1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
2 
3 /*
4  * Xen frontend/backend page directory based shared buffer
5  * helper module.
6  *
7  * Copyright (C) 2018 EPAM Systems Inc.
8  *
9  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
10  */
11 
12 #ifndef __XEN_FRONT_PGDIR_SHBUF_H_
13 #define __XEN_FRONT_PGDIR_SHBUF_H_
14 
15 #include <linux/kernel.h>
16 
17 #include <xen/grant_table.h>
18 
19 struct xen_front_pgdir_shbuf_ops;
20 
21 struct xen_front_pgdir_shbuf {
22 	/*
23 	 * Number of references granted for the backend use:
24 	 *
25 	 *  - for frontend allocated/imported buffers this holds the number
26 	 *    of grant references for the page directory and the pages
27 	 *    of the buffer
28 	 *
29 	 *  - for the buffer provided by the backend this only holds the number
30 	 *    of grant references for the page directory itself as grant
31 	 *    references for the buffer will be provided by the backend.
32 	 */
33 	int num_grefs;
34 	grant_ref_t *grefs;
35 	/* Page directory backing storage. */
36 	u8 *directory;
37 
38 	/*
39 	 * Number of pages for the shared buffer itself (excluding the page
40 	 * directory).
41 	 */
42 	int num_pages;
43 	/*
44 	 * Backing storage of the shared buffer: these are the pages being
45 	 * shared.
46 	 */
47 	struct page **pages;
48 
49 	struct xenbus_device *xb_dev;
50 
51 	/* These are the ops used internally depending on be_alloc mode. */
52 	const struct xen_front_pgdir_shbuf_ops *ops;
53 
54 	/* Xen map handles for the buffer allocated by the backend. */
55 	grant_handle_t *backend_map_handles;
56 };
57 
58 struct xen_front_pgdir_shbuf_cfg {
59 	struct xenbus_device *xb_dev;
60 
61 	/* Number of pages of the buffer backing storage. */
62 	int num_pages;
63 	/* Pages of the buffer to be shared. */
64 	struct page **pages;
65 
66 	/*
67 	 * This is allocated outside because there are use-cases when
68 	 * the buffer structure is allocated as a part of a bigger one.
69 	 */
70 	struct xen_front_pgdir_shbuf *pgdir;
71 	/*
72 	 * Mode of grant reference sharing: if set then backend will share
73 	 * grant references to the buffer with the frontend.
74 	 */
75 	int be_alloc;
76 };
77 
78 int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg);
79 
80 grant_ref_t
81 xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf);
82 
83 int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf);
84 
85 int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf);
86 
87 void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf);
88 
89 #endif /* __XEN_FRONT_PGDIR_SHBUF_H_ */
90