KVM: Add kvm trace userspace interface

This interface allows user a space application to read the trace of kvm
related events through relayfs.

Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/Kconfig

@@ -50,6 +50,17 @@ config KVM_AMD
 	  Provides support for KVM on AMD processors equipped with the AMD-V
 	  (SVM) extensions.
 
+config KVM_TRACE
+	bool "KVM trace support"
+	depends on KVM && MARKERS && SYSFS
+	select RELAY
+	select DEBUG_FS
+	default n
+	---help---
+	  This option allows reading a trace of kvm-related events through
+	  relayfs.  Note the ABI is not considered stable and will be
+	  modified in future updates.
+
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.
 source drivers/lguest/Kconfig