KVM: nVMX: track NMI blocking state separately for each VMCS

vmx_recover_nmi_blocking is using a cached value of the guest
interruptibility info, which is stored in vmx->nmi_known_unmasked.
vmx_recover_nmi_blocking is run for both normal and nested guests,
so the cached value must be per-VMCS.

This fixes eventinj.flat in a nested non-EPT environment.  With EPT it
works, because the EPT violation handler doesn't have the
vmx->nmi_known_unmasked optimization (it is unnecessary because, unlike
vmx_recover_nmi_blocking, it can just look at the exit qualification).

Thanks to Wanpeng Li for debugging the testcase and providing an initial
patch.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx.c

@@ -198,7 +198,8 @@ struct loaded_vmcs {
 	struct vmcs *vmcs;
 	struct vmcs *shadow_vmcs;
 	int cpu;
-	int launched;
+	bool launched;
+	bool nmi_known_unmasked;
 	struct list_head loaded_vmcss_on_cpu_link;
 };
 
@@ -5510,10 +5511,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	if (!is_guest_mode(vcpu)) {
 	++vcpu->stat.nmi_injections;
-		vmx->nmi_known_unmasked = false;
-	}
+	vmx->loaded_vmcs->nmi_known_unmasked = false;
 
 	if (vmx->rmode.vm86_active) {
 		if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR, 0) != EMULATE_DONE)
@@ -5527,16 +5526,21 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 
 static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
 {
-	if (to_vmx(vcpu)->nmi_known_unmasked)
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	bool masked;
+
+	if (vmx->loaded_vmcs->nmi_known_unmasked)
 		return false;
-	return vmcs_read32(GUEST_INTERRUPTIBILITY_INFO)	& GUEST_INTR_STATE_NMI;
+	masked = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_NMI;
+	vmx->loaded_vmcs->nmi_known_unmasked = !masked;
+	return masked;
 }
 
 static void vmx_set_nmi_mask(struct kvm_vcpu *vcpu, bool masked)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	vmx->nmi_known_unmasked = !masked;
+	vmx->loaded_vmcs->nmi_known_unmasked = !masked;
 	if (masked)
 		vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
 			      GUEST_INTR_STATE_NMI);
@@ -8736,7 +8740,7 @@ static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
 
 	idtv_info_valid = vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK;
 
-	if (vmx->nmi_known_unmasked)
+	if (vmx->loaded_vmcs->nmi_known_unmasked)
 		return;
 	/*
 	 * Can't use vmx->exit_intr_info since we're not sure what
@@ -8760,7 +8764,7 @@ static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
 		vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
 			      GUEST_INTR_STATE_NMI);
 	else
-		vmx->nmi_known_unmasked =
+		vmx->loaded_vmcs->nmi_known_unmasked =
 			!(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO)
 			  & GUEST_INTR_STATE_NMI);
 }