--- Gnu-Mach/i386/i386at/mem.c	2020/09/02 04:49:24	1.1.1.2
+++ Gnu-Mach/i386/i386at/mem.c	2020/09/02 04:55:40	1.1.1.3
@@ -36,12 +36,24 @@ dev_t		dev;
 vm_offset_t	off;
 vm_prot_t	prot;
 {
+	struct vm_page *p;
+
 	if (off == 0)
 		return 0;
-	else if (off < 0xa0000)
+
+	/*
+	 * The legacy device mappings are included in the page tables and
+	 * need their own test.
+	 */
+	if (off >= 0xa0000 && off < 0x100000)
+		goto out;
+
+	p = vm_page_lookup_pa(off);
+
+	if (p != NULL) {
 		return -1;
-	else if (off >= 0x100000 && off < phys_last_addr)
-		return -1;
-	else
-		return i386_btop(off);
+	}
+
+out:
+	return i386_btop(off);
 }