root/drivers/gpu/drm/i915/gem/i915_gem_shmem.c

DEFINITIONS

1. check_release_pagevec
2. shmem_get_pages
3. shmem_truncate
4. shmem_writeback
5. __i915_gem_object_release_shmem
6. shmem_put_pages
7. shmem_pwrite
8. shmem_release
9. create_shmem
10. i915_gem_object_create_shmem
11. i915_gem_object_create_shmem_from_data

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2014-2016 Intel Corporation
   5  */
   6 
   7 #include <linux/pagevec.h>
   8 #include <linux/swap.h>
   9 
  10 #include "i915_drv.h"
  11 #include "i915_gem_object.h"
  12 #include "i915_scatterlist.h"
  13 #include "i915_trace.h"
  14 
  15 /*
  16  * Move pages to appropriate lru and release the pagevec, decrementing the
  17  * ref count of those pages.
  18  */
  19 static void check_release_pagevec(struct pagevec *pvec)
  20 {
  21         check_move_unevictable_pages(pvec);
  22         __pagevec_release(pvec);
  23         cond_resched();
  24 }
  25 
  26 static int shmem_get_pages(struct drm_i915_gem_object *obj)
  27 {
  28         struct drm_i915_private *i915 = to_i915(obj->base.dev);
  29         const unsigned long page_count = obj->base.size / PAGE_SIZE;
  30         unsigned long i;
  31         struct address_space *mapping;
  32         struct sg_table *st;
  33         struct scatterlist *sg;
  34         struct sgt_iter sgt_iter;
  35         struct page *page;
  36         unsigned long last_pfn = 0;     /* suppress gcc warning */
  37         unsigned int max_segment = i915_sg_segment_size();
  38         unsigned int sg_page_sizes;
  39         struct pagevec pvec;
  40         gfp_t noreclaim;
  41         int ret;
  42 
  43         /*
  44          * Assert that the object is not currently in any GPU domain. As it
  45          * wasn't in the GTT, there shouldn't be any way it could have been in
  46          * a GPU cache
  47          */
  48         GEM_BUG_ON(obj->read_domains & I915_GEM_GPU_DOMAINS);
  49         GEM_BUG_ON(obj->write_domain & I915_GEM_GPU_DOMAINS);
  50 
  51         /*
  52          * If there's no chance of allocating enough pages for the whole
  53          * object, bail early.
  54          */
  55         if (page_count > totalram_pages())
  56                 return -ENOMEM;
  57 
  58         st = kmalloc(sizeof(*st), GFP_KERNEL);
  59         if (!st)
  60                 return -ENOMEM;
  61 
  62 rebuild_st:
  63         if (sg_alloc_table(st, page_count, GFP_KERNEL)) {
  64                 kfree(st);
  65                 return -ENOMEM;
  66         }
  67 
  68         /*
  69          * Get the list of pages out of our struct file.  They'll be pinned
  70          * at this point until we release them.
  71          *
  72          * Fail silently without starting the shrinker
  73          */
  74         mapping = obj->base.filp->f_mapping;
  75         mapping_set_unevictable(mapping);
  76         noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
  77         noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
  78 
  79         sg = st->sgl;
  80         st->nents = 0;
  81         sg_page_sizes = 0;
  82         for (i = 0; i < page_count; i++) {
  83                 const unsigned int shrink[] = {
  84                         I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
  85                         0,
  86                 }, *s = shrink;
  87                 gfp_t gfp = noreclaim;
  88 
  89                 do {
  90                         cond_resched();
  91                         page = shmem_read_mapping_page_gfp(mapping, i, gfp);
  92                         if (!IS_ERR(page))
  93                                 break;
  94 
  95                         if (!*s) {
  96                                 ret = PTR_ERR(page);
  97                                 goto err_sg;
  98                         }
  99 
 100                         i915_gem_shrink(i915, 2 * page_count, NULL, *s++);
 101 
 102                         /*
 103                          * We've tried hard to allocate the memory by reaping
 104                          * our own buffer, now let the real VM do its job and
 105                          * go down in flames if truly OOM.
 106                          *
 107                          * However, since graphics tend to be disposable,
 108                          * defer the oom here by reporting the ENOMEM back
 109                          * to userspace.
 110                          */
 111                         if (!*s) {
 112                                 /* reclaim and warn, but no oom */
 113                                 gfp = mapping_gfp_mask(mapping);
 114 
 115                                 /*
 116                                  * Our bo are always dirty and so we require
 117                                  * kswapd to reclaim our pages (direct reclaim
 118                                  * does not effectively begin pageout of our
 119                                  * buffers on its own). However, direct reclaim
 120                                  * only waits for kswapd when under allocation
 121                                  * congestion. So as a result __GFP_RECLAIM is
 122                                  * unreliable and fails to actually reclaim our
 123                                  * dirty pages -- unless you try over and over
 124                                  * again with !__GFP_NORETRY. However, we still
 125                                  * want to fail this allocation rather than
 126                                  * trigger the out-of-memory killer and for
 127                                  * this we want __GFP_RETRY_MAYFAIL.
 128                                  */
 129                                 gfp |= __GFP_RETRY_MAYFAIL;
 130                         }
 131                 } while (1);
 132 
 133                 if (!i ||
 134                     sg->length >= max_segment ||
 135                     page_to_pfn(page) != last_pfn + 1) {
 136                         if (i) {
 137                                 sg_page_sizes |= sg->length;
 138                                 sg = sg_next(sg);
 139                         }
 140                         st->nents++;
 141                         sg_set_page(sg, page, PAGE_SIZE, 0);
 142                 } else {
 143                         sg->length += PAGE_SIZE;
 144                 }
 145                 last_pfn = page_to_pfn(page);
 146 
 147                 /* Check that the i965g/gm workaround works. */
 148                 WARN_ON((gfp & __GFP_DMA32) && (last_pfn >= 0x00100000UL));
 149         }
 150         if (sg) { /* loop terminated early; short sg table */
 151                 sg_page_sizes |= sg->length;
 152                 sg_mark_end(sg);
 153         }
 154 
 155         /* Trim unused sg entries to avoid wasting memory. */
 156         i915_sg_trim(st);
 157 
 158         ret = i915_gem_gtt_prepare_pages(obj, st);
 159         if (ret) {
 160                 /*
 161                  * DMA remapping failed? One possible cause is that
 162                  * it could not reserve enough large entries, asking
 163                  * for PAGE_SIZE chunks instead may be helpful.
 164                  */
 165                 if (max_segment > PAGE_SIZE) {
 166                         for_each_sgt_page(page, sgt_iter, st)
 167                                 put_page(page);
 168                         sg_free_table(st);
 169 
 170                         max_segment = PAGE_SIZE;
 171                         goto rebuild_st;
 172                 } else {
 173                         dev_warn(&i915->drm.pdev->dev,
 174                                  "Failed to DMA remap %lu pages\n",
 175                                  page_count);
 176                         goto err_pages;
 177                 }
 178         }
 179 
 180         if (i915_gem_object_needs_bit17_swizzle(obj))
 181                 i915_gem_object_do_bit_17_swizzle(obj, st);
 182 
 183         __i915_gem_object_set_pages(obj, st, sg_page_sizes);
 184 
 185         return 0;
 186 
 187 err_sg:
 188         sg_mark_end(sg);
 189 err_pages:
 190         mapping_clear_unevictable(mapping);
 191         pagevec_init(&pvec);
 192         for_each_sgt_page(page, sgt_iter, st) {
 193                 if (!pagevec_add(&pvec, page))
 194                         check_release_pagevec(&pvec);
 195         }
 196         if (pagevec_count(&pvec))
 197                 check_release_pagevec(&pvec);
 198         sg_free_table(st);
 199         kfree(st);
 200 
 201         /*
 202          * shmemfs first checks if there is enough memory to allocate the page
 203          * and reports ENOSPC should there be insufficient, along with the usual
 204          * ENOMEM for a genuine allocation failure.
 205          *
 206          * We use ENOSPC in our driver to mean that we have run out of aperture
 207          * space and so want to translate the error from shmemfs back to our
 208          * usual understanding of ENOMEM.
 209          */
 210         if (ret == -ENOSPC)
 211                 ret = -ENOMEM;
 212 
 213         return ret;
 214 }
 215 
 216 static void
 217 shmem_truncate(struct drm_i915_gem_object *obj)
 218 {
 219         /*
 220          * Our goal here is to return as much of the memory as
 221          * is possible back to the system as we are called from OOM.
 222          * To do this we must instruct the shmfs to drop all of its
 223          * backing pages, *now*.
 224          */
 225         shmem_truncate_range(file_inode(obj->base.filp), 0, (loff_t)-1);
 226         obj->mm.madv = __I915_MADV_PURGED;
 227         obj->mm.pages = ERR_PTR(-EFAULT);
 228 }
 229 
 230 static void
 231 shmem_writeback(struct drm_i915_gem_object *obj)
 232 {
 233         struct address_space *mapping;
 234         struct writeback_control wbc = {
 235                 .sync_mode = WB_SYNC_NONE,
 236                 .nr_to_write = SWAP_CLUSTER_MAX,
 237                 .range_start = 0,
 238                 .range_end = LLONG_MAX,
 239                 .for_reclaim = 1,
 240         };
 241         unsigned long i;
 242 
 243         /*
 244          * Leave mmapings intact (GTT will have been revoked on unbinding,
 245          * leaving only CPU mmapings around) and add those pages to the LRU
 246          * instead of invoking writeback so they are aged and paged out
 247          * as normal.
 248          */
 249         mapping = obj->base.filp->f_mapping;
 250 
 251         /* Begin writeback on each dirty page */
 252         for (i = 0; i < obj->base.size >> PAGE_SHIFT; i++) {
 253                 struct page *page;
 254 
 255                 page = find_lock_entry(mapping, i);
 256                 if (!page || xa_is_value(page))
 257                         continue;
 258 
 259                 if (!page_mapped(page) && clear_page_dirty_for_io(page)) {
 260                         int ret;
 261 
 262                         SetPageReclaim(page);
 263                         ret = mapping->a_ops->writepage(page, &wbc);
 264                         if (!PageWriteback(page))
 265                                 ClearPageReclaim(page);
 266                         if (!ret)
 267                                 goto put;
 268                 }
 269                 unlock_page(page);
 270 put:
 271                 put_page(page);
 272         }
 273 }
 274 
 275 void
 276 __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
 277                                 struct sg_table *pages,
 278                                 bool needs_clflush)
 279 {
 280         GEM_BUG_ON(obj->mm.madv == __I915_MADV_PURGED);
 281 
 282         if (obj->mm.madv == I915_MADV_DONTNEED)
 283                 obj->mm.dirty = false;
 284 
 285         if (needs_clflush &&
 286             (obj->read_domains & I915_GEM_DOMAIN_CPU) == 0 &&
 287             !(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
 288                 drm_clflush_sg(pages);
 289 
 290         __start_cpu_write(obj);
 291 }
 292 
 293 static void
 294 shmem_put_pages(struct drm_i915_gem_object *obj, struct sg_table *pages)
 295 {
 296         struct sgt_iter sgt_iter;
 297         struct pagevec pvec;
 298         struct page *page;
 299 
 300         __i915_gem_object_release_shmem(obj, pages, true);
 301 
 302         i915_gem_gtt_finish_pages(obj, pages);
 303 
 304         if (i915_gem_object_needs_bit17_swizzle(obj))
 305                 i915_gem_object_save_bit_17_swizzle(obj, pages);
 306 
 307         mapping_clear_unevictable(file_inode(obj->base.filp)->i_mapping);
 308 
 309         pagevec_init(&pvec);
 310         for_each_sgt_page(page, sgt_iter, pages) {
 311                 if (obj->mm.dirty)
 312                         set_page_dirty(page);
 313 
 314                 if (obj->mm.madv == I915_MADV_WILLNEED)
 315                         mark_page_accessed(page);
 316 
 317                 if (!pagevec_add(&pvec, page))
 318                         check_release_pagevec(&pvec);
 319         }
 320         if (pagevec_count(&pvec))
 321                 check_release_pagevec(&pvec);
 322         obj->mm.dirty = false;
 323 
 324         sg_free_table(pages);
 325         kfree(pages);
 326 }
 327 
 328 static int
 329 shmem_pwrite(struct drm_i915_gem_object *obj,
 330              const struct drm_i915_gem_pwrite *arg)
 331 {
 332         struct address_space *mapping = obj->base.filp->f_mapping;
 333         char __user *user_data = u64_to_user_ptr(arg->data_ptr);
 334         u64 remain, offset;
 335         unsigned int pg;
 336 
 337         /* Caller already validated user args */
 338         GEM_BUG_ON(!access_ok(user_data, arg->size));
 339 
 340         /*
 341          * Before we instantiate/pin the backing store for our use, we
 342          * can prepopulate the shmemfs filp efficiently using a write into
 343          * the pagecache. We avoid the penalty of instantiating all the
 344          * pages, important if the user is just writing to a few and never
 345          * uses the object on the GPU, and using a direct write into shmemfs
 346          * allows it to avoid the cost of retrieving a page (either swapin
 347          * or clearing-before-use) before it is overwritten.
 348          */
 349         if (i915_gem_object_has_pages(obj))
 350                 return -ENODEV;
 351 
 352         if (obj->mm.madv != I915_MADV_WILLNEED)
 353                 return -EFAULT;
 354 
 355         /*
 356          * Before the pages are instantiated the object is treated as being
 357          * in the CPU domain. The pages will be clflushed as required before
 358          * use, and we can freely write into the pages directly. If userspace
 359          * races pwrite with any other operation; corruption will ensue -
 360          * that is userspace's prerogative!
 361          */
 362 
 363         remain = arg->size;
 364         offset = arg->offset;
 365         pg = offset_in_page(offset);
 366 
 367         do {
 368                 unsigned int len, unwritten;
 369                 struct page *page;
 370                 void *data, *vaddr;
 371                 int err;
 372                 char c;
 373 
 374                 len = PAGE_SIZE - pg;
 375                 if (len > remain)
 376                         len = remain;
 377 
 378                 /* Prefault the user page to reduce potential recursion */
 379                 err = __get_user(c, user_data);
 380                 if (err)
 381                         return err;
 382 
 383                 err = __get_user(c, user_data + len - 1);
 384                 if (err)
 385                         return err;
 386 
 387                 err = pagecache_write_begin(obj->base.filp, mapping,
 388                                             offset, len, 0,
 389                                             &page, &data);
 390                 if (err < 0)
 391                         return err;
 392 
 393                 vaddr = kmap_atomic(page);
 394                 unwritten = __copy_from_user_inatomic(vaddr + pg,
 395                                                       user_data,
 396                                                       len);
 397                 kunmap_atomic(vaddr);
 398 
 399                 err = pagecache_write_end(obj->base.filp, mapping,
 400                                           offset, len, len - unwritten,
 401                                           page, data);
 402                 if (err < 0)
 403                         return err;
 404 
 405                 /* We don't handle -EFAULT, leave it to the caller to check */
 406                 if (unwritten)
 407                         return -ENODEV;
 408 
 409                 remain -= len;
 410                 user_data += len;
 411                 offset += len;
 412                 pg = 0;
 413         } while (remain);
 414 
 415         return 0;
 416 }
 417 
 418 static void shmem_release(struct drm_i915_gem_object *obj)
 419 {
 420         fput(obj->base.filp);
 421 }
 422 
 423 const struct drm_i915_gem_object_ops i915_gem_shmem_ops = {
 424         .flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
 425                  I915_GEM_OBJECT_IS_SHRINKABLE,
 426 
 427         .get_pages = shmem_get_pages,
 428         .put_pages = shmem_put_pages,
 429         .truncate = shmem_truncate,
 430         .writeback = shmem_writeback,
 431 
 432         .pwrite = shmem_pwrite,
 433 
 434         .release = shmem_release,
 435 };
 436 
 437 static int create_shmem(struct drm_i915_private *i915,
 438                         struct drm_gem_object *obj,
 439                         size_t size)
 440 {
 441         unsigned long flags = VM_NORESERVE;
 442         struct file *filp;
 443 
 444         drm_gem_private_object_init(&i915->drm, obj, size);
 445 
 446         if (i915->mm.gemfs)
 447                 filp = shmem_file_setup_with_mnt(i915->mm.gemfs, "i915", size,
 448                                                  flags);
 449         else
 450                 filp = shmem_file_setup("i915", size, flags);
 451         if (IS_ERR(filp))
 452                 return PTR_ERR(filp);
 453 
 454         obj->filp = filp;
 455         return 0;
 456 }
 457 
 458 struct drm_i915_gem_object *
 459 i915_gem_object_create_shmem(struct drm_i915_private *i915, u64 size)
 460 {
 461         struct drm_i915_gem_object *obj;
 462         struct address_space *mapping;
 463         unsigned int cache_level;
 464         gfp_t mask;
 465         int ret;
 466 
 467         /* There is a prevalence of the assumption that we fit the object's
 468          * page count inside a 32bit _signed_ variable. Let's document this and
 469          * catch if we ever need to fix it. In the meantime, if you do spot
 470          * such a local variable, please consider fixing!
 471          */
 472         if (size >> PAGE_SHIFT > INT_MAX)
 473                 return ERR_PTR(-E2BIG);
 474 
 475         if (overflows_type(size, obj->base.size))
 476                 return ERR_PTR(-E2BIG);
 477 
 478         obj = i915_gem_object_alloc();
 479         if (!obj)
 480                 return ERR_PTR(-ENOMEM);
 481 
 482         ret = create_shmem(i915, &obj->base, size);
 483         if (ret)
 484                 goto fail;
 485 
 486         mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
 487         if (IS_I965GM(i915) || IS_I965G(i915)) {
 488                 /* 965gm cannot relocate objects above 4GiB. */
 489                 mask &= ~__GFP_HIGHMEM;
 490                 mask |= __GFP_DMA32;
 491         }
 492 
 493         mapping = obj->base.filp->f_mapping;
 494         mapping_set_gfp_mask(mapping, mask);
 495         GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));
 496 
 497         i915_gem_object_init(obj, &i915_gem_shmem_ops);
 498 
 499         obj->write_domain = I915_GEM_DOMAIN_CPU;
 500         obj->read_domains = I915_GEM_DOMAIN_CPU;
 501 
 502         if (HAS_LLC(i915))
 503                 /* On some devices, we can have the GPU use the LLC (the CPU
 504                  * cache) for about a 10% performance improvement
 505                  * compared to uncached.  Graphics requests other than
 506                  * display scanout are coherent with the CPU in
 507                  * accessing this cache.  This means in this mode we
 508                  * don't need to clflush on the CPU side, and on the
 509                  * GPU side we only need to flush internal caches to
 510                  * get data visible to the CPU.
 511                  *
 512                  * However, we maintain the display planes as UC, and so
 513                  * need to rebind when first used as such.
 514                  */
 515                 cache_level = I915_CACHE_LLC;
 516         else
 517                 cache_level = I915_CACHE_NONE;
 518 
 519         i915_gem_object_set_cache_coherency(obj, cache_level);
 520 
 521         trace_i915_gem_object_create(obj);
 522 
 523         return obj;
 524 
 525 fail:
 526         i915_gem_object_free(obj);
 527         return ERR_PTR(ret);
 528 }
 529 
 530 /* Allocate a new GEM object and fill it with the supplied data */
 531 struct drm_i915_gem_object *
 532 i915_gem_object_create_shmem_from_data(struct drm_i915_private *dev_priv,
 533                                        const void *data, size_t size)
 534 {
 535         struct drm_i915_gem_object *obj;
 536         struct file *file;
 537         size_t offset;
 538         int err;
 539 
 540         obj = i915_gem_object_create_shmem(dev_priv, round_up(size, PAGE_SIZE));
 541         if (IS_ERR(obj))
 542                 return obj;
 543 
 544         GEM_BUG_ON(obj->write_domain != I915_GEM_DOMAIN_CPU);
 545 
 546         file = obj->base.filp;
 547         offset = 0;
 548         do {
 549                 unsigned int len = min_t(typeof(size), size, PAGE_SIZE);
 550                 struct page *page;
 551                 void *pgdata, *vaddr;
 552 
 553                 err = pagecache_write_begin(file, file->f_mapping,
 554                                             offset, len, 0,
 555                                             &page, &pgdata);
 556                 if (err < 0)
 557                         goto fail;
 558 
 559                 vaddr = kmap(page);
 560                 memcpy(vaddr, data, len);
 561                 kunmap(page);
 562 
 563                 err = pagecache_write_end(file, file->f_mapping,
 564                                           offset, len, len,
 565                                           page, pgdata);
 566                 if (err < 0)
 567                         goto fail;
 568 
 569                 size -= len;
 570                 data += len;
 571                 offset += len;
 572         } while (size);
 573 
 574         return obj;
 575 
 576 fail:
 577         i915_gem_object_put(obj);
 578         return ERR_PTR(err);
 579 }