KVM: VMX: Cache vmcs.EXIT_INTR_INFO using arch avail_reg flags

Introduce a new "extended register" type, EXIT_INFO_2 (to pair with the
nomenclature in .get_exit_info()), and use it to cache VMX's
vmcs.EXIT_INTR_INFO.  Drop a comment in vmx_recover_nmi_blocking() that
is obsoleted by the generic caching mechanism.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200415203454.8296-6-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -171,6 +171,7 @@ enum kvm_reg {
 	VCPU_EXREG_RFLAGS,
 	VCPU_EXREG_SEGMENTS,
 	VCPU_EXREG_EXIT_INFO_1,
+	VCPU_EXREG_EXIT_INFO_2,
 };
 
 enum {

arch/x86/kvm/vmx/nested.c

@@ -5419,7 +5419,7 @@ static int handle_vmfunc(struct kvm_vcpu *vcpu)
 
 fail:
 	nested_vmx_vmexit(vcpu, vmx->exit_reason,
-			  vmcs_read32(VM_EXIT_INTR_INFO),
+			  vmx_get_intr_info(vcpu),
 			  vmx_get_exit_qual(vcpu));
 	return 1;
 }
@@ -5652,7 +5652,7 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu, u32 exit_reason)
 
 	switch (exit_reason) {
 	case EXIT_REASON_EXCEPTION_NMI:
-		intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+		intr_info = vmx_get_intr_info(vcpu);
 		if (is_nmi(intr_info))
 			return true;
 		else if (is_page_fault(intr_info))
@@ -5708,12 +5708,12 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu, u32 exit_reason)
  */
 static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, u32 exit_reason)
 {
+	u32 intr_info = vmx_get_intr_info(vcpu);
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
-	u32 intr_info;
 
 	switch (exit_reason) {
 	case EXIT_REASON_EXCEPTION_NMI:
-		intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+		intr_info = vmx_get_intr_info(vcpu);
 		if (is_nmi(intr_info))
 			return true;
 		else if (is_page_fault(intr_info))
@@ -5848,7 +5848,7 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
 		goto reflect_vmexit;
 	}
 
-	exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	exit_intr_info = vmx_get_intr_info(vcpu);
 	exit_qual = vmx_get_exit_qual(vcpu);
 
 	trace_kvm_nested_vmexit(kvm_rip_read(vcpu), exit_reason, exit_qual,

arch/x86/kvm/vmx/vmx.c

@@ -5635,7 +5635,7 @@ static const int kvm_vmx_max_exit_handlers =
 static void vmx_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2)
 {
 	*info1 = vmx_get_exit_qual(vcpu);
-	*info2 = vmcs_read32(VM_EXIT_INTR_INFO);
+	*info2 = vmx_get_intr_info(vcpu);
 }
 
 static void vmx_destroy_pml_buffer(struct vcpu_vmx *vmx)
@@ -6298,16 +6298,16 @@ static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu)
 
 static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
 {
-	vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
 
 	/* if exit due to PF check for async PF */
-	if (is_page_fault(vmx->exit_intr_info)) {
+	if (is_page_fault(intr_info)) {
 		vmx->vcpu.arch.apf.host_apf_reason = kvm_read_and_reset_pf_reason();
 	/* Handle machine checks before interrupts are enabled */
-	} else if (is_machine_check(vmx->exit_intr_info)) {
+	} else if (is_machine_check(intr_info)) {
 		kvm_machine_check();
 	/* We need to handle NMIs before interrupts are enabled */
-	} else if (is_nmi(vmx->exit_intr_info)) {
+	} else if (is_nmi(intr_info)) {
 		kvm_before_interrupt(&vmx->vcpu);
 		asm("int $2");
 		kvm_after_interrupt(&vmx->vcpu);
@@ -6322,9 +6322,8 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
 	unsigned long tmp;
 #endif
 	gate_desc *desc;
-	u32 intr_info;
+	u32 intr_info = vmx_get_intr_info(vcpu);
 
-	intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
 	if (WARN_ONCE(!is_external_intr(intr_info),
 	    "KVM: unexpected VM-Exit interrupt info: 0x%x", intr_info))
 		return;
@@ -6405,11 +6404,8 @@ static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
 	if (enable_vnmi) {
 		if (vmx->loaded_vmcs->nmi_known_unmasked)
 			return;
-		/*
-		 * Can't use vmx->exit_intr_info since we're not sure what
-		 * the exit reason is.
-		 */
-		exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+
+		exit_intr_info = vmx_get_intr_info(&vmx->vcpu);
 		unblock_nmi = (exit_intr_info & INTR_INFO_UNBLOCK_NMI) != 0;
 		vector = exit_intr_info & INTR_INFO_VECTOR_MASK;
 		/*

arch/x86/kvm/vmx/vmx.h

@@ -451,7 +451,8 @@ static inline void vmx_register_cache_reset(struct kvm_vcpu *vcpu)
 				  | (1 << VCPU_EXREG_PDPTR)
 				  | (1 << VCPU_EXREG_SEGMENTS)
 				  | (1 << VCPU_EXREG_CR3)
-				  | (1 << VCPU_EXREG_EXIT_INFO_1));
+				  | (1 << VCPU_EXREG_EXIT_INFO_1)
+				  | (1 << VCPU_EXREG_EXIT_INFO_2));
 	vcpu->arch.regs_dirty = 0;
 }
 
@@ -506,6 +507,17 @@ static inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
 	return vmx->exit_qualification;
 }
 
+static inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+	if (!kvm_register_is_available(vcpu, VCPU_EXREG_EXIT_INFO_2)) {
+		kvm_register_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_2);
+		vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	}
+	return vmx->exit_intr_info;
+}
+
 struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags);
 void free_vmcs(struct vmcs *vmcs);
 int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs);