Index: sys/arm64/arm64/nexus.c
===================================================================
--- sys/arm64/arm64/nexus.c
+++ sys/arm64/arm64/nexus.c
@@ -118,6 +118,8 @@
 static int nexus_release_resource(device_t, device_t, int, int,
     struct resource *);
 
+static uint64_t nexus_get_parange(void);
+
 static int nexus_setup_intr(device_t dev, device_t child, struct resource *res,
     int flags, driver_filter_t *filt, driver_intr_t *intr, void *arg, void **cookiep);
 static int nexus_teardown_intr(device_t, device_t, struct resource *, void *);
@@ -163,11 +165,11 @@
 {
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = BUS_SPACE_MAXADDR;
+	mem_rman.rm_end = nexus_get_parange();
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "I/O memory addresses";
 	if (rman_init(&mem_rman) ||
-	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR))
+	    rman_manage_region(&mem_rman, 0, mem_rman.rm_end))
 		panic("nexus_attach mem_rman");
 	irq_rman.rm_start = 0;
 	irq_rman.rm_end = ~0;
@@ -480,6 +482,48 @@
 	return (0);
 }
 
+static uint64_t
+nexus_get_parange(void)
+{
+	uint64_t mmfr0, parange;
+
+	if (!get_kernel_reg(ID_AA64MMFR0_EL1, &mmfr0)) {
+		/* chosen arbitrarily */
+		mmfr0 = ID_AA64MMFR0_PARange_1T;
+	}
+
+	switch (ID_AA64MMFR0_PARange_VAL(mmfr0)) {
+	case ID_AA64MMFR0_PARange_4G:
+		parange = (vm_paddr_t)4 << 30 /* GiB */;
+		break;
+	case ID_AA64MMFR0_PARange_64G:
+		parange = (vm_paddr_t)64 << 30 /* GiB */;
+		break;
+	case ID_AA64MMFR0_PARange_1T:
+		parange = (vm_paddr_t)1 << 40 /* TiB */;
+		break;
+	case ID_AA64MMFR0_PARange_4T:
+		parange = (vm_paddr_t)4 << 40 /* TiB */;
+		break;
+	case ID_AA64MMFR0_PARange_16T:
+		parange = (vm_paddr_t)16 << 40 /* TiB */;
+		break;
+	case ID_AA64MMFR0_PARange_256T:
+		parange = (vm_paddr_t)256 << 40 /* TiB */;
+		break;
+	case ID_AA64MMFR0_PARange_4P:
+		parange = (vm_paddr_t)4 << 50 /* PiB */;
+		break;
+	default:
+		/* chosen arbitrarily */
+		parange = (vm_paddr_t)1 << 40 /* TiB */;
+		printf("Unknown value for PARange in mmfr0 (%#lx)\n", mmfr0);
+		break;
+	}
+
+	return (parange);
+}
+
 #ifdef FDT
 static device_method_t nexus_fdt_methods[] = {
 	/* Device interface */