sandbox: vm: encode vm_page zone id within p_flags

sandbox/vm/page.c

@@ -131,3 +131,17 @@ size_t vm_bytes_to_pages(size_t bytes)
 	bytes >>= VM_PAGE_SHIFT;
 	return bytes;
 }
+
+vm_zone_t *vm_page_get_zone(vm_page_t *pg)
+{
+	vm_pg_data_t *node = vm_pg_data_get(pg->p_node);
+	if (!node) {
+		return 0;
+	}
+
+	if (pg->p_zone >= VM_MAX_ZONES) {
+		return NULL;
+	}
+	
+	return &node->pg_zones[pg->p_zone];
+}