v4.19.13 snapshot.
diff --git a/include/xen/tmem.h b/include/xen/tmem.h
new file mode 100644
index 0000000..c80bafe
--- /dev/null
+++ b/include/xen/tmem.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _XEN_TMEM_H
+#define _XEN_TMEM_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_XEN_TMEM_MODULE
+#define tmem_enabled true
+#else
+/* defined in drivers/xen/tmem.c */
+extern bool tmem_enabled;
+#endif
+
+#ifdef CONFIG_XEN_SELFBALLOONING
+extern int xen_selfballoon_init(bool, bool);
+#endif
+
+#endif /* _XEN_TMEM_H */