[PATCH 1/5] Implement #NMI exiting for nested SVM

[Alexander Graf <agraf@suse.de>]

When injecting an NMI to the l1 guest while it was running the l2 guest, we
didn't #VMEXIT but just injected the NMI to the l2 guest.

Let's be closer to real hardware and #VMEXIT if we're supposed to do so.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 arch/x86/kvm/svm.c |   38 ++++++++++++++++++++++++++++++++------
 1 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 9a4daca..f12a669 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1375,6 +1375,21 @@ static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 	return nested_svm_exit_handled(svm);
 }
 
+static inline int nested_svm_nmi(struct vcpu_svm *svm)
+{
+	if (!is_nested(svm))
+		return 0;
+
+	svm->vmcb->control.exit_code = SVM_EXIT_NMI;
+
+	if (nested_svm_exit_handled(svm)) {
+		nsvm_printk("VMexit -> NMI\n");
+		return 1;
+	}
+
+	return 0;
+}
+
 static inline int nested_svm_intr(struct vcpu_svm *svm)
 {
 	if (!is_nested(svm))
@@ -2462,7 +2477,9 @@ static int svm_nmi_allowed(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct vmcb *vmcb = svm->vmcb;
 	return !(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
-		!(svm->vcpu.arch.hflags & HF_NMI_MASK);
+		!(svm->vcpu.arch.hflags & HF_NMI_MASK) &&
+		gif_set(svm) &&
+		!is_nested(svm);
 }
 
 static int svm_interrupt_allowed(struct kvm_vcpu *vcpu)
@@ -2488,22 +2505,31 @@ static void enable_irq_window(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 	nsvm_printk("Trying to open IRQ window\n");
 
-	nested_svm_intr(svm);
+	if (nested_svm_intr(svm))
+		return;
 
 	/* In case GIF=0 we can't rely on the CPU to tell us when
 	 * GIF becomes 1, because that's a separate STGI/VMRUN intercept.
 	 * The next time we get that intercept, this function will be
 	 * called again though and we'll get the vintr intercept. */
-	if (gif_set(svm)) {
-		svm_set_vintr(svm);
-		svm_inject_irq(svm, 0x0);
-	}
+	if (!gif_set(svm))
+		return;
+
+	svm_set_vintr(svm);
+	svm_inject_irq(svm, 0x0);
 }
 
 static void enable_nmi_window(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	if (nested_svm_nmi(svm))
+		return;
+
+	/* NMI is deferred until GIF == 1. Setting GIF will cause a #VMEXIT */
+	if (!gif_set(svm))
+		return;
+
 	if ((svm->vcpu.arch.hflags & (HF_NMI_MASK | HF_IRET_MASK))
 	    == HF_NMI_MASK)
 		return; /* IRET will cause a vm exit */
-- 
1.6.0.2