1 files changed, 89 insertions, 0 deletions
diff --git a/include/xen/xen-front-pgdir-shbuf.h b/include/xen/xen-front-pgdir-shbuf.h
new file mode 100644
index 000000000000..150ef7ec51ec
--- /dev/null
+++ b/include/xen/xen-front-pgdir-shbuf.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ * Xen frontend/backend page directory based shared buffer
+ * helper module.
+ *
+ * Copyright (C) 2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_FRONT_PGDIR_SHBUF_H_
+#define __XEN_FRONT_PGDIR_SHBUF_H_
+
+#include <linux/kernel.h>
+
+#include <xen/grant_table.h>
+
+struct xen_front_pgdir_shbuf_ops;
+
+struct xen_front_pgdir_shbuf {
+	/*
+	 * Number of references granted for the backend use:
+	 *
+	 *  - for frontend allocated/imported buffers this holds the number
+	 *    of grant references for the page directory and the pages
+	 *    of the buffer
+	 *
+	 *  - for the buffer provided by the backend this only holds the number
+	 *    of grant references for the page directory itself as grant
+	 *    references for the buffer will be provided by the backend.
+	 */
+	int num_grefs;
+	grant_ref_t *grefs;
+	/* Page directory backing storage. */
+	u8 *directory;
+
+	/*
+	 * Number of pages for the shared buffer itself (excluding the page
+	 * directory).
+	 */
+	int num_pages;
+	/*
+	 * Backing storage of the shared buffer: these are the pages being
+	 * shared.
+	 */
+	struct page **pages;
+
+	struct xenbus_device *xb_dev;
+
+	/* These are the ops used internally depending on be_alloc mode. */
+	const struct xen_front_pgdir_shbuf_ops *ops;
+
+	/* Xen map handles for the buffer allocated by the backend. */
+	grant_handle_t *backend_map_handles;
+};
+
+struct xen_front_pgdir_shbuf_cfg {
+	struct xenbus_device *xb_dev;
+
+	/* Number of pages of the buffer backing storage. */
+	int num_pages;
+	/* Pages of the buffer to be shared. */
+	struct page **pages;
+
+	/*
+	 * This is allocated outside because there are use-cases when
+	 * the buffer structure is allocated as a part of a bigger one.
+	 */
+	struct xen_front_pgdir_shbuf *pgdir;
+	/*
+	 * Mode of grant reference sharing: if set then backend will share
+	 * grant references to the buffer with the frontend.
+	 */
+	int be_alloc;
+};
+
+int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg);
+
+grant_ref_t
+xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf);
+
+int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf);
+
+int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf);
+
+void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf);
+
+#endif /* __XEN_FRONT_PGDIR_SHBUF_H_ */