lib/test_hmm.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This is a module to test the HMM (Heterogeneous Memory Management)
   4  * mirror and zone device private memory migration APIs of the kernel.
   5  * Userspace programs can register with the driver to mirror their own address
   6  * space and can use the device to read/write any valid virtual address.
   7  */
   8 #include <linux/init.h>
   9 #include <linux/fs.h>
  10 #include <linux/mm.h>
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/cdev.h>
  14 #include <linux/device.h>
  15 #include <linux/memremap.h>
  16 #include <linux/mutex.h>
  17 #include <linux/rwsem.h>
  18 #include <linux/sched.h>
  19 #include <linux/slab.h>
  20 #include <linux/highmem.h>
  21 #include <linux/delay.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/hmm.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/swap.h>
  26 #include <linux/swapops.h>
  27 #include <linux/sched/mm.h>
  28 #include <linux/platform_device.h>
  29 #include <linux/rmap.h>
  30 #include <linux/mmu_notifier.h>
  31 #include <linux/migrate.h>
  32
  33 #include "test_hmm_uapi.h"
  34
  35 #define DMIRROR_NDEVICES                2
  36 #define DMIRROR_RANGE_FAULT_TIMEOUT     1000
  37 #define DEVMEM_CHUNK_SIZE               (256 * 1024 * 1024U)
  38 #define DEVMEM_CHUNKS_RESERVE           16
  39
  40 static const struct dev_pagemap_ops dmirror_devmem_ops;
  41 static const struct mmu_interval_notifier_ops dmirror_min_ops;
  42 static dev_t dmirror_dev;
  43
  44 struct dmirror_device;
  45
  46 struct dmirror_bounce {
  47         void                    *ptr;
  48         unsigned long           size;
  49         unsigned long           addr;
  50         unsigned long           cpages;
  51 };
  52
  53 #define DPT_XA_TAG_ATOMIC 1UL
  54 #define DPT_XA_TAG_WRITE 3UL
  55
  56 /*
  57  * Data structure to track address ranges and register for mmu interval
  58  * notifier updates.
  59  */
  60 struct dmirror_interval {
  61         struct mmu_interval_notifier    notifier;
  62         struct dmirror                  *dmirror;
  63 };
  64
  65 /*
  66  * Data attached to the open device file.
  67  * Note that it might be shared after a fork().
  68  */
  69 struct dmirror {
  70         struct dmirror_device           *mdevice;
  71         struct xarray                   pt;
  72         struct mmu_interval_notifier    notifier;
  73         struct mutex                    mutex;
  74 };
  75
  76 /*
  77  * ZONE_DEVICE pages for migration and simulating device memory.
  78  */
  79 struct dmirror_chunk {
  80         struct dev_pagemap      pagemap;
  81         struct dmirror_device   *mdevice;
  82 };
  83
  84 /*
  85  * Per device data.
  86  */
  87 struct dmirror_device {
  88         struct cdev             cdevice;
  89         struct hmm_devmem       *devmem;
  90
  91         unsigned int            devmem_capacity;
  92         unsigned int            devmem_count;
  93         struct dmirror_chunk    **devmem_chunks;
  94         struct mutex            devmem_lock;    /* protects the above */
  95
  96         unsigned long           calloc;
  97         unsigned long           cfree;
  98         struct page             *free_pages;
  99         spinlock_t              lock;           /* protects the above */
 100 };
 101
 102 static struct dmirror_device dmirror_devices[DMIRROR_NDEVICES];
 103
 104 static int dmirror_bounce_init(struct dmirror_bounce *bounce,
 105                                unsigned long addr,
 106                                unsigned long size)
 107 {
 108         bounce->addr = addr;
 109         bounce->size = size;
 110         bounce->cpages = 0;
 111         bounce->ptr = vmalloc(size);
 112         if (!bounce->ptr)
 113                 return -ENOMEM;
 114         return 0;
 115 }
 116
 117 static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
 118 {
 119         vfree(bounce->ptr);
 120 }
 121
 122 static int dmirror_fops_open(struct inode *inode, struct file *filp)
 123 {
 124         struct cdev *cdev = inode->i_cdev;
 125         struct dmirror *dmirror;
 126         int ret;
 127
 128         /* Mirror this process address space */
 129         dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
 130         if (dmirror == NULL)
 131                 return -ENOMEM;
 132
 133         dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
 134         mutex_init(&dmirror->mutex);
 135         xa_init(&dmirror->pt);
 136
 137         ret = mmu_interval_notifier_insert(&dmirror->notifier, current->mm,
 138                                 0, ULONG_MAX & PAGE_MASK, &dmirror_min_ops);
 139         if (ret) {
 140                 kfree(dmirror);
 141                 return ret;
 142         }
 143
 144         filp->private_data = dmirror;
 145         return 0;
 146 }
 147
 148 static int dmirror_fops_release(struct inode *inode, struct file *filp)
 149 {
 150         struct dmirror *dmirror = filp->private_data;
 151
 152         mmu_interval_notifier_remove(&dmirror->notifier);
 153         xa_destroy(&dmirror->pt);
 154         kfree(dmirror);
 155         return 0;
 156 }
 157
 158 static struct dmirror_device *dmirror_page_to_device(struct page *page)
 159
 160 {
 161         return container_of(page->pgmap, struct dmirror_chunk,
 162                             pagemap)->mdevice;
 163 }
 164
 165 static int dmirror_do_fault(struct dmirror *dmirror, struct hmm_range *range)
 166 {
 167         unsigned long *pfns = range->hmm_pfns;
 168         unsigned long pfn;
 169
 170         for (pfn = (range->start >> PAGE_SHIFT);
 171              pfn < (range->end >> PAGE_SHIFT);
 172              pfn++, pfns++) {
 173                 struct page *page;
 174                 void *entry;
 175
 176                 /*
 177                  * Since we asked for hmm_range_fault() to populate pages,
 178                  * it shouldn't return an error entry on success.
 179                  */
 180                 WARN_ON(*pfns & HMM_PFN_ERROR);
 181                 WARN_ON(!(*pfns & HMM_PFN_VALID));
 182
 183                 page = hmm_pfn_to_page(*pfns);
 184                 WARN_ON(!page);
 185
 186                 entry = page;
 187                 if (*pfns & HMM_PFN_WRITE)
 188                         entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
 189                 else if (WARN_ON(range->default_flags & HMM_PFN_WRITE))
 190                         return -EFAULT;
 191                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 192                 if (xa_is_err(entry))
 193                         return xa_err(entry);
 194         }
 195
 196         return 0;
 197 }
 198
 199 static void dmirror_do_update(struct dmirror *dmirror, unsigned long start,
 200                               unsigned long end)
 201 {
 202         unsigned long pfn;
 203         void *entry;
 204
 205         /*
 206          * The XArray doesn't hold references to pages since it relies on
 207          * the mmu notifier to clear page pointers when they become stale.
 208          * Therefore, it is OK to just clear the entry.
 209          */
 210         xa_for_each_range(&dmirror->pt, pfn, entry, start >> PAGE_SHIFT,
 211                           end >> PAGE_SHIFT)
 212                 xa_erase(&dmirror->pt, pfn);
 213 }
 214
 215 static bool dmirror_interval_invalidate(struct mmu_interval_notifier *mni,
 216                                 const struct mmu_notifier_range *range,
 217                                 unsigned long cur_seq)
 218 {
 219         struct dmirror *dmirror = container_of(mni, struct dmirror, notifier);
 220
 221         /*
 222          * Ignore invalidation callbacks for device private pages since
 223          * the invalidation is handled as part of the migration process.
 224          */
 225         if (range->event == MMU_NOTIFY_MIGRATE &&
 226             range->owner == dmirror->mdevice)
 227                 return true;
 228
 229         if (mmu_notifier_range_blockable(range))
 230                 mutex_lock(&dmirror->mutex);
 231         else if (!mutex_trylock(&dmirror->mutex))
 232                 return false;
 233
 234         mmu_interval_set_seq(mni, cur_seq);
 235         dmirror_do_update(dmirror, range->start, range->end);
 236
 237         mutex_unlock(&dmirror->mutex);
 238         return true;
 239 }
 240
 241 static const struct mmu_interval_notifier_ops dmirror_min_ops = {
 242         .invalidate = dmirror_interval_invalidate,
 243 };
 244
 245 static int dmirror_range_fault(struct dmirror *dmirror,
 246                                 struct hmm_range *range)
 247 {
 248         struct mm_struct *mm = dmirror->notifier.mm;
 249         unsigned long timeout =
 250                 jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 251         int ret;
 252
 253         while (true) {
 254                 if (time_after(jiffies, timeout)) {
 255                         ret = -EBUSY;
 256                         goto out;
 257                 }
 258
 259                 range->notifier_seq = mmu_interval_read_begin(range->notifier);
 260                 mmap_read_lock(mm);
 261                 ret = hmm_range_fault(range);
 262                 mmap_read_unlock(mm);
 263                 if (ret) {
 264                         if (ret == -EBUSY)
 265                                 continue;
 266                         goto out;
 267                 }
 268
 269                 mutex_lock(&dmirror->mutex);
 270                 if (mmu_interval_read_retry(range->notifier,
 271                                             range->notifier_seq)) {
 272                         mutex_unlock(&dmirror->mutex);
 273                         continue;
 274                 }
 275                 break;
 276         }
 277
 278         ret = dmirror_do_fault(dmirror, range);
 279
 280         mutex_unlock(&dmirror->mutex);
 281 out:
 282         return ret;
 283 }
 284
 285 static int dmirror_fault(struct dmirror *dmirror, unsigned long start,
 286                          unsigned long end, bool write)
 287 {
 288         struct mm_struct *mm = dmirror->notifier.mm;
 289         unsigned long addr;
 290         unsigned long pfns[64];
 291         struct hmm_range range = {
 292                 .notifier = &dmirror->notifier,
 293                 .hmm_pfns = pfns,
 294                 .pfn_flags_mask = 0,
 295                 .default_flags =
 296                         HMM_PFN_REQ_FAULT | (write ? HMM_PFN_REQ_WRITE : 0),
 297                 .dev_private_owner = dmirror->mdevice,
 298         };
 299         int ret = 0;
 300
 301         /* Since the mm is for the mirrored process, get a reference first. */
 302         if (!mmget_not_zero(mm))
 303                 return 0;
 304
 305         for (addr = start; addr < end; addr = range.end) {
 306                 range.start = addr;
 307                 range.end = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
 308
 309                 ret = dmirror_range_fault(dmirror, &range);
 310                 if (ret)
 311                         break;
 312         }
 313
 314         mmput(mm);
 315         return ret;
 316 }
 317
 318 static int dmirror_do_read(struct dmirror *dmirror, unsigned long start,
 319                            unsigned long end, struct dmirror_bounce *bounce)
 320 {
 321         unsigned long pfn;
 322         void *ptr;
 323
 324         ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
 325
 326         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 327                 void *entry;
 328                 struct page *page;
 329                 void *tmp;
 330
 331                 entry = xa_load(&dmirror->pt, pfn);
 332                 page = xa_untag_pointer(entry);
 333                 if (!page)
 334                         return -ENOENT;
 335
 336                 tmp = kmap(page);
 337                 memcpy(ptr, tmp, PAGE_SIZE);
 338                 kunmap(page);
 339
 340                 ptr += PAGE_SIZE;
 341                 bounce->cpages++;
 342         }
 343
 344         return 0;
 345 }
 346
 347 static int dmirror_read(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 348 {
 349         struct dmirror_bounce bounce;
 350         unsigned long start, end;
 351         unsigned long size = cmd->npages << PAGE_SHIFT;
 352         int ret;
 353
 354         start = cmd->addr;
 355         end = start + size;
 356         if (end < start)
 357                 return -EINVAL;
 358
 359         ret = dmirror_bounce_init(&bounce, start, size);
 360         if (ret)
 361                 return ret;
 362
 363         while (1) {
 364                 mutex_lock(&dmirror->mutex);
 365                 ret = dmirror_do_read(dmirror, start, end, &bounce);
 366                 mutex_unlock(&dmirror->mutex);
 367                 if (ret != -ENOENT)
 368                         break;
 369
 370                 start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
 371                 ret = dmirror_fault(dmirror, start, end, false);
 372                 if (ret)
 373                         break;
 374                 cmd->faults++;
 375         }
 376
 377         if (ret == 0) {
 378                 if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
 379                                  bounce.size))
 380                         ret = -EFAULT;
 381         }
 382         cmd->cpages = bounce.cpages;
 383         dmirror_bounce_fini(&bounce);
 384         return ret;
 385 }
 386
 387 static int dmirror_do_write(struct dmirror *dmirror, unsigned long start,
 388                             unsigned long end, struct dmirror_bounce *bounce)
 389 {
 390         unsigned long pfn;
 391         void *ptr;
 392
 393         ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
 394
 395         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 396                 void *entry;
 397                 struct page *page;
 398                 void *tmp;
 399
 400                 entry = xa_load(&dmirror->pt, pfn);
 401                 page = xa_untag_pointer(entry);
 402                 if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE)
 403                         return -ENOENT;
 404
 405                 tmp = kmap(page);
 406                 memcpy(tmp, ptr, PAGE_SIZE);
 407                 kunmap(page);
 408
 409                 ptr += PAGE_SIZE;
 410                 bounce->cpages++;
 411         }
 412
 413         return 0;
 414 }
 415
 416 static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 417 {
 418         struct dmirror_bounce bounce;
 419         unsigned long start, end;
 420         unsigned long size = cmd->npages << PAGE_SHIFT;
 421         int ret;
 422
 423         start = cmd->addr;
 424         end = start + size;
 425         if (end < start)
 426                 return -EINVAL;
 427
 428         ret = dmirror_bounce_init(&bounce, start, size);
 429         if (ret)
 430                 return ret;
 431         if (copy_from_user(bounce.ptr, u64_to_user_ptr(cmd->ptr),
 432                            bounce.size)) {
 433                 ret = -EFAULT;
 434                 goto fini;
 435         }
 436
 437         while (1) {
 438                 mutex_lock(&dmirror->mutex);
 439                 ret = dmirror_do_write(dmirror, start, end, &bounce);
 440                 mutex_unlock(&dmirror->mutex);
 441                 if (ret != -ENOENT)
 442                         break;
 443
 444                 start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
 445                 ret = dmirror_fault(dmirror, start, end, true);
 446                 if (ret)
 447                         break;
 448                 cmd->faults++;
 449         }
 450
 451 fini:
 452         cmd->cpages = bounce.cpages;
 453         dmirror_bounce_fini(&bounce);
 454         return ret;
 455 }
 456
 457 static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 458                                    struct page **ppage)
 459 {
 460         struct dmirror_chunk *devmem;
 461         struct resource *res;
 462         unsigned long pfn;
 463         unsigned long pfn_first;
 464         unsigned long pfn_last;
 465         void *ptr;
 466
 467         devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
 468         if (!devmem)
 469                 return false;
 470
 471         res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
 472                                       "hmm_dmirror");
 473         if (IS_ERR(res))
 474                 goto err_devmem;
 475
 476         devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
 477         devmem->pagemap.range.start = res->start;
 478         devmem->pagemap.range.end = res->end;
 479         devmem->pagemap.nr_range = 1;
 480         devmem->pagemap.ops = &dmirror_devmem_ops;
 481         devmem->pagemap.owner = mdevice;
 482
 483         mutex_lock(&mdevice->devmem_lock);
 484
 485         if (mdevice->devmem_count == mdevice->devmem_capacity) {
 486                 struct dmirror_chunk **new_chunks;
 487                 unsigned int new_capacity;
 488
 489                 new_capacity = mdevice->devmem_capacity +
 490                                 DEVMEM_CHUNKS_RESERVE;
 491                 new_chunks = krealloc(mdevice->devmem_chunks,
 492                                 sizeof(new_chunks[0]) * new_capacity,
 493                                 GFP_KERNEL);
 494                 if (!new_chunks)
 495                         goto err_release;
 496                 mdevice->devmem_capacity = new_capacity;
 497                 mdevice->devmem_chunks = new_chunks;
 498         }
 499
 500         ptr = memremap_pages(&devmem->pagemap, numa_node_id());
 501         if (IS_ERR(ptr))
 502                 goto err_release;
 503
 504         devmem->mdevice = mdevice;
 505         pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
 506         pfn_last = pfn_first + (range_len(&devmem->pagemap.range) >> PAGE_SHIFT);
 507         mdevice->devmem_chunks[mdevice->devmem_count++] = devmem;
 508
 509         mutex_unlock(&mdevice->devmem_lock);
 510
 511         pr_info("added new %u MB chunk (total %u chunks, %u MB) PFNs [0x%lx 0x%lx)\n",
 512                 DEVMEM_CHUNK_SIZE / (1024 * 1024),
 513                 mdevice->devmem_count,
 514                 mdevice->devmem_count * (DEVMEM_CHUNK_SIZE / (1024 * 1024)),
 515                 pfn_first, pfn_last);
 516
 517         spin_lock(&mdevice->lock);
 518         for (pfn = pfn_first; pfn < pfn_last; pfn++) {
 519                 struct page *page = pfn_to_page(pfn);
 520
 521                 page->zone_device_data = mdevice->free_pages;
 522                 mdevice->free_pages = page;
 523         }
 524         if (ppage) {
 525                 *ppage = mdevice->free_pages;
 526                 mdevice->free_pages = (*ppage)->zone_device_data;
 527                 mdevice->calloc++;
 528         }
 529         spin_unlock(&mdevice->lock);
 530
 531         return true;
 532
 533 err_release:
 534         mutex_unlock(&mdevice->devmem_lock);
 535         release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
 536 err_devmem:
 537         kfree(devmem);
 538
 539         return false;
 540 }
 541
 542 static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
 543 {
 544         struct page *dpage = NULL;
 545         struct page *rpage;
 546
 547         /*
 548          * This is a fake device so we alloc real system memory to store
 549          * our device memory.
 550          */
 551         rpage = alloc_page(GFP_HIGHUSER);
 552         if (!rpage)
 553                 return NULL;
 554
 555         spin_lock(&mdevice->lock);
 556
 557         if (mdevice->free_pages) {
 558                 dpage = mdevice->free_pages;
 559                 mdevice->free_pages = dpage->zone_device_data;
 560                 mdevice->calloc++;
 561                 spin_unlock(&mdevice->lock);
 562         } else {
 563                 spin_unlock(&mdevice->lock);
 564                 if (!dmirror_allocate_chunk(mdevice, &dpage))
 565                         goto error;
 566         }
 567
 568         dpage->zone_device_data = rpage;
 569         lock_page(dpage);
 570         return dpage;
 571
 572 error:
 573         __free_page(rpage);
 574         return NULL;
 575 }
 576
 577 static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
 578                                            struct dmirror *dmirror)
 579 {
 580         struct dmirror_device *mdevice = dmirror->mdevice;
 581         const unsigned long *src = args->src;
 582         unsigned long *dst = args->dst;
 583         unsigned long addr;
 584
 585         for (addr = args->start; addr < args->end; addr += PAGE_SIZE,
 586                                                    src++, dst++) {
 587                 struct page *spage;
 588                 struct page *dpage;
 589                 struct page *rpage;
 590
 591                 if (!(*src & MIGRATE_PFN_MIGRATE))
 592                         continue;
 593
 594                 /*
 595                  * Note that spage might be NULL which is OK since it is an
 596                  * unallocated pte_none() or read-only zero page.
 597                  */
 598                 spage = migrate_pfn_to_page(*src);
 599
 600                 dpage = dmirror_devmem_alloc_page(mdevice);
 601                 if (!dpage)
 602                         continue;
 603
 604                 rpage = dpage->zone_device_data;
 605                 if (spage)
 606                         copy_highpage(rpage, spage);
 607                 else
 608                         clear_highpage(rpage);
 609
 610                 /*
 611                  * Normally, a device would use the page->zone_device_data to
 612                  * point to the mirror but here we use it to hold the page for
 613                  * the simulated device memory and that page holds the pointer
 614                  * to the mirror.
 615                  */
 616                 rpage->zone_device_data = dmirror;
 617
 618                 *dst = migrate_pfn(page_to_pfn(dpage));
 619                 if ((*src & MIGRATE_PFN_WRITE) ||
 620                     (!spage && args->vma->vm_flags & VM_WRITE))
 621                         *dst |= MIGRATE_PFN_WRITE;
 622         }
 623 }
 624
 625 static int dmirror_check_atomic(struct dmirror *dmirror, unsigned long start,
 626                              unsigned long end)
 627 {
 628         unsigned long pfn;
 629
 630         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 631                 void *entry;
 632
 633                 entry = xa_load(&dmirror->pt, pfn);
 634                 if (xa_pointer_tag(entry) == DPT_XA_TAG_ATOMIC)
 635                         return -EPERM;
 636         }
 637
 638         return 0;
 639 }
 640
 641 static int dmirror_atomic_map(unsigned long start, unsigned long end,
 642                               struct page **pages, struct dmirror *dmirror)
 643 {
 644         unsigned long pfn, mapped = 0;
 645         int i;
 646
 647         /* Map the migrated pages into the device's page tables. */
 648         mutex_lock(&dmirror->mutex);
 649
 650         for (i = 0, pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++, i++) {
 651                 void *entry;
 652
 653                 if (!pages[i])
 654                         continue;
 655
 656                 entry = pages[i];
 657                 entry = xa_tag_pointer(entry, DPT_XA_TAG_ATOMIC);
 658                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 659                 if (xa_is_err(entry)) {
 660                         mutex_unlock(&dmirror->mutex);
 661                         return xa_err(entry);
 662                 }
 663
 664                 mapped++;
 665         }
 666
 667         mutex_unlock(&dmirror->mutex);
 668         return mapped;
 669 }
 670
 671 static int dmirror_migrate_finalize_and_map(struct migrate_vma *args,
 672                                             struct dmirror *dmirror)
 673 {
 674         unsigned long start = args->start;
 675         unsigned long end = args->end;
 676         const unsigned long *src = args->src;
 677         const unsigned long *dst = args->dst;
 678         unsigned long pfn;
 679
 680         /* Map the migrated pages into the device's page tables. */
 681         mutex_lock(&dmirror->mutex);
 682
 683         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++,
 684                                                                 src++, dst++) {
 685                 struct page *dpage;
 686                 void *entry;
 687
 688                 if (!(*src & MIGRATE_PFN_MIGRATE))
 689                         continue;
 690
 691                 dpage = migrate_pfn_to_page(*dst);
 692                 if (!dpage)
 693                         continue;
 694
 695                 /*
 696                  * Store the page that holds the data so the page table
 697                  * doesn't have to deal with ZONE_DEVICE private pages.
 698                  */
 699                 entry = dpage->zone_device_data;
 700                 if (*dst & MIGRATE_PFN_WRITE)
 701                         entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
 702                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 703                 if (xa_is_err(entry)) {
 704                         mutex_unlock(&dmirror->mutex);
 705                         return xa_err(entry);
 706                 }
 707         }
 708
 709         mutex_unlock(&dmirror->mutex);
 710         return 0;
 711 }
 712
 713 static int dmirror_exclusive(struct dmirror *dmirror,
 714                              struct hmm_dmirror_cmd *cmd)
 715 {
 716         unsigned long start, end, addr;
 717         unsigned long size = cmd->npages << PAGE_SHIFT;
 718         struct mm_struct *mm = dmirror->notifier.mm;
 719         struct page *pages[64];
 720         struct dmirror_bounce bounce;
 721         unsigned long next;
 722         int ret;
 723
 724         start = cmd->addr;
 725         end = start + size;
 726         if (end < start)
 727                 return -EINVAL;
 728
 729         /* Since the mm is for the mirrored process, get a reference first. */
 730         if (!mmget_not_zero(mm))
 731                 return -EINVAL;
 732
 733         mmap_read_lock(mm);
 734         for (addr = start; addr < end; addr = next) {
 735                 unsigned long mapped;
 736                 int i;
 737
 738                 if (end < addr + (ARRAY_SIZE(pages) << PAGE_SHIFT))
 739                         next = end;
 740                 else
 741                         next = addr + (ARRAY_SIZE(pages) << PAGE_SHIFT);
 742
 743                 ret = make_device_exclusive_range(mm, addr, next, pages, NULL);
 744                 mapped = dmirror_atomic_map(addr, next, pages, dmirror);
 745                 for (i = 0; i < ret; i++) {
 746                         if (pages[i]) {
 747                                 unlock_page(pages[i]);
 748                                 put_page(pages[i]);
 749                         }
 750                 }
 751
 752                 if (addr + (mapped << PAGE_SHIFT) < next) {
 753                         mmap_read_unlock(mm);
 754                         mmput(mm);
 755                         return -EBUSY;
 756                 }
 757         }
 758         mmap_read_unlock(mm);
 759         mmput(mm);
 760
 761         /* Return the migrated data for verification. */
 762         ret = dmirror_bounce_init(&bounce, start, size);
 763         if (ret)
 764                 return ret;
 765         mutex_lock(&dmirror->mutex);
 766         ret = dmirror_do_read(dmirror, start, end, &bounce);
 767         mutex_unlock(&dmirror->mutex);
 768         if (ret == 0) {
 769                 if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
 770                                  bounce.size))
 771                         ret = -EFAULT;
 772         }
 773
 774         cmd->cpages = bounce.cpages;
 775         dmirror_bounce_fini(&bounce);
 776         return ret;
 777 }
 778
 779 static int dmirror_migrate(struct dmirror *dmirror,
 780                            struct hmm_dmirror_cmd *cmd)
 781 {
 782         unsigned long start, end, addr;
 783         unsigned long size = cmd->npages << PAGE_SHIFT;
 784         struct mm_struct *mm = dmirror->notifier.mm;
 785         struct vm_area_struct *vma;
 786         unsigned long src_pfns[64];
 787         unsigned long dst_pfns[64];
 788         struct dmirror_bounce bounce;
 789         struct migrate_vma args;
 790         unsigned long next;
 791         int ret;
 792
 793         start = cmd->addr;
 794         end = start + size;
 795         if (end < start)
 796                 return -EINVAL;
 797
 798         /* Since the mm is for the mirrored process, get a reference first. */
 799         if (!mmget_not_zero(mm))
 800                 return -EINVAL;
 801
 802         mmap_read_lock(mm);
 803         for (addr = start; addr < end; addr = next) {
 804                 vma = vma_lookup(mm, addr);
 805                 if (!vma || !(vma->vm_flags & VM_READ)) {
 806                         ret = -EINVAL;
 807                         goto out;
 808                 }
 809                 next = min(end, addr + (ARRAY_SIZE(src_pfns) << PAGE_SHIFT));
 810                 if (next > vma->vm_end)
 811                         next = vma->vm_end;
 812
 813                 args.vma = vma;
 814                 args.src = src_pfns;
 815                 args.dst = dst_pfns;
 816                 args.start = addr;
 817                 args.end = next;
 818                 args.pgmap_owner = dmirror->mdevice;
 819                 args.flags = MIGRATE_VMA_SELECT_SYSTEM;
 820                 ret = migrate_vma_setup(&args);
 821                 if (ret)
 822                         goto out;
 823
 824                 dmirror_migrate_alloc_and_copy(&args, dmirror);
 825                 migrate_vma_pages(&args);
 826                 dmirror_migrate_finalize_and_map(&args, dmirror);
 827                 migrate_vma_finalize(&args);
 828         }
 829         mmap_read_unlock(mm);
 830         mmput(mm);
 831
 832         /* Return the migrated data for verification. */
 833         ret = dmirror_bounce_init(&bounce, start, size);
 834         if (ret)
 835                 return ret;
 836         mutex_lock(&dmirror->mutex);
 837         ret = dmirror_do_read(dmirror, start, end, &bounce);
 838         mutex_unlock(&dmirror->mutex);
 839         if (ret == 0) {
 840                 if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
 841                                  bounce.size))
 842                         ret = -EFAULT;
 843         }
 844         cmd->cpages = bounce.cpages;
 845         dmirror_bounce_fini(&bounce);
 846         return ret;
 847
 848 out:
 849         mmap_read_unlock(mm);
 850         mmput(mm);
 851         return ret;
 852 }
 853
 854 static void dmirror_mkentry(struct dmirror *dmirror, struct hmm_range *range,
 855                             unsigned char *perm, unsigned long entry)
 856 {
 857         struct page *page;
 858
 859         if (entry & HMM_PFN_ERROR) {
 860                 *perm = HMM_DMIRROR_PROT_ERROR;
 861                 return;
 862         }
 863         if (!(entry & HMM_PFN_VALID)) {
 864                 *perm = HMM_DMIRROR_PROT_NONE;
 865                 return;
 866         }
 867
 868         page = hmm_pfn_to_page(entry);
 869         if (is_device_private_page(page)) {
 870                 /* Is the page migrated to this device or some other? */
 871                 if (dmirror->mdevice == dmirror_page_to_device(page))
 872                         *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL;
 873                 else
 874                         *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE;
 875         } else if (is_zero_pfn(page_to_pfn(page)))
 876                 *perm = HMM_DMIRROR_PROT_ZERO;
 877         else
 878                 *perm = HMM_DMIRROR_PROT_NONE;
 879         if (entry & HMM_PFN_WRITE)
 880                 *perm |= HMM_DMIRROR_PROT_WRITE;
 881         else
 882                 *perm |= HMM_DMIRROR_PROT_READ;
 883         if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PMD_SHIFT)
 884                 *perm |= HMM_DMIRROR_PROT_PMD;
 885         else if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PUD_SHIFT)
 886                 *perm |= HMM_DMIRROR_PROT_PUD;
 887 }
 888
 889 static bool dmirror_snapshot_invalidate(struct mmu_interval_notifier *mni,
 890                                 const struct mmu_notifier_range *range,
 891                                 unsigned long cur_seq)
 892 {
 893         struct dmirror_interval *dmi =
 894                 container_of(mni, struct dmirror_interval, notifier);
 895         struct dmirror *dmirror = dmi->dmirror;
 896
 897         if (mmu_notifier_range_blockable(range))
 898                 mutex_lock(&dmirror->mutex);
 899         else if (!mutex_trylock(&dmirror->mutex))
 900                 return false;
 901
 902         /*
 903          * Snapshots only need to set the sequence number since any
 904          * invalidation in the interval invalidates the whole snapshot.
 905          */
 906         mmu_interval_set_seq(mni, cur_seq);
 907
 908         mutex_unlock(&dmirror->mutex);
 909         return true;
 910 }
 911
 912 static const struct mmu_interval_notifier_ops dmirror_mrn_ops = {
 913         .invalidate = dmirror_snapshot_invalidate,
 914 };
 915
 916 static int dmirror_range_snapshot(struct dmirror *dmirror,
 917                                   struct hmm_range *range,
 918                                   unsigned char *perm)
 919 {
 920         struct mm_struct *mm = dmirror->notifier.mm;
 921         struct dmirror_interval notifier;
 922         unsigned long timeout =
 923                 jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 924         unsigned long i;
 925         unsigned long n;
 926         int ret = 0;
 927
 928         notifier.dmirror = dmirror;
 929         range->notifier = &notifier.notifier;
 930
 931         ret = mmu_interval_notifier_insert(range->notifier, mm,
 932                         range->start, range->end - range->start,
 933                         &dmirror_mrn_ops);
 934         if (ret)
 935                 return ret;
 936
 937         while (true) {
 938                 if (time_after(jiffies, timeout)) {
 939                         ret = -EBUSY;
 940                         goto out;
 941                 }
 942
 943                 range->notifier_seq = mmu_interval_read_begin(range->notifier);
 944
 945                 mmap_read_lock(mm);
 946                 ret = hmm_range_fault(range);
 947                 mmap_read_unlock(mm);
 948                 if (ret) {
 949                         if (ret == -EBUSY)
 950                                 continue;
 951                         goto out;
 952                 }
 953
 954                 mutex_lock(&dmirror->mutex);
 955                 if (mmu_interval_read_retry(range->notifier,
 956                                             range->notifier_seq)) {
 957                         mutex_unlock(&dmirror->mutex);
 958                         continue;
 959                 }
 960                 break;
 961         }
 962
 963         n = (range->end - range->start) >> PAGE_SHIFT;
 964         for (i = 0; i < n; i++)
 965                 dmirror_mkentry(dmirror, range, perm + i, range->hmm_pfns[i]);
 966
 967         mutex_unlock(&dmirror->mutex);
 968 out:
 969         mmu_interval_notifier_remove(range->notifier);
 970         return ret;
 971 }
 972
 973 static int dmirror_snapshot(struct dmirror *dmirror,
 974                             struct hmm_dmirror_cmd *cmd)
 975 {
 976         struct mm_struct *mm = dmirror->notifier.mm;
 977         unsigned long start, end;
 978         unsigned long size = cmd->npages << PAGE_SHIFT;
 979         unsigned long addr;
 980         unsigned long next;
 981         unsigned long pfns[64];
 982         unsigned char perm[64];
 983         char __user *uptr;
 984         struct hmm_range range = {
 985                 .hmm_pfns = pfns,
 986                 .dev_private_owner = dmirror->mdevice,
 987         };
 988         int ret = 0;
 989
 990         start = cmd->addr;
 991         end = start + size;
 992         if (end < start)
 993                 return -EINVAL;
 994
 995         /* Since the mm is for the mirrored process, get a reference first. */
 996         if (!mmget_not_zero(mm))
 997                 return -EINVAL;
 998
 999         /*
1000          * Register a temporary notifier to detect invalidations even if it
1001          * overlaps with other mmu_interval_notifiers.
1002          */
1003         uptr = u64_to_user_ptr(cmd->ptr);
1004         for (addr = start; addr < end; addr = next) {
1005                 unsigned long n;
1006
1007                 next = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
1008                 range.start = addr;
1009                 range.end = next;
1010
1011                 ret = dmirror_range_snapshot(dmirror, &range, perm);
1012                 if (ret)
1013                         break;
1014
1015                 n = (range.end - range.start) >> PAGE_SHIFT;
1016                 if (copy_to_user(uptr, perm, n)) {
1017                         ret = -EFAULT;
1018                         break;
1019                 }
1020
1021                 cmd->cpages += n;
1022                 uptr += n;
1023         }
1024         mmput(mm);
1025
1026         return ret;
1027 }
1028
1029 static long dmirror_fops_unlocked_ioctl(struct file *filp,
1030                                         unsigned int command,
1031                                         unsigned long arg)
1032 {
1033         void __user *uarg = (void __user *)arg;
1034         struct hmm_dmirror_cmd cmd;
1035         struct dmirror *dmirror;
1036         int ret;
1037
1038         dmirror = filp->private_data;
1039         if (!dmirror)
1040                 return -EINVAL;
1041
1042         if (copy_from_user(&cmd, uarg, sizeof(cmd)))
1043                 return -EFAULT;
1044
1045         if (cmd.addr & ~PAGE_MASK)
1046                 return -EINVAL;
1047         if (cmd.addr >= (cmd.addr + (cmd.npages << PAGE_SHIFT)))
1048                 return -EINVAL;
1049
1050         cmd.cpages = 0;
1051         cmd.faults = 0;
1052
1053         switch (command) {
1054         case HMM_DMIRROR_READ:
1055                 ret = dmirror_read(dmirror, &cmd);
1056                 break;
1057
1058         case HMM_DMIRROR_WRITE:
1059                 ret = dmirror_write(dmirror, &cmd);
1060                 break;
1061
1062         case HMM_DMIRROR_MIGRATE:
1063                 ret = dmirror_migrate(dmirror, &cmd);
1064                 break;
1065
1066         case HMM_DMIRROR_EXCLUSIVE:
1067                 ret = dmirror_exclusive(dmirror, &cmd);
1068                 break;
1069
1070         case HMM_DMIRROR_CHECK_EXCLUSIVE:
1071                 ret = dmirror_check_atomic(dmirror, cmd.addr,
1072                                         cmd.addr + (cmd.npages << PAGE_SHIFT));
1073                 break;
1074
1075         case HMM_DMIRROR_SNAPSHOT:
1076                 ret = dmirror_snapshot(dmirror, &cmd);
1077                 break;
1078
1079         default:
1080                 return -EINVAL;
1081         }
1082         if (ret)
1083                 return ret;
1084
1085         if (copy_to_user(uarg, &cmd, sizeof(cmd)))
1086                 return -EFAULT;
1087
1088         return 0;
1089 }
1090
1091 static int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma)
1092 {
1093         unsigned long addr;
1094
1095         for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
1096                 struct page *page;
1097                 int ret;
1098
1099                 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
1100                 if (!page)
1101                         return -ENOMEM;
1102
1103                 ret = vm_insert_page(vma, addr, page);
1104                 if (ret) {
1105                         __free_page(page);
1106                         return ret;
1107                 }
1108                 put_page(page);
1109         }
1110
1111         return 0;
1112 }
1113
1114 static const struct file_operations dmirror_fops = {
1115         .open           = dmirror_fops_open,
1116         .release        = dmirror_fops_release,
1117         .mmap           = dmirror_fops_mmap,
1118         .unlocked_ioctl = dmirror_fops_unlocked_ioctl,
1119         .llseek         = default_llseek,
1120         .owner          = THIS_MODULE,
1121 };
1122
1123 static void dmirror_devmem_free(struct page *page)
1124 {
1125         struct page *rpage = page->zone_device_data;
1126         struct dmirror_device *mdevice;
1127
1128         if (rpage)
1129                 __free_page(rpage);
1130
1131         mdevice = dmirror_page_to_device(page);
1132
1133         spin_lock(&mdevice->lock);
1134         mdevice->cfree++;
1135         page->zone_device_data = mdevice->free_pages;
1136         mdevice->free_pages = page;
1137         spin_unlock(&mdevice->lock);
1138 }
1139
1140 static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
1141                                                       struct dmirror *dmirror)
1142 {
1143         const unsigned long *src = args->src;
1144         unsigned long *dst = args->dst;
1145         unsigned long start = args->start;
1146         unsigned long end = args->end;
1147         unsigned long addr;
1148
1149         for (addr = start; addr < end; addr += PAGE_SIZE,
1150                                        src++, dst++) {
1151                 struct page *dpage, *spage;
1152
1153                 spage = migrate_pfn_to_page(*src);
1154                 if (!spage || !(*src & MIGRATE_PFN_MIGRATE))
1155                         continue;
1156                 spage = spage->zone_device_data;
1157
1158                 dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);
1159                 if (!dpage)
1160                         continue;
1161
1162                 lock_page(dpage);
1163                 xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);
1164                 copy_highpage(dpage, spage);
1165                 *dst = migrate_pfn(page_to_pfn(dpage));
1166                 if (*src & MIGRATE_PFN_WRITE)
1167                         *dst |= MIGRATE_PFN_WRITE;
1168         }
1169         return 0;
1170 }
1171
1172 static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
1173 {
1174         struct migrate_vma args;
1175         unsigned long src_pfns;
1176         unsigned long dst_pfns;
1177         struct page *rpage;
1178         struct dmirror *dmirror;
1179         vm_fault_t ret;
1180
1181         /*
1182          * Normally, a device would use the page->zone_device_data to point to
1183          * the mirror but here we use it to hold the page for the simulated
1184          * device memory and that page holds the pointer to the mirror.
1185          */
1186         rpage = vmf->page->zone_device_data;
1187         dmirror = rpage->zone_device_data;
1188
1189         /* FIXME demonstrate how we can adjust migrate range */
1190         args.vma = vmf->vma;
1191         args.start = vmf->address;
1192         args.end = args.start + PAGE_SIZE;
1193         args.src = &src_pfns;
1194         args.dst = &dst_pfns;
1195         args.pgmap_owner = dmirror->mdevice;
1196         args.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
1197
1198         if (migrate_vma_setup(&args))
1199                 return VM_FAULT_SIGBUS;
1200
1201         ret = dmirror_devmem_fault_alloc_and_copy(&args, dmirror);
1202         if (ret)
1203                 return ret;
1204         migrate_vma_pages(&args);
1205         /*
1206          * No device finalize step is needed since
1207          * dmirror_devmem_fault_alloc_and_copy() will have already
1208          * invalidated the device page table.
1209          */
1210         migrate_vma_finalize(&args);
1211         return 0;
1212 }
1213
1214 static const struct dev_pagemap_ops dmirror_devmem_ops = {
1215         .page_free      = dmirror_devmem_free,
1216         .migrate_to_ram = dmirror_devmem_fault,
1217 };
1218
1219 static int dmirror_device_init(struct dmirror_device *mdevice, int id)
1220 {
1221         dev_t dev;
1222         int ret;
1223
1224         dev = MKDEV(MAJOR(dmirror_dev), id);
1225         mutex_init(&mdevice->devmem_lock);
1226         spin_lock_init(&mdevice->lock);
1227
1228         cdev_init(&mdevice->cdevice, &dmirror_fops);
1229         mdevice->cdevice.owner = THIS_MODULE;
1230         ret = cdev_add(&mdevice->cdevice, dev, 1);
1231         if (ret)
1232                 return ret;
1233
1234         /* Build a list of free ZONE_DEVICE private struct pages */
1235         dmirror_allocate_chunk(mdevice, NULL);
1236
1237         return 0;
1238 }
1239
1240 static void dmirror_device_remove(struct dmirror_device *mdevice)
1241 {
1242         unsigned int i;
1243
1244         if (mdevice->devmem_chunks) {
1245                 for (i = 0; i < mdevice->devmem_count; i++) {
1246                         struct dmirror_chunk *devmem =
1247                                 mdevice->devmem_chunks[i];
1248
1249                         memunmap_pages(&devmem->pagemap);
1250                         release_mem_region(devmem->pagemap.range.start,
1251                                            range_len(&devmem->pagemap.range));
1252                         kfree(devmem);
1253                 }
1254                 kfree(mdevice->devmem_chunks);
1255         }
1256
1257         cdev_del(&mdevice->cdevice);
1258 }
1259
1260 static int __init hmm_dmirror_init(void)
1261 {
1262         int ret;
1263         int id;
1264
1265         ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
1266                                   "HMM_DMIRROR");
1267         if (ret)
1268                 goto err_unreg;
1269
1270         for (id = 0; id < DMIRROR_NDEVICES; id++) {
1271                 ret = dmirror_device_init(dmirror_devices + id, id);
1272                 if (ret)
1273                         goto err_chrdev;
1274         }
1275
1276         pr_info("HMM test module loaded. This is only for testing HMM.\n");
1277         return 0;
1278
1279 err_chrdev:
1280         while (--id >= 0)
1281                 dmirror_device_remove(dmirror_devices + id);
1282         unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
1283 err_unreg:
1284         return ret;
1285 }
1286
1287 static void __exit hmm_dmirror_exit(void)
1288 {
1289         int id;
1290
1291         for (id = 0; id < DMIRROR_NDEVICES; id++)
1292                 dmirror_device_remove(dmirror_devices + id);
1293         unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
1294 }
1295
1296 module_init(hmm_dmirror_init);
1297 module_exit(hmm_dmirror_exit);
1298 MODULE_LICENSE("GPL");