Index: pvbus.c
===================================================================
RCS file: /cvs/src/sys/dev/pv/pvbus.c,v
retrieving revision 1.7
diff -u -p -r1.7 pvbus.c
--- pvbus.c	13 Nov 2015 22:41:34 -0000	1.7
+++ pvbus.c	15 Nov 2015 13:59:00 -0000
@@ -129,7 +129,8 @@ pvbus_attach(struct device *parent, stru
 		}
 
 		for (i = 0; i < PVBUS_MAX; i++) {
-			if (memcmp(pvbus_types[i].signature, r.str,
+			if (pvbus_types[i].signature == NULL ||
+			    memcmp(pvbus_types[i].signature, r.str,
 			    CPUID_HV_SIGNATURE_STRLEN) != 0)
 				continue;
 			hv = &sc->pvbus_hv[i];