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/Kconfig b/arch/x86/kvm/Kconfig
index 970bbd4..ddc131f 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -64,6 +64,13 @@
 	  To compile this as a module, choose M here: the module
 	  will be called kvm-amd.
 
+config KVM_MMU_AUDIT
+	bool "Audit KVM MMU"
+	depends on KVM && TRACEPOINTS
+	---help---
+	 This option adds a R/W kVM module parameter 'mmu_audit', which allows
+	 audit  KVM MMU at runtime.
+
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.
 source drivers/vhost/Kconfig