diff --git a/sys/amd64/amd64/efirt_machdep.c b/sys/amd64/amd64/efirt_machdep.c
--- a/sys/amd64/amd64/efirt_machdep.c
+++ b/sys/amd64/amd64/efirt_machdep.c
@@ -190,6 +190,7 @@
 	vm_offset_t va;
 	uint64_t idx;
 	int bits, i, mode;
+	bool map_pz = true;
 
 	obj_1t1_pt = vm_pager_allocate(OBJT_PHYS, NULL, ptoa(1 +
 	    NPML4EPG + NPML4EPG * NPDPEPG + NPML4EPG * NPDPEPG * NPDEPG),
@@ -272,6 +273,22 @@
 			}
 		}
 		VM_OBJECT_WUNLOCK(obj_1t1_pt);
+		if (p->md_phys == 0)
+			map_pz = false;
+	}
+
+	/*
+	 * Some BIOSes tend to access phys 0 during efirt calls,
+	 * so map it if we haven't yet.
+	 */
+	if (map_pz) {
+		VM_OBJECT_WLOCK(obj_1t1_pt);
+		pte = efi_1t1_pte(0);
+		/* Assume Write-Back */
+		bits = pmap_cache_bits(kernel_pmap, VM_MEMATTR_WRITE_BACK,
+		    false) | X86_PG_RW | X86_PG_V;
+		pte_store(pte, bits);
+		VM_OBJECT_WUNLOCK(obj_1t1_pt);
 	}
 
 	return (true);