_addr;
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@ -135,6 +135,11 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
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return -EINVAL;
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}
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best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
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if (kvm_hlt_in_guest(vcpu->kvm) && best &&
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(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
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best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
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/* Update physical-address width */
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vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
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kvm_mmu_reset_context(vcpu);
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@ -1380,7 +1380,6 @@ static void init_vmcb(struct vcpu_svm *svm)
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set_intercept(svm, INTERCEPT_RDPMC);
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set_intercept(svm, INTERCEPT_CPUID);
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set_intercept(svm, INTERCEPT_INVD);
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set_intercept(svm, INTERCEPT_HLT);
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set_intercept(svm, INTERCEPT_INVLPG);
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set_intercept(svm, INTERCEPT_INVLPGA);
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set_intercept(svm, INTERCEPT_IOIO_PROT);
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@ -1403,6 +1402,9 @@ static void init_vmcb(struct vcpu_svm *svm)
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set_intercept(svm, INTERCEPT_MWAIT);
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}
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if (!kvm_hlt_in_guest(svm->vcpu.kvm))
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set_intercept(svm, INTERCEPT_HLT);
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control->iopm_base_pa = __sme_set(iopm_base);
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control->msrpm_base_pa = __sme_set(__pa(svm->msrpm));
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control->int_ctl = V_INTR_MASKING_MASK;
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@ -2556,6 +2556,19 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit
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return 0;
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}
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static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
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{
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/*
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* Ensure that we clear the HLT state in the VMCS. We don't need to
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* explicitly skip the instruction because if the HLT state is set,
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* then the instruction is already executing and RIP has already been
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* advanced.
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*/
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if (kvm_hlt_in_guest(vcpu->kvm) &&
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vmcs_read32(GUEST_ACTIVITY_STATE) == GUEST_ACTIVITY_HLT)
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vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
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}
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static void vmx_queue_exception(struct kvm_vcpu *vcpu)
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{
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struct vcpu_vmx *vmx = to_vmx(vcpu);
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@ -2586,6 +2599,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
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intr_info |= INTR_TYPE_HARD_EXCEPTION;
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vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
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vmx_clear_hlt(vcpu);
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}
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static bool vmx_rdtscp_supported(void)
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@ -5545,6 +5560,8 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
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if (kvm_mwait_in_guest(vmx->vcpu.kvm))
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exec_control &= ~(CPU_BASED_MWAIT_EXITING |
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CPU_BASED_MONITOR_EXITING);
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if (kvm_hlt_in_guest(vmx->vcpu.kvm))
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exec_control &= ~CPU_BASED_HLT_EXITING;
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return exec_control;
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}
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@ -5906,6 +5923,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
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update_exception_bitmap(vcpu);
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vpid_sync_context(vmx->vpid);
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if (init_event)
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vmx_clear_hlt(vcpu);
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}
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/*
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@ -5976,6 +5995,8 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
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} else
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intr |= INTR_TYPE_EXT_INTR;
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vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
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vmx_clear_hlt(vcpu);
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}
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static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
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@ -6006,6 +6027,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
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vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
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INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
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vmx_clear_hlt(vcpu);
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}
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static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
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@ -12347,6 +12370,7 @@ static int vmx_pre_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
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vmx->nested.smm.vmxon = vmx->nested.vmxon;
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vmx->nested.vmxon = false;
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vmx_clear_hlt(vcpu);
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return 0;
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}
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@ -2878,6 +2878,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
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r = KVM_CLOCK_TSC_STABLE;
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break;
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case KVM_CAP_X86_DISABLE_EXITS:
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r |= KVM_X86_DISABLE_EXITS_HTL;
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if(kvm_can_mwait_in_guest())
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r |= KVM_X86_DISABLE_EXITS_MWAIT;
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break;
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@ -4232,6 +4233,8 @@ split_irqchip_unlock:
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if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) &&
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kvm_can_mwait_in_guest())
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kvm->arch.mwait_in_guest = true;
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if (cap->args[0] & KVM_X86_DISABLE_EXITS_HTL)
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kvm->arch.hlt_in_guest = true;
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r = 0;
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break;
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default:
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@ -265,11 +265,18 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
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})
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#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
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#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT)
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#define KVM_X86_DISABLE_EXITS_HTL (1 << 1)
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#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \
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KVM_X86_DISABLE_EXITS_HTL)
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static inline bool kvm_mwait_in_guest(struct kvm *kvm)
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{
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return kvm->arch.mwait_in_guest;
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}
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static inline bool kvm_hlt_in_guest(struct kvm *kvm)
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{
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return kvm->arch.hlt_in_guest;
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}
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#endif
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