diff --git a/sys/arm64/arm64/nexus.c b/sys/arm64/arm64/nexus.c
--- a/sys/arm64/arm64/nexus.c
+++ b/sys/arm64/arm64/nexus.c
@@ -112,6 +112,7 @@
 static bus_get_resource_list_t	nexus_get_reslist;
 static bus_map_resource_t	nexus_map_resource;
 static bus_release_resource_t	nexus_release_resource;
+static bus_unmap_resource_t	nexus_unmap_resource;
 
 #ifdef SMP
 static bus_bind_intr_t		nexus_bind_intr;
@@ -141,6 +142,7 @@
 	DEVMETHOD(bus_map_resource,	nexus_map_resource),
 	DEVMETHOD(bus_release_resource,	nexus_release_resource),
 	DEVMETHOD(bus_set_resource,	bus_generic_rl_set_resource),
+	DEVMETHOD(bus_unmap_resource,	nexus_unmap_resource),
 #ifdef SMP
 	DEVMETHOD(bus_bind_intr,	nexus_bind_intr),
 #endif
@@ -494,6 +496,21 @@
 	return (0);
 }
 
+static int
+nexus_unmap_resource(device_t bus, device_t child, int type, struct resource *r,
+    struct resource_map *map)
+{
+
+	switch (type) {
+	case SYS_RES_MEMORY:
+	case SYS_RES_IOPORT:
+		pmap_unmapdev(map->r_vaddr, map->r_size);
+		return (0);
+	default:
+		return (EINVAL);
+	}
+}
+
 #ifdef FDT
 static device_method_t nexus_fdt_methods[] = {
 	/* Device interface */
diff --git a/sys/riscv/riscv/nexus.c b/sys/riscv/riscv/nexus.c
--- a/sys/riscv/riscv/nexus.c
+++ b/sys/riscv/riscv/nexus.c
@@ -87,6 +87,7 @@
 static bus_get_resource_list_t	nexus_get_reslist;
 static bus_map_resource_t	nexus_map_resource;
 static bus_release_resource_t	nexus_release_resource;
+static bus_unmap_resource_t	nexus_unmap_resource;
 
 static bus_config_intr_t	nexus_config_intr;
 static bus_describe_intr_t	nexus_describe_intr;
@@ -118,6 +119,7 @@
 	DEVMETHOD(bus_map_resource,	nexus_map_resource),
 	DEVMETHOD(bus_set_resource,	bus_generic_rl_set_resource),
 	DEVMETHOD(bus_release_resource,	nexus_release_resource),
+	DEVMETHOD(bus_unmap_resource,	nexus_unmap_resource),
 	DEVMETHOD(bus_config_intr,	nexus_config_intr),
 	DEVMETHOD(bus_describe_intr,	nexus_describe_intr),
 	DEVMETHOD(bus_setup_intr,	nexus_setup_intr),
@@ -456,6 +458,20 @@
 	return (0);
 }
 
+static int
+nexus_unmap_resource(device_t bus, device_t child, int type, struct resource *r,
+    struct resource_map *map)
+{
+	switch (type) {
+	case SYS_RES_MEMORY:
+	case SYS_RES_IOPORT:
+		pmap_unmapdev(map->r_vaddr, map->r_size);
+		return (0);
+	default:
+		return (EINVAL);
+	}
+}
+
 static int
 nexus_ofw_map_intr(device_t dev, device_t child, phandle_t iparent, int icells,
     pcell_t *intr)