In pmap_copy(), when the copied region is mapped with superpage but does

not cover entire superpage, avoid copying.  Doing partial copy would
require demotion, which is incompatible with the already held locks.

Reported by:    cperciva
Reviewed by:    alc
Sponsored by:	The FreeBSD Foundation
MFC after:      1 week
Approved by:	re (delphij)

sys/amd64/amd64/pmap.c

@@ -4356,6 +4356,8 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
 			continue;
 			
 		if (srcptepaddr & PG_PS) {
+			if ((addr & PDRMASK) != 0 || addr + NBPDR > end_addr)
+				continue;
 			dstmpde = pmap_allocpde(dst_pmap, addr, NULL);
 			if (dstmpde == NULL)
 				break;