drivers/gpu/drm/ttm/ttm_memory.c

   1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
   2 /**************************************************************************
   3  *
   4  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
   5  * All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the
   9  * "Software"), to deal in the Software without restriction, including
  10  * without limitation the rights to use, copy, modify, merge, publish,
  11  * distribute, sub license, and/or sell copies of the Software, and to
  12  * permit persons to whom the Software is furnished to do so, subject to
  13  * the following conditions:
  14  *
  15  * The above copyright notice and this permission notice (including the
  16  * next paragraph) shall be included in all copies or substantial portions
  17  * of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  22  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  23  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  24  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  25  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  26  *
  27  **************************************************************************/
  28
  29 #define pr_fmt(fmt) "[TTM] " fmt
  30
  31 #include <drm/ttm/ttm_memory.h>
  32 #include <drm/ttm/ttm_module.h>
  33 #include <drm/ttm/ttm_page_alloc.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/sched.h>
  36 #include <linux/wait.h>
  37 #include <linux/mm.h>
  38 #include <linux/module.h>
  39 #include <linux/slab.h>
  40 #include <linux/swap.h>
  41
  42 #define TTM_MEMORY_ALLOC_RETRIES 4
  43
  44 struct ttm_mem_global ttm_mem_glob;
  45 EXPORT_SYMBOL(ttm_mem_glob);
  46
  47 struct ttm_mem_zone {
  48         struct kobject kobj;
  49         struct ttm_mem_global *glob;
  50         const char *name;
  51         uint64_t zone_mem;
  52         uint64_t emer_mem;
  53         uint64_t max_mem;
  54         uint64_t swap_limit;
  55         uint64_t used_mem;
  56 };
  57
  58 static struct attribute ttm_mem_sys = {
  59         .name = "zone_memory",
  60         .mode = S_IRUGO
  61 };
  62 static struct attribute ttm_mem_emer = {
  63         .name = "emergency_memory",
  64         .mode = S_IRUGO | S_IWUSR
  65 };
  66 static struct attribute ttm_mem_max = {
  67         .name = "available_memory",
  68         .mode = S_IRUGO | S_IWUSR
  69 };
  70 static struct attribute ttm_mem_swap = {
  71         .name = "swap_limit",
  72         .mode = S_IRUGO | S_IWUSR
  73 };
  74 static struct attribute ttm_mem_used = {
  75         .name = "used_memory",
  76         .mode = S_IRUGO
  77 };
  78
  79 static void ttm_mem_zone_kobj_release(struct kobject *kobj)
  80 {
  81         struct ttm_mem_zone *zone =
  82                 container_of(kobj, struct ttm_mem_zone, kobj);
  83
  84         pr_info("Zone %7s: Used memory at exit: %llu kiB\n",
  85                 zone->name, (unsigned long long)zone->used_mem >> 10);
  86         kfree(zone);
  87 }
  88
  89 static ssize_t ttm_mem_zone_show(struct kobject *kobj,
  90                                  struct attribute *attr,
  91                                  char *buffer)
  92 {
  93         struct ttm_mem_zone *zone =
  94                 container_of(kobj, struct ttm_mem_zone, kobj);
  95         uint64_t val = 0;
  96
  97         spin_lock(&zone->glob->lock);
  98         if (attr == &ttm_mem_sys)
  99                 val = zone->zone_mem;
 100         else if (attr == &ttm_mem_emer)
 101                 val = zone->emer_mem;
 102         else if (attr == &ttm_mem_max)
 103                 val = zone->max_mem;
 104         else if (attr == &ttm_mem_swap)
 105                 val = zone->swap_limit;
 106         else if (attr == &ttm_mem_used)
 107                 val = zone->used_mem;
 108         spin_unlock(&zone->glob->lock);
 109
 110         return snprintf(buffer, PAGE_SIZE, "%llu\n",
 111                         (unsigned long long) val >> 10);
 112 }
 113
 114 static void ttm_check_swapping(struct ttm_mem_global *glob);
 115
 116 static ssize_t ttm_mem_zone_store(struct kobject *kobj,
 117                                   struct attribute *attr,
 118                                   const char *buffer,
 119                                   size_t size)
 120 {
 121         struct ttm_mem_zone *zone =
 122                 container_of(kobj, struct ttm_mem_zone, kobj);
 123         int chars;
 124         unsigned long val;
 125         uint64_t val64;
 126
 127         chars = sscanf(buffer, "%lu", &val);
 128         if (chars == 0)
 129                 return size;
 130
 131         val64 = val;
 132         val64 <<= 10;
 133
 134         spin_lock(&zone->glob->lock);
 135         if (val64 > zone->zone_mem)
 136                 val64 = zone->zone_mem;
 137         if (attr == &ttm_mem_emer) {
 138                 zone->emer_mem = val64;
 139                 if (zone->max_mem > val64)
 140                         zone->max_mem = val64;
 141         } else if (attr == &ttm_mem_max) {
 142                 zone->max_mem = val64;
 143                 if (zone->emer_mem < val64)
 144                         zone->emer_mem = val64;
 145         } else if (attr == &ttm_mem_swap)
 146                 zone->swap_limit = val64;
 147         spin_unlock(&zone->glob->lock);
 148
 149         ttm_check_swapping(zone->glob);
 150
 151         return size;
 152 }
 153
 154 static struct attribute *ttm_mem_zone_attrs[] = {
 155         &ttm_mem_sys,
 156         &ttm_mem_emer,
 157         &ttm_mem_max,
 158         &ttm_mem_swap,
 159         &ttm_mem_used,
 160         NULL
 161 };
 162
 163 static const struct sysfs_ops ttm_mem_zone_ops = {
 164         .show = &ttm_mem_zone_show,
 165         .store = &ttm_mem_zone_store
 166 };
 167
 168 static struct kobj_type ttm_mem_zone_kobj_type = {
 169         .release = &ttm_mem_zone_kobj_release,
 170         .sysfs_ops = &ttm_mem_zone_ops,
 171         .default_attrs = ttm_mem_zone_attrs,
 172 };
 173
 174 static struct attribute ttm_mem_global_lower_mem_limit = {
 175         .name = "lower_mem_limit",
 176         .mode = S_IRUGO | S_IWUSR
 177 };
 178
 179 static ssize_t ttm_mem_global_show(struct kobject *kobj,
 180                                  struct attribute *attr,
 181                                  char *buffer)
 182 {
 183         struct ttm_mem_global *glob =
 184                 container_of(kobj, struct ttm_mem_global, kobj);
 185         uint64_t val = 0;
 186
 187         spin_lock(&glob->lock);
 188         val = glob->lower_mem_limit;
 189         spin_unlock(&glob->lock);
 190         /* convert from number of pages to KB */
 191         val <<= (PAGE_SHIFT - 10);
 192         return snprintf(buffer, PAGE_SIZE, "%llu\n",
 193                         (unsigned long long) val);
 194 }
 195
 196 static ssize_t ttm_mem_global_store(struct kobject *kobj,
 197                                   struct attribute *attr,
 198                                   const char *buffer,
 199                                   size_t size)
 200 {
 201         int chars;
 202         uint64_t val64;
 203         unsigned long val;
 204         struct ttm_mem_global *glob =
 205                 container_of(kobj, struct ttm_mem_global, kobj);
 206
 207         chars = sscanf(buffer, "%lu", &val);
 208         if (chars == 0)
 209                 return size;
 210
 211         val64 = val;
 212         /* convert from KB to number of pages */
 213         val64 >>= (PAGE_SHIFT - 10);
 214
 215         spin_lock(&glob->lock);
 216         glob->lower_mem_limit = val64;
 217         spin_unlock(&glob->lock);
 218
 219         return size;
 220 }
 221
 222 static struct attribute *ttm_mem_global_attrs[] = {
 223         &ttm_mem_global_lower_mem_limit,
 224         NULL
 225 };
 226
 227 static const struct sysfs_ops ttm_mem_global_ops = {
 228         .show = &ttm_mem_global_show,
 229         .store = &ttm_mem_global_store,
 230 };
 231
 232 static struct kobj_type ttm_mem_glob_kobj_type = {
 233         .sysfs_ops = &ttm_mem_global_ops,
 234         .default_attrs = ttm_mem_global_attrs,
 235 };
 236
 237 static bool ttm_zones_above_swap_target(struct ttm_mem_global *glob,
 238                                         bool from_wq, uint64_t extra)
 239 {
 240         unsigned int i;
 241         struct ttm_mem_zone *zone;
 242         uint64_t target;
 243
 244         for (i = 0; i < glob->num_zones; ++i) {
 245                 zone = glob->zones[i];
 246
 247                 if (from_wq)
 248                         target = zone->swap_limit;
 249                 else if (capable(CAP_SYS_ADMIN))
 250                         target = zone->emer_mem;
 251                 else
 252                         target = zone->max_mem;
 253
 254                 target = (extra > target) ? 0ULL : target;
 255
 256                 if (zone->used_mem > target)
 257                         return true;
 258         }
 259         return false;
 260 }
 261
 262 /**
 263  * At this point we only support a single shrink callback.
 264  * Extend this if needed, perhaps using a linked list of callbacks.
 265  * Note that this function is reentrant:
 266  * many threads may try to swap out at any given time.
 267  */
 268
 269 static void ttm_shrink(struct ttm_mem_global *glob, bool from_wq,
 270                         uint64_t extra, struct ttm_operation_ctx *ctx)
 271 {
 272         int ret;
 273
 274         spin_lock(&glob->lock);
 275
 276         while (ttm_zones_above_swap_target(glob, from_wq, extra)) {
 277                 spin_unlock(&glob->lock);
 278                 ret = ttm_bo_swapout(glob->bo_glob, ctx);
 279                 spin_lock(&glob->lock);
 280                 if (unlikely(ret != 0))
 281                         break;
 282         }
 283
 284         spin_unlock(&glob->lock);
 285 }
 286
 287 static void ttm_shrink_work(struct work_struct *work)
 288 {
 289         struct ttm_operation_ctx ctx = {
 290                 .interruptible = false,
 291                 .no_wait_gpu = false
 292         };
 293         struct ttm_mem_global *glob =
 294             container_of(work, struct ttm_mem_global, work);
 295
 296         ttm_shrink(glob, true, 0ULL, &ctx);
 297 }
 298
 299 static int ttm_mem_init_kernel_zone(struct ttm_mem_global *glob,
 300                                     const struct sysinfo *si)
 301 {
 302         struct ttm_mem_zone *zone = kzalloc(sizeof(*zone), GFP_KERNEL);
 303         uint64_t mem;
 304         int ret;
 305
 306         if (unlikely(!zone))
 307                 return -ENOMEM;
 308
 309         mem = si->totalram - si->totalhigh;
 310         mem *= si->mem_unit;
 311
 312         zone->name = "kernel";
 313         zone->zone_mem = mem;
 314         zone->max_mem = mem >> 1;
 315         zone->emer_mem = (mem >> 1) + (mem >> 2);
 316         zone->swap_limit = zone->max_mem - (mem >> 3);
 317         zone->used_mem = 0;
 318         zone->glob = glob;
 319         glob->zone_kernel = zone;
 320         ret = kobject_init_and_add(
 321                 &zone->kobj, &ttm_mem_zone_kobj_type, &glob->kobj, zone->name);
 322         if (unlikely(ret != 0)) {
 323                 kobject_put(&zone->kobj);
 324                 return ret;
 325         }
 326         glob->zones[glob->num_zones++] = zone;
 327         return 0;
 328 }
 329
 330 #ifdef CONFIG_HIGHMEM
 331 static int ttm_mem_init_highmem_zone(struct ttm_mem_global *glob,
 332                                      const struct sysinfo *si)
 333 {
 334         struct ttm_mem_zone *zone;
 335         uint64_t mem;
 336         int ret;
 337
 338         if (si->totalhigh == 0)
 339                 return 0;
 340
 341         zone = kzalloc(sizeof(*zone), GFP_KERNEL);
 342         if (unlikely(!zone))
 343                 return -ENOMEM;
 344
 345         mem = si->totalram;
 346         mem *= si->mem_unit;
 347
 348         zone->name = "highmem";
 349         zone->zone_mem = mem;
 350         zone->max_mem = mem >> 1;
 351         zone->emer_mem = (mem >> 1) + (mem >> 2);
 352         zone->swap_limit = zone->max_mem - (mem >> 3);
 353         zone->used_mem = 0;
 354         zone->glob = glob;
 355         glob->zone_highmem = zone;
 356         ret = kobject_init_and_add(
 357                 &zone->kobj, &ttm_mem_zone_kobj_type, &glob->kobj, "%s",
 358                 zone->name);
 359         if (unlikely(ret != 0)) {
 360                 kobject_put(&zone->kobj);
 361                 return ret;
 362         }
 363         glob->zones[glob->num_zones++] = zone;
 364         return 0;
 365 }
 366 #else
 367 static int ttm_mem_init_dma32_zone(struct ttm_mem_global *glob,
 368                                    const struct sysinfo *si)
 369 {
 370         struct ttm_mem_zone *zone = kzalloc(sizeof(*zone), GFP_KERNEL);
 371         uint64_t mem;
 372         int ret;
 373
 374         if (unlikely(!zone))
 375                 return -ENOMEM;
 376
 377         mem = si->totalram;
 378         mem *= si->mem_unit;
 379
 380         /**
 381          * No special dma32 zone needed.
 382          */
 383
 384         if (mem <= ((uint64_t) 1ULL << 32)) {
 385                 kfree(zone);
 386                 return 0;
 387         }
 388
 389         /*
 390          * Limit max dma32 memory to 4GB for now
 391          * until we can figure out how big this
 392          * zone really is.
 393          */
 394
 395         mem = ((uint64_t) 1ULL << 32);
 396         zone->name = "dma32";
 397         zone->zone_mem = mem;
 398         zone->max_mem = mem >> 1;
 399         zone->emer_mem = (mem >> 1) + (mem >> 2);
 400         zone->swap_limit = zone->max_mem - (mem >> 3);
 401         zone->used_mem = 0;
 402         zone->glob = glob;
 403         glob->zone_dma32 = zone;
 404         ret = kobject_init_and_add(
 405                 &zone->kobj, &ttm_mem_zone_kobj_type, &glob->kobj, zone->name);
 406         if (unlikely(ret != 0)) {
 407                 kobject_put(&zone->kobj);
 408                 return ret;
 409         }
 410         glob->zones[glob->num_zones++] = zone;
 411         return 0;
 412 }
 413 #endif
 414
 415 int ttm_mem_global_init(struct ttm_mem_global *glob)
 416 {
 417         struct sysinfo si;
 418         int ret;
 419         int i;
 420         struct ttm_mem_zone *zone;
 421
 422         spin_lock_init(&glob->lock);
 423         glob->swap_queue = create_singlethread_workqueue("ttm_swap");
 424         INIT_WORK(&glob->work, ttm_shrink_work);
 425         ret = kobject_init_and_add(
 426                 &glob->kobj, &ttm_mem_glob_kobj_type, ttm_get_kobj(), "memory_accounting");
 427         if (unlikely(ret != 0)) {
 428                 kobject_put(&glob->kobj);
 429                 return ret;
 430         }
 431
 432         si_meminfo(&si);
 433
 434         /* set it as 0 by default to keep original behavior of OOM */
 435         glob->lower_mem_limit = 0;
 436
 437         ret = ttm_mem_init_kernel_zone(glob, &si);
 438         if (unlikely(ret != 0))
 439                 goto out_no_zone;
 440 #ifdef CONFIG_HIGHMEM
 441         ret = ttm_mem_init_highmem_zone(glob, &si);
 442         if (unlikely(ret != 0))
 443                 goto out_no_zone;
 444 #else
 445         ret = ttm_mem_init_dma32_zone(glob, &si);
 446         if (unlikely(ret != 0))
 447                 goto out_no_zone;
 448 #endif
 449         for (i = 0; i < glob->num_zones; ++i) {
 450                 zone = glob->zones[i];
 451                 pr_info("Zone %7s: Available graphics memory: %llu kiB\n",
 452                         zone->name, (unsigned long long)zone->max_mem >> 10);
 453         }
 454         ttm_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
 455         ttm_dma_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
 456         return 0;
 457 out_no_zone:
 458         ttm_mem_global_release(glob);
 459         return ret;
 460 }
 461
 462 void ttm_mem_global_release(struct ttm_mem_global *glob)
 463 {
 464         unsigned int i;
 465         struct ttm_mem_zone *zone;
 466
 467         /* let the page allocator first stop the shrink work. */
 468         ttm_page_alloc_fini();
 469         ttm_dma_page_alloc_fini();
 470
 471         flush_workqueue(glob->swap_queue);
 472         destroy_workqueue(glob->swap_queue);
 473         glob->swap_queue = NULL;
 474         for (i = 0; i < glob->num_zones; ++i) {
 475                 zone = glob->zones[i];
 476                 kobject_del(&zone->kobj);
 477                 kobject_put(&zone->kobj);
 478                         }
 479         kobject_del(&glob->kobj);
 480         kobject_put(&glob->kobj);
 481 }
 482
 483 static void ttm_check_swapping(struct ttm_mem_global *glob)
 484 {
 485         bool needs_swapping = false;
 486         unsigned int i;
 487         struct ttm_mem_zone *zone;
 488
 489         spin_lock(&glob->lock);
 490         for (i = 0; i < glob->num_zones; ++i) {
 491                 zone = glob->zones[i];
 492                 if (zone->used_mem > zone->swap_limit) {
 493                         needs_swapping = true;
 494                         break;
 495                 }
 496         }
 497
 498         spin_unlock(&glob->lock);
 499
 500         if (unlikely(needs_swapping))
 501                 (void)queue_work(glob->swap_queue, &glob->work);
 502
 503 }
 504
 505 static void ttm_mem_global_free_zone(struct ttm_mem_global *glob,
 506                                      struct ttm_mem_zone *single_zone,
 507                                      uint64_t amount)
 508 {
 509         unsigned int i;
 510         struct ttm_mem_zone *zone;
 511
 512         spin_lock(&glob->lock);
 513         for (i = 0; i < glob->num_zones; ++i) {
 514                 zone = glob->zones[i];
 515                 if (single_zone && zone != single_zone)
 516                         continue;
 517                 zone->used_mem -= amount;
 518         }
 519         spin_unlock(&glob->lock);
 520 }
 521
 522 void ttm_mem_global_free(struct ttm_mem_global *glob,
 523                          uint64_t amount)
 524 {
 525         return ttm_mem_global_free_zone(glob, NULL, amount);
 526 }
 527 EXPORT_SYMBOL(ttm_mem_global_free);
 528
 529 /*
 530  * check if the available mem is under lower memory limit
 531  *
 532  * a. if no swap disk at all or free swap space is under swap_mem_limit
 533  * but available system mem is bigger than sys_mem_limit, allow TTM
 534  * allocation;
 535  *
 536  * b. if the available system mem is less than sys_mem_limit but free
 537  * swap disk is bigger than swap_mem_limit, allow TTM allocation.
 538  */
 539 bool
 540 ttm_check_under_lowerlimit(struct ttm_mem_global *glob,
 541                         uint64_t num_pages,
 542                         struct ttm_operation_ctx *ctx)
 543 {
 544         int64_t available;
 545
 546         if (ctx->flags & TTM_OPT_FLAG_FORCE_ALLOC)
 547                 return false;
 548
 549         available = get_nr_swap_pages() + si_mem_available();
 550         available -= num_pages;
 551         if (available < glob->lower_mem_limit)
 552                 return true;
 553
 554         return false;
 555 }
 556 EXPORT_SYMBOL(ttm_check_under_lowerlimit);
 557
 558 static int ttm_mem_global_reserve(struct ttm_mem_global *glob,
 559                                   struct ttm_mem_zone *single_zone,
 560                                   uint64_t amount, bool reserve)
 561 {
 562         uint64_t limit;
 563         int ret = -ENOMEM;
 564         unsigned int i;
 565         struct ttm_mem_zone *zone;
 566
 567         spin_lock(&glob->lock);
 568         for (i = 0; i < glob->num_zones; ++i) {
 569                 zone = glob->zones[i];
 570                 if (single_zone && zone != single_zone)
 571                         continue;
 572
 573                 limit = (capable(CAP_SYS_ADMIN)) ?
 574                         zone->emer_mem : zone->max_mem;
 575
 576                 if (zone->used_mem > limit)
 577                         goto out_unlock;
 578         }
 579
 580         if (reserve) {
 581                 for (i = 0; i < glob->num_zones; ++i) {
 582                         zone = glob->zones[i];
 583                         if (single_zone && zone != single_zone)
 584                                 continue;
 585                         zone->used_mem += amount;
 586                 }
 587         }
 588
 589         ret = 0;
 590 out_unlock:
 591         spin_unlock(&glob->lock);
 592         ttm_check_swapping(glob);
 593
 594         return ret;
 595 }
 596
 597
 598 static int ttm_mem_global_alloc_zone(struct ttm_mem_global *glob,
 599                                      struct ttm_mem_zone *single_zone,
 600                                      uint64_t memory,
 601                                      struct ttm_operation_ctx *ctx)
 602 {
 603         int count = TTM_MEMORY_ALLOC_RETRIES;
 604
 605         while (unlikely(ttm_mem_global_reserve(glob,
 606                                                single_zone,
 607                                                memory, true)
 608                         != 0)) {
 609                 if (ctx->no_wait_gpu)
 610                         return -ENOMEM;
 611                 if (unlikely(count-- == 0))
 612                         return -ENOMEM;
 613                 ttm_shrink(glob, false, memory + (memory >> 2) + 16, ctx);
 614         }
 615
 616         return 0;
 617 }
 618
 619 int ttm_mem_global_alloc(struct ttm_mem_global *glob, uint64_t memory,
 620                          struct ttm_operation_ctx *ctx)
 621 {
 622         /**
 623          * Normal allocations of kernel memory are registered in
 624          * all zones.
 625          */
 626
 627         return ttm_mem_global_alloc_zone(glob, NULL, memory, ctx);
 628 }
 629 EXPORT_SYMBOL(ttm_mem_global_alloc);
 630
 631 int ttm_mem_global_alloc_page(struct ttm_mem_global *glob,
 632                               struct page *page, uint64_t size,
 633                               struct ttm_operation_ctx *ctx)
 634 {
 635         struct ttm_mem_zone *zone = NULL;
 636
 637         /**
 638          * Page allocations may be registed in a single zone
 639          * only if highmem or !dma32.
 640          */
 641
 642 #ifdef CONFIG_HIGHMEM
 643         if (PageHighMem(page) && glob->zone_highmem != NULL)
 644                 zone = glob->zone_highmem;
 645 #else
 646         if (glob->zone_dma32 && page_to_pfn(page) > 0x00100000UL)
 647                 zone = glob->zone_kernel;
 648 #endif
 649         return ttm_mem_global_alloc_zone(glob, zone, size, ctx);
 650 }
 651
 652 void ttm_mem_global_free_page(struct ttm_mem_global *glob, struct page *page,
 653                               uint64_t size)
 654 {
 655         struct ttm_mem_zone *zone = NULL;
 656
 657 #ifdef CONFIG_HIGHMEM
 658         if (PageHighMem(page) && glob->zone_highmem != NULL)
 659                 zone = glob->zone_highmem;
 660 #else
 661         if (glob->zone_dma32 && page_to_pfn(page) > 0x00100000UL)
 662                 zone = glob->zone_kernel;
 663 #endif
 664         ttm_mem_global_free_zone(glob, zone, size);
 665 }
 666
 667 size_t ttm_round_pot(size_t size)
 668 {
 669         if ((size & (size - 1)) == 0)
 670                 return size;
 671         else if (size > PAGE_SIZE)
 672                 return PAGE_ALIGN(size);
 673         else {
 674                 size_t tmp_size = 4;
 675
 676                 while (tmp_size < size)
 677                         tmp_size <<= 1;
 678
 679                 return tmp_size;
 680         }
 681         return 0;
 682 }
 683 EXPORT_SYMBOL(ttm_round_pot);
 684
 685 uint64_t ttm_get_kernel_zone_memory_size(struct ttm_mem_global *glob)
 686 {
 687         return glob->zone_kernel->max_mem;
 688 }
 689 EXPORT_SYMBOL(ttm_get_kernel_zone_memory_size);