drivers/gpu/drm/xen/xen_drm_front_shbuf.c

   1 // SPDX-License-Identifier: GPL-2.0 OR MIT
   2
   3 /*
   4  *  Xen para-virtual DRM device
   5  *
   6  * Copyright (C) 2016-2018 EPAM Systems Inc.
   7  *
   8  * Author: Oleksandr Andrushchenko <[email protected]>
   9  */
  10
  11 #include <drm/drmP.h>
  12
  13 #if defined(CONFIG_X86)
  14 #include <drm/drm_cache.h>
  15 #endif
  16 #include <linux/errno.h>
  17 #include <linux/mm.h>
  18
  19 #include <asm/xen/hypervisor.h>
  20 #include <xen/balloon.h>
  21 #include <xen/xen.h>
  22 #include <xen/xenbus.h>
  23 #include <xen/interface/io/ring.h>
  24 #include <xen/interface/io/displif.h>
  25
  26 #include "xen_drm_front.h"
  27 #include "xen_drm_front_shbuf.h"
  28
  29 struct xen_drm_front_shbuf_ops {
  30         /*
  31          * Calculate number of grefs required to handle this buffer,
  32          * e.g. if grefs are required for page directory only or the buffer
  33          * pages as well.
  34          */
  35         void (*calc_num_grefs)(struct xen_drm_front_shbuf *buf);
  36         /* Fill page directory according to para-virtual display protocol. */
  37         void (*fill_page_dir)(struct xen_drm_front_shbuf *buf);
  38         /* Claim grant references for the pages of the buffer. */
  39         int (*grant_refs_for_buffer)(struct xen_drm_front_shbuf *buf,
  40                                      grant_ref_t *priv_gref_head, int gref_idx);
  41         /* Map grant references of the buffer. */
  42         int (*map)(struct xen_drm_front_shbuf *buf);
  43         /* Unmap grant references of the buffer. */
  44         int (*unmap)(struct xen_drm_front_shbuf *buf);
  45 };
  46
  47 grant_ref_t xen_drm_front_shbuf_get_dir_start(struct xen_drm_front_shbuf *buf)
  48 {
  49         if (!buf->grefs)
  50                 return GRANT_INVALID_REF;
  51
  52         return buf->grefs[0];
  53 }
  54
  55 int xen_drm_front_shbuf_map(struct xen_drm_front_shbuf *buf)
  56 {
  57         if (buf->ops->map)
  58                 return buf->ops->map(buf);
  59
  60         /* no need to map own grant references */
  61         return 0;
  62 }
  63
  64 int xen_drm_front_shbuf_unmap(struct xen_drm_front_shbuf *buf)
  65 {
  66         if (buf->ops->unmap)
  67                 return buf->ops->unmap(buf);
  68
  69         /* no need to unmap own grant references */
  70         return 0;
  71 }
  72
  73 void xen_drm_front_shbuf_flush(struct xen_drm_front_shbuf *buf)
  74 {
  75 #if defined(CONFIG_X86)
  76         drm_clflush_pages(buf->pages, buf->num_pages);
  77 #endif
  78 }
  79
  80 void xen_drm_front_shbuf_free(struct xen_drm_front_shbuf *buf)
  81 {
  82         if (buf->grefs) {
  83                 int i;
  84
  85                 for (i = 0; i < buf->num_grefs; i++)
  86                         if (buf->grefs[i] != GRANT_INVALID_REF)
  87                                 gnttab_end_foreign_access(buf->grefs[i],
  88                                                           0, 0UL);
  89         }
  90         kfree(buf->grefs);
  91         kfree(buf->directory);
  92         kfree(buf);
  93 }
  94
  95 /*
  96  * number of grefs a page can hold with respect to the
  97  * struct xendispl_page_directory header
  98  */
  99 #define XEN_DRM_NUM_GREFS_PER_PAGE ((PAGE_SIZE - \
 100                 offsetof(struct xendispl_page_directory, gref)) / \
 101                 sizeof(grant_ref_t))
 102
 103 static int get_num_pages_dir(struct xen_drm_front_shbuf *buf)
 104 {
 105         /* number of pages the page directory consumes itself */
 106         return DIV_ROUND_UP(buf->num_pages, XEN_DRM_NUM_GREFS_PER_PAGE);
 107 }
 108
 109 static void backend_calc_num_grefs(struct xen_drm_front_shbuf *buf)
 110 {
 111         /* only for pages the page directory consumes itself */
 112         buf->num_grefs = get_num_pages_dir(buf);
 113 }
 114
 115 static void guest_calc_num_grefs(struct xen_drm_front_shbuf *buf)
 116 {
 117         /*
 118          * number of pages the page directory consumes itself
 119          * plus grefs for the buffer pages
 120          */
 121         buf->num_grefs = get_num_pages_dir(buf) + buf->num_pages;
 122 }
 123
 124 #define xen_page_to_vaddr(page) \
 125                 ((uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
 126
 127 static int backend_unmap(struct xen_drm_front_shbuf *buf)
 128 {
 129         struct gnttab_unmap_grant_ref *unmap_ops;
 130         int i, ret;
 131
 132         if (!buf->pages || !buf->backend_map_handles || !buf->grefs)
 133                 return 0;
 134
 135         unmap_ops = kcalloc(buf->num_pages, sizeof(*unmap_ops),
 136                             GFP_KERNEL);
 137         if (!unmap_ops) {
 138                 DRM_ERROR("Failed to get memory while unmapping\n");
 139                 return -ENOMEM;
 140         }
 141
 142         for (i = 0; i < buf->num_pages; i++) {
 143                 phys_addr_t addr;
 144
 145                 addr = xen_page_to_vaddr(buf->pages[i]);
 146                 gnttab_set_unmap_op(&unmap_ops[i], addr, GNTMAP_host_map,
 147                                     buf->backend_map_handles[i]);
 148         }
 149
 150         ret = gnttab_unmap_refs(unmap_ops, NULL, buf->pages,
 151                                 buf->num_pages);
 152
 153         for (i = 0; i < buf->num_pages; i++) {
 154                 if (unlikely(unmap_ops[i].status != GNTST_okay))
 155                         DRM_ERROR("Failed to unmap page %d: %d\n",
 156                                   i, unmap_ops[i].status);
 157         }
 158
 159         if (ret)
 160                 DRM_ERROR("Failed to unmap grant references, ret %d", ret);
 161
 162         kfree(unmap_ops);
 163         kfree(buf->backend_map_handles);
 164         buf->backend_map_handles = NULL;
 165         return ret;
 166 }
 167
 168 static int backend_map(struct xen_drm_front_shbuf *buf)
 169 {
 170         struct gnttab_map_grant_ref *map_ops = NULL;
 171         unsigned char *ptr;
 172         int ret, cur_gref, cur_dir_page, cur_page, grefs_left;
 173
 174         map_ops = kcalloc(buf->num_pages, sizeof(*map_ops), GFP_KERNEL);
 175         if (!map_ops)
 176                 return -ENOMEM;
 177
 178         buf->backend_map_handles = kcalloc(buf->num_pages,
 179                                            sizeof(*buf->backend_map_handles),
 180                                            GFP_KERNEL);
 181         if (!buf->backend_map_handles) {
 182                 kfree(map_ops);
 183                 return -ENOMEM;
 184         }
 185
 186         /*
 187          * read page directory to get grefs from the backend: for external
 188          * buffer we only allocate buf->grefs for the page directory,
 189          * so buf->num_grefs has number of pages in the page directory itself
 190          */
 191         ptr = buf->directory;
 192         grefs_left = buf->num_pages;
 193         cur_page = 0;
 194         for (cur_dir_page = 0; cur_dir_page < buf->num_grefs; cur_dir_page++) {
 195                 struct xendispl_page_directory *page_dir =
 196                                 (struct xendispl_page_directory *)ptr;
 197                 int to_copy = XEN_DRM_NUM_GREFS_PER_PAGE;
 198
 199                 if (to_copy > grefs_left)
 200                         to_copy = grefs_left;
 201
 202                 for (cur_gref = 0; cur_gref < to_copy; cur_gref++) {
 203                         phys_addr_t addr;
 204
 205                         addr = xen_page_to_vaddr(buf->pages[cur_page]);
 206                         gnttab_set_map_op(&map_ops[cur_page], addr,
 207                                           GNTMAP_host_map,
 208                                           page_dir->gref[cur_gref],
 209                                           buf->xb_dev->otherend_id);
 210                         cur_page++;
 211                 }
 212
 213                 grefs_left -= to_copy;
 214                 ptr += PAGE_SIZE;
 215         }
 216         ret = gnttab_map_refs(map_ops, NULL, buf->pages, buf->num_pages);
 217
 218         /* save handles even if error, so we can unmap */
 219         for (cur_page = 0; cur_page < buf->num_pages; cur_page++) {
 220                 buf->backend_map_handles[cur_page] = map_ops[cur_page].handle;
 221                 if (unlikely(map_ops[cur_page].status != GNTST_okay))
 222                         DRM_ERROR("Failed to map page %d: %d\n",
 223                                   cur_page, map_ops[cur_page].status);
 224         }
 225
 226         if (ret) {
 227                 DRM_ERROR("Failed to map grant references, ret %d", ret);
 228                 backend_unmap(buf);
 229         }
 230
 231         kfree(map_ops);
 232         return ret;
 233 }
 234
 235 static void backend_fill_page_dir(struct xen_drm_front_shbuf *buf)
 236 {
 237         struct xendispl_page_directory *page_dir;
 238         unsigned char *ptr;
 239         int i, num_pages_dir;
 240
 241         ptr = buf->directory;
 242         num_pages_dir = get_num_pages_dir(buf);
 243
 244         /* fill only grefs for the page directory itself */
 245         for (i = 0; i < num_pages_dir - 1; i++) {
 246                 page_dir = (struct xendispl_page_directory *)ptr;
 247
 248                 page_dir->gref_dir_next_page = buf->grefs[i + 1];
 249                 ptr += PAGE_SIZE;
 250         }
 251         /* last page must say there is no more pages */
 252         page_dir = (struct xendispl_page_directory *)ptr;
 253         page_dir->gref_dir_next_page = GRANT_INVALID_REF;
 254 }
 255
 256 static void guest_fill_page_dir(struct xen_drm_front_shbuf *buf)
 257 {
 258         unsigned char *ptr;
 259         int cur_gref, grefs_left, to_copy, i, num_pages_dir;
 260
 261         ptr = buf->directory;
 262         num_pages_dir = get_num_pages_dir(buf);
 263
 264         /*
 265          * while copying, skip grefs at start, they are for pages
 266          * granted for the page directory itself
 267          */
 268         cur_gref = num_pages_dir;
 269         grefs_left = buf->num_pages;
 270         for (i = 0; i < num_pages_dir; i++) {
 271                 struct xendispl_page_directory *page_dir =
 272                                 (struct xendispl_page_directory *)ptr;
 273
 274                 if (grefs_left <= XEN_DRM_NUM_GREFS_PER_PAGE) {
 275                         to_copy = grefs_left;
 276                         page_dir->gref_dir_next_page = GRANT_INVALID_REF;
 277                 } else {
 278                         to_copy = XEN_DRM_NUM_GREFS_PER_PAGE;
 279                         page_dir->gref_dir_next_page = buf->grefs[i + 1];
 280                 }
 281                 memcpy(&page_dir->gref, &buf->grefs[cur_gref],
 282                        to_copy * sizeof(grant_ref_t));
 283                 ptr += PAGE_SIZE;
 284                 grefs_left -= to_copy;
 285                 cur_gref += to_copy;
 286         }
 287 }
 288
 289 static int guest_grant_refs_for_buffer(struct xen_drm_front_shbuf *buf,
 290                                        grant_ref_t *priv_gref_head,
 291                                        int gref_idx)
 292 {
 293         int i, cur_ref, otherend_id;
 294
 295         otherend_id = buf->xb_dev->otherend_id;
 296         for (i = 0; i < buf->num_pages; i++) {
 297                 cur_ref = gnttab_claim_grant_reference(priv_gref_head);
 298                 if (cur_ref < 0)
 299                         return cur_ref;
 300
 301                 gnttab_grant_foreign_access_ref(cur_ref, otherend_id,
 302                                                 xen_page_to_gfn(buf->pages[i]),
 303                                                 0);
 304                 buf->grefs[gref_idx++] = cur_ref;
 305         }
 306         return 0;
 307 }
 308
 309 static int grant_references(struct xen_drm_front_shbuf *buf)
 310 {
 311         grant_ref_t priv_gref_head;
 312         int ret, i, j, cur_ref;
 313         int otherend_id, num_pages_dir;
 314
 315         ret = gnttab_alloc_grant_references(buf->num_grefs, &priv_gref_head);
 316         if (ret < 0) {
 317                 DRM_ERROR("Cannot allocate grant references\n");
 318                 return ret;
 319         }
 320
 321         otherend_id = buf->xb_dev->otherend_id;
 322         j = 0;
 323         num_pages_dir = get_num_pages_dir(buf);
 324         for (i = 0; i < num_pages_dir; i++) {
 325                 unsigned long frame;
 326
 327                 cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
 328                 if (cur_ref < 0)
 329                         return cur_ref;
 330
 331                 frame = xen_page_to_gfn(virt_to_page(buf->directory +
 332                                         PAGE_SIZE * i));
 333                 gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
 334                 buf->grefs[j++] = cur_ref;
 335         }
 336
 337         if (buf->ops->grant_refs_for_buffer) {
 338                 ret = buf->ops->grant_refs_for_buffer(buf, &priv_gref_head, j);
 339                 if (ret)
 340                         return ret;
 341         }
 342
 343         gnttab_free_grant_references(priv_gref_head);
 344         return 0;
 345 }
 346
 347 static int alloc_storage(struct xen_drm_front_shbuf *buf)
 348 {
 349         buf->grefs = kcalloc(buf->num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
 350         if (!buf->grefs)
 351                 return -ENOMEM;
 352
 353         buf->directory = kcalloc(get_num_pages_dir(buf), PAGE_SIZE, GFP_KERNEL);
 354         if (!buf->directory)
 355                 return -ENOMEM;
 356
 357         return 0;
 358 }
 359
 360 /*
 361  * For be allocated buffers we don't need grant_refs_for_buffer as those
 362  * grant references are allocated at backend side
 363  */
 364 static const struct xen_drm_front_shbuf_ops backend_ops = {
 365         .calc_num_grefs = backend_calc_num_grefs,
 366         .fill_page_dir = backend_fill_page_dir,
 367         .map = backend_map,
 368         .unmap = backend_unmap
 369 };
 370
 371 /* For locally granted references we do not need to map/unmap the references */
 372 static const struct xen_drm_front_shbuf_ops local_ops = {
 373         .calc_num_grefs = guest_calc_num_grefs,
 374         .fill_page_dir = guest_fill_page_dir,
 375         .grant_refs_for_buffer = guest_grant_refs_for_buffer,
 376 };
 377
 378 struct xen_drm_front_shbuf *
 379 xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg)
 380 {
 381         struct xen_drm_front_shbuf *buf;
 382         int ret;
 383
 384         buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 385         if (!buf)
 386                 return ERR_PTR(-ENOMEM);
 387
 388         if (cfg->be_alloc)
 389                 buf->ops = &backend_ops;
 390         else
 391                 buf->ops = &local_ops;
 392
 393         buf->xb_dev = cfg->xb_dev;
 394         buf->num_pages = DIV_ROUND_UP(cfg->size, PAGE_SIZE);
 395         buf->pages = cfg->pages;
 396
 397         buf->ops->calc_num_grefs(buf);
 398
 399         ret = alloc_storage(buf);
 400         if (ret)
 401                 goto fail;
 402
 403         ret = grant_references(buf);
 404         if (ret)
 405                 goto fail;
 406
 407         buf->ops->fill_page_dir(buf);
 408
 409         return buf;
 410
 411 fail:
 412         xen_drm_front_shbuf_free(buf);
 413         return ERR_PTR(ret);
 414 }