From f9f3acd0d06f5d92e6ce0434a271fdc25e1ae9b4 Mon Sep 17 00:00:00 2001
From: Gleb Natapov <gleb@redhat.com>
Date: Fri, 1 Apr 2011 11:26:29 -0300
Subject: [PATCH] --- yaml --- r: 247994 b: refs/heads/master c:
 1499e54af03ae51a937c59035bc86002deae0572 h: refs/heads/master v: v3

---
 [refs]                   |  2 +-
 trunk/arch/x86/kvm/x86.c | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index b7ec7e5d2814..afadc53632b3 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c761e5868e6737abe0464636ebd7fcbb6814c626
+refs/heads/master: 1499e54af03ae51a937c59035bc86002deae0572
diff --git a/trunk/arch/x86/kvm/x86.c b/trunk/arch/x86/kvm/x86.c
index b9402d5fa0e9..692c70d6fd02 100644
--- a/trunk/arch/x86/kvm/x86.c
+++ b/trunk/arch/x86/kvm/x86.c
@@ -5171,6 +5171,7 @@ static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
 static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 {
 	int r;
+	bool nmi_pending;
 	bool req_int_win = !irqchip_in_kernel(vcpu->kvm) &&
 		vcpu->run->request_interrupt_window;
 
@@ -5214,11 +5215,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	if (unlikely(r))
 		goto out;
 
+	/*
+	 * An NMI can be injected between local nmi_pending read and
+	 * vcpu->arch.nmi_pending read inside inject_pending_event().
+	 * But in that case, KVM_REQ_EVENT will be set, which makes
+	 * the race described above benign.
+	 */
+	nmi_pending = ACCESS_ONCE(vcpu->arch.nmi_pending);
+
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
 		inject_pending_event(vcpu);
 
 		/* enable NMI/IRQ window open exits if needed */
-		if (vcpu->arch.nmi_pending)
+		if (nmi_pending)
 			kvm_x86_ops->enable_nmi_window(vcpu);
 		else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
 			kvm_x86_ops->enable_irq_window(vcpu);