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