sound/xen/xen_snd_front_shbuf.c

   1 // SPDX-License-Identifier: GPL-2.0 OR MIT
   2
   3 /*
   4  * Xen para-virtual sound device
   5  *
   6  * Copyright (C) 2016-2018 EPAM Systems Inc.
   7  *
   8  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <xen/xen.h>
  13 #include <xen/xenbus.h>
  14
  15 #include "xen_snd_front_shbuf.h"
  16
  17 grant_ref_t xen_snd_front_shbuf_get_dir_start(struct xen_snd_front_shbuf *buf)
  18 {
  19         if (!buf->grefs)
  20                 return GRANT_INVALID_REF;
  21
  22         return buf->grefs[0];
  23 }
  24
  25 void xen_snd_front_shbuf_clear(struct xen_snd_front_shbuf *buf)
  26 {
  27         memset(buf, 0, sizeof(*buf));
  28 }
  29
  30 void xen_snd_front_shbuf_free(struct xen_snd_front_shbuf *buf)
  31 {
  32         int i;
  33
  34         if (buf->grefs) {
  35                 for (i = 0; i < buf->num_grefs; i++)
  36                         if (buf->grefs[i] != GRANT_INVALID_REF)
  37                                 gnttab_end_foreign_access(buf->grefs[i],
  38                                                           0, 0UL);
  39                 kfree(buf->grefs);
  40         }
  41         kfree(buf->directory);
  42         free_pages_exact(buf->buffer, buf->buffer_sz);
  43         xen_snd_front_shbuf_clear(buf);
  44 }
  45
  46 /*
  47  * number of grant references a page can hold with respect to the
  48  * xensnd_page_directory header
  49  */
  50 #define XENSND_NUM_GREFS_PER_PAGE ((XEN_PAGE_SIZE - \
  51                 offsetof(struct xensnd_page_directory, gref)) / \
  52                 sizeof(grant_ref_t))
  53
  54 static void fill_page_dir(struct xen_snd_front_shbuf *buf,
  55                           int num_pages_dir)
  56 {
  57         struct xensnd_page_directory *page_dir;
  58         unsigned char *ptr;
  59         int i, cur_gref, grefs_left, to_copy;
  60
  61         ptr = buf->directory;
  62         grefs_left = buf->num_grefs - num_pages_dir;
  63         /*
  64          * skip grant references at the beginning, they are for pages granted
  65          * for the page directory itself
  66          */
  67         cur_gref = num_pages_dir;
  68         for (i = 0; i < num_pages_dir; i++) {
  69                 page_dir = (struct xensnd_page_directory *)ptr;
  70                 if (grefs_left <= XENSND_NUM_GREFS_PER_PAGE) {
  71                         to_copy = grefs_left;
  72                         page_dir->gref_dir_next_page = GRANT_INVALID_REF;
  73                 } else {
  74                         to_copy = XENSND_NUM_GREFS_PER_PAGE;
  75                         page_dir->gref_dir_next_page = buf->grefs[i + 1];
  76                 }
  77
  78                 memcpy(&page_dir->gref, &buf->grefs[cur_gref],
  79                        to_copy * sizeof(grant_ref_t));
  80
  81                 ptr += XEN_PAGE_SIZE;
  82                 grefs_left -= to_copy;
  83                 cur_gref += to_copy;
  84         }
  85 }
  86
  87 static int grant_references(struct xenbus_device *xb_dev,
  88                             struct xen_snd_front_shbuf *buf,
  89                             int num_pages_dir, int num_pages_buffer,
  90                             int num_grefs)
  91 {
  92         grant_ref_t priv_gref_head;
  93         unsigned long frame;
  94         int ret, i, j, cur_ref;
  95         int otherend_id;
  96
  97         ret = gnttab_alloc_grant_references(num_grefs, &priv_gref_head);
  98         if (ret)
  99                 return ret;
 100
 101         buf->num_grefs = num_grefs;
 102         otherend_id = xb_dev->otherend_id;
 103         j = 0;
 104
 105         for (i = 0; i < num_pages_dir; i++) {
 106                 cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
 107                 if (cur_ref < 0) {
 108                         ret = cur_ref;
 109                         goto fail;
 110                 }
 111
 112                 frame = xen_page_to_gfn(virt_to_page(buf->directory +
 113                                                      XEN_PAGE_SIZE * i));
 114                 gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
 115                 buf->grefs[j++] = cur_ref;
 116         }
 117
 118         for (i = 0; i < num_pages_buffer; i++) {
 119                 cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
 120                 if (cur_ref < 0) {
 121                         ret = cur_ref;
 122                         goto fail;
 123                 }
 124
 125                 frame = xen_page_to_gfn(virt_to_page(buf->buffer +
 126                                                      XEN_PAGE_SIZE * i));
 127                 gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
 128                 buf->grefs[j++] = cur_ref;
 129         }
 130
 131         gnttab_free_grant_references(priv_gref_head);
 132         fill_page_dir(buf, num_pages_dir);
 133         return 0;
 134
 135 fail:
 136         gnttab_free_grant_references(priv_gref_head);
 137         return ret;
 138 }
 139
 140 static int alloc_int_buffers(struct xen_snd_front_shbuf *buf,
 141                              int num_pages_dir, int num_pages_buffer,
 142                              int num_grefs)
 143 {
 144         buf->grefs = kcalloc(num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
 145         if (!buf->grefs)
 146                 return -ENOMEM;
 147
 148         buf->directory = kcalloc(num_pages_dir, XEN_PAGE_SIZE, GFP_KERNEL);
 149         if (!buf->directory)
 150                 goto fail;
 151
 152         buf->buffer_sz = num_pages_buffer * XEN_PAGE_SIZE;
 153         buf->buffer = alloc_pages_exact(buf->buffer_sz, GFP_KERNEL);
 154         if (!buf->buffer)
 155                 goto fail;
 156
 157         return 0;
 158
 159 fail:
 160         kfree(buf->grefs);
 161         buf->grefs = NULL;
 162         kfree(buf->directory);
 163         buf->directory = NULL;
 164         return -ENOMEM;
 165 }
 166
 167 int xen_snd_front_shbuf_alloc(struct xenbus_device *xb_dev,
 168                               struct xen_snd_front_shbuf *buf,
 169                               unsigned int buffer_sz)
 170 {
 171         int num_pages_buffer, num_pages_dir, num_grefs;
 172         int ret;
 173
 174         xen_snd_front_shbuf_clear(buf);
 175
 176         num_pages_buffer = DIV_ROUND_UP(buffer_sz, XEN_PAGE_SIZE);
 177         /* number of pages the page directory consumes itself */
 178         num_pages_dir = DIV_ROUND_UP(num_pages_buffer,
 179                                      XENSND_NUM_GREFS_PER_PAGE);
 180         num_grefs = num_pages_buffer + num_pages_dir;
 181
 182         ret = alloc_int_buffers(buf, num_pages_dir,
 183                                 num_pages_buffer, num_grefs);
 184         if (ret < 0)
 185                 return ret;
 186
 187         ret = grant_references(xb_dev, buf, num_pages_dir, num_pages_buffer,
 188                                num_grefs);
 189         if (ret < 0)
 190                 return ret;
 191
 192         fill_page_dir(buf, num_pages_dir);
 193         return 0;
 194 }