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                4
  36 #define DMIRROR_RANGE_FAULT_TIMEOUT     1000
  37 #define DEVMEM_CHUNK_SIZE               (256 * 1024 * 1024U)
  38 #define DEVMEM_CHUNKS_RESERVE           16
  39
  40 /*
  41  * For device_private pages, dpage is just a dummy struct page
  42  * representing a piece of device memory. dmirror_devmem_alloc_page
  43  * allocates a real system memory page as backing storage to fake a
  44  * real device. zone_device_data points to that backing page. But
  45  * for device_coherent memory, the struct page represents real
  46  * physical CPU-accessible memory that we can use directly.
  47  */
  48 #define BACKING_PAGE(page) (is_device_private_page((page)) ? \
  49                            (page)->zone_device_data : (page))
  50
  51 static unsigned long spm_addr_dev0;
  52 module_param(spm_addr_dev0, long, 0644);
  53 MODULE_PARM_DESC(spm_addr_dev0,
  54                 "Specify start address for SPM (special purpose memory) used for device 0. By setting this Coherent device type will be used. Make sure spm_addr_dev1 is set too. Minimum SPM size should be DEVMEM_CHUNK_SIZE.");
  55
  56 static unsigned long spm_addr_dev1;
  57 module_param(spm_addr_dev1, long, 0644);
  58 MODULE_PARM_DESC(spm_addr_dev1,
  59                 "Specify start address for SPM (special purpose memory) used for device 1. By setting this Coherent device type will be used. Make sure spm_addr_dev0 is set too. Minimum SPM size should be DEVMEM_CHUNK_SIZE.");
  60
  61 static const struct dev_pagemap_ops dmirror_devmem_ops;
  62 static const struct mmu_interval_notifier_ops dmirror_min_ops;
  63 static dev_t dmirror_dev;
  64
  65 struct dmirror_device;
  66
  67 struct dmirror_bounce {
  68         void                    *ptr;
  69         unsigned long           size;
  70         unsigned long           addr;
  71         unsigned long           cpages;
  72 };
  73
  74 #define DPT_XA_TAG_ATOMIC 1UL
  75 #define DPT_XA_TAG_WRITE 3UL
  76
  77 /*
  78  * Data structure to track address ranges and register for mmu interval
  79  * notifier updates.
  80  */
  81 struct dmirror_interval {
  82         struct mmu_interval_notifier    notifier;
  83         struct dmirror                  *dmirror;
  84 };
  85
  86 /*
  87  * Data attached to the open device file.
  88  * Note that it might be shared after a fork().
  89  */
  90 struct dmirror {
  91         struct dmirror_device           *mdevice;
  92         struct xarray                   pt;
  93         struct mmu_interval_notifier    notifier;
  94         struct mutex                    mutex;
  95 };
  96
  97 /*
  98  * ZONE_DEVICE pages for migration and simulating device memory.
  99  */
 100 struct dmirror_chunk {
 101         struct dev_pagemap      pagemap;
 102         struct dmirror_device   *mdevice;
 103 };
 104
 105 /*
 106  * Per device data.
 107  */
 108 struct dmirror_device {
 109         struct cdev             cdevice;
 110         unsigned int            zone_device_type;
 111         struct device           device;
 112
 113         unsigned int            devmem_capacity;
 114         unsigned int            devmem_count;
 115         struct dmirror_chunk    **devmem_chunks;
 116         struct mutex            devmem_lock;    /* protects the above */
 117
 118         unsigned long           calloc;
 119         unsigned long           cfree;
 120         struct page             *free_pages;
 121         spinlock_t              lock;           /* protects the above */
 122 };
 123
 124 static struct dmirror_device dmirror_devices[DMIRROR_NDEVICES];
 125
 126 static int dmirror_bounce_init(struct dmirror_bounce *bounce,
 127                                unsigned long addr,
 128                                unsigned long size)
 129 {
 130         bounce->addr = addr;
 131         bounce->size = size;
 132         bounce->cpages = 0;
 133         bounce->ptr = vmalloc(size);
 134         if (!bounce->ptr)
 135                 return -ENOMEM;
 136         return 0;
 137 }
 138
 139 static bool dmirror_is_private_zone(struct dmirror_device *mdevice)
 140 {
 141         return (mdevice->zone_device_type ==
 142                 HMM_DMIRROR_MEMORY_DEVICE_PRIVATE) ? true : false;
 143 }
 144
 145 static enum migrate_vma_direction
 146 dmirror_select_device(struct dmirror *dmirror)
 147 {
 148         return (dmirror->mdevice->zone_device_type ==
 149                 HMM_DMIRROR_MEMORY_DEVICE_PRIVATE) ?
 150                 MIGRATE_VMA_SELECT_DEVICE_PRIVATE :
 151                 MIGRATE_VMA_SELECT_DEVICE_COHERENT;
 152 }
 153
 154 static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
 155 {
 156         vfree(bounce->ptr);
 157 }
 158
 159 static int dmirror_fops_open(struct inode *inode, struct file *filp)
 160 {
 161         struct cdev *cdev = inode->i_cdev;
 162         struct dmirror *dmirror;
 163         int ret;
 164
 165         /* Mirror this process address space */
 166         dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
 167         if (dmirror == NULL)
 168                 return -ENOMEM;
 169
 170         dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
 171         mutex_init(&dmirror->mutex);
 172         xa_init(&dmirror->pt);
 173
 174         ret = mmu_interval_notifier_insert(&dmirror->notifier, current->mm,
 175                                 0, ULONG_MAX & PAGE_MASK, &dmirror_min_ops);
 176         if (ret) {
 177                 kfree(dmirror);
 178                 return ret;
 179         }
 180
 181         filp->private_data = dmirror;
 182         return 0;
 183 }
 184
 185 static int dmirror_fops_release(struct inode *inode, struct file *filp)
 186 {
 187         struct dmirror *dmirror = filp->private_data;
 188
 189         mmu_interval_notifier_remove(&dmirror->notifier);
 190         xa_destroy(&dmirror->pt);
 191         kfree(dmirror);
 192         return 0;
 193 }
 194
 195 static struct dmirror_device *dmirror_page_to_device(struct page *page)
 196
 197 {
 198         return container_of(page->pgmap, struct dmirror_chunk,
 199                             pagemap)->mdevice;
 200 }
 201
 202 static int dmirror_do_fault(struct dmirror *dmirror, struct hmm_range *range)
 203 {
 204         unsigned long *pfns = range->hmm_pfns;
 205         unsigned long pfn;
 206
 207         for (pfn = (range->start >> PAGE_SHIFT);
 208              pfn < (range->end >> PAGE_SHIFT);
 209              pfn++, pfns++) {
 210                 struct page *page;
 211                 void *entry;
 212
 213                 /*
 214                  * Since we asked for hmm_range_fault() to populate pages,
 215                  * it shouldn't return an error entry on success.
 216                  */
 217                 WARN_ON(*pfns & HMM_PFN_ERROR);
 218                 WARN_ON(!(*pfns & HMM_PFN_VALID));
 219
 220                 page = hmm_pfn_to_page(*pfns);
 221                 WARN_ON(!page);
 222
 223                 entry = page;
 224                 if (*pfns & HMM_PFN_WRITE)
 225                         entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
 226                 else if (WARN_ON(range->default_flags & HMM_PFN_WRITE))
 227                         return -EFAULT;
 228                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 229                 if (xa_is_err(entry))
 230                         return xa_err(entry);
 231         }
 232
 233         return 0;
 234 }
 235
 236 static void dmirror_do_update(struct dmirror *dmirror, unsigned long start,
 237                               unsigned long end)
 238 {
 239         unsigned long pfn;
 240         void *entry;
 241
 242         /*
 243          * The XArray doesn't hold references to pages since it relies on
 244          * the mmu notifier to clear page pointers when they become stale.
 245          * Therefore, it is OK to just clear the entry.
 246          */
 247         xa_for_each_range(&dmirror->pt, pfn, entry, start >> PAGE_SHIFT,
 248                           end >> PAGE_SHIFT)
 249                 xa_erase(&dmirror->pt, pfn);
 250 }
 251
 252 static bool dmirror_interval_invalidate(struct mmu_interval_notifier *mni,
 253                                 const struct mmu_notifier_range *range,
 254                                 unsigned long cur_seq)
 255 {
 256         struct dmirror *dmirror = container_of(mni, struct dmirror, notifier);
 257
 258         /*
 259          * Ignore invalidation callbacks for device private pages since
 260          * the invalidation is handled as part of the migration process.
 261          */
 262         if (range->event == MMU_NOTIFY_MIGRATE &&
 263             range->owner == dmirror->mdevice)
 264                 return true;
 265
 266         if (mmu_notifier_range_blockable(range))
 267                 mutex_lock(&dmirror->mutex);
 268         else if (!mutex_trylock(&dmirror->mutex))
 269                 return false;
 270
 271         mmu_interval_set_seq(mni, cur_seq);
 272         dmirror_do_update(dmirror, range->start, range->end);
 273
 274         mutex_unlock(&dmirror->mutex);
 275         return true;
 276 }
 277
 278 static const struct mmu_interval_notifier_ops dmirror_min_ops = {
 279         .invalidate = dmirror_interval_invalidate,
 280 };
 281
 282 static int dmirror_range_fault(struct dmirror *dmirror,
 283                                 struct hmm_range *range)
 284 {
 285         struct mm_struct *mm = dmirror->notifier.mm;
 286         unsigned long timeout =
 287                 jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 288         int ret;
 289
 290         while (true) {
 291                 if (time_after(jiffies, timeout)) {
 292                         ret = -EBUSY;
 293                         goto out;
 294                 }
 295
 296                 range->notifier_seq = mmu_interval_read_begin(range->notifier);
 297                 mmap_read_lock(mm);
 298                 ret = hmm_range_fault(range);
 299                 mmap_read_unlock(mm);
 300                 if (ret) {
 301                         if (ret == -EBUSY)
 302                                 continue;
 303                         goto out;
 304                 }
 305
 306                 mutex_lock(&dmirror->mutex);
 307                 if (mmu_interval_read_retry(range->notifier,
 308                                             range->notifier_seq)) {
 309                         mutex_unlock(&dmirror->mutex);
 310                         continue;
 311                 }
 312                 break;
 313         }
 314
 315         ret = dmirror_do_fault(dmirror, range);
 316
 317         mutex_unlock(&dmirror->mutex);
 318 out:
 319         return ret;
 320 }
 321
 322 static int dmirror_fault(struct dmirror *dmirror, unsigned long start,
 323                          unsigned long end, bool write)
 324 {
 325         struct mm_struct *mm = dmirror->notifier.mm;
 326         unsigned long addr;
 327         unsigned long pfns[64];
 328         struct hmm_range range = {
 329                 .notifier = &dmirror->notifier,
 330                 .hmm_pfns = pfns,
 331                 .pfn_flags_mask = 0,
 332                 .default_flags =
 333                         HMM_PFN_REQ_FAULT | (write ? HMM_PFN_REQ_WRITE : 0),
 334                 .dev_private_owner = dmirror->mdevice,
 335         };
 336         int ret = 0;
 337
 338         /* Since the mm is for the mirrored process, get a reference first. */
 339         if (!mmget_not_zero(mm))
 340                 return 0;
 341
 342         for (addr = start; addr < end; addr = range.end) {
 343                 range.start = addr;
 344                 range.end = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
 345
 346                 ret = dmirror_range_fault(dmirror, &range);
 347                 if (ret)
 348                         break;
 349         }
 350
 351         mmput(mm);
 352         return ret;
 353 }
 354
 355 static int dmirror_do_read(struct dmirror *dmirror, unsigned long start,
 356                            unsigned long end, struct dmirror_bounce *bounce)
 357 {
 358         unsigned long pfn;
 359         void *ptr;
 360
 361         ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
 362
 363         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 364                 void *entry;
 365                 struct page *page;
 366                 void *tmp;
 367
 368                 entry = xa_load(&dmirror->pt, pfn);
 369                 page = xa_untag_pointer(entry);
 370                 if (!page)
 371                         return -ENOENT;
 372
 373                 tmp = kmap(page);
 374                 memcpy(ptr, tmp, PAGE_SIZE);
 375                 kunmap(page);
 376
 377                 ptr += PAGE_SIZE;
 378                 bounce->cpages++;
 379         }
 380
 381         return 0;
 382 }
 383
 384 static int dmirror_read(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 385 {
 386         struct dmirror_bounce bounce;
 387         unsigned long start, end;
 388         unsigned long size = cmd->npages << PAGE_SHIFT;
 389         int ret;
 390
 391         start = cmd->addr;
 392         end = start + size;
 393         if (end < start)
 394                 return -EINVAL;
 395
 396         ret = dmirror_bounce_init(&bounce, start, size);
 397         if (ret)
 398                 return ret;
 399
 400         while (1) {
 401                 mutex_lock(&dmirror->mutex);
 402                 ret = dmirror_do_read(dmirror, start, end, &bounce);
 403                 mutex_unlock(&dmirror->mutex);
 404                 if (ret != -ENOENT)
 405                         break;
 406
 407                 start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
 408                 ret = dmirror_fault(dmirror, start, end, false);
 409                 if (ret)
 410                         break;
 411                 cmd->faults++;
 412         }
 413
 414         if (ret == 0) {
 415                 if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
 416                                  bounce.size))
 417                         ret = -EFAULT;
 418         }
 419         cmd->cpages = bounce.cpages;
 420         dmirror_bounce_fini(&bounce);
 421         return ret;
 422 }
 423
 424 static int dmirror_do_write(struct dmirror *dmirror, unsigned long start,
 425                             unsigned long end, struct dmirror_bounce *bounce)
 426 {
 427         unsigned long pfn;
 428         void *ptr;
 429
 430         ptr = bounce->ptr + ((start - bounce->addr) & PAGE_MASK);
 431
 432         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 433                 void *entry;
 434                 struct page *page;
 435                 void *tmp;
 436
 437                 entry = xa_load(&dmirror->pt, pfn);
 438                 page = xa_untag_pointer(entry);
 439                 if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE)
 440                         return -ENOENT;
 441
 442                 tmp = kmap(page);
 443                 memcpy(tmp, ptr, PAGE_SIZE);
 444                 kunmap(page);
 445
 446                 ptr += PAGE_SIZE;
 447                 bounce->cpages++;
 448         }
 449
 450         return 0;
 451 }
 452
 453 static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 454 {
 455         struct dmirror_bounce bounce;
 456         unsigned long start, end;
 457         unsigned long size = cmd->npages << PAGE_SHIFT;
 458         int ret;
 459
 460         start = cmd->addr;
 461         end = start + size;
 462         if (end < start)
 463                 return -EINVAL;
 464
 465         ret = dmirror_bounce_init(&bounce, start, size);
 466         if (ret)
 467                 return ret;
 468         if (copy_from_user(bounce.ptr, u64_to_user_ptr(cmd->ptr),
 469                            bounce.size)) {
 470                 ret = -EFAULT;
 471                 goto fini;
 472         }
 473
 474         while (1) {
 475                 mutex_lock(&dmirror->mutex);
 476                 ret = dmirror_do_write(dmirror, start, end, &bounce);
 477                 mutex_unlock(&dmirror->mutex);
 478                 if (ret != -ENOENT)
 479                         break;
 480
 481                 start = cmd->addr + (bounce.cpages << PAGE_SHIFT);
 482                 ret = dmirror_fault(dmirror, start, end, true);
 483                 if (ret)
 484                         break;
 485                 cmd->faults++;
 486         }
 487
 488 fini:
 489         cmd->cpages = bounce.cpages;
 490         dmirror_bounce_fini(&bounce);
 491         return ret;
 492 }
 493
 494 static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
 495                                    struct page **ppage)
 496 {
 497         struct dmirror_chunk *devmem;
 498         struct resource *res = NULL;
 499         unsigned long pfn;
 500         unsigned long pfn_first;
 501         unsigned long pfn_last;
 502         void *ptr;
 503         int ret = -ENOMEM;
 504
 505         devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
 506         if (!devmem)
 507                 return ret;
 508
 509         switch (mdevice->zone_device_type) {
 510         case HMM_DMIRROR_MEMORY_DEVICE_PRIVATE:
 511                 res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
 512                                               "hmm_dmirror");
 513                 if (IS_ERR_OR_NULL(res))
 514                         goto err_devmem;
 515                 devmem->pagemap.range.start = res->start;
 516                 devmem->pagemap.range.end = res->end;
 517                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
 518                 break;
 519         case HMM_DMIRROR_MEMORY_DEVICE_COHERENT:
 520                 devmem->pagemap.range.start = (MINOR(mdevice->cdevice.dev) - 2) ?
 521                                                         spm_addr_dev0 :
 522                                                         spm_addr_dev1;
 523                 devmem->pagemap.range.end = devmem->pagemap.range.start +
 524                                             DEVMEM_CHUNK_SIZE - 1;
 525                 devmem->pagemap.type = MEMORY_DEVICE_COHERENT;
 526                 break;
 527         default:
 528                 ret = -EINVAL;
 529                 goto err_devmem;
 530         }
 531
 532         devmem->pagemap.nr_range = 1;
 533         devmem->pagemap.ops = &dmirror_devmem_ops;
 534         devmem->pagemap.owner = mdevice;
 535
 536         mutex_lock(&mdevice->devmem_lock);
 537
 538         if (mdevice->devmem_count == mdevice->devmem_capacity) {
 539                 struct dmirror_chunk **new_chunks;
 540                 unsigned int new_capacity;
 541
 542                 new_capacity = mdevice->devmem_capacity +
 543                                 DEVMEM_CHUNKS_RESERVE;
 544                 new_chunks = krealloc(mdevice->devmem_chunks,
 545                                 sizeof(new_chunks[0]) * new_capacity,
 546                                 GFP_KERNEL);
 547                 if (!new_chunks)
 548                         goto err_release;
 549                 mdevice->devmem_capacity = new_capacity;
 550                 mdevice->devmem_chunks = new_chunks;
 551         }
 552         ptr = memremap_pages(&devmem->pagemap, numa_node_id());
 553         if (IS_ERR_OR_NULL(ptr)) {
 554                 if (ptr)
 555                         ret = PTR_ERR(ptr);
 556                 else
 557                         ret = -EFAULT;
 558                 goto err_release;
 559         }
 560
 561         devmem->mdevice = mdevice;
 562         pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
 563         pfn_last = pfn_first + (range_len(&devmem->pagemap.range) >> PAGE_SHIFT);
 564         mdevice->devmem_chunks[mdevice->devmem_count++] = devmem;
 565
 566         mutex_unlock(&mdevice->devmem_lock);
 567
 568         pr_info("added new %u MB chunk (total %u chunks, %u MB) PFNs [0x%lx 0x%lx)\n",
 569                 DEVMEM_CHUNK_SIZE / (1024 * 1024),
 570                 mdevice->devmem_count,
 571                 mdevice->devmem_count * (DEVMEM_CHUNK_SIZE / (1024 * 1024)),
 572                 pfn_first, pfn_last);
 573
 574         spin_lock(&mdevice->lock);
 575         for (pfn = pfn_first; pfn < pfn_last; pfn++) {
 576                 struct page *page = pfn_to_page(pfn);
 577
 578                 page->zone_device_data = mdevice->free_pages;
 579                 mdevice->free_pages = page;
 580         }
 581         if (ppage) {
 582                 *ppage = mdevice->free_pages;
 583                 mdevice->free_pages = (*ppage)->zone_device_data;
 584                 mdevice->calloc++;
 585         }
 586         spin_unlock(&mdevice->lock);
 587
 588         return 0;
 589
 590 err_release:
 591         mutex_unlock(&mdevice->devmem_lock);
 592         if (res && devmem->pagemap.type == MEMORY_DEVICE_PRIVATE)
 593                 release_mem_region(devmem->pagemap.range.start,
 594                                    range_len(&devmem->pagemap.range));
 595 err_devmem:
 596         kfree(devmem);
 597
 598         return ret;
 599 }
 600
 601 static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
 602 {
 603         struct page *dpage = NULL;
 604         struct page *rpage = NULL;
 605
 606         /*
 607          * For ZONE_DEVICE private type, this is a fake device so we allocate
 608          * real system memory to store our device memory.
 609          * For ZONE_DEVICE coherent type we use the actual dpage to store the
 610          * data and ignore rpage.
 611          */
 612         if (dmirror_is_private_zone(mdevice)) {
 613                 rpage = alloc_page(GFP_HIGHUSER);
 614                 if (!rpage)
 615                         return NULL;
 616         }
 617         spin_lock(&mdevice->lock);
 618
 619         if (mdevice->free_pages) {
 620                 dpage = mdevice->free_pages;
 621                 mdevice->free_pages = dpage->zone_device_data;
 622                 mdevice->calloc++;
 623                 spin_unlock(&mdevice->lock);
 624         } else {
 625                 spin_unlock(&mdevice->lock);
 626                 if (dmirror_allocate_chunk(mdevice, &dpage))
 627                         goto error;
 628         }
 629
 630         dpage->zone_device_data = rpage;
 631         lock_page(dpage);
 632         return dpage;
 633
 634 error:
 635         if (rpage)
 636                 __free_page(rpage);
 637         return NULL;
 638 }
 639
 640 static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
 641                                            struct dmirror *dmirror)
 642 {
 643         struct dmirror_device *mdevice = dmirror->mdevice;
 644         const unsigned long *src = args->src;
 645         unsigned long *dst = args->dst;
 646         unsigned long addr;
 647
 648         for (addr = args->start; addr < args->end; addr += PAGE_SIZE,
 649                                                    src++, dst++) {
 650                 struct page *spage;
 651                 struct page *dpage;
 652                 struct page *rpage;
 653
 654                 if (!(*src & MIGRATE_PFN_MIGRATE))
 655                         continue;
 656
 657                 /*
 658                  * Note that spage might be NULL which is OK since it is an
 659                  * unallocated pte_none() or read-only zero page.
 660                  */
 661                 spage = migrate_pfn_to_page(*src);
 662                 if (WARN(spage && is_zone_device_page(spage),
 663                      "page already in device spage pfn: 0x%lx\n",
 664                      page_to_pfn(spage)))
 665                         continue;
 666
 667                 dpage = dmirror_devmem_alloc_page(mdevice);
 668                 if (!dpage)
 669                         continue;
 670
 671                 rpage = BACKING_PAGE(dpage);
 672                 if (spage)
 673                         copy_highpage(rpage, spage);
 674                 else
 675                         clear_highpage(rpage);
 676
 677                 /*
 678                  * Normally, a device would use the page->zone_device_data to
 679                  * point to the mirror but here we use it to hold the page for
 680                  * the simulated device memory and that page holds the pointer
 681                  * to the mirror.
 682                  */
 683                 rpage->zone_device_data = dmirror;
 684
 685                 pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",
 686                          page_to_pfn(spage), page_to_pfn(dpage));
 687                 *dst = migrate_pfn(page_to_pfn(dpage));
 688                 if ((*src & MIGRATE_PFN_WRITE) ||
 689                     (!spage && args->vma->vm_flags & VM_WRITE))
 690                         *dst |= MIGRATE_PFN_WRITE;
 691         }
 692 }
 693
 694 static int dmirror_check_atomic(struct dmirror *dmirror, unsigned long start,
 695                              unsigned long end)
 696 {
 697         unsigned long pfn;
 698
 699         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
 700                 void *entry;
 701
 702                 entry = xa_load(&dmirror->pt, pfn);
 703                 if (xa_pointer_tag(entry) == DPT_XA_TAG_ATOMIC)
 704                         return -EPERM;
 705         }
 706
 707         return 0;
 708 }
 709
 710 static int dmirror_atomic_map(unsigned long start, unsigned long end,
 711                               struct page **pages, struct dmirror *dmirror)
 712 {
 713         unsigned long pfn, mapped = 0;
 714         int i;
 715
 716         /* Map the migrated pages into the device's page tables. */
 717         mutex_lock(&dmirror->mutex);
 718
 719         for (i = 0, pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++, i++) {
 720                 void *entry;
 721
 722                 if (!pages[i])
 723                         continue;
 724
 725                 entry = pages[i];
 726                 entry = xa_tag_pointer(entry, DPT_XA_TAG_ATOMIC);
 727                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 728                 if (xa_is_err(entry)) {
 729                         mutex_unlock(&dmirror->mutex);
 730                         return xa_err(entry);
 731                 }
 732
 733                 mapped++;
 734         }
 735
 736         mutex_unlock(&dmirror->mutex);
 737         return mapped;
 738 }
 739
 740 static int dmirror_migrate_finalize_and_map(struct migrate_vma *args,
 741                                             struct dmirror *dmirror)
 742 {
 743         unsigned long start = args->start;
 744         unsigned long end = args->end;
 745         const unsigned long *src = args->src;
 746         const unsigned long *dst = args->dst;
 747         unsigned long pfn;
 748
 749         /* Map the migrated pages into the device's page tables. */
 750         mutex_lock(&dmirror->mutex);
 751
 752         for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++,
 753                                                                 src++, dst++) {
 754                 struct page *dpage;
 755                 void *entry;
 756
 757                 if (!(*src & MIGRATE_PFN_MIGRATE))
 758                         continue;
 759
 760                 dpage = migrate_pfn_to_page(*dst);
 761                 if (!dpage)
 762                         continue;
 763
 764                 entry = BACKING_PAGE(dpage);
 765                 if (*dst & MIGRATE_PFN_WRITE)
 766                         entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
 767                 entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
 768                 if (xa_is_err(entry)) {
 769                         mutex_unlock(&dmirror->mutex);
 770                         return xa_err(entry);
 771                 }
 772         }
 773
 774         mutex_unlock(&dmirror->mutex);
 775         return 0;
 776 }
 777
 778 static int dmirror_exclusive(struct dmirror *dmirror,
 779                              struct hmm_dmirror_cmd *cmd)
 780 {
 781         unsigned long start, end, addr;
 782         unsigned long size = cmd->npages << PAGE_SHIFT;
 783         struct mm_struct *mm = dmirror->notifier.mm;
 784         struct page *pages[64];
 785         struct dmirror_bounce bounce;
 786         unsigned long next;
 787         int ret;
 788
 789         start = cmd->addr;
 790         end = start + size;
 791         if (end < start)
 792                 return -EINVAL;
 793
 794         /* Since the mm is for the mirrored process, get a reference first. */
 795         if (!mmget_not_zero(mm))
 796                 return -EINVAL;
 797
 798         mmap_read_lock(mm);
 799         for (addr = start; addr < end; addr = next) {
 800                 unsigned long mapped = 0;
 801                 int i;
 802
 803                 if (end < addr + (ARRAY_SIZE(pages) << PAGE_SHIFT))
 804                         next = end;
 805                 else
 806                         next = addr + (ARRAY_SIZE(pages) << PAGE_SHIFT);
 807
 808                 ret = make_device_exclusive_range(mm, addr, next, pages, NULL);
 809                 /*
 810                  * Do dmirror_atomic_map() iff all pages are marked for
 811                  * exclusive access to avoid accessing uninitialized
 812                  * fields of pages.
 813                  */
 814                 if (ret == (next - addr) >> PAGE_SHIFT)
 815                         mapped = dmirror_atomic_map(addr, next, pages, dmirror);
 816                 for (i = 0; i < ret; i++) {
 817                         if (pages[i]) {
 818                                 unlock_page(pages[i]);
 819                                 put_page(pages[i]);
 820                         }
 821                 }
 822
 823                 if (addr + (mapped << PAGE_SHIFT) < next) {
 824                         mmap_read_unlock(mm);
 825                         mmput(mm);
 826                         return -EBUSY;
 827                 }
 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
 845         cmd->cpages = bounce.cpages;
 846         dmirror_bounce_fini(&bounce);
 847         return ret;
 848 }
 849
 850 static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
 851                                                       struct dmirror *dmirror)
 852 {
 853         const unsigned long *src = args->src;
 854         unsigned long *dst = args->dst;
 855         unsigned long start = args->start;
 856         unsigned long end = args->end;
 857         unsigned long addr;
 858
 859         for (addr = start; addr < end; addr += PAGE_SIZE,
 860                                        src++, dst++) {
 861                 struct page *dpage, *spage;
 862
 863                 spage = migrate_pfn_to_page(*src);
 864                 if (!spage || !(*src & MIGRATE_PFN_MIGRATE))
 865                         continue;
 866
 867                 if (WARN_ON(!is_device_private_page(spage) &&
 868                             !is_device_coherent_page(spage)))
 869                         continue;
 870                 spage = BACKING_PAGE(spage);
 871                 dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);
 872                 if (!dpage)
 873                         continue;
 874                 pr_debug("migrating from dev to sys pfn src: 0x%lx pfn dst: 0x%lx\n",
 875                          page_to_pfn(spage), page_to_pfn(dpage));
 876
 877                 lock_page(dpage);
 878                 xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);
 879                 copy_highpage(dpage, spage);
 880                 *dst = migrate_pfn(page_to_pfn(dpage));
 881                 if (*src & MIGRATE_PFN_WRITE)
 882                         *dst |= MIGRATE_PFN_WRITE;
 883         }
 884         return 0;
 885 }
 886
 887 static unsigned long
 888 dmirror_successful_migrated_pages(struct migrate_vma *migrate)
 889 {
 890         unsigned long cpages = 0;
 891         unsigned long i;
 892
 893         for (i = 0; i < migrate->npages; i++) {
 894                 if (migrate->src[i] & MIGRATE_PFN_VALID &&
 895                     migrate->src[i] & MIGRATE_PFN_MIGRATE)
 896                         cpages++;
 897         }
 898         return cpages;
 899 }
 900
 901 static int dmirror_migrate_to_system(struct dmirror *dmirror,
 902                                      struct hmm_dmirror_cmd *cmd)
 903 {
 904         unsigned long start, end, addr;
 905         unsigned long size = cmd->npages << PAGE_SHIFT;
 906         struct mm_struct *mm = dmirror->notifier.mm;
 907         struct vm_area_struct *vma;
 908         unsigned long src_pfns[64] = { 0 };
 909         unsigned long dst_pfns[64] = { 0 };
 910         struct migrate_vma args;
 911         unsigned long next;
 912         int ret;
 913
 914         start = cmd->addr;
 915         end = start + size;
 916         if (end < start)
 917                 return -EINVAL;
 918
 919         /* Since the mm is for the mirrored process, get a reference first. */
 920         if (!mmget_not_zero(mm))
 921                 return -EINVAL;
 922
 923         cmd->cpages = 0;
 924         mmap_read_lock(mm);
 925         for (addr = start; addr < end; addr = next) {
 926                 vma = vma_lookup(mm, addr);
 927                 if (!vma || !(vma->vm_flags & VM_READ)) {
 928                         ret = -EINVAL;
 929                         goto out;
 930                 }
 931                 next = min(end, addr + (ARRAY_SIZE(src_pfns) << PAGE_SHIFT));
 932                 if (next > vma->vm_end)
 933                         next = vma->vm_end;
 934
 935                 args.vma = vma;
 936                 args.src = src_pfns;
 937                 args.dst = dst_pfns;
 938                 args.start = addr;
 939                 args.end = next;
 940                 args.pgmap_owner = dmirror->mdevice;
 941                 args.flags = dmirror_select_device(dmirror);
 942
 943                 ret = migrate_vma_setup(&args);
 944                 if (ret)
 945                         goto out;
 946
 947                 pr_debug("Migrating from device mem to sys mem\n");
 948                 dmirror_devmem_fault_alloc_and_copy(&args, dmirror);
 949
 950                 migrate_vma_pages(&args);
 951                 cmd->cpages += dmirror_successful_migrated_pages(&args);
 952                 migrate_vma_finalize(&args);
 953         }
 954 out:
 955         mmap_read_unlock(mm);
 956         mmput(mm);
 957
 958         return ret;
 959 }
 960
 961 static int dmirror_migrate_to_device(struct dmirror *dmirror,
 962                                 struct hmm_dmirror_cmd *cmd)
 963 {
 964         unsigned long start, end, addr;
 965         unsigned long size = cmd->npages << PAGE_SHIFT;
 966         struct mm_struct *mm = dmirror->notifier.mm;
 967         struct vm_area_struct *vma;
 968         unsigned long src_pfns[64] = { 0 };
 969         unsigned long dst_pfns[64] = { 0 };
 970         struct dmirror_bounce bounce;
 971         struct migrate_vma args;
 972         unsigned long next;
 973         int ret;
 974
 975         start = cmd->addr;
 976         end = start + size;
 977         if (end < start)
 978                 return -EINVAL;
 979
 980         /* Since the mm is for the mirrored process, get a reference first. */
 981         if (!mmget_not_zero(mm))
 982                 return -EINVAL;
 983
 984         mmap_read_lock(mm);
 985         for (addr = start; addr < end; addr = next) {
 986                 vma = vma_lookup(mm, addr);
 987                 if (!vma || !(vma->vm_flags & VM_READ)) {
 988                         ret = -EINVAL;
 989                         goto out;
 990                 }
 991                 next = min(end, addr + (ARRAY_SIZE(src_pfns) << PAGE_SHIFT));
 992                 if (next > vma->vm_end)
 993                         next = vma->vm_end;
 994
 995                 args.vma = vma;
 996                 args.src = src_pfns;
 997                 args.dst = dst_pfns;
 998                 args.start = addr;
 999                 args.end = next;
1000                 args.pgmap_owner = dmirror->mdevice;
1001                 args.flags = MIGRATE_VMA_SELECT_SYSTEM;
1002                 ret = migrate_vma_setup(&args);
1003                 if (ret)
1004                         goto out;
1005
1006                 pr_debug("Migrating from sys mem to device mem\n");
1007                 dmirror_migrate_alloc_and_copy(&args, dmirror);
1008                 migrate_vma_pages(&args);
1009                 dmirror_migrate_finalize_and_map(&args, dmirror);
1010                 migrate_vma_finalize(&args);
1011         }
1012         mmap_read_unlock(mm);
1013         mmput(mm);
1014
1015         /*
1016          * Return the migrated data for verification.
1017          * Only for pages in device zone
1018          */
1019         ret = dmirror_bounce_init(&bounce, start, size);
1020         if (ret)
1021                 return ret;
1022         mutex_lock(&dmirror->mutex);
1023         ret = dmirror_do_read(dmirror, start, end, &bounce);
1024         mutex_unlock(&dmirror->mutex);
1025         if (ret == 0) {
1026                 if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr,
1027                                  bounce.size))
1028                         ret = -EFAULT;
1029         }
1030         cmd->cpages = bounce.cpages;
1031         dmirror_bounce_fini(&bounce);
1032         return ret;
1033
1034 out:
1035         mmap_read_unlock(mm);
1036         mmput(mm);
1037         return ret;
1038 }
1039
1040 static void dmirror_mkentry(struct dmirror *dmirror, struct hmm_range *range,
1041                             unsigned char *perm, unsigned long entry)
1042 {
1043         struct page *page;
1044
1045         if (entry & HMM_PFN_ERROR) {
1046                 *perm = HMM_DMIRROR_PROT_ERROR;
1047                 return;
1048         }
1049         if (!(entry & HMM_PFN_VALID)) {
1050                 *perm = HMM_DMIRROR_PROT_NONE;
1051                 return;
1052         }
1053
1054         page = hmm_pfn_to_page(entry);
1055         if (is_device_private_page(page)) {
1056                 /* Is the page migrated to this device or some other? */
1057                 if (dmirror->mdevice == dmirror_page_to_device(page))
1058                         *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL;
1059                 else
1060                         *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE;
1061         } else if (is_device_coherent_page(page)) {
1062                 /* Is the page migrated to this device or some other? */
1063                 if (dmirror->mdevice == dmirror_page_to_device(page))
1064                         *perm = HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL;
1065                 else
1066                         *perm = HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE;
1067         } else if (is_zero_pfn(page_to_pfn(page)))
1068                 *perm = HMM_DMIRROR_PROT_ZERO;
1069         else
1070                 *perm = HMM_DMIRROR_PROT_NONE;
1071         if (entry & HMM_PFN_WRITE)
1072                 *perm |= HMM_DMIRROR_PROT_WRITE;
1073         else
1074                 *perm |= HMM_DMIRROR_PROT_READ;
1075         if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PMD_SHIFT)
1076                 *perm |= HMM_DMIRROR_PROT_PMD;
1077         else if (hmm_pfn_to_map_order(entry) + PAGE_SHIFT == PUD_SHIFT)
1078                 *perm |= HMM_DMIRROR_PROT_PUD;
1079 }
1080
1081 static bool dmirror_snapshot_invalidate(struct mmu_interval_notifier *mni,
1082                                 const struct mmu_notifier_range *range,
1083                                 unsigned long cur_seq)
1084 {
1085         struct dmirror_interval *dmi =
1086                 container_of(mni, struct dmirror_interval, notifier);
1087         struct dmirror *dmirror = dmi->dmirror;
1088
1089         if (mmu_notifier_range_blockable(range))
1090                 mutex_lock(&dmirror->mutex);
1091         else if (!mutex_trylock(&dmirror->mutex))
1092                 return false;
1093
1094         /*
1095          * Snapshots only need to set the sequence number since any
1096          * invalidation in the interval invalidates the whole snapshot.
1097          */
1098         mmu_interval_set_seq(mni, cur_seq);
1099
1100         mutex_unlock(&dmirror->mutex);
1101         return true;
1102 }
1103
1104 static const struct mmu_interval_notifier_ops dmirror_mrn_ops = {
1105         .invalidate = dmirror_snapshot_invalidate,
1106 };
1107
1108 static int dmirror_range_snapshot(struct dmirror *dmirror,
1109                                   struct hmm_range *range,
1110                                   unsigned char *perm)
1111 {
1112         struct mm_struct *mm = dmirror->notifier.mm;
1113         struct dmirror_interval notifier;
1114         unsigned long timeout =
1115                 jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
1116         unsigned long i;
1117         unsigned long n;
1118         int ret = 0;
1119
1120         notifier.dmirror = dmirror;
1121         range->notifier = &notifier.notifier;
1122
1123         ret = mmu_interval_notifier_insert(range->notifier, mm,
1124                         range->start, range->end - range->start,
1125                         &dmirror_mrn_ops);
1126         if (ret)
1127                 return ret;
1128
1129         while (true) {
1130                 if (time_after(jiffies, timeout)) {
1131                         ret = -EBUSY;
1132                         goto out;
1133                 }
1134
1135                 range->notifier_seq = mmu_interval_read_begin(range->notifier);
1136
1137                 mmap_read_lock(mm);
1138                 ret = hmm_range_fault(range);
1139                 mmap_read_unlock(mm);
1140                 if (ret) {
1141                         if (ret == -EBUSY)
1142                                 continue;
1143                         goto out;
1144                 }
1145
1146                 mutex_lock(&dmirror->mutex);
1147                 if (mmu_interval_read_retry(range->notifier,
1148                                             range->notifier_seq)) {
1149                         mutex_unlock(&dmirror->mutex);
1150                         continue;
1151                 }
1152                 break;
1153         }
1154
1155         n = (range->end - range->start) >> PAGE_SHIFT;
1156         for (i = 0; i < n; i++)
1157                 dmirror_mkentry(dmirror, range, perm + i, range->hmm_pfns[i]);
1158
1159         mutex_unlock(&dmirror->mutex);
1160 out:
1161         mmu_interval_notifier_remove(range->notifier);
1162         return ret;
1163 }
1164
1165 static int dmirror_snapshot(struct dmirror *dmirror,
1166                             struct hmm_dmirror_cmd *cmd)
1167 {
1168         struct mm_struct *mm = dmirror->notifier.mm;
1169         unsigned long start, end;
1170         unsigned long size = cmd->npages << PAGE_SHIFT;
1171         unsigned long addr;
1172         unsigned long next;
1173         unsigned long pfns[64];
1174         unsigned char perm[64];
1175         char __user *uptr;
1176         struct hmm_range range = {
1177                 .hmm_pfns = pfns,
1178                 .dev_private_owner = dmirror->mdevice,
1179         };
1180         int ret = 0;
1181
1182         start = cmd->addr;
1183         end = start + size;
1184         if (end < start)
1185                 return -EINVAL;
1186
1187         /* Since the mm is for the mirrored process, get a reference first. */
1188         if (!mmget_not_zero(mm))
1189                 return -EINVAL;
1190
1191         /*
1192          * Register a temporary notifier to detect invalidations even if it
1193          * overlaps with other mmu_interval_notifiers.
1194          */
1195         uptr = u64_to_user_ptr(cmd->ptr);
1196         for (addr = start; addr < end; addr = next) {
1197                 unsigned long n;
1198
1199                 next = min(addr + (ARRAY_SIZE(pfns) << PAGE_SHIFT), end);
1200                 range.start = addr;
1201                 range.end = next;
1202
1203                 ret = dmirror_range_snapshot(dmirror, &range, perm);
1204                 if (ret)
1205                         break;
1206
1207                 n = (range.end - range.start) >> PAGE_SHIFT;
1208                 if (copy_to_user(uptr, perm, n)) {
1209                         ret = -EFAULT;
1210                         break;
1211                 }
1212
1213                 cmd->cpages += n;
1214                 uptr += n;
1215         }
1216         mmput(mm);
1217
1218         return ret;
1219 }
1220
1221 static long dmirror_fops_unlocked_ioctl(struct file *filp,
1222                                         unsigned int command,
1223                                         unsigned long arg)
1224 {
1225         void __user *uarg = (void __user *)arg;
1226         struct hmm_dmirror_cmd cmd;
1227         struct dmirror *dmirror;
1228         int ret;
1229
1230         dmirror = filp->private_data;
1231         if (!dmirror)
1232                 return -EINVAL;
1233
1234         if (copy_from_user(&cmd, uarg, sizeof(cmd)))
1235                 return -EFAULT;
1236
1237         if (cmd.addr & ~PAGE_MASK)
1238                 return -EINVAL;
1239         if (cmd.addr >= (cmd.addr + (cmd.npages << PAGE_SHIFT)))
1240                 return -EINVAL;
1241
1242         cmd.cpages = 0;
1243         cmd.faults = 0;
1244
1245         switch (command) {
1246         case HMM_DMIRROR_READ:
1247                 ret = dmirror_read(dmirror, &cmd);
1248                 break;
1249
1250         case HMM_DMIRROR_WRITE:
1251                 ret = dmirror_write(dmirror, &cmd);
1252                 break;
1253
1254         case HMM_DMIRROR_MIGRATE_TO_DEV:
1255                 ret = dmirror_migrate_to_device(dmirror, &cmd);
1256                 break;
1257
1258         case HMM_DMIRROR_MIGRATE_TO_SYS:
1259                 ret = dmirror_migrate_to_system(dmirror, &cmd);
1260                 break;
1261
1262         case HMM_DMIRROR_EXCLUSIVE:
1263                 ret = dmirror_exclusive(dmirror, &cmd);
1264                 break;
1265
1266         case HMM_DMIRROR_CHECK_EXCLUSIVE:
1267                 ret = dmirror_check_atomic(dmirror, cmd.addr,
1268                                         cmd.addr + (cmd.npages << PAGE_SHIFT));
1269                 break;
1270
1271         case HMM_DMIRROR_SNAPSHOT:
1272                 ret = dmirror_snapshot(dmirror, &cmd);
1273                 break;
1274
1275         default:
1276                 return -EINVAL;
1277         }
1278         if (ret)
1279                 return ret;
1280
1281         if (copy_to_user(uarg, &cmd, sizeof(cmd)))
1282                 return -EFAULT;
1283
1284         return 0;
1285 }
1286
1287 static int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma)
1288 {
1289         unsigned long addr;
1290
1291         for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
1292                 struct page *page;
1293                 int ret;
1294
1295                 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
1296                 if (!page)
1297                         return -ENOMEM;
1298
1299                 ret = vm_insert_page(vma, addr, page);
1300                 if (ret) {
1301                         __free_page(page);
1302                         return ret;
1303                 }
1304                 put_page(page);
1305         }
1306
1307         return 0;
1308 }
1309
1310 static const struct file_operations dmirror_fops = {
1311         .open           = dmirror_fops_open,
1312         .release        = dmirror_fops_release,
1313         .mmap           = dmirror_fops_mmap,
1314         .unlocked_ioctl = dmirror_fops_unlocked_ioctl,
1315         .llseek         = default_llseek,
1316         .owner          = THIS_MODULE,
1317 };
1318
1319 static void dmirror_devmem_free(struct page *page)
1320 {
1321         struct page *rpage = BACKING_PAGE(page);
1322         struct dmirror_device *mdevice;
1323
1324         if (rpage != page)
1325                 __free_page(rpage);
1326
1327         mdevice = dmirror_page_to_device(page);
1328         spin_lock(&mdevice->lock);
1329         mdevice->cfree++;
1330         page->zone_device_data = mdevice->free_pages;
1331         mdevice->free_pages = page;
1332         spin_unlock(&mdevice->lock);
1333 }
1334
1335 static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
1336 {
1337         struct migrate_vma args;
1338         unsigned long src_pfns = 0;
1339         unsigned long dst_pfns = 0;
1340         struct page *rpage;
1341         struct dmirror *dmirror;
1342         vm_fault_t ret;
1343
1344         /*
1345          * Normally, a device would use the page->zone_device_data to point to
1346          * the mirror but here we use it to hold the page for the simulated
1347          * device memory and that page holds the pointer to the mirror.
1348          */
1349         rpage = vmf->page->zone_device_data;
1350         dmirror = rpage->zone_device_data;
1351
1352         /* FIXME demonstrate how we can adjust migrate range */
1353         args.vma = vmf->vma;
1354         args.start = vmf->address;
1355         args.end = args.start + PAGE_SIZE;
1356         args.src = &src_pfns;
1357         args.dst = &dst_pfns;
1358         args.pgmap_owner = dmirror->mdevice;
1359         args.flags = dmirror_select_device(dmirror);
1360
1361         if (migrate_vma_setup(&args))
1362                 return VM_FAULT_SIGBUS;
1363
1364         ret = dmirror_devmem_fault_alloc_and_copy(&args, dmirror);
1365         if (ret)
1366                 return ret;
1367         migrate_vma_pages(&args);
1368         /*
1369          * No device finalize step is needed since
1370          * dmirror_devmem_fault_alloc_and_copy() will have already
1371          * invalidated the device page table.
1372          */
1373         migrate_vma_finalize(&args);
1374         return 0;
1375 }
1376
1377 static const struct dev_pagemap_ops dmirror_devmem_ops = {
1378         .page_free      = dmirror_devmem_free,
1379         .migrate_to_ram = dmirror_devmem_fault,
1380 };
1381
1382 static int dmirror_device_init(struct dmirror_device *mdevice, int id)
1383 {
1384         dev_t dev;
1385         int ret;
1386
1387         dev = MKDEV(MAJOR(dmirror_dev), id);
1388         mutex_init(&mdevice->devmem_lock);
1389         spin_lock_init(&mdevice->lock);
1390
1391         cdev_init(&mdevice->cdevice, &dmirror_fops);
1392         mdevice->cdevice.owner = THIS_MODULE;
1393         device_initialize(&mdevice->device);
1394         mdevice->device.devt = dev;
1395
1396         ret = dev_set_name(&mdevice->device, "hmm_dmirror%u", id);
1397         if (ret)
1398                 return ret;
1399
1400         ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
1401         if (ret)
1402                 return ret;
1403
1404         /* Build a list of free ZONE_DEVICE struct pages */
1405         return dmirror_allocate_chunk(mdevice, NULL);
1406 }
1407
1408 static void dmirror_device_remove(struct dmirror_device *mdevice)
1409 {
1410         unsigned int i;
1411
1412         if (mdevice->devmem_chunks) {
1413                 for (i = 0; i < mdevice->devmem_count; i++) {
1414                         struct dmirror_chunk *devmem =
1415                                 mdevice->devmem_chunks[i];
1416
1417                         memunmap_pages(&devmem->pagemap);
1418                         if (devmem->pagemap.type == MEMORY_DEVICE_PRIVATE)
1419                                 release_mem_region(devmem->pagemap.range.start,
1420                                                    range_len(&devmem->pagemap.range));
1421                         kfree(devmem);
1422                 }
1423                 kfree(mdevice->devmem_chunks);
1424         }
1425
1426         cdev_device_del(&mdevice->cdevice, &mdevice->device);
1427 }
1428
1429 static int __init hmm_dmirror_init(void)
1430 {
1431         int ret;
1432         int id = 0;
1433         int ndevices = 0;
1434
1435         ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
1436                                   "HMM_DMIRROR");
1437         if (ret)
1438                 goto err_unreg;
1439
1440         memset(dmirror_devices, 0, DMIRROR_NDEVICES * sizeof(dmirror_devices[0]));
1441         dmirror_devices[ndevices++].zone_device_type =
1442                                 HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
1443         dmirror_devices[ndevices++].zone_device_type =
1444                                 HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
1445         if (spm_addr_dev0 && spm_addr_dev1) {
1446                 dmirror_devices[ndevices++].zone_device_type =
1447                                         HMM_DMIRROR_MEMORY_DEVICE_COHERENT;
1448                 dmirror_devices[ndevices++].zone_device_type =
1449                                         HMM_DMIRROR_MEMORY_DEVICE_COHERENT;
1450         }
1451         for (id = 0; id < ndevices; id++) {
1452                 ret = dmirror_device_init(dmirror_devices + id, id);
1453                 if (ret)
1454                         goto err_chrdev;
1455         }
1456
1457         pr_info("HMM test module loaded. This is only for testing HMM.\n");
1458         return 0;
1459
1460 err_chrdev:
1461         while (--id >= 0)
1462                 dmirror_device_remove(dmirror_devices + id);
1463         unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
1464 err_unreg:
1465         return ret;
1466 }
1467
1468 static void __exit hmm_dmirror_exit(void)
1469 {
1470         int id;
1471
1472         for (id = 0; id < DMIRROR_NDEVICES; id++)
1473                 if (dmirror_devices[id].zone_device_type)
1474                         dmirror_device_remove(dmirror_devices + id);
1475         unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
1476 }
1477
1478 module_init(hmm_dmirror_init);
1479 module_exit(hmm_dmirror_exit);
1480 MODULE_LICENSE("GPL");