drivers/xen/gntdev-dmabuf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 /*
   4  * Xen dma-buf functionality for gntdev.
   5  *
   6  * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c.
   7  *
   8  * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/dma-buf.h>
  14 #include <linux/dma-direct.h>
  15 #include <linux/slab.h>
  16 #include <linux/types.h>
  17 #include <linux/uaccess.h>
  18
  19 #include <xen/xen.h>
  20 #include <xen/grant_table.h>
  21
  22 #include "gntdev-common.h"
  23 #include "gntdev-dmabuf.h"
  24
  25 #ifndef GRANT_INVALID_REF
  26 /*
  27  * Note on usage of grant reference 0 as invalid grant reference:
  28  * grant reference 0 is valid, but never exposed to a driver,
  29  * because of the fact it is already in use/reserved by the PV console.
  30  */
  31 #define GRANT_INVALID_REF       0
  32 #endif
  33
  34 struct gntdev_dmabuf {
  35         struct gntdev_dmabuf_priv *priv;
  36         struct dma_buf *dmabuf;
  37         struct list_head next;
  38         int fd;
  39
  40         union {
  41                 struct {
  42                         /* Exported buffers are reference counted. */
  43                         struct kref refcount;
  44
  45                         struct gntdev_priv *priv;
  46                         struct gntdev_grant_map *map;
  47                 } exp;
  48                 struct {
  49                         /* Granted references of the imported buffer. */
  50                         grant_ref_t *refs;
  51                         /* Scatter-gather table of the imported buffer. */
  52                         struct sg_table *sgt;
  53                         /* dma-buf attachment of the imported buffer. */
  54                         struct dma_buf_attachment *attach;
  55                 } imp;
  56         } u;
  57
  58         /* Number of pages this buffer has. */
  59         int nr_pages;
  60         /* Pages of this buffer (only for dma-buf export). */
  61         struct page **pages;
  62 };
  63
  64 struct gntdev_dmabuf_wait_obj {
  65         struct list_head next;
  66         struct gntdev_dmabuf *gntdev_dmabuf;
  67         struct completion completion;
  68 };
  69
  70 struct gntdev_dmabuf_attachment {
  71         struct sg_table *sgt;
  72         enum dma_data_direction dir;
  73 };
  74
  75 struct gntdev_dmabuf_priv {
  76         /* List of exported DMA buffers. */
  77         struct list_head exp_list;
  78         /* List of wait objects. */
  79         struct list_head exp_wait_list;
  80         /* List of imported DMA buffers. */
  81         struct list_head imp_list;
  82         /* This is the lock which protects dma_buf_xxx lists. */
  83         struct mutex lock;
  84         /*
  85          * We reference this file while exporting dma-bufs, so
  86          * the grant device context is not destroyed while there are
  87          * external users alive.
  88          */
  89         struct file *filp;
  90 };
  91
  92 /* DMA buffer export support. */
  93
  94 /* Implementation of wait for exported DMA buffer to be released. */
  95
  96 static void dmabuf_exp_release(struct kref *kref);
  97
  98 static struct gntdev_dmabuf_wait_obj *
  99 dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv,
 100                         struct gntdev_dmabuf *gntdev_dmabuf)
 101 {
 102         struct gntdev_dmabuf_wait_obj *obj;
 103
 104         obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 105         if (!obj)
 106                 return ERR_PTR(-ENOMEM);
 107
 108         init_completion(&obj->completion);
 109         obj->gntdev_dmabuf = gntdev_dmabuf;
 110
 111         mutex_lock(&priv->lock);
 112         list_add(&obj->next, &priv->exp_wait_list);
 113         /* Put our reference and wait for gntdev_dmabuf's release to fire. */
 114         kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
 115         mutex_unlock(&priv->lock);
 116         return obj;
 117 }
 118
 119 static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv,
 120                                      struct gntdev_dmabuf_wait_obj *obj)
 121 {
 122         mutex_lock(&priv->lock);
 123         list_del(&obj->next);
 124         mutex_unlock(&priv->lock);
 125         kfree(obj);
 126 }
 127
 128 static int dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj *obj,
 129                                     u32 wait_to_ms)
 130 {
 131         if (wait_for_completion_timeout(&obj->completion,
 132                         msecs_to_jiffies(wait_to_ms)) <= 0)
 133                 return -ETIMEDOUT;
 134
 135         return 0;
 136 }
 137
 138 static void dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv *priv,
 139                                        struct gntdev_dmabuf *gntdev_dmabuf)
 140 {
 141         struct gntdev_dmabuf_wait_obj *obj;
 142
 143         list_for_each_entry(obj, &priv->exp_wait_list, next)
 144                 if (obj->gntdev_dmabuf == gntdev_dmabuf) {
 145                         pr_debug("Found gntdev_dmabuf in the wait list, wake\n");
 146                         complete_all(&obj->completion);
 147                         break;
 148                 }
 149 }
 150
 151 static struct gntdev_dmabuf *
 152 dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv *priv, int fd)
 153 {
 154         struct gntdev_dmabuf *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
 155
 156         mutex_lock(&priv->lock);
 157         list_for_each_entry(gntdev_dmabuf, &priv->exp_list, next)
 158                 if (gntdev_dmabuf->fd == fd) {
 159                         pr_debug("Found gntdev_dmabuf in the wait list\n");
 160                         kref_get(&gntdev_dmabuf->u.exp.refcount);
 161                         ret = gntdev_dmabuf;
 162                         break;
 163                 }
 164         mutex_unlock(&priv->lock);
 165         return ret;
 166 }
 167
 168 static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
 169                                     int wait_to_ms)
 170 {
 171         struct gntdev_dmabuf *gntdev_dmabuf;
 172         struct gntdev_dmabuf_wait_obj *obj;
 173         int ret;
 174
 175         pr_debug("Will wait for dma-buf with fd %d\n", fd);
 176         /*
 177          * Try to find the DMA buffer: if not found means that
 178          * either the buffer has already been released or file descriptor
 179          * provided is wrong.
 180          */
 181         gntdev_dmabuf = dmabuf_exp_wait_obj_get_dmabuf(priv, fd);
 182         if (IS_ERR(gntdev_dmabuf))
 183                 return PTR_ERR(gntdev_dmabuf);
 184
 185         /*
 186          * gntdev_dmabuf still exists and is reference count locked by us now,
 187          * so prepare to wait: allocate wait object and add it to the wait list,
 188          * so we can find it on release.
 189          */
 190         obj = dmabuf_exp_wait_obj_new(priv, gntdev_dmabuf);
 191         if (IS_ERR(obj))
 192                 return PTR_ERR(obj);
 193
 194         ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms);
 195         dmabuf_exp_wait_obj_free(priv, obj);
 196         return ret;
 197 }
 198
 199 /* DMA buffer export support. */
 200
 201 static struct sg_table *
 202 dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages)
 203 {
 204         struct sg_table *sgt;
 205         int ret;
 206
 207         sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
 208         if (!sgt) {
 209                 ret = -ENOMEM;
 210                 goto out;
 211         }
 212
 213         ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0,
 214                                         nr_pages << PAGE_SHIFT,
 215                                         GFP_KERNEL);
 216         if (ret)
 217                 goto out;
 218
 219         return sgt;
 220
 221 out:
 222         kfree(sgt);
 223         return ERR_PTR(ret);
 224 }
 225
 226 static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf,
 227                                  struct dma_buf_attachment *attach)
 228 {
 229         struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach;
 230
 231         gntdev_dmabuf_attach = kzalloc(sizeof(*gntdev_dmabuf_attach),
 232                                        GFP_KERNEL);
 233         if (!gntdev_dmabuf_attach)
 234                 return -ENOMEM;
 235
 236         gntdev_dmabuf_attach->dir = DMA_NONE;
 237         attach->priv = gntdev_dmabuf_attach;
 238         return 0;
 239 }
 240
 241 static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf,
 242                                   struct dma_buf_attachment *attach)
 243 {
 244         struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
 245
 246         if (gntdev_dmabuf_attach) {
 247                 struct sg_table *sgt = gntdev_dmabuf_attach->sgt;
 248
 249                 if (sgt) {
 250                         if (gntdev_dmabuf_attach->dir != DMA_NONE)
 251                                 dma_unmap_sgtable(attach->dev, sgt,
 252                                                   gntdev_dmabuf_attach->dir,
 253                                                   DMA_ATTR_SKIP_CPU_SYNC);
 254                         sg_free_table(sgt);
 255                 }
 256
 257                 kfree(sgt);
 258                 kfree(gntdev_dmabuf_attach);
 259                 attach->priv = NULL;
 260         }
 261 }
 262
 263 static struct sg_table *
 264 dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach,
 265                            enum dma_data_direction dir)
 266 {
 267         struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
 268         struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv;
 269         struct sg_table *sgt;
 270
 271         pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages,
 272                  attach->dev);
 273
 274         if (dir == DMA_NONE || !gntdev_dmabuf_attach)
 275                 return ERR_PTR(-EINVAL);
 276
 277         /* Return the cached mapping when possible. */
 278         if (gntdev_dmabuf_attach->dir == dir)
 279                 return gntdev_dmabuf_attach->sgt;
 280
 281         /*
 282          * Two mappings with different directions for the same attachment are
 283          * not allowed.
 284          */
 285         if (gntdev_dmabuf_attach->dir != DMA_NONE)
 286                 return ERR_PTR(-EBUSY);
 287
 288         sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages,
 289                                   gntdev_dmabuf->nr_pages);
 290         if (!IS_ERR(sgt)) {
 291                 if (dma_map_sgtable(attach->dev, sgt, dir,
 292                                     DMA_ATTR_SKIP_CPU_SYNC)) {
 293                         sg_free_table(sgt);
 294                         kfree(sgt);
 295                         sgt = ERR_PTR(-ENOMEM);
 296                 } else {
 297                         gntdev_dmabuf_attach->sgt = sgt;
 298                         gntdev_dmabuf_attach->dir = dir;
 299                 }
 300         }
 301         if (IS_ERR(sgt))
 302                 pr_debug("Failed to map sg table for dev %p\n", attach->dev);
 303         return sgt;
 304 }
 305
 306 static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach,
 307                                          struct sg_table *sgt,
 308                                          enum dma_data_direction dir)
 309 {
 310         /* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */
 311 }
 312
 313 static void dmabuf_exp_release(struct kref *kref)
 314 {
 315         struct gntdev_dmabuf *gntdev_dmabuf =
 316                 container_of(kref, struct gntdev_dmabuf, u.exp.refcount);
 317
 318         dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf);
 319         list_del(&gntdev_dmabuf->next);
 320         fput(gntdev_dmabuf->priv->filp);
 321         kfree(gntdev_dmabuf);
 322 }
 323
 324 static void dmabuf_exp_remove_map(struct gntdev_priv *priv,
 325                                   struct gntdev_grant_map *map)
 326 {
 327         mutex_lock(&priv->lock);
 328         list_del(&map->next);
 329         gntdev_put_map(NULL /* already removed */, map);
 330         mutex_unlock(&priv->lock);
 331 }
 332
 333 static void dmabuf_exp_ops_release(struct dma_buf *dma_buf)
 334 {
 335         struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv;
 336         struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv;
 337
 338         dmabuf_exp_remove_map(gntdev_dmabuf->u.exp.priv,
 339                               gntdev_dmabuf->u.exp.map);
 340         mutex_lock(&priv->lock);
 341         kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
 342         mutex_unlock(&priv->lock);
 343 }
 344
 345 static const struct dma_buf_ops dmabuf_exp_ops =  {
 346         .attach = dmabuf_exp_ops_attach,
 347         .detach = dmabuf_exp_ops_detach,
 348         .map_dma_buf = dmabuf_exp_ops_map_dma_buf,
 349         .unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf,
 350         .release = dmabuf_exp_ops_release,
 351 };
 352
 353 struct gntdev_dmabuf_export_args {
 354         struct gntdev_priv *priv;
 355         struct gntdev_grant_map *map;
 356         struct gntdev_dmabuf_priv *dmabuf_priv;
 357         struct device *dev;
 358         int count;
 359         struct page **pages;
 360         u32 fd;
 361 };
 362
 363 static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args)
 364 {
 365         DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 366         struct gntdev_dmabuf *gntdev_dmabuf;
 367         int ret;
 368
 369         gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL);
 370         if (!gntdev_dmabuf)
 371                 return -ENOMEM;
 372
 373         kref_init(&gntdev_dmabuf->u.exp.refcount);
 374
 375         gntdev_dmabuf->priv = args->dmabuf_priv;
 376         gntdev_dmabuf->nr_pages = args->count;
 377         gntdev_dmabuf->pages = args->pages;
 378         gntdev_dmabuf->u.exp.priv = args->priv;
 379         gntdev_dmabuf->u.exp.map = args->map;
 380
 381         exp_info.exp_name = KBUILD_MODNAME;
 382         if (args->dev->driver && args->dev->driver->owner)
 383                 exp_info.owner = args->dev->driver->owner;
 384         else
 385                 exp_info.owner = THIS_MODULE;
 386         exp_info.ops = &dmabuf_exp_ops;
 387         exp_info.size = args->count << PAGE_SHIFT;
 388         exp_info.flags = O_RDWR;
 389         exp_info.priv = gntdev_dmabuf;
 390
 391         gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info);
 392         if (IS_ERR(gntdev_dmabuf->dmabuf)) {
 393                 ret = PTR_ERR(gntdev_dmabuf->dmabuf);
 394                 gntdev_dmabuf->dmabuf = NULL;
 395                 goto fail;
 396         }
 397
 398         ret = dma_buf_fd(gntdev_dmabuf->dmabuf, O_CLOEXEC);
 399         if (ret < 0)
 400                 goto fail;
 401
 402         gntdev_dmabuf->fd = ret;
 403         args->fd = ret;
 404
 405         pr_debug("Exporting DMA buffer with fd %d\n", ret);
 406
 407         mutex_lock(&args->dmabuf_priv->lock);
 408         list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list);
 409         mutex_unlock(&args->dmabuf_priv->lock);
 410         get_file(gntdev_dmabuf->priv->filp);
 411         return 0;
 412
 413 fail:
 414         if (gntdev_dmabuf->dmabuf)
 415                 dma_buf_put(gntdev_dmabuf->dmabuf);
 416         kfree(gntdev_dmabuf);
 417         return ret;
 418 }
 419
 420 static struct gntdev_grant_map *
 421 dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
 422                                  int count)
 423 {
 424         struct gntdev_grant_map *map;
 425
 426         if (unlikely(gntdev_test_page_count(count)))
 427                 return ERR_PTR(-EINVAL);
 428
 429         if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) &&
 430             (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) {
 431                 pr_debug("Wrong dma-buf flags: 0x%x\n", dmabuf_flags);
 432                 return ERR_PTR(-EINVAL);
 433         }
 434
 435         map = gntdev_alloc_map(priv, count, dmabuf_flags);
 436         if (!map)
 437                 return ERR_PTR(-ENOMEM);
 438
 439         return map;
 440 }
 441
 442 static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
 443                                 int count, u32 domid, u32 *refs, u32 *fd)
 444 {
 445         struct gntdev_grant_map *map;
 446         struct gntdev_dmabuf_export_args args;
 447         int i, ret;
 448
 449         map = dmabuf_exp_alloc_backing_storage(priv, flags, count);
 450         if (IS_ERR(map))
 451                 return PTR_ERR(map);
 452
 453         for (i = 0; i < count; i++) {
 454                 map->grants[i].domid = domid;
 455                 map->grants[i].ref = refs[i];
 456         }
 457
 458         mutex_lock(&priv->lock);
 459         gntdev_add_map(priv, map);
 460         mutex_unlock(&priv->lock);
 461
 462         map->flags |= GNTMAP_host_map;
 463 #if defined(CONFIG_X86)
 464         map->flags |= GNTMAP_device_map;
 465 #endif
 466
 467         ret = gntdev_map_grant_pages(map);
 468         if (ret < 0)
 469                 goto out;
 470
 471         args.priv = priv;
 472         args.map = map;
 473         args.dev = priv->dma_dev;
 474         args.dmabuf_priv = priv->dmabuf_priv;
 475         args.count = map->count;
 476         args.pages = map->pages;
 477         args.fd = -1; /* Shut up unnecessary gcc warning for i386 */
 478
 479         ret = dmabuf_exp_from_pages(&args);
 480         if (ret < 0)
 481                 goto out;
 482
 483         *fd = args.fd;
 484         return 0;
 485
 486 out:
 487         dmabuf_exp_remove_map(priv, map);
 488         return ret;
 489 }
 490
 491 /* DMA buffer import support. */
 492
 493 static int
 494 dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
 495                                 int count, int domid)
 496 {
 497         grant_ref_t priv_gref_head;
 498         int i, ret;
 499
 500         ret = gnttab_alloc_grant_references(count, &priv_gref_head);
 501         if (ret < 0) {
 502                 pr_debug("Cannot allocate grant references, ret %d\n", ret);
 503                 return ret;
 504         }
 505
 506         for (i = 0; i < count; i++) {
 507                 int cur_ref;
 508
 509                 cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
 510                 if (cur_ref < 0) {
 511                         ret = cur_ref;
 512                         pr_debug("Cannot claim grant reference, ret %d\n", ret);
 513                         goto out;
 514                 }
 515
 516                 gnttab_grant_foreign_access_ref(cur_ref, domid,
 517                                                 gfns[i], 0);
 518                 refs[i] = cur_ref;
 519         }
 520
 521         return 0;
 522
 523 out:
 524         gnttab_free_grant_references(priv_gref_head);
 525         return ret;
 526 }
 527
 528 static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
 529 {
 530         int i;
 531
 532         for (i = 0; i < count; i++)
 533                 if (refs[i] != GRANT_INVALID_REF)
 534                         gnttab_end_foreign_access(refs[i], 0, 0UL);
 535 }
 536
 537 static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
 538 {
 539         kfree(gntdev_dmabuf->u.imp.refs);
 540         kfree(gntdev_dmabuf);
 541 }
 542
 543 static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
 544 {
 545         struct gntdev_dmabuf *gntdev_dmabuf;
 546         int i;
 547
 548         gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL);
 549         if (!gntdev_dmabuf)
 550                 goto fail_no_free;
 551
 552         gntdev_dmabuf->u.imp.refs = kcalloc(count,
 553                                             sizeof(gntdev_dmabuf->u.imp.refs[0]),
 554                                             GFP_KERNEL);
 555         if (!gntdev_dmabuf->u.imp.refs)
 556                 goto fail;
 557
 558         gntdev_dmabuf->nr_pages = count;
 559
 560         for (i = 0; i < count; i++)
 561                 gntdev_dmabuf->u.imp.refs[i] = GRANT_INVALID_REF;
 562
 563         return gntdev_dmabuf;
 564
 565 fail:
 566         dmabuf_imp_free_storage(gntdev_dmabuf);
 567 fail_no_free:
 568         return ERR_PTR(-ENOMEM);
 569 }
 570
 571 static struct gntdev_dmabuf *
 572 dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
 573                    int fd, int count, int domid)
 574 {
 575         struct gntdev_dmabuf *gntdev_dmabuf, *ret;
 576         struct dma_buf *dma_buf;
 577         struct dma_buf_attachment *attach;
 578         struct sg_table *sgt;
 579         struct sg_dma_page_iter sg_iter;
 580         unsigned long *gfns;
 581         int i;
 582
 583         dma_buf = dma_buf_get(fd);
 584         if (IS_ERR(dma_buf))
 585                 return ERR_CAST(dma_buf);
 586
 587         gntdev_dmabuf = dmabuf_imp_alloc_storage(count);
 588         if (IS_ERR(gntdev_dmabuf)) {
 589                 ret = gntdev_dmabuf;
 590                 goto fail_put;
 591         }
 592
 593         gntdev_dmabuf->priv = priv;
 594         gntdev_dmabuf->fd = fd;
 595
 596         attach = dma_buf_attach(dma_buf, dev);
 597         if (IS_ERR(attach)) {
 598                 ret = ERR_CAST(attach);
 599                 goto fail_free_obj;
 600         }
 601
 602         gntdev_dmabuf->u.imp.attach = attach;
 603
 604         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
 605         if (IS_ERR(sgt)) {
 606                 ret = ERR_CAST(sgt);
 607                 goto fail_detach;
 608         }
 609
 610         /* Check that we have zero offset. */
 611         if (sgt->sgl->offset) {
 612                 ret = ERR_PTR(-EINVAL);
 613                 pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n",
 614                          sgt->sgl->offset);
 615                 goto fail_unmap;
 616         }
 617
 618         /* Check number of pages that imported buffer has. */
 619         if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) {
 620                 ret = ERR_PTR(-EINVAL);
 621                 pr_debug("DMA buffer has %zu pages, user-space expects %d\n",
 622                          attach->dmabuf->size, gntdev_dmabuf->nr_pages);
 623                 goto fail_unmap;
 624         }
 625
 626         gntdev_dmabuf->u.imp.sgt = sgt;
 627
 628         gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
 629         if (!gfns) {
 630                 ret = ERR_PTR(-ENOMEM);
 631                 goto fail_unmap;
 632         }
 633
 634         /*
 635          * Now convert sgt to array of gfns without accessing underlying pages.
 636          * It is not allowed to access the underlying struct page of an sg table
 637          * exported by DMA-buf, but since we deal with special Xen dma device here
 638          * (not a normal physical one) look at the dma addresses in the sg table
 639          * and then calculate gfns directly from them.
 640          */
 641         i = 0;
 642         for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
 643                 dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
 644                 unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
 645
 646                 gfns[i++] = pfn_to_gfn(pfn);
 647         }
 648
 649         ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
 650                                                       gntdev_dmabuf->u.imp.refs,
 651                                                       count, domid));
 652         kfree(gfns);
 653         if (IS_ERR(ret))
 654                 goto fail_end_access;
 655
 656         pr_debug("Imported DMA buffer with fd %d\n", fd);
 657
 658         mutex_lock(&priv->lock);
 659         list_add(&gntdev_dmabuf->next, &priv->imp_list);
 660         mutex_unlock(&priv->lock);
 661
 662         return gntdev_dmabuf;
 663
 664 fail_end_access:
 665         dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, count);
 666 fail_unmap:
 667         dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
 668 fail_detach:
 669         dma_buf_detach(dma_buf, attach);
 670 fail_free_obj:
 671         dmabuf_imp_free_storage(gntdev_dmabuf);
 672 fail_put:
 673         dma_buf_put(dma_buf);
 674         return ret;
 675 }
 676
 677 /*
 678  * Find the hyper dma-buf by its file descriptor and remove
 679  * it from the buffer's list.
 680  */
 681 static struct gntdev_dmabuf *
 682 dmabuf_imp_find_unlink(struct gntdev_dmabuf_priv *priv, int fd)
 683 {
 684         struct gntdev_dmabuf *q, *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
 685
 686         mutex_lock(&priv->lock);
 687         list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next) {
 688                 if (gntdev_dmabuf->fd == fd) {
 689                         pr_debug("Found gntdev_dmabuf in the import list\n");
 690                         ret = gntdev_dmabuf;
 691                         list_del(&gntdev_dmabuf->next);
 692                         break;
 693                 }
 694         }
 695         mutex_unlock(&priv->lock);
 696         return ret;
 697 }
 698
 699 static int dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
 700 {
 701         struct gntdev_dmabuf *gntdev_dmabuf;
 702         struct dma_buf_attachment *attach;
 703         struct dma_buf *dma_buf;
 704
 705         gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
 706         if (IS_ERR(gntdev_dmabuf))
 707                 return PTR_ERR(gntdev_dmabuf);
 708
 709         pr_debug("Releasing DMA buffer with fd %d\n", fd);
 710
 711         dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
 712                                       gntdev_dmabuf->nr_pages);
 713
 714         attach = gntdev_dmabuf->u.imp.attach;
 715
 716         if (gntdev_dmabuf->u.imp.sgt)
 717                 dma_buf_unmap_attachment(attach, gntdev_dmabuf->u.imp.sgt,
 718                                          DMA_BIDIRECTIONAL);
 719         dma_buf = attach->dmabuf;
 720         dma_buf_detach(attach->dmabuf, attach);
 721         dma_buf_put(dma_buf);
 722
 723         dmabuf_imp_free_storage(gntdev_dmabuf);
 724         return 0;
 725 }
 726
 727 static void dmabuf_imp_release_all(struct gntdev_dmabuf_priv *priv)
 728 {
 729         struct gntdev_dmabuf *q, *gntdev_dmabuf;
 730
 731         list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next)
 732                 dmabuf_imp_release(priv, gntdev_dmabuf->fd);
 733 }
 734
 735 /* DMA buffer IOCTL support. */
 736
 737 long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv, int use_ptemod,
 738                                        struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
 739 {
 740         struct ioctl_gntdev_dmabuf_exp_from_refs op;
 741         u32 *refs;
 742         long ret;
 743
 744         if (use_ptemod) {
 745                 pr_debug("Cannot provide dma-buf: use_ptemode %d\n",
 746                          use_ptemod);
 747                 return -EINVAL;
 748         }
 749
 750         if (copy_from_user(&op, u, sizeof(op)) != 0)
 751                 return -EFAULT;
 752
 753         if (unlikely(gntdev_test_page_count(op.count)))
 754                 return -EINVAL;
 755
 756         refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
 757         if (!refs)
 758                 return -ENOMEM;
 759
 760         if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
 761                 ret = -EFAULT;
 762                 goto out;
 763         }
 764
 765         ret = dmabuf_exp_from_refs(priv, op.flags, op.count,
 766                                    op.domid, refs, &op.fd);
 767         if (ret)
 768                 goto out;
 769
 770         if (copy_to_user(u, &op, sizeof(op)) != 0)
 771                 ret = -EFAULT;
 772
 773 out:
 774         kfree(refs);
 775         return ret;
 776 }
 777
 778 long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
 779                                            struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
 780 {
 781         struct ioctl_gntdev_dmabuf_exp_wait_released op;
 782
 783         if (copy_from_user(&op, u, sizeof(op)) != 0)
 784                 return -EFAULT;
 785
 786         return dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
 787                                         op.wait_to_ms);
 788 }
 789
 790 long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
 791                                      struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
 792 {
 793         struct ioctl_gntdev_dmabuf_imp_to_refs op;
 794         struct gntdev_dmabuf *gntdev_dmabuf;
 795         long ret;
 796
 797         if (copy_from_user(&op, u, sizeof(op)) != 0)
 798                 return -EFAULT;
 799
 800         if (unlikely(gntdev_test_page_count(op.count)))
 801                 return -EINVAL;
 802
 803         gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
 804                                            priv->dma_dev, op.fd,
 805                                            op.count, op.domid);
 806         if (IS_ERR(gntdev_dmabuf))
 807                 return PTR_ERR(gntdev_dmabuf);
 808
 809         if (copy_to_user(u->refs, gntdev_dmabuf->u.imp.refs,
 810                          sizeof(*u->refs) * op.count) != 0) {
 811                 ret = -EFAULT;
 812                 goto out_release;
 813         }
 814         return 0;
 815
 816 out_release:
 817         dmabuf_imp_release(priv->dmabuf_priv, op.fd);
 818         return ret;
 819 }
 820
 821 long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
 822                                      struct ioctl_gntdev_dmabuf_imp_release __user *u)
 823 {
 824         struct ioctl_gntdev_dmabuf_imp_release op;
 825
 826         if (copy_from_user(&op, u, sizeof(op)) != 0)
 827                 return -EFAULT;
 828
 829         return dmabuf_imp_release(priv->dmabuf_priv, op.fd);
 830 }
 831
 832 struct gntdev_dmabuf_priv *gntdev_dmabuf_init(struct file *filp)
 833 {
 834         struct gntdev_dmabuf_priv *priv;
 835
 836         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 837         if (!priv)
 838                 return ERR_PTR(-ENOMEM);
 839
 840         mutex_init(&priv->lock);
 841         INIT_LIST_HEAD(&priv->exp_list);
 842         INIT_LIST_HEAD(&priv->exp_wait_list);
 843         INIT_LIST_HEAD(&priv->imp_list);
 844
 845         priv->filp = filp;
 846
 847         return priv;
 848 }
 849
 850 void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
 851 {
 852         dmabuf_imp_release_all(priv);
 853         kfree(priv);
 854 }