Index: sys/amd64/vmm/amd/svm.c
===================================================================
--- sys/amd64/vmm/amd/svm.c	(revision 267030)
+++ sys/amd64/vmm/amd/svm.c	(working copy)
@@ -1304,6 +1304,21 @@
 	desc->base = seg->base;
 	desc->limit = seg->limit;
 
+	/*
+	 * VT-x uses bit 16 (Unusable) to indicate a segment that has been
+	 * loaded with a NULL segment selector. The 'desc->access' field is
+	 * interpreted in the VT-x format by the processor-independent code.
+	 *
+	 * SVM uses the 'P' bit to convey the same information so convert it
+	 * into the VT-x format. For more details refer to section
+	 * "Segment State in the VMCB" in APMv2.
+	 */
+	if (type == VM_REG_GUEST_CS && type == VM_REG_GUEST_TR)
+		desc->access |= 0x80;		/* CS and TS always present */
+
+	if (!(desc->access & 0x80))
+		desc->access |= 0x10000;	/* Unusable segment */
+
 	return (0);
 }