KVM: Clear exception queue before emulating an instruction

If we're emulating an instruction, either it will succeed, in which case
any previously queued exception will be spurious, or we will requeue the
same exception.
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/x86.c

@@ -20,6 +20,7 @@
 #include "i8254.h"
 #include "tss.h"
 #include "kvm_cache_regs.h"
+#include "x86.h"
 
 #include <linux/clocksource.h>
 #include <linux/kvm.h>
@@ -2121,6 +2122,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 	int r;
 	struct decode_cache *c;
 
+	kvm_clear_exception_queue(vcpu);
 	vcpu->arch.mmio_fault_cr2 = cr2;
 	/*
 	 * TODO: fix x86_emulate.c to use guest_read/write_register

arch/x86/kvm/x86.h

+#ifndef ARCH_X86_KVM_X86_H
+#define ARCH_X86_KVM_X86_H
+
+#include <linux/kvm_host.h>
+
+static inline void kvm_clear_exception_queue(struct kvm_vcpu *vcpu)
+{
+	vcpu->arch.exception.pending = false;
+}
+
+#endif