Index: head/sys/amd64/include/cpufunc.h
===================================================================
--- head/sys/amd64/include/cpufunc.h
+++ head/sys/amd64/include/cpufunc.h
@@ -116,6 +116,13 @@
 }
 
 static __inline void
+clwb(u_long addr)
+{
+
+	__asm __volatile("clwb %0" : : "m" (*(char *)addr));
+}
+
+static __inline void
 clts(void)
 {