KVM: VMX: Provide support for user space injected NMIs

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>
Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 38d138566617..f16a62c79267 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2360,6 +2360,7 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 {
         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;
@@ -2428,6 +2429,30 @@ static void do_interrupt_requests(struct kvm_vcpu *vcpu,
 {
         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
+                            || kvm_run->request_nmi_window)
+                                enable_nmi_window(vcpu);
+                        else if (vcpu->arch.irq_summary
+                                 || kvm_run->request_interrupt_window)
+                                enable_irq_window(vcpu);
+                        return;
+                }
+                if (!vcpu->arch.nmi_window_open || kvm_run->request_nmi_window)
+                        enable_nmi_window(vcpu);
+        }
+
         if (vcpu->arch.interrupt_window_open) {
                 if (vcpu->arch.irq_summary && !vcpu->arch.interrupt.pending)
                         kvm_do_inject_irq(vcpu);
@@ -2959,6 +2984,14 @@ static int handle_nmi_window(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         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 NMI, 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;
 }