KVM: MMU: support disable/enable mmu audit dynamicly

Add a r/w module parameter named 'mmu_audit', it can control audit
enable/disable:

enable:
  echo 1 > /sys/module/kvm/parameters/mmu_audit

disable:
  echo 0 > /sys/module/kvm/parameters/mmu_audit

This patch not change the logic

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index 3aab0f0..b60b4fd 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -195,6 +195,25 @@
 
 	TP_ARGS(sp)
 );
+
+TRACE_EVENT(
+	kvm_mmu_audit,
+	TP_PROTO(struct kvm_vcpu *vcpu, int audit_point),
+	TP_ARGS(vcpu, audit_point),
+
+	TP_STRUCT__entry(
+		__field(struct kvm_vcpu *, vcpu)
+		__field(int, audit_point)
+	),
+
+	TP_fast_assign(
+		__entry->vcpu = vcpu;
+		__entry->audit_point = audit_point;
+	),
+
+	TP_printk("vcpu:%d %s", __entry->vcpu->cpu,
+		  audit_point_name[__entry->audit_point])
+);
 #endif /* _TRACE_KVMMMU_H */
 
 #undef TRACE_INCLUDE_PATH