LXR linux/include/xen/xen-front-pgdir-shbuf.h

   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
  19struct xen_front_pgdir_shbuf_ops;
  20
  21struct 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
  58struct 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
  78int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg);
  79
  80grant_ref_t
  81xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf);
  82
  83int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf);
  84
  85int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf);
  86
  87void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf);
  88
  89#endif /* __XEN_FRONT_PGDIR_SHBUF_H_ */
  90