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/mount.h>
  21 #include <linux/magic.h>
  22 #include <linux/pseudo_fs.h>
  23 #include <linux/page_reporting.h>
  24
  25 /*
  26  * Balloon device works in 4K page units.  So each page is pointed to by
  27  * multiple balloon pages.  All memory counters in this driver are in balloon
  28  * page units.
  29  */
  30 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  31 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  32 /* Maximum number of (4k) pages to deflate on OOM notifications. */
  33 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
  34 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
  35
  36 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
  37                                              __GFP_NOMEMALLOC)
  38 /* The order of free page blocks to report to host */
  39 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
  40 /* The size of a free page block in bytes */
  41 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
  42         (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
  43 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
  44
  45 #ifdef CONFIG_BALLOON_COMPACTION
  46 static struct vfsmount *balloon_mnt;
  47 #endif
  48
  49 enum virtio_balloon_vq {
  50         VIRTIO_BALLOON_VQ_INFLATE,
  51         VIRTIO_BALLOON_VQ_DEFLATE,
  52         VIRTIO_BALLOON_VQ_STATS,
  53         VIRTIO_BALLOON_VQ_FREE_PAGE,
  54         VIRTIO_BALLOON_VQ_REPORTING,
  55         VIRTIO_BALLOON_VQ_MAX
  56 };
  57
  58 enum virtio_balloon_config_read {
  59         VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
  60 };
  61
  62 struct virtio_balloon {
  63         struct virtio_device *vdev;
  64         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
  65
  66         /* Balloon's own wq for cpu-intensive work items */
  67         struct workqueue_struct *balloon_wq;
  68         /* The free page reporting work item submitted to the balloon wq */
  69         struct work_struct report_free_page_work;
  70
  71         /* The balloon servicing is delegated to a freezable workqueue. */
  72         struct work_struct update_balloon_stats_work;
  73         struct work_struct update_balloon_size_work;
  74
  75         /* Prevent updating balloon when it is being canceled. */
  76         spinlock_t stop_update_lock;
  77         bool stop_update;
  78         /* Bitmap to indicate if reading the related config fields are needed */
  79         unsigned long config_read_bitmap;
  80
  81         /* The list of allocated free pages, waiting to be given back to mm */
  82         struct list_head free_page_list;
  83         spinlock_t free_page_list_lock;
  84         /* The number of free page blocks on the above list */
  85         unsigned long num_free_page_blocks;
  86         /*
  87          * The cmd id received from host.
  88          * Read it via virtio_balloon_cmd_id_received to get the latest value
  89          * sent from host.
  90          */
  91         u32 cmd_id_received_cache;
  92         /* The cmd id that is actively in use */
  93         __virtio32 cmd_id_active;
  94         /* Buffer to store the stop sign */
  95         __virtio32 cmd_id_stop;
  96
  97         /* Waiting for host to ack the pages we released. */
  98         wait_queue_head_t acked;
  99
 100         /* Number of balloon pages we've told the Host we're not using. */
 101         unsigned int num_pages;
 102         /*
 103          * The pages we've told the Host we're not using are enqueued
 104          * at vb_dev_info->pages list.
 105          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 106          * to num_pages above.
 107          */
 108         struct balloon_dev_info vb_dev_info;
 109
 110         /* Synchronize access/update to this struct virtio_balloon elements */
 111         struct mutex balloon_lock;
 112
 113         /* The array of pfns we tell the Host about. */
 114         unsigned int num_pfns;
 115         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 116
 117         /* Memory statistics */
 118         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 119
 120         /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
 121         struct shrinker shrinker;
 122
 123         /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
 124         struct notifier_block oom_nb;
 125
 126         /* Free page reporting device */
 127         struct virtqueue *reporting_vq;
 128         struct page_reporting_dev_info pr_dev_info;
 129 };
 130
 131 static struct virtio_device_id id_table[] = {
 132         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 133         { 0 },
 134 };
 135
 136 static u32 page_to_balloon_pfn(struct page *page)
 137 {
 138         unsigned long pfn = page_to_pfn(page);
 139
 140         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 141         /* Convert pfn from Linux page size to balloon page size. */
 142         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 143 }
 144
 145 static void balloon_ack(struct virtqueue *vq)
 146 {
 147         struct virtio_balloon *vb = vq->vdev->priv;
 148
 149         wake_up(&vb->acked);
 150 }
 151
 152 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 153 {
 154         struct scatterlist sg;
 155         unsigned int len;
 156
 157         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 158
 159         /* We should always be able to add one buffer to an empty queue. */
 160         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 161         virtqueue_kick(vq);
 162
 163         /* When host has read buffer, this completes via balloon_ack */
 164         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 165
 166 }
 167
 168 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
 169                                    struct scatterlist *sg, unsigned int nents)
 170 {
 171         struct virtio_balloon *vb =
 172                 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
 173         struct virtqueue *vq = vb->reporting_vq;
 174         unsigned int unused, err;
 175
 176         /* We should always be able to add these buffers to an empty queue. */
 177         err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
 178
 179         /*
 180          * In the extremely unlikely case that something has occurred and we
 181          * are able to trigger an error we will simply display a warning
 182          * and exit without actually processing the pages.
 183          */
 184         if (WARN_ON_ONCE(err))
 185                 return err;
 186
 187         virtqueue_kick(vq);
 188
 189         /* When host has read buffer, this completes via balloon_ack */
 190         wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
 191
 192         return 0;
 193 }
 194
 195 static void set_page_pfns(struct virtio_balloon *vb,
 196                           __virtio32 pfns[], struct page *page)
 197 {
 198         unsigned int i;
 199
 200         BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
 201
 202         /*
 203          * Set balloon pfns pointing at this page.
 204          * Note that the first pfn points at start of the page.
 205          */
 206         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 207                 pfns[i] = cpu_to_virtio32(vb->vdev,
 208                                           page_to_balloon_pfn(page) + i);
 209 }
 210
 211 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 212 {
 213         unsigned num_allocated_pages;
 214         unsigned num_pfns;
 215         struct page *page;
 216         LIST_HEAD(pages);
 217
 218         /* We can only do one array worth at a time. */
 219         num = min(num, ARRAY_SIZE(vb->pfns));
 220
 221         for (num_pfns = 0; num_pfns < num;
 222              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 223                 struct page *page = balloon_page_alloc();
 224
 225                 if (!page) {
 226                         dev_info_ratelimited(&vb->vdev->dev,
 227                                              "Out of puff! Can't get %u pages\n",
 228                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 229                         /* Sleep for at least 1/5 of a second before retry. */
 230                         msleep(200);
 231                         break;
 232                 }
 233
 234                 balloon_page_push(&pages, page);
 235         }
 236
 237         mutex_lock(&vb->balloon_lock);
 238
 239         vb->num_pfns = 0;
 240
 241         while ((page = balloon_page_pop(&pages))) {
 242                 balloon_page_enqueue(&vb->vb_dev_info, page);
 243
 244                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 245                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 246                 if (!virtio_has_feature(vb->vdev,
 247                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 248                         adjust_managed_page_count(page, -1);
 249                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
 250         }
 251
 252         num_allocated_pages = vb->num_pfns;
 253         /* Did we get any? */
 254         if (vb->num_pfns != 0)
 255                 tell_host(vb, vb->inflate_vq);
 256         mutex_unlock(&vb->balloon_lock);
 257
 258         return num_allocated_pages;
 259 }
 260
 261 static void release_pages_balloon(struct virtio_balloon *vb,
 262                                  struct list_head *pages)
 263 {
 264         struct page *page, *next;
 265
 266         list_for_each_entry_safe(page, next, pages, lru) {
 267                 if (!virtio_has_feature(vb->vdev,
 268                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 269                         adjust_managed_page_count(page, 1);
 270                 list_del(&page->lru);
 271                 put_page(page); /* balloon reference */
 272         }
 273 }
 274
 275 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 276 {
 277         unsigned num_freed_pages;
 278         struct page *page;
 279         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 280         LIST_HEAD(pages);
 281
 282         /* We can only do one array worth at a time. */
 283         num = min(num, ARRAY_SIZE(vb->pfns));
 284
 285         mutex_lock(&vb->balloon_lock);
 286         /* We can't release more pages than taken */
 287         num = min(num, (size_t)vb->num_pages);
 288         for (vb->num_pfns = 0; vb->num_pfns < num;
 289              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 290                 page = balloon_page_dequeue(vb_dev_info);
 291                 if (!page)
 292                         break;
 293                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 294                 list_add(&page->lru, &pages);
 295                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 296         }
 297
 298         num_freed_pages = vb->num_pfns;
 299         /*
 300          * Note that if
 301          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 302          * is true, we *have* to do it in this order
 303          */
 304         if (vb->num_pfns != 0)
 305                 tell_host(vb, vb->deflate_vq);
 306         release_pages_balloon(vb, &pages);
 307         mutex_unlock(&vb->balloon_lock);
 308         return num_freed_pages;
 309 }
 310
 311 static inline void update_stat(struct virtio_balloon *vb, int idx,
 312                                u16 tag, u64 val)
 313 {
 314         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 315         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 316         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 317 }
 318
 319 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 320
 321 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 322 {
 323         unsigned long events[NR_VM_EVENT_ITEMS];
 324         struct sysinfo i;
 325         unsigned int idx = 0;
 326         long available;
 327         unsigned long caches;
 328
 329         all_vm_events(events);
 330         si_meminfo(&i);
 331
 332         available = si_mem_available();
 333         caches = global_node_page_state(NR_FILE_PAGES);
 334
 335 #ifdef CONFIG_VM_EVENT_COUNTERS
 336         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 337                                 pages_to_bytes(events[PSWPIN]));
 338         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 339                                 pages_to_bytes(events[PSWPOUT]));
 340         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 341         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 342 #ifdef CONFIG_HUGETLB_PAGE
 343         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
 344                     events[HTLB_BUDDY_PGALLOC]);
 345         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
 346                     events[HTLB_BUDDY_PGALLOC_FAIL]);
 347 #endif
 348 #endif
 349         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 350                                 pages_to_bytes(i.freeram));
 351         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 352                                 pages_to_bytes(i.totalram));
 353         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 354                                 pages_to_bytes(available));
 355         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
 356                                 pages_to_bytes(caches));
 357
 358         return idx;
 359 }
 360
 361 /*
 362  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 363  * the stats queue operates in reverse.  The driver initializes the virtqueue
 364  * with a single buffer.  From that point forward, all conversations consist of
 365  * a hypervisor request (a call to this function) which directs us to refill
 366  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 367  * we delegate the job to a freezable workqueue that will do the actual work via
 368  * stats_handle_request().
 369  */
 370 static void stats_request(struct virtqueue *vq)
 371 {
 372         struct virtio_balloon *vb = vq->vdev->priv;
 373
 374         spin_lock(&vb->stop_update_lock);
 375         if (!vb->stop_update)
 376                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 377         spin_unlock(&vb->stop_update_lock);
 378 }
 379
 380 static void stats_handle_request(struct virtio_balloon *vb)
 381 {
 382         struct virtqueue *vq;
 383         struct scatterlist sg;
 384         unsigned int len, num_stats;
 385
 386         num_stats = update_balloon_stats(vb);
 387
 388         vq = vb->stats_vq;
 389         if (!virtqueue_get_buf(vq, &len))
 390                 return;
 391         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 392         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 393         virtqueue_kick(vq);
 394 }
 395
 396 static inline s64 towards_target(struct virtio_balloon *vb)
 397 {
 398         s64 target;
 399         u32 num_pages;
 400
 401         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 402                      &num_pages);
 403
 404         /* Legacy balloon config space is LE, unlike all other devices. */
 405         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 406                 num_pages = le32_to_cpu((__force __le32)num_pages);
 407
 408         target = num_pages;
 409         return target - vb->num_pages;
 410 }
 411
 412 /* Gives back @num_to_return blocks of free pages to mm. */
 413 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 414                                              unsigned long num_to_return)
 415 {
 416         struct page *page;
 417         unsigned long num_returned;
 418
 419         spin_lock_irq(&vb->free_page_list_lock);
 420         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 421                 page = balloon_page_pop(&vb->free_page_list);
 422                 if (!page)
 423                         break;
 424                 free_pages((unsigned long)page_address(page),
 425                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 426         }
 427         vb->num_free_page_blocks -= num_returned;
 428         spin_unlock_irq(&vb->free_page_list_lock);
 429
 430         return num_returned;
 431 }
 432
 433 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 434 {
 435         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 436                 return;
 437
 438         /* No need to queue the work if the bit was already set. */
 439         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 440                              &vb->config_read_bitmap))
 441                 return;
 442
 443         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 444 }
 445
 446 static void virtballoon_changed(struct virtio_device *vdev)
 447 {
 448         struct virtio_balloon *vb = vdev->priv;
 449         unsigned long flags;
 450
 451         spin_lock_irqsave(&vb->stop_update_lock, flags);
 452         if (!vb->stop_update) {
 453                 queue_work(system_freezable_wq,
 454                            &vb->update_balloon_size_work);
 455                 virtio_balloon_queue_free_page_work(vb);
 456         }
 457         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 458 }
 459
 460 static void update_balloon_size(struct virtio_balloon *vb)
 461 {
 462         u32 actual = vb->num_pages;
 463
 464         /* Legacy balloon config space is LE, unlike all other devices. */
 465         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 466                 actual = (__force u32)cpu_to_le32(actual);
 467
 468         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 469                       &actual);
 470 }
 471
 472 static void update_balloon_stats_func(struct work_struct *work)
 473 {
 474         struct virtio_balloon *vb;
 475
 476         vb = container_of(work, struct virtio_balloon,
 477                           update_balloon_stats_work);
 478         stats_handle_request(vb);
 479 }
 480
 481 static void update_balloon_size_func(struct work_struct *work)
 482 {
 483         struct virtio_balloon *vb;
 484         s64 diff;
 485
 486         vb = container_of(work, struct virtio_balloon,
 487                           update_balloon_size_work);
 488         diff = towards_target(vb);
 489
 490         if (!diff)
 491                 return;
 492
 493         if (diff > 0)
 494                 diff -= fill_balloon(vb, diff);
 495         else
 496                 diff += leak_balloon(vb, -diff);
 497         update_balloon_size(vb);
 498
 499         if (diff)
 500                 queue_work(system_freezable_wq, work);
 501 }
 502
 503 static int init_vqs(struct virtio_balloon *vb)
 504 {
 505         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 506         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 507         const char *names[VIRTIO_BALLOON_VQ_MAX];
 508         int err;
 509
 510         /*
 511          * Inflateq and deflateq are used unconditionally. The names[]
 512          * will be NULL if the related feature is not enabled, which will
 513          * cause no allocation for the corresponding virtqueue in find_vqs.
 514          */
 515         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
 516         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 517         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 518         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 519         callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
 520         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 521         callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 522         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 523         names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
 524
 525         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 526                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
 527                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
 528         }
 529
 530         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 531                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
 532                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 533         }
 534
 535         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 536                 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
 537                 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
 538         }
 539
 540         err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
 541                                          vqs, callbacks, names, NULL, NULL);
 542         if (err)
 543                 return err;
 544
 545         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 546         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 547         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 548                 struct scatterlist sg;
 549                 unsigned int num_stats;
 550                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 551
 552                 /*
 553                  * Prime this virtqueue with one buffer so the hypervisor can
 554                  * use it to signal us later (it can't be broken yet!).
 555                  */
 556                 num_stats = update_balloon_stats(vb);
 557
 558                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 559                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 560                                            GFP_KERNEL);
 561                 if (err) {
 562                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 563                                  __func__);
 564                         return err;
 565                 }
 566                 virtqueue_kick(vb->stats_vq);
 567         }
 568
 569         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 570                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 571
 572         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
 573                 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
 574
 575         return 0;
 576 }
 577
 578 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 579 {
 580         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 581                                &vb->config_read_bitmap))
 582                 virtio_cread(vb->vdev, struct virtio_balloon_config,
 583                              free_page_hint_cmd_id,
 584                              &vb->cmd_id_received_cache);
 585
 586         return vb->cmd_id_received_cache;
 587 }
 588
 589 static int send_cmd_id_start(struct virtio_balloon *vb)
 590 {
 591         struct scatterlist sg;
 592         struct virtqueue *vq = vb->free_page_vq;
 593         int err, unused;
 594
 595         /* Detach all the used buffers from the vq */
 596         while (virtqueue_get_buf(vq, &unused))
 597                 ;
 598
 599         vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
 600                                         virtio_balloon_cmd_id_received(vb));
 601         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 602         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 603         if (!err)
 604                 virtqueue_kick(vq);
 605         return err;
 606 }
 607
 608 static int send_cmd_id_stop(struct virtio_balloon *vb)
 609 {
 610         struct scatterlist sg;
 611         struct virtqueue *vq = vb->free_page_vq;
 612         int err, unused;
 613
 614         /* Detach all the used buffers from the vq */
 615         while (virtqueue_get_buf(vq, &unused))
 616                 ;
 617
 618         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 619         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 620         if (!err)
 621                 virtqueue_kick(vq);
 622         return err;
 623 }
 624
 625 static int get_free_page_and_send(struct virtio_balloon *vb)
 626 {
 627         struct virtqueue *vq = vb->free_page_vq;
 628         struct page *page;
 629         struct scatterlist sg;
 630         int err, unused;
 631         void *p;
 632
 633         /* Detach all the used buffers from the vq */
 634         while (virtqueue_get_buf(vq, &unused))
 635                 ;
 636
 637         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 638                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 639         /*
 640          * When the allocation returns NULL, it indicates that we have got all
 641          * the possible free pages, so return -EINTR to stop.
 642          */
 643         if (!page)
 644                 return -EINTR;
 645
 646         p = page_address(page);
 647         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 648         /* There is always 1 entry reserved for the cmd id to use. */
 649         if (vq->num_free > 1) {
 650                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 651                 if (unlikely(err)) {
 652                         free_pages((unsigned long)p,
 653                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 654                         return err;
 655                 }
 656                 virtqueue_kick(vq);
 657                 spin_lock_irq(&vb->free_page_list_lock);
 658                 balloon_page_push(&vb->free_page_list, page);
 659                 vb->num_free_page_blocks++;
 660                 spin_unlock_irq(&vb->free_page_list_lock);
 661         } else {
 662                 /*
 663                  * The vq has no available entry to add this page block, so
 664                  * just free it.
 665                  */
 666                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 667         }
 668
 669         return 0;
 670 }
 671
 672 static int send_free_pages(struct virtio_balloon *vb)
 673 {
 674         int err;
 675         u32 cmd_id_active;
 676
 677         while (1) {
 678                 /*
 679                  * If a stop id or a new cmd id was just received from host,
 680                  * stop the reporting.
 681                  */
 682                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 683                 if (unlikely(cmd_id_active !=
 684                              virtio_balloon_cmd_id_received(vb)))
 685                         break;
 686
 687                 /*
 688                  * The free page blocks are allocated and sent to host one by
 689                  * one.
 690                  */
 691                 err = get_free_page_and_send(vb);
 692                 if (err == -EINTR)
 693                         break;
 694                 else if (unlikely(err))
 695                         return err;
 696         }
 697
 698         return 0;
 699 }
 700
 701 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 702 {
 703         int err;
 704         struct device *dev = &vb->vdev->dev;
 705
 706         /* Start by sending the received cmd id to host with an outbuf. */
 707         err = send_cmd_id_start(vb);
 708         if (unlikely(err))
 709                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 710
 711         err = send_free_pages(vb);
 712         if (unlikely(err))
 713                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 714
 715         /* End by sending a stop id to host with an outbuf. */
 716         err = send_cmd_id_stop(vb);
 717         if (unlikely(err))
 718                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 719 }
 720
 721 static void report_free_page_func(struct work_struct *work)
 722 {
 723         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 724                                                  report_free_page_work);
 725         u32 cmd_id_received;
 726
 727         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 728         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 729                 /* Pass ULONG_MAX to give back all the free pages */
 730                 return_free_pages_to_mm(vb, ULONG_MAX);
 731         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 732                    cmd_id_received !=
 733                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 734                 virtio_balloon_report_free_page(vb);
 735         }
 736 }
 737
 738 #ifdef CONFIG_BALLOON_COMPACTION
 739 /*
 740  * virtballoon_migratepage - perform the balloon page migration on behalf of
 741  *                           a compation thread.     (called under page lock)
 742  * @vb_dev_info: the balloon device
 743  * @newpage: page that will replace the isolated page after migration finishes.
 744  * @page   : the isolated (old) page that is about to be migrated to newpage.
 745  * @mode   : compaction mode -- not used for balloon page migration.
 746  *
 747  * After a ballooned page gets isolated by compaction procedures, this is the
 748  * function that performs the page migration on behalf of a compaction thread
 749  * The page migration for virtio balloon is done in a simple swap fashion which
 750  * follows these two macro steps:
 751  *  1) insert newpage into vb->pages list and update the host about it;
 752  *  2) update the host about the old page removed from vb->pages list;
 753  *
 754  * This function preforms the balloon page migration task.
 755  * Called through balloon_mapping->a_ops->migratepage
 756  */
 757 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 758                 struct page *newpage, struct page *page, enum migrate_mode mode)
 759 {
 760         struct virtio_balloon *vb = container_of(vb_dev_info,
 761                         struct virtio_balloon, vb_dev_info);
 762         unsigned long flags;
 763
 764         /*
 765          * In order to avoid lock contention while migrating pages concurrently
 766          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 767          * this turn, as it is easier to retry the page migration later.
 768          * This also prevents fill_balloon() getting stuck into a mutex
 769          * recursion in the case it ends up triggering memory compaction
 770          * while it is attempting to inflate the ballon.
 771          */
 772         if (!mutex_trylock(&vb->balloon_lock))
 773                 return -EAGAIN;
 774
 775         get_page(newpage); /* balloon reference */
 776
 777         /*
 778           * When we migrate a page to a different zone and adjusted the
 779           * managed page count when inflating, we have to fixup the count of
 780           * both involved zones.
 781           */
 782         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 783             page_zone(page) != page_zone(newpage)) {
 784                 adjust_managed_page_count(page, 1);
 785                 adjust_managed_page_count(newpage, -1);
 786         }
 787
 788         /* balloon's page migration 1st step  -- inflate "newpage" */
 789         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 790         balloon_page_insert(vb_dev_info, newpage);
 791         vb_dev_info->isolated_pages--;
 792         __count_vm_event(BALLOON_MIGRATE);
 793         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 794         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 795         set_page_pfns(vb, vb->pfns, newpage);
 796         tell_host(vb, vb->inflate_vq);
 797
 798         /* balloon's page migration 2nd step -- deflate "page" */
 799         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 800         balloon_page_delete(page);
 801         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 802         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 803         set_page_pfns(vb, vb->pfns, page);
 804         tell_host(vb, vb->deflate_vq);
 805
 806         mutex_unlock(&vb->balloon_lock);
 807
 808         put_page(page); /* balloon reference */
 809
 810         return MIGRATEPAGE_SUCCESS;
 811 }
 812
 813 static int balloon_init_fs_context(struct fs_context *fc)
 814 {
 815         return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
 816 }
 817
 818 static struct file_system_type balloon_fs = {
 819         .name           = "balloon-kvm",
 820         .init_fs_context = balloon_init_fs_context,
 821         .kill_sb        = kill_anon_super,
 822 };
 823
 824 #endif /* CONFIG_BALLOON_COMPACTION */
 825
 826 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 827                                        unsigned long pages_to_free)
 828 {
 829         unsigned long blocks_to_free, blocks_freed;
 830
 831         pages_to_free = round_up(pages_to_free,
 832                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 833         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 834         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 835
 836         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 837 }
 838
 839 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 840                                                   struct shrink_control *sc)
 841 {
 842         struct virtio_balloon *vb = container_of(shrinker,
 843                                         struct virtio_balloon, shrinker);
 844
 845         return shrink_free_pages(vb, sc->nr_to_scan);
 846 }
 847
 848 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 849                                                    struct shrink_control *sc)
 850 {
 851         struct virtio_balloon *vb = container_of(shrinker,
 852                                         struct virtio_balloon, shrinker);
 853
 854         return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 855 }
 856
 857 static int virtio_balloon_oom_notify(struct notifier_block *nb,
 858                                      unsigned long dummy, void *parm)
 859 {
 860         struct virtio_balloon *vb = container_of(nb,
 861                                                  struct virtio_balloon, oom_nb);
 862         unsigned long *freed = parm;
 863
 864         *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
 865                   VIRTIO_BALLOON_PAGES_PER_PAGE;
 866         update_balloon_size(vb);
 867
 868         return NOTIFY_OK;
 869 }
 870
 871 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 872 {
 873         unregister_shrinker(&vb->shrinker);
 874 }
 875
 876 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 877 {
 878         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
 879         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
 880         vb->shrinker.seeks = DEFAULT_SEEKS;
 881
 882         return register_shrinker(&vb->shrinker);
 883 }
 884
 885 static int virtballoon_probe(struct virtio_device *vdev)
 886 {
 887         struct virtio_balloon *vb;
 888         int err;
 889
 890         if (!vdev->config->get) {
 891                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 892                         __func__);
 893                 return -EINVAL;
 894         }
 895
 896         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 897         if (!vb) {
 898                 err = -ENOMEM;
 899                 goto out;
 900         }
 901
 902         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 903         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 904         spin_lock_init(&vb->stop_update_lock);
 905         mutex_init(&vb->balloon_lock);
 906         init_waitqueue_head(&vb->acked);
 907         vb->vdev = vdev;
 908
 909         balloon_devinfo_init(&vb->vb_dev_info);
 910
 911         err = init_vqs(vb);
 912         if (err)
 913                 goto out_free_vb;
 914
 915 #ifdef CONFIG_BALLOON_COMPACTION
 916         balloon_mnt = kern_mount(&balloon_fs);
 917         if (IS_ERR(balloon_mnt)) {
 918                 err = PTR_ERR(balloon_mnt);
 919                 goto out_del_vqs;
 920         }
 921
 922         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 923         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 924         if (IS_ERR(vb->vb_dev_info.inode)) {
 925                 err = PTR_ERR(vb->vb_dev_info.inode);
 926                 goto out_kern_unmount;
 927         }
 928         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 929 #endif
 930         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 931                 /*
 932                  * There is always one entry reserved for cmd id, so the ring
 933                  * size needs to be at least two to report free page hints.
 934                  */
 935                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 936                         err = -ENOSPC;
 937                         goto out_iput;
 938                 }
 939                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 940                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 941                 if (!vb->balloon_wq) {
 942                         err = -ENOMEM;
 943                         goto out_iput;
 944                 }
 945                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 946                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 947                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 948                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 949                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 950                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 951                 spin_lock_init(&vb->free_page_list_lock);
 952                 INIT_LIST_HEAD(&vb->free_page_list);
 953                 /*
 954                  * We're allowed to reuse any free pages, even if they are
 955                  * still to be processed by the host.
 956                  */
 957                 err = virtio_balloon_register_shrinker(vb);
 958                 if (err)
 959                         goto out_del_balloon_wq;
 960         }
 961
 962         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
 963                 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
 964                 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
 965                 err = register_oom_notifier(&vb->oom_nb);
 966                 if (err < 0)
 967                         goto out_unregister_shrinker;
 968         }
 969
 970         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
 971                 /* Start with poison val of 0 representing general init */
 972                 __u32 poison_val = 0;
 973
 974                 /*
 975                  * Let the hypervisor know that we are expecting a
 976                  * specific value to be written back in balloon pages.
 977                  */
 978                 if (!want_init_on_free())
 979                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
 980
 981                 virtio_cwrite(vb->vdev, struct virtio_balloon_config,
 982                               poison_val, &poison_val);
 983         }
 984
 985         vb->pr_dev_info.report = virtballoon_free_page_report;
 986         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 987                 unsigned int capacity;
 988
 989                 capacity = virtqueue_get_vring_size(vb->reporting_vq);
 990                 if (capacity < PAGE_REPORTING_CAPACITY) {
 991                         err = -ENOSPC;
 992                         goto out_unregister_oom;
 993                 }
 994
 995                 err = page_reporting_register(&vb->pr_dev_info);
 996                 if (err)
 997                         goto out_unregister_oom;
 998         }
 999
1000         virtio_device_ready(vdev);
1001
1002         if (towards_target(vb))
1003                 virtballoon_changed(vdev);
1004         return 0;
1005
1006 out_unregister_oom:
1007         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1008                 unregister_oom_notifier(&vb->oom_nb);
1009 out_unregister_shrinker:
1010         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1011                 virtio_balloon_unregister_shrinker(vb);
1012 out_del_balloon_wq:
1013         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1014                 destroy_workqueue(vb->balloon_wq);
1015 out_iput:
1016 #ifdef CONFIG_BALLOON_COMPACTION
1017         iput(vb->vb_dev_info.inode);
1018 out_kern_unmount:
1019         kern_unmount(balloon_mnt);
1020 out_del_vqs:
1021 #endif
1022         vdev->config->del_vqs(vdev);
1023 out_free_vb:
1024         kfree(vb);
1025 out:
1026         return err;
1027 }
1028
1029 static void remove_common(struct virtio_balloon *vb)
1030 {
1031         /* There might be pages left in the balloon: free them. */
1032         while (vb->num_pages)
1033                 leak_balloon(vb, vb->num_pages);
1034         update_balloon_size(vb);
1035
1036         /* There might be free pages that are being reported: release them. */
1037         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1038                 return_free_pages_to_mm(vb, ULONG_MAX);
1039
1040         /* Now we reset the device so we can clean up the queues. */
1041         vb->vdev->config->reset(vb->vdev);
1042
1043         vb->vdev->config->del_vqs(vb->vdev);
1044 }
1045
1046 static void virtballoon_remove(struct virtio_device *vdev)
1047 {
1048         struct virtio_balloon *vb = vdev->priv;
1049
1050         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1051                 page_reporting_unregister(&vb->pr_dev_info);
1052         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1053                 unregister_oom_notifier(&vb->oom_nb);
1054         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1055                 virtio_balloon_unregister_shrinker(vb);
1056         spin_lock_irq(&vb->stop_update_lock);
1057         vb->stop_update = true;
1058         spin_unlock_irq(&vb->stop_update_lock);
1059         cancel_work_sync(&vb->update_balloon_size_work);
1060         cancel_work_sync(&vb->update_balloon_stats_work);
1061
1062         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1063                 cancel_work_sync(&vb->report_free_page_work);
1064                 destroy_workqueue(vb->balloon_wq);
1065         }
1066
1067         remove_common(vb);
1068 #ifdef CONFIG_BALLOON_COMPACTION
1069         if (vb->vb_dev_info.inode)
1070                 iput(vb->vb_dev_info.inode);
1071
1072         kern_unmount(balloon_mnt);
1073 #endif
1074         kfree(vb);
1075 }
1076
1077 #ifdef CONFIG_PM_SLEEP
1078 static int virtballoon_freeze(struct virtio_device *vdev)
1079 {
1080         struct virtio_balloon *vb = vdev->priv;
1081
1082         /*
1083          * The workqueue is already frozen by the PM core before this
1084          * function is called.
1085          */
1086         remove_common(vb);
1087         return 0;
1088 }
1089
1090 static int virtballoon_restore(struct virtio_device *vdev)
1091 {
1092         struct virtio_balloon *vb = vdev->priv;
1093         int ret;
1094
1095         ret = init_vqs(vdev->priv);
1096         if (ret)
1097                 return ret;
1098
1099         virtio_device_ready(vdev);
1100
1101         if (towards_target(vb))
1102                 virtballoon_changed(vdev);
1103         update_balloon_size(vb);
1104         return 0;
1105 }
1106 #endif
1107
1108 static int virtballoon_validate(struct virtio_device *vdev)
1109 {
1110         /* Tell the host whether we care about poisoned pages. */
1111         if (!want_init_on_free() &&
1112             (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
1113              !page_poisoning_enabled()))
1114                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1115
1116         __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1117         return 0;
1118 }
1119
1120 static unsigned int features[] = {
1121         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1122         VIRTIO_BALLOON_F_STATS_VQ,
1123         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1124         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1125         VIRTIO_BALLOON_F_PAGE_POISON,
1126         VIRTIO_BALLOON_F_REPORTING,
1127 };
1128
1129 static struct virtio_driver virtio_balloon_driver = {
1130         .feature_table = features,
1131         .feature_table_size = ARRAY_SIZE(features),
1132         .driver.name =  KBUILD_MODNAME,
1133         .driver.owner = THIS_MODULE,
1134         .id_table =     id_table,
1135         .validate =     virtballoon_validate,
1136         .probe =        virtballoon_probe,
1137         .remove =       virtballoon_remove,
1138         .config_changed = virtballoon_changed,
1139 #ifdef CONFIG_PM_SLEEP
1140         .freeze =       virtballoon_freeze,
1141         .restore =      virtballoon_restore,
1142 #endif
1143 };
1144
1145 module_virtio_driver(virtio_balloon_driver);
1146 MODULE_DEVICE_TABLE(virtio, id_table);
1147 MODULE_DESCRIPTION("Virtio balloon driver");
1148 MODULE_LICENSE("GPL");