drivers/virtio/virtio_balloon.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
   4  * Tosatti's implementations.
   5  *
   6  *  Copyright 2008 Rusty Russell IBM Corporation
   7  */
   8
   9 #include <linux/virtio.h>
  10 #include <linux/virtio_balloon.h>
  11 #include <linux/swap.h>
  12 #include <linux/workqueue.h>
  13 #include <linux/delay.h>
  14 #include <linux/slab.h>
  15 #include <linux/module.h>
  16 #include <linux/balloon_compaction.h>
  17 #include <linux/oom.h>
  18 #include <linux/wait.h>
  19 #include <linux/mm.h>
  20 #include <linux/page_reporting.h>
  21
  22 /*
  23  * Balloon device works in 4K page units.  So each page is pointed to by
  24  * multiple balloon pages.  All memory counters in this driver are in balloon
  25  * page units.
  26  */
  27 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  28 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  29 /* Maximum number of (4k) pages to deflate on OOM notifications. */
  30 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
  31 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
  32
  33 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
  34                                              __GFP_NOMEMALLOC)
  35 /* The order of free page blocks to report to host */
  36 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER MAX_PAGE_ORDER
  37 /* The size of a free page block in bytes */
  38 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
  39         (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
  40 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
  41
  42 enum virtio_balloon_vq {
  43         VIRTIO_BALLOON_VQ_INFLATE,
  44         VIRTIO_BALLOON_VQ_DEFLATE,
  45         VIRTIO_BALLOON_VQ_STATS,
  46         VIRTIO_BALLOON_VQ_FREE_PAGE,
  47         VIRTIO_BALLOON_VQ_REPORTING,
  48         VIRTIO_BALLOON_VQ_MAX
  49 };
  50
  51 enum virtio_balloon_config_read {
  52         VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
  53 };
  54
  55 struct virtio_balloon {
  56         struct virtio_device *vdev;
  57         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
  58
  59         /* Balloon's own wq for cpu-intensive work items */
  60         struct workqueue_struct *balloon_wq;
  61         /* The free page reporting work item submitted to the balloon wq */
  62         struct work_struct report_free_page_work;
  63
  64         /* The balloon servicing is delegated to a freezable workqueue. */
  65         struct work_struct update_balloon_stats_work;
  66         struct work_struct update_balloon_size_work;
  67
  68         /* Prevent updating balloon when it is being canceled. */
  69         spinlock_t stop_update_lock;
  70         bool stop_update;
  71         /* Bitmap to indicate if reading the related config fields are needed */
  72         unsigned long config_read_bitmap;
  73
  74         /* The list of allocated free pages, waiting to be given back to mm */
  75         struct list_head free_page_list;
  76         spinlock_t free_page_list_lock;
  77         /* The number of free page blocks on the above list */
  78         unsigned long num_free_page_blocks;
  79         /*
  80          * The cmd id received from host.
  81          * Read it via virtio_balloon_cmd_id_received to get the latest value
  82          * sent from host.
  83          */
  84         u32 cmd_id_received_cache;
  85         /* The cmd id that is actively in use */
  86         __virtio32 cmd_id_active;
  87         /* Buffer to store the stop sign */
  88         __virtio32 cmd_id_stop;
  89
  90         /* Waiting for host to ack the pages we released. */
  91         wait_queue_head_t acked;
  92
  93         /* Number of balloon pages we've told the Host we're not using. */
  94         unsigned int num_pages;
  95         /*
  96          * The pages we've told the Host we're not using are enqueued
  97          * at vb_dev_info->pages list.
  98          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
  99          * to num_pages above.
 100          */
 101         struct balloon_dev_info vb_dev_info;
 102
 103         /* Synchronize access/update to this struct virtio_balloon elements */
 104         struct mutex balloon_lock;
 105
 106         /* The array of pfns we tell the Host about. */
 107         unsigned int num_pfns;
 108         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 109
 110         /* Memory statistics */
 111         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 112
 113         /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
 114         struct shrinker *shrinker;
 115
 116         /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
 117         struct notifier_block oom_nb;
 118
 119         /* Free page reporting device */
 120         struct virtqueue *reporting_vq;
 121         struct page_reporting_dev_info pr_dev_info;
 122
 123         /* State for keeping the wakeup_source active while adjusting the balloon */
 124         spinlock_t wakeup_lock;
 125         bool processing_wakeup_event;
 126         u32 wakeup_signal_mask;
 127 };
 128
 129 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST (1 << 0)
 130 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS (1 << 1)
 131
 132 static const struct virtio_device_id id_table[] = {
 133         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 134         { 0 },
 135 };
 136
 137 static u32 page_to_balloon_pfn(struct page *page)
 138 {
 139         unsigned long pfn = page_to_pfn(page);
 140
 141         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 142         /* Convert pfn from Linux page size to balloon page size. */
 143         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 144 }
 145
 146 static void start_wakeup_event(struct virtio_balloon *vb, u32 mask)
 147 {
 148         unsigned long flags;
 149
 150         spin_lock_irqsave(&vb->wakeup_lock, flags);
 151         vb->wakeup_signal_mask |= mask;
 152         if (!vb->processing_wakeup_event) {
 153                 vb->processing_wakeup_event = true;
 154                 pm_stay_awake(&vb->vdev->dev);
 155         }
 156         spin_unlock_irqrestore(&vb->wakeup_lock, flags);
 157 }
 158
 159 static void process_wakeup_event(struct virtio_balloon *vb, u32 mask)
 160 {
 161         spin_lock_irq(&vb->wakeup_lock);
 162         vb->wakeup_signal_mask &= ~mask;
 163         spin_unlock_irq(&vb->wakeup_lock);
 164 }
 165
 166 static void finish_wakeup_event(struct virtio_balloon *vb)
 167 {
 168         spin_lock_irq(&vb->wakeup_lock);
 169         if (!vb->wakeup_signal_mask && vb->processing_wakeup_event) {
 170                 vb->processing_wakeup_event = false;
 171                 pm_relax(&vb->vdev->dev);
 172         }
 173         spin_unlock_irq(&vb->wakeup_lock);
 174 }
 175
 176 static void balloon_ack(struct virtqueue *vq)
 177 {
 178         struct virtio_balloon *vb = vq->vdev->priv;
 179
 180         wake_up(&vb->acked);
 181 }
 182
 183 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 184 {
 185         struct scatterlist sg;
 186         unsigned int len;
 187
 188         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 189
 190         /* We should always be able to add one buffer to an empty queue. */
 191         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 192         virtqueue_kick(vq);
 193
 194         /* When host has read buffer, this completes via balloon_ack */
 195         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 196
 197 }
 198
 199 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
 200                                    struct scatterlist *sg, unsigned int nents)
 201 {
 202         struct virtio_balloon *vb =
 203                 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
 204         struct virtqueue *vq = vb->reporting_vq;
 205         unsigned int unused, err;
 206
 207         /* We should always be able to add these buffers to an empty queue. */
 208         err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
 209
 210         /*
 211          * In the extremely unlikely case that something has occurred and we
 212          * are able to trigger an error we will simply display a warning
 213          * and exit without actually processing the pages.
 214          */
 215         if (WARN_ON_ONCE(err))
 216                 return err;
 217
 218         virtqueue_kick(vq);
 219
 220         /* When host has read buffer, this completes via balloon_ack */
 221         wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
 222
 223         return 0;
 224 }
 225
 226 static void set_page_pfns(struct virtio_balloon *vb,
 227                           __virtio32 pfns[], struct page *page)
 228 {
 229         unsigned int i;
 230
 231         BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
 232
 233         /*
 234          * Set balloon pfns pointing at this page.
 235          * Note that the first pfn points at start of the page.
 236          */
 237         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 238                 pfns[i] = cpu_to_virtio32(vb->vdev,
 239                                           page_to_balloon_pfn(page) + i);
 240 }
 241
 242 static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
 243 {
 244         unsigned int num_allocated_pages;
 245         unsigned int num_pfns;
 246         struct page *page;
 247         LIST_HEAD(pages);
 248
 249         /* We can only do one array worth at a time. */
 250         num = min(num, ARRAY_SIZE(vb->pfns));
 251
 252         for (num_pfns = 0; num_pfns < num;
 253              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 254                 struct page *page = balloon_page_alloc();
 255
 256                 if (!page) {
 257                         dev_info_ratelimited(&vb->vdev->dev,
 258                                              "Out of puff! Can't get %u pages\n",
 259                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 260                         /* Sleep for at least 1/5 of a second before retry. */
 261                         msleep(200);
 262                         break;
 263                 }
 264
 265                 balloon_page_push(&pages, page);
 266         }
 267
 268         mutex_lock(&vb->balloon_lock);
 269
 270         vb->num_pfns = 0;
 271
 272         while ((page = balloon_page_pop(&pages))) {
 273                 balloon_page_enqueue(&vb->vb_dev_info, page);
 274
 275                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 276                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 277                 if (!virtio_has_feature(vb->vdev,
 278                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 279                         adjust_managed_page_count(page, -1);
 280                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
 281         }
 282
 283         num_allocated_pages = vb->num_pfns;
 284         /* Did we get any? */
 285         if (vb->num_pfns != 0)
 286                 tell_host(vb, vb->inflate_vq);
 287         mutex_unlock(&vb->balloon_lock);
 288
 289         return num_allocated_pages;
 290 }
 291
 292 static void release_pages_balloon(struct virtio_balloon *vb,
 293                                  struct list_head *pages)
 294 {
 295         struct page *page, *next;
 296
 297         list_for_each_entry_safe(page, next, pages, lru) {
 298                 if (!virtio_has_feature(vb->vdev,
 299                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 300                         adjust_managed_page_count(page, 1);
 301                 list_del(&page->lru);
 302                 put_page(page); /* balloon reference */
 303         }
 304 }
 305
 306 static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num)
 307 {
 308         unsigned int num_freed_pages;
 309         struct page *page;
 310         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 311         LIST_HEAD(pages);
 312
 313         /* We can only do one array worth at a time. */
 314         num = min(num, ARRAY_SIZE(vb->pfns));
 315
 316         mutex_lock(&vb->balloon_lock);
 317         /* We can't release more pages than taken */
 318         num = min(num, (size_t)vb->num_pages);
 319         for (vb->num_pfns = 0; vb->num_pfns < num;
 320              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 321                 page = balloon_page_dequeue(vb_dev_info);
 322                 if (!page)
 323                         break;
 324                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 325                 list_add(&page->lru, &pages);
 326                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 327         }
 328
 329         num_freed_pages = vb->num_pfns;
 330         /*
 331          * Note that if
 332          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 333          * is true, we *have* to do it in this order
 334          */
 335         if (vb->num_pfns != 0)
 336                 tell_host(vb, vb->deflate_vq);
 337         release_pages_balloon(vb, &pages);
 338         mutex_unlock(&vb->balloon_lock);
 339         return num_freed_pages;
 340 }
 341
 342 static inline void update_stat(struct virtio_balloon *vb, int idx,
 343                                u16 tag, u64 val)
 344 {
 345         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 346         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 347         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 348 }
 349
 350 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 351
 352 #ifdef CONFIG_VM_EVENT_COUNTERS
 353 /* Return the number of entries filled by vm events */
 354 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
 355 {
 356         unsigned long events[NR_VM_EVENT_ITEMS];
 357         unsigned int idx = 0;
 358         unsigned int zid;
 359         unsigned long stall = 0;
 360
 361         all_vm_events(events);
 362         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 363                     pages_to_bytes(events[PSWPIN]));
 364         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 365                     pages_to_bytes(events[PSWPOUT]));
 366         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 367         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 368         update_stat(vb, idx++, VIRTIO_BALLOON_S_OOM_KILL, events[OOM_KILL]);
 369
 370         /* sum all the stall events */
 371         for (zid = 0; zid < MAX_NR_ZONES; zid++)
 372                 stall += events[ALLOCSTALL_NORMAL - ZONE_NORMAL + zid];
 373
 374         update_stat(vb, idx++, VIRTIO_BALLOON_S_ALLOC_STALL, stall);
 375
 376         update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_SCAN,
 377                     pages_to_bytes(events[PGSCAN_KSWAPD]));
 378         update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_SCAN,
 379                     pages_to_bytes(events[PGSCAN_DIRECT]));
 380         update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_RECLAIM,
 381                     pages_to_bytes(events[PGSTEAL_KSWAPD]));
 382         update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_RECLAIM,
 383                     pages_to_bytes(events[PGSTEAL_DIRECT]));
 384
 385 #ifdef CONFIG_HUGETLB_PAGE
 386         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
 387                     events[HTLB_BUDDY_PGALLOC]);
 388         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
 389                     events[HTLB_BUDDY_PGALLOC_FAIL]);
 390 #endif /* CONFIG_HUGETLB_PAGE */
 391
 392         return idx;
 393 }
 394 #else /* CONFIG_VM_EVENT_COUNTERS */
 395 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
 396 {
 397         return 0;
 398 }
 399 #endif /* CONFIG_VM_EVENT_COUNTERS */
 400
 401 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 402 {
 403         struct sysinfo i;
 404         unsigned int idx;
 405         long available;
 406         unsigned long caches;
 407
 408         idx = update_balloon_vm_stats(vb);
 409
 410         si_meminfo(&i);
 411         available = si_mem_available();
 412         caches = global_node_page_state(NR_FILE_PAGES);
 413         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 414                                 pages_to_bytes(i.freeram));
 415         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 416                                 pages_to_bytes(i.totalram));
 417         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 418                                 pages_to_bytes(available));
 419         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
 420                                 pages_to_bytes(caches));
 421
 422         return idx;
 423 }
 424
 425 /*
 426  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 427  * the stats queue operates in reverse.  The driver initializes the virtqueue
 428  * with a single buffer.  From that point forward, all conversations consist of
 429  * a hypervisor request (a call to this function) which directs us to refill
 430  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 431  * we delegate the job to a freezable workqueue that will do the actual work via
 432  * stats_handle_request().
 433  */
 434 static void stats_request(struct virtqueue *vq)
 435 {
 436         struct virtio_balloon *vb = vq->vdev->priv;
 437
 438         spin_lock(&vb->stop_update_lock);
 439         if (!vb->stop_update) {
 440                 start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
 441                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 442         }
 443         spin_unlock(&vb->stop_update_lock);
 444 }
 445
 446 static void stats_handle_request(struct virtio_balloon *vb)
 447 {
 448         struct virtqueue *vq;
 449         struct scatterlist sg;
 450         unsigned int len, num_stats;
 451
 452         num_stats = update_balloon_stats(vb);
 453
 454         vq = vb->stats_vq;
 455         if (!virtqueue_get_buf(vq, &len))
 456                 return;
 457         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 458         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 459         virtqueue_kick(vq);
 460 }
 461
 462 static inline s64 towards_target(struct virtio_balloon *vb)
 463 {
 464         s64 target;
 465         u32 num_pages;
 466
 467         /* Legacy balloon config space is LE, unlike all other devices. */
 468         virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
 469                         &num_pages);
 470
 471         /*
 472          * Aligned up to guest page size to avoid inflating and deflating
 473          * balloon endlessly.
 474          */
 475         target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
 476         return target - vb->num_pages;
 477 }
 478
 479 /* Gives back @num_to_return blocks of free pages to mm. */
 480 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 481                                              unsigned long num_to_return)
 482 {
 483         struct page *page;
 484         unsigned long num_returned;
 485
 486         spin_lock_irq(&vb->free_page_list_lock);
 487         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 488                 page = balloon_page_pop(&vb->free_page_list);
 489                 if (!page)
 490                         break;
 491                 free_pages((unsigned long)page_address(page),
 492                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 493         }
 494         vb->num_free_page_blocks -= num_returned;
 495         spin_unlock_irq(&vb->free_page_list_lock);
 496
 497         return num_returned;
 498 }
 499
 500 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 501 {
 502         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 503                 return;
 504
 505         /* No need to queue the work if the bit was already set. */
 506         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 507                              &vb->config_read_bitmap))
 508                 return;
 509
 510         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 511 }
 512
 513 static void start_update_balloon_size(struct virtio_balloon *vb)
 514 {
 515         start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
 516         queue_work(system_freezable_wq, &vb->update_balloon_size_work);
 517 }
 518
 519 static void virtballoon_changed(struct virtio_device *vdev)
 520 {
 521         struct virtio_balloon *vb = vdev->priv;
 522         unsigned long flags;
 523
 524         spin_lock_irqsave(&vb->stop_update_lock, flags);
 525         if (!vb->stop_update) {
 526                 start_update_balloon_size(vb);
 527                 virtio_balloon_queue_free_page_work(vb);
 528         }
 529         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 530 }
 531
 532 static void update_balloon_size(struct virtio_balloon *vb)
 533 {
 534         u32 actual = vb->num_pages;
 535
 536         /* Legacy balloon config space is LE, unlike all other devices. */
 537         virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
 538                          &actual);
 539 }
 540
 541 static void update_balloon_stats_func(struct work_struct *work)
 542 {
 543         struct virtio_balloon *vb;
 544
 545         vb = container_of(work, struct virtio_balloon,
 546                           update_balloon_stats_work);
 547
 548         process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
 549         stats_handle_request(vb);
 550         finish_wakeup_event(vb);
 551 }
 552
 553 static void update_balloon_size_func(struct work_struct *work)
 554 {
 555         struct virtio_balloon *vb;
 556         s64 diff;
 557
 558         vb = container_of(work, struct virtio_balloon,
 559                           update_balloon_size_work);
 560
 561         process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
 562
 563         diff = towards_target(vb);
 564
 565         if (diff) {
 566                 if (diff > 0)
 567                         diff -= fill_balloon(vb, diff);
 568                 else
 569                         diff += leak_balloon(vb, -diff);
 570                 update_balloon_size(vb);
 571         }
 572
 573         if (diff)
 574                 queue_work(system_freezable_wq, work);
 575         else
 576                 finish_wakeup_event(vb);
 577 }
 578
 579 static int init_vqs(struct virtio_balloon *vb)
 580 {
 581         struct virtqueue_info vqs_info[VIRTIO_BALLOON_VQ_MAX] = {};
 582         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 583         int err;
 584
 585         /*
 586          * Inflateq and deflateq are used unconditionally. The names[]
 587          * will be NULL if the related feature is not enabled, which will
 588          * cause no allocation for the corresponding virtqueue in find_vqs.
 589          */
 590         vqs_info[VIRTIO_BALLOON_VQ_INFLATE].callback = balloon_ack;
 591         vqs_info[VIRTIO_BALLOON_VQ_INFLATE].name = "inflate";
 592         vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].callback = balloon_ack;
 593         vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].name = "deflate";
 594
 595         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 596                 vqs_info[VIRTIO_BALLOON_VQ_STATS].name = "stats";
 597                 vqs_info[VIRTIO_BALLOON_VQ_STATS].callback = stats_request;
 598         }
 599
 600         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 601                 vqs_info[VIRTIO_BALLOON_VQ_FREE_PAGE].name = "free_page_vq";
 602
 603         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 604                 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].name = "reporting_vq";
 605                 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].callback = balloon_ack;
 606         }
 607
 608         err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
 609                               vqs_info, NULL);
 610         if (err)
 611                 return err;
 612
 613         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 614         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 615         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 616                 struct scatterlist sg;
 617                 unsigned int num_stats;
 618                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 619
 620                 /*
 621                  * Prime this virtqueue with one buffer so the hypervisor can
 622                  * use it to signal us later (it can't be broken yet!).
 623                  */
 624                 num_stats = update_balloon_stats(vb);
 625
 626                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 627                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 628                                            GFP_KERNEL);
 629                 if (err) {
 630                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 631                                  __func__);
 632                         return err;
 633                 }
 634                 virtqueue_kick(vb->stats_vq);
 635         }
 636
 637         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 638                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 639
 640         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
 641                 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
 642
 643         return 0;
 644 }
 645
 646 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 647 {
 648         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 649                                &vb->config_read_bitmap)) {
 650                 /* Legacy balloon config space is LE, unlike all other devices. */
 651                 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
 652                                 free_page_hint_cmd_id,
 653                                 &vb->cmd_id_received_cache);
 654         }
 655
 656         return vb->cmd_id_received_cache;
 657 }
 658
 659 static int send_cmd_id_start(struct virtio_balloon *vb)
 660 {
 661         struct scatterlist sg;
 662         struct virtqueue *vq = vb->free_page_vq;
 663         int err, unused;
 664
 665         /* Detach all the used buffers from the vq */
 666         while (virtqueue_get_buf(vq, &unused))
 667                 ;
 668
 669         vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 670                                         virtio_balloon_cmd_id_received(vb));
 671         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 672         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 673         if (!err)
 674                 virtqueue_kick(vq);
 675         return err;
 676 }
 677
 678 static int send_cmd_id_stop(struct virtio_balloon *vb)
 679 {
 680         struct scatterlist sg;
 681         struct virtqueue *vq = vb->free_page_vq;
 682         int err, unused;
 683
 684         /* Detach all the used buffers from the vq */
 685         while (virtqueue_get_buf(vq, &unused))
 686                 ;
 687
 688         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 689         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 690         if (!err)
 691                 virtqueue_kick(vq);
 692         return err;
 693 }
 694
 695 static int get_free_page_and_send(struct virtio_balloon *vb)
 696 {
 697         struct virtqueue *vq = vb->free_page_vq;
 698         struct page *page;
 699         struct scatterlist sg;
 700         int err, unused;
 701         void *p;
 702
 703         /* Detach all the used buffers from the vq */
 704         while (virtqueue_get_buf(vq, &unused))
 705                 ;
 706
 707         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 708                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 709         /*
 710          * When the allocation returns NULL, it indicates that we have got all
 711          * the possible free pages, so return -EINTR to stop.
 712          */
 713         if (!page)
 714                 return -EINTR;
 715
 716         p = page_address(page);
 717         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 718         /* There is always 1 entry reserved for the cmd id to use. */
 719         if (vq->num_free > 1) {
 720                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 721                 if (unlikely(err)) {
 722                         free_pages((unsigned long)p,
 723                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 724                         return err;
 725                 }
 726                 virtqueue_kick(vq);
 727                 spin_lock_irq(&vb->free_page_list_lock);
 728                 balloon_page_push(&vb->free_page_list, page);
 729                 vb->num_free_page_blocks++;
 730                 spin_unlock_irq(&vb->free_page_list_lock);
 731         } else {
 732                 /*
 733                  * The vq has no available entry to add this page block, so
 734                  * just free it.
 735                  */
 736                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 737         }
 738
 739         return 0;
 740 }
 741
 742 static int send_free_pages(struct virtio_balloon *vb)
 743 {
 744         int err;
 745         u32 cmd_id_active;
 746
 747         while (1) {
 748                 /*
 749                  * If a stop id or a new cmd id was just received from host,
 750                  * stop the reporting.
 751                  */
 752                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 753                 if (unlikely(cmd_id_active !=
 754                              virtio_balloon_cmd_id_received(vb)))
 755                         break;
 756
 757                 /*
 758                  * The free page blocks are allocated and sent to host one by
 759                  * one.
 760                  */
 761                 err = get_free_page_and_send(vb);
 762                 if (err == -EINTR)
 763                         break;
 764                 else if (unlikely(err))
 765                         return err;
 766         }
 767
 768         return 0;
 769 }
 770
 771 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 772 {
 773         int err;
 774         struct device *dev = &vb->vdev->dev;
 775
 776         /* Start by sending the received cmd id to host with an outbuf. */
 777         err = send_cmd_id_start(vb);
 778         if (unlikely(err))
 779                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 780
 781         err = send_free_pages(vb);
 782         if (unlikely(err))
 783                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 784
 785         /* End by sending a stop id to host with an outbuf. */
 786         err = send_cmd_id_stop(vb);
 787         if (unlikely(err))
 788                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 789 }
 790
 791 static void report_free_page_func(struct work_struct *work)
 792 {
 793         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 794                                                  report_free_page_work);
 795         u32 cmd_id_received;
 796
 797         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 798         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 799                 /* Pass ULONG_MAX to give back all the free pages */
 800                 return_free_pages_to_mm(vb, ULONG_MAX);
 801         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 802                    cmd_id_received !=
 803                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 804                 virtio_balloon_report_free_page(vb);
 805         }
 806 }
 807
 808 #ifdef CONFIG_BALLOON_COMPACTION
 809 /*
 810  * virtballoon_migratepage - perform the balloon page migration on behalf of
 811  *                           a compaction thread.     (called under page lock)
 812  * @vb_dev_info: the balloon device
 813  * @newpage: page that will replace the isolated page after migration finishes.
 814  * @page   : the isolated (old) page that is about to be migrated to newpage.
 815  * @mode   : compaction mode -- not used for balloon page migration.
 816  *
 817  * After a ballooned page gets isolated by compaction procedures, this is the
 818  * function that performs the page migration on behalf of a compaction thread
 819  * The page migration for virtio balloon is done in a simple swap fashion which
 820  * follows these two macro steps:
 821  *  1) insert newpage into vb->pages list and update the host about it;
 822  *  2) update the host about the old page removed from vb->pages list;
 823  *
 824  * This function preforms the balloon page migration task.
 825  * Called through movable_operations->migrate_page
 826  */
 827 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 828                 struct page *newpage, struct page *page, enum migrate_mode mode)
 829 {
 830         struct virtio_balloon *vb = container_of(vb_dev_info,
 831                         struct virtio_balloon, vb_dev_info);
 832         unsigned long flags;
 833
 834         /*
 835          * In order to avoid lock contention while migrating pages concurrently
 836          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 837          * this turn, as it is easier to retry the page migration later.
 838          * This also prevents fill_balloon() getting stuck into a mutex
 839          * recursion in the case it ends up triggering memory compaction
 840          * while it is attempting to inflate the ballon.
 841          */
 842         if (!mutex_trylock(&vb->balloon_lock))
 843                 return -EAGAIN;
 844
 845         get_page(newpage); /* balloon reference */
 846
 847         /*
 848           * When we migrate a page to a different zone and adjusted the
 849           * managed page count when inflating, we have to fixup the count of
 850           * both involved zones.
 851           */
 852         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 853             page_zone(page) != page_zone(newpage)) {
 854                 adjust_managed_page_count(page, 1);
 855                 adjust_managed_page_count(newpage, -1);
 856         }
 857
 858         /* balloon's page migration 1st step  -- inflate "newpage" */
 859         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 860         balloon_page_insert(vb_dev_info, newpage);
 861         vb_dev_info->isolated_pages--;
 862         __count_vm_event(BALLOON_MIGRATE);
 863         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 864         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 865         set_page_pfns(vb, vb->pfns, newpage);
 866         tell_host(vb, vb->inflate_vq);
 867
 868         /* balloon's page migration 2nd step -- deflate "page" */
 869         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 870         balloon_page_delete(page);
 871         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 872         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 873         set_page_pfns(vb, vb->pfns, page);
 874         tell_host(vb, vb->deflate_vq);
 875
 876         mutex_unlock(&vb->balloon_lock);
 877
 878         put_page(page); /* balloon reference */
 879
 880         return MIGRATEPAGE_SUCCESS;
 881 }
 882 #endif /* CONFIG_BALLOON_COMPACTION */
 883
 884 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 885                                        unsigned long pages_to_free)
 886 {
 887         unsigned long blocks_to_free, blocks_freed;
 888
 889         pages_to_free = round_up(pages_to_free,
 890                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 891         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 892         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 893
 894         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 895 }
 896
 897 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 898                                                   struct shrink_control *sc)
 899 {
 900         struct virtio_balloon *vb = shrinker->private_data;
 901
 902         return shrink_free_pages(vb, sc->nr_to_scan);
 903 }
 904
 905 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 906                                                    struct shrink_control *sc)
 907 {
 908         struct virtio_balloon *vb = shrinker->private_data;
 909
 910         return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 911 }
 912
 913 static int virtio_balloon_oom_notify(struct notifier_block *nb,
 914                                      unsigned long dummy, void *parm)
 915 {
 916         struct virtio_balloon *vb = container_of(nb,
 917                                                  struct virtio_balloon, oom_nb);
 918         unsigned long *freed = parm;
 919
 920         *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
 921                   VIRTIO_BALLOON_PAGES_PER_PAGE;
 922         update_balloon_size(vb);
 923
 924         return NOTIFY_OK;
 925 }
 926
 927 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 928 {
 929         shrinker_free(vb->shrinker);
 930 }
 931
 932 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 933 {
 934         vb->shrinker = shrinker_alloc(0, "virtio-balloon");
 935         if (!vb->shrinker)
 936                 return -ENOMEM;
 937
 938         vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
 939         vb->shrinker->count_objects = virtio_balloon_shrinker_count;
 940         vb->shrinker->private_data = vb;
 941
 942         shrinker_register(vb->shrinker);
 943
 944         return 0;
 945 }
 946
 947 static int virtballoon_probe(struct virtio_device *vdev)
 948 {
 949         struct virtio_balloon *vb;
 950         int err;
 951
 952         if (!vdev->config->get) {
 953                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 954                         __func__);
 955                 return -EINVAL;
 956         }
 957
 958         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 959         if (!vb) {
 960                 err = -ENOMEM;
 961                 goto out;
 962         }
 963
 964         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 965         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 966         spin_lock_init(&vb->stop_update_lock);
 967         mutex_init(&vb->balloon_lock);
 968         init_waitqueue_head(&vb->acked);
 969         vb->vdev = vdev;
 970
 971         balloon_devinfo_init(&vb->vb_dev_info);
 972
 973         err = init_vqs(vb);
 974         if (err)
 975                 goto out_free_vb;
 976
 977 #ifdef CONFIG_BALLOON_COMPACTION
 978         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 979 #endif
 980         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 981                 /*
 982                  * There is always one entry reserved for cmd id, so the ring
 983                  * size needs to be at least two to report free page hints.
 984                  */
 985                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 986                         err = -ENOSPC;
 987                         goto out_del_vqs;
 988                 }
 989                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 990                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 991                 if (!vb->balloon_wq) {
 992                         err = -ENOMEM;
 993                         goto out_del_vqs;
 994                 }
 995                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 996                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 997                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 998                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 999                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
1000                                                   VIRTIO_BALLOON_CMD_ID_STOP);
1001                 spin_lock_init(&vb->free_page_list_lock);
1002                 INIT_LIST_HEAD(&vb->free_page_list);
1003                 /*
1004                  * We're allowed to reuse any free pages, even if they are
1005                  * still to be processed by the host.
1006                  */
1007                 err = virtio_balloon_register_shrinker(vb);
1008                 if (err)
1009                         goto out_del_balloon_wq;
1010         }
1011
1012         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
1013                 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
1014                 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
1015                 err = register_oom_notifier(&vb->oom_nb);
1016                 if (err < 0)
1017                         goto out_unregister_shrinker;
1018         }
1019
1020         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
1021                 /* Start with poison val of 0 representing general init */
1022                 __u32 poison_val = 0;
1023
1024                 /*
1025                  * Let the hypervisor know that we are expecting a
1026                  * specific value to be written back in balloon pages.
1027                  *
1028                  * If the PAGE_POISON value was larger than a byte we would
1029                  * need to byte swap poison_val here to guarantee it is
1030                  * little-endian. However for now it is a single byte so we
1031                  * can pass it as-is.
1032                  */
1033                 if (!want_init_on_free())
1034                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
1035
1036                 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
1037                                  poison_val, &poison_val);
1038         }
1039
1040         vb->pr_dev_info.report = virtballoon_free_page_report;
1041         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
1042                 unsigned int capacity;
1043
1044                 capacity = virtqueue_get_vring_size(vb->reporting_vq);
1045                 if (capacity < PAGE_REPORTING_CAPACITY) {
1046                         err = -ENOSPC;
1047                         goto out_unregister_oom;
1048                 }
1049
1050                 /*
1051                  * The default page reporting order is @pageblock_order, which
1052                  * corresponds to 512MB in size on ARM64 when 64KB base page
1053                  * size is used. The page reporting won't be triggered if the
1054                  * freeing page can't come up with a free area like that huge.
1055                  * So we specify the page reporting order to 5, corresponding
1056                  * to 2MB. It helps to avoid THP splitting if 4KB base page
1057                  * size is used by host.
1058                  *
1059                  * Ideally, the page reporting order is selected based on the
1060                  * host's base page size. However, it needs more work to report
1061                  * that value. The hard-coded order would be fine currently.
1062                  */
1063 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
1064                 vb->pr_dev_info.order = 5;
1065 #endif
1066
1067                 err = page_reporting_register(&vb->pr_dev_info);
1068                 if (err)
1069                         goto out_unregister_oom;
1070         }
1071
1072         spin_lock_init(&vb->wakeup_lock);
1073
1074         /*
1075          * The virtio balloon itself can't wake up the device, but it is
1076          * responsible for processing wakeup events passed up from the transport
1077          * layer. Wakeup sources don't support nesting/chaining calls, so we use
1078          * our own wakeup source to ensure wakeup events are properly handled
1079          * without trampling on the transport layer's wakeup source.
1080          */
1081         device_set_wakeup_capable(&vb->vdev->dev, true);
1082
1083         virtio_device_ready(vdev);
1084
1085         if (towards_target(vb))
1086                 virtballoon_changed(vdev);
1087         return 0;
1088
1089 out_unregister_oom:
1090         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1091                 unregister_oom_notifier(&vb->oom_nb);
1092 out_unregister_shrinker:
1093         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1094                 virtio_balloon_unregister_shrinker(vb);
1095 out_del_balloon_wq:
1096         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1097                 destroy_workqueue(vb->balloon_wq);
1098 out_del_vqs:
1099         vdev->config->del_vqs(vdev);
1100 out_free_vb:
1101         kfree(vb);
1102 out:
1103         return err;
1104 }
1105
1106 static void remove_common(struct virtio_balloon *vb)
1107 {
1108         /* There might be pages left in the balloon: free them. */
1109         while (vb->num_pages)
1110                 leak_balloon(vb, vb->num_pages);
1111         update_balloon_size(vb);
1112
1113         /* There might be free pages that are being reported: release them. */
1114         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1115                 return_free_pages_to_mm(vb, ULONG_MAX);
1116
1117         /* Now we reset the device so we can clean up the queues. */
1118         virtio_reset_device(vb->vdev);
1119
1120         vb->vdev->config->del_vqs(vb->vdev);
1121 }
1122
1123 static void virtballoon_remove(struct virtio_device *vdev)
1124 {
1125         struct virtio_balloon *vb = vdev->priv;
1126
1127         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1128                 page_reporting_unregister(&vb->pr_dev_info);
1129         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1130                 unregister_oom_notifier(&vb->oom_nb);
1131         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1132                 virtio_balloon_unregister_shrinker(vb);
1133         spin_lock_irq(&vb->stop_update_lock);
1134         vb->stop_update = true;
1135         spin_unlock_irq(&vb->stop_update_lock);
1136         cancel_work_sync(&vb->update_balloon_size_work);
1137         cancel_work_sync(&vb->update_balloon_stats_work);
1138
1139         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1140                 cancel_work_sync(&vb->report_free_page_work);
1141                 destroy_workqueue(vb->balloon_wq);
1142         }
1143
1144         remove_common(vb);
1145         kfree(vb);
1146 }
1147
1148 #ifdef CONFIG_PM_SLEEP
1149 static int virtballoon_freeze(struct virtio_device *vdev)
1150 {
1151         struct virtio_balloon *vb = vdev->priv;
1152
1153         /*
1154          * The workqueue is already frozen by the PM core before this
1155          * function is called.
1156          */
1157         remove_common(vb);
1158         return 0;
1159 }
1160
1161 static int virtballoon_restore(struct virtio_device *vdev)
1162 {
1163         struct virtio_balloon *vb = vdev->priv;
1164         int ret;
1165
1166         ret = init_vqs(vdev->priv);
1167         if (ret)
1168                 return ret;
1169
1170         virtio_device_ready(vdev);
1171
1172         if (towards_target(vb))
1173                 virtballoon_changed(vdev);
1174         update_balloon_size(vb);
1175         return 0;
1176 }
1177 #endif
1178
1179 static int virtballoon_validate(struct virtio_device *vdev)
1180 {
1181         /*
1182          * Inform the hypervisor that our pages are poisoned or
1183          * initialized. If we cannot do that then we should disable
1184          * page reporting as it could potentially change the contents
1185          * of our free pages.
1186          */
1187         if (!want_init_on_free() && !page_poisoning_enabled_static())
1188                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1189         else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1190                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1191
1192         __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1193         return 0;
1194 }
1195
1196 static unsigned int features[] = {
1197         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1198         VIRTIO_BALLOON_F_STATS_VQ,
1199         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1200         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1201         VIRTIO_BALLOON_F_PAGE_POISON,
1202         VIRTIO_BALLOON_F_REPORTING,
1203 };
1204
1205 static struct virtio_driver virtio_balloon_driver = {
1206         .feature_table = features,
1207         .feature_table_size = ARRAY_SIZE(features),
1208         .driver.name =  KBUILD_MODNAME,
1209         .id_table =     id_table,
1210         .validate =     virtballoon_validate,
1211         .probe =        virtballoon_probe,
1212         .remove =       virtballoon_remove,
1213         .config_changed = virtballoon_changed,
1214 #ifdef CONFIG_PM_SLEEP
1215         .freeze =       virtballoon_freeze,
1216         .restore =      virtballoon_restore,
1217 #endif
1218 };
1219
1220 module_virtio_driver(virtio_balloon_driver);
1221 MODULE_DEVICE_TABLE(virtio, id_table);
1222 MODULE_DESCRIPTION("Virtio balloon driver");
1223 MODULE_LICENSE("GPL");