[PATCH 7/9] VMX: Provide support for user space injected NMIs

[Jan Kiszka <jan.kiszka@siemens.com>]

This patch adds the required bits to the VMX side for user space
injected NMIs. As with the preexisting in-kernel irqchip support, the
CPU must provide the "virtual NMI" feature for proper tracking of the
NMI blocking state.

Based on the original patch by Sheng Yang.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/x86/kvm/vmx.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

Index: b/arch/x86/kvm/vmx.c
===================================================================
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2356,6 +2356,7 @@ static void vmx_inject_nmi(struct kvm_vc
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
+	++vcpu->stat.nmi_injections;
 	if (vcpu->arch.rmode.active) {
 		vmx->rmode.irq.pending = true;
 		vmx->rmode.irq.vector = NMI_VECTOR;
@@ -2424,6 +2425,26 @@ static void do_interrupt_requests(struct
 {
 	vmx_update_window_states(vcpu);
 
+	if (cpu_has_virtual_nmis()) {
+		if (vcpu->arch.nmi_pending && !vcpu->arch.nmi_injected) {
+			if (vcpu->arch.nmi_window_open) {
+				vcpu->arch.nmi_pending = false;
+				vcpu->arch.nmi_injected = true;
+			} else {
+				enable_nmi_window(vcpu);
+				return;
+			}
+		}
+		if (vcpu->arch.nmi_injected) {
+			vmx_inject_nmi(vcpu);
+			if (vcpu->arch.nmi_pending)
+				enable_nmi_window(vcpu);
+			else if (vcpu->arch.irq_summary)
+				enable_irq_window(vcpu);
+			return;
+		}
+	}
+
 	if (vcpu->arch.interrupt_window_open) {
 		if (vcpu->arch.irq_summary && !vcpu->arch.interrupt.pending)
 			kvm_do_inject_irq(vcpu);
@@ -2936,6 +2957,14 @@ static int handle_nmi_window(struct kvm_
 	vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control);
 	++vcpu->stat.nmi_window_exits;
 
+	/*
+	 * If the user space waits to inject a NNI, exit as soon as possible
+	 */
+	if (kvm_run->request_nmi_window && !vcpu->arch.nmi_pending) {
+		kvm_run->exit_reason = KVM_EXIT_NMI_WINDOW_OPEN;
+		return 0;
+	}
+
 	return 1;
 }