drivers/virtio/virtio_balloon.c

   1 /*
   2  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
   3  * Tosatti's implementations.
   4  *
   5  *  Copyright 2008 Rusty Russell IBM Corporation
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  This program is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with this program; if not, write to the Free Software
  19  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20  */
  21
  22 #include <linux/virtio.h>
  23 #include <linux/virtio_balloon.h>
  24 #include <linux/swap.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/delay.h>
  27 #include <linux/slab.h>
  28 #include <linux/module.h>
  29 #include <linux/balloon_compaction.h>
  30 #include <linux/oom.h>
  31 #include <linux/wait.h>
  32 #include <linux/mm.h>
  33
  34 /*
  35  * Balloon device works in 4K page units.  So each page is pointed to by
  36  * multiple balloon pages.  All memory counters in this driver are in balloon
  37  * page units.
  38  */
  39 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  40 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  41 #define OOM_VBALLOON_DEFAULT_PAGES 256
  42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  43
  44 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
  45 module_param(oom_pages, int, S_IRUSR | S_IWUSR);
  46 MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
  47
  48 struct virtio_balloon {
  49         struct virtio_device *vdev;
  50         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  51
  52         /* The balloon servicing is delegated to a freezable workqueue. */
  53         struct work_struct update_balloon_stats_work;
  54         struct work_struct update_balloon_size_work;
  55
  56         /* Prevent updating balloon when it is being canceled. */
  57         spinlock_t stop_update_lock;
  58         bool stop_update;
  59
  60         /* Waiting for host to ack the pages we released. */
  61         wait_queue_head_t acked;
  62
  63         /* Number of balloon pages we've told the Host we're not using. */
  64         unsigned int num_pages;
  65         /*
  66          * The pages we've told the Host we're not using are enqueued
  67          * at vb_dev_info->pages list.
  68          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
  69          * to num_pages above.
  70          */
  71         struct balloon_dev_info vb_dev_info;
  72
  73         /* Synchronize access/update to this struct virtio_balloon elements */
  74         struct mutex balloon_lock;
  75
  76         /* The array of pfns we tell the Host about. */
  77         unsigned int num_pfns;
  78         u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
  79
  80         /* Memory statistics */
  81         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
  82
  83         /* To register callback in oom notifier call chain */
  84         struct notifier_block nb;
  85 };
  86
  87 static struct virtio_device_id id_table[] = {
  88         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
  89         { 0 },
  90 };
  91
  92 static u32 page_to_balloon_pfn(struct page *page)
  93 {
  94         unsigned long pfn = page_to_pfn(page);
  95
  96         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
  97         /* Convert pfn from Linux page size to balloon page size. */
  98         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
  99 }
 100
 101 static struct page *balloon_pfn_to_page(u32 pfn)
 102 {
 103         BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
 104         return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
 105 }
 106
 107 static void balloon_ack(struct virtqueue *vq)
 108 {
 109         struct virtio_balloon *vb = vq->vdev->priv;
 110
 111         wake_up(&vb->acked);
 112 }
 113
 114 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 115 {
 116         struct scatterlist sg;
 117         unsigned int len;
 118
 119         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 120
 121         /* We should always be able to add one buffer to an empty queue. */
 122         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 123         virtqueue_kick(vq);
 124
 125         /* When host has read buffer, this completes via balloon_ack */
 126         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 127
 128 }
 129
 130 static void set_page_pfns(u32 pfns[], struct page *page)
 131 {
 132         unsigned int i;
 133
 134         /* Set balloon pfns pointing at this page.
 135          * Note that the first pfn points at start of the page. */
 136         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 137                 pfns[i] = page_to_balloon_pfn(page) + i;
 138 }
 139
 140 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 141 {
 142         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 143         unsigned num_allocated_pages;
 144
 145         /* We can only do one array worth at a time. */
 146         num = min(num, ARRAY_SIZE(vb->pfns));
 147
 148         mutex_lock(&vb->balloon_lock);
 149         for (vb->num_pfns = 0; vb->num_pfns < num;
 150              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 151                 struct page *page = balloon_page_enqueue(vb_dev_info);
 152
 153                 if (!page) {
 154                         dev_info_ratelimited(&vb->vdev->dev,
 155                                              "Out of puff! Can't get %u pages\n",
 156                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 157                         /* Sleep for at least 1/5 of a second before retry. */
 158                         msleep(200);
 159                         break;
 160                 }
 161                 set_page_pfns(vb->pfns + vb->num_pfns, page);
 162                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 163                 if (!virtio_has_feature(vb->vdev,
 164                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 165                         adjust_managed_page_count(page, -1);
 166         }
 167
 168         num_allocated_pages = vb->num_pfns;
 169         /* Did we get any? */
 170         if (vb->num_pfns != 0)
 171                 tell_host(vb, vb->inflate_vq);
 172         mutex_unlock(&vb->balloon_lock);
 173
 174         return num_allocated_pages;
 175 }
 176
 177 static void release_pages_balloon(struct virtio_balloon *vb)
 178 {
 179         unsigned int i;
 180
 181         /* Find pfns pointing at start of each page, get pages and free them. */
 182         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 183                 struct page *page = balloon_pfn_to_page(vb->pfns[i]);
 184                 if (!virtio_has_feature(vb->vdev,
 185                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 186                         adjust_managed_page_count(page, 1);
 187                 put_page(page); /* balloon reference */
 188         }
 189 }
 190
 191 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 192 {
 193         unsigned num_freed_pages;
 194         struct page *page;
 195         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 196
 197         /* We can only do one array worth at a time. */
 198         num = min(num, ARRAY_SIZE(vb->pfns));
 199
 200         mutex_lock(&vb->balloon_lock);
 201         for (vb->num_pfns = 0; vb->num_pfns < num;
 202              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 203                 page = balloon_page_dequeue(vb_dev_info);
 204                 if (!page)
 205                         break;
 206                 set_page_pfns(vb->pfns + vb->num_pfns, page);
 207                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 208         }
 209
 210         num_freed_pages = vb->num_pfns;
 211         /*
 212          * Note that if
 213          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 214          * is true, we *have* to do it in this order
 215          */
 216         if (vb->num_pfns != 0)
 217                 tell_host(vb, vb->deflate_vq);
 218         release_pages_balloon(vb);
 219         mutex_unlock(&vb->balloon_lock);
 220         return num_freed_pages;
 221 }
 222
 223 static inline void update_stat(struct virtio_balloon *vb, int idx,
 224                                u16 tag, u64 val)
 225 {
 226         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 227         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 228         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 229 }
 230
 231 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 232
 233 static void update_balloon_stats(struct virtio_balloon *vb)
 234 {
 235         unsigned long events[NR_VM_EVENT_ITEMS];
 236         struct sysinfo i;
 237         int idx = 0;
 238         long available;
 239
 240         all_vm_events(events);
 241         si_meminfo(&i);
 242
 243         available = si_mem_available();
 244
 245         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 246                                 pages_to_bytes(events[PSWPIN]));
 247         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 248                                 pages_to_bytes(events[PSWPOUT]));
 249         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 250         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 251         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 252                                 pages_to_bytes(i.freeram));
 253         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 254                                 pages_to_bytes(i.totalram));
 255         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 256                                 pages_to_bytes(available));
 257 }
 258
 259 /*
 260  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 261  * the stats queue operates in reverse.  The driver initializes the virtqueue
 262  * with a single buffer.  From that point forward, all conversations consist of
 263  * a hypervisor request (a call to this function) which directs us to refill
 264  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 265  * we delegate the job to a freezable workqueue that will do the actual work via
 266  * stats_handle_request().
 267  */
 268 static void stats_request(struct virtqueue *vq)
 269 {
 270         struct virtio_balloon *vb = vq->vdev->priv;
 271
 272         spin_lock(&vb->stop_update_lock);
 273         if (!vb->stop_update)
 274                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 275         spin_unlock(&vb->stop_update_lock);
 276 }
 277
 278 static void stats_handle_request(struct virtio_balloon *vb)
 279 {
 280         struct virtqueue *vq;
 281         struct scatterlist sg;
 282         unsigned int len;
 283
 284         update_balloon_stats(vb);
 285
 286         vq = vb->stats_vq;
 287         if (!virtqueue_get_buf(vq, &len))
 288                 return;
 289         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 290         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 291         virtqueue_kick(vq);
 292 }
 293
 294 static void virtballoon_changed(struct virtio_device *vdev)
 295 {
 296         struct virtio_balloon *vb = vdev->priv;
 297         unsigned long flags;
 298
 299         spin_lock_irqsave(&vb->stop_update_lock, flags);
 300         if (!vb->stop_update)
 301                 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
 302         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 303 }
 304
 305 static inline s64 towards_target(struct virtio_balloon *vb)
 306 {
 307         s64 target;
 308         u32 num_pages;
 309
 310         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 311                      &num_pages);
 312
 313         /* Legacy balloon config space is LE, unlike all other devices. */
 314         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 315                 num_pages = le32_to_cpu((__force __le32)num_pages);
 316
 317         target = num_pages;
 318         return target - vb->num_pages;
 319 }
 320
 321 static void update_balloon_size(struct virtio_balloon *vb)
 322 {
 323         u32 actual = vb->num_pages;
 324
 325         /* Legacy balloon config space is LE, unlike all other devices. */
 326         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 327                 actual = (__force u32)cpu_to_le32(actual);
 328
 329         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 330                       &actual);
 331 }
 332
 333 /*
 334  * virtballoon_oom_notify - release pages when system is under severe
 335  *                          memory pressure (called from out_of_memory())
 336  * @self : notifier block struct
 337  * @dummy: not used
 338  * @parm : returned - number of freed pages
 339  *
 340  * The balancing of memory by use of the virtio balloon should not cause
 341  * the termination of processes while there are pages in the balloon.
 342  * If virtio balloon manages to release some memory, it will make the
 343  * system return and retry the allocation that forced the OOM killer
 344  * to run.
 345  */
 346 static int virtballoon_oom_notify(struct notifier_block *self,
 347                                   unsigned long dummy, void *parm)
 348 {
 349         struct virtio_balloon *vb;
 350         unsigned long *freed;
 351         unsigned num_freed_pages;
 352
 353         vb = container_of(self, struct virtio_balloon, nb);
 354         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 355                 return NOTIFY_OK;
 356
 357         freed = parm;
 358         num_freed_pages = leak_balloon(vb, oom_pages);
 359         update_balloon_size(vb);
 360         *freed += num_freed_pages;
 361
 362         return NOTIFY_OK;
 363 }
 364
 365 static void update_balloon_stats_func(struct work_struct *work)
 366 {
 367         struct virtio_balloon *vb;
 368
 369         vb = container_of(work, struct virtio_balloon,
 370                           update_balloon_stats_work);
 371         stats_handle_request(vb);
 372 }
 373
 374 static void update_balloon_size_func(struct work_struct *work)
 375 {
 376         struct virtio_balloon *vb;
 377         s64 diff;
 378
 379         vb = container_of(work, struct virtio_balloon,
 380                           update_balloon_size_work);
 381         diff = towards_target(vb);
 382
 383         if (diff > 0)
 384                 diff -= fill_balloon(vb, diff);
 385         else if (diff < 0)
 386                 diff += leak_balloon(vb, -diff);
 387         update_balloon_size(vb);
 388
 389         if (diff)
 390                 queue_work(system_freezable_wq, work);
 391 }
 392
 393 static int init_vqs(struct virtio_balloon *vb)
 394 {
 395         struct virtqueue *vqs[3];
 396         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
 397         static const char * const names[] = { "inflate", "deflate", "stats" };
 398         int err, nvqs;
 399
 400         /*
 401          * We expect two virtqueues: inflate and deflate, and
 402          * optionally stat.
 403          */
 404         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
 405         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
 406         if (err)
 407                 return err;
 408
 409         vb->inflate_vq = vqs[0];
 410         vb->deflate_vq = vqs[1];
 411         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 412                 struct scatterlist sg;
 413                 vb->stats_vq = vqs[2];
 414
 415                 /*
 416                  * Prime this virtqueue with one buffer so the hypervisor can
 417                  * use it to signal us later (it can't be broken yet!).
 418                  */
 419                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
 420                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
 421                     < 0)
 422                         BUG();
 423                 virtqueue_kick(vb->stats_vq);
 424         }
 425         return 0;
 426 }
 427
 428 #ifdef CONFIG_BALLOON_COMPACTION
 429 /*
 430  * virtballoon_migratepage - perform the balloon page migration on behalf of
 431  *                           a compation thread.     (called under page lock)
 432  * @vb_dev_info: the balloon device
 433  * @newpage: page that will replace the isolated page after migration finishes.
 434  * @page   : the isolated (old) page that is about to be migrated to newpage.
 435  * @mode   : compaction mode -- not used for balloon page migration.
 436  *
 437  * After a ballooned page gets isolated by compaction procedures, this is the
 438  * function that performs the page migration on behalf of a compaction thread
 439  * The page migration for virtio balloon is done in a simple swap fashion which
 440  * follows these two macro steps:
 441  *  1) insert newpage into vb->pages list and update the host about it;
 442  *  2) update the host about the old page removed from vb->pages list;
 443  *
 444  * This function preforms the balloon page migration task.
 445  * Called through balloon_mapping->a_ops->migratepage
 446  */
 447 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 448                 struct page *newpage, struct page *page, enum migrate_mode mode)
 449 {
 450         struct virtio_balloon *vb = container_of(vb_dev_info,
 451                         struct virtio_balloon, vb_dev_info);
 452         unsigned long flags;
 453
 454         /*
 455          * In order to avoid lock contention while migrating pages concurrently
 456          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 457          * this turn, as it is easier to retry the page migration later.
 458          * This also prevents fill_balloon() getting stuck into a mutex
 459          * recursion in the case it ends up triggering memory compaction
 460          * while it is attempting to inflate the ballon.
 461          */
 462         if (!mutex_trylock(&vb->balloon_lock))
 463                 return -EAGAIN;
 464
 465         get_page(newpage); /* balloon reference */
 466
 467         /* balloon's page migration 1st step  -- inflate "newpage" */
 468         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 469         balloon_page_insert(vb_dev_info, newpage);
 470         vb_dev_info->isolated_pages--;
 471         __count_vm_event(BALLOON_MIGRATE);
 472         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 473         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 474         set_page_pfns(vb->pfns, newpage);
 475         tell_host(vb, vb->inflate_vq);
 476
 477         /* balloon's page migration 2nd step -- deflate "page" */
 478         balloon_page_delete(page);
 479         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 480         set_page_pfns(vb->pfns, page);
 481         tell_host(vb, vb->deflate_vq);
 482
 483         mutex_unlock(&vb->balloon_lock);
 484
 485         put_page(page); /* balloon reference */
 486
 487         return MIGRATEPAGE_SUCCESS;
 488 }
 489 #endif /* CONFIG_BALLOON_COMPACTION */
 490
 491 static int virtballoon_probe(struct virtio_device *vdev)
 492 {
 493         struct virtio_balloon *vb;
 494         int err;
 495
 496         if (!vdev->config->get) {
 497                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 498                         __func__);
 499                 return -EINVAL;
 500         }
 501
 502         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 503         if (!vb) {
 504                 err = -ENOMEM;
 505                 goto out;
 506         }
 507
 508         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 509         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 510         spin_lock_init(&vb->stop_update_lock);
 511         vb->stop_update = false;
 512         vb->num_pages = 0;
 513         mutex_init(&vb->balloon_lock);
 514         init_waitqueue_head(&vb->acked);
 515         vb->vdev = vdev;
 516
 517         balloon_devinfo_init(&vb->vb_dev_info);
 518 #ifdef CONFIG_BALLOON_COMPACTION
 519         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 520 #endif
 521
 522         err = init_vqs(vb);
 523         if (err)
 524                 goto out_free_vb;
 525
 526         vb->nb.notifier_call = virtballoon_oom_notify;
 527         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 528         err = register_oom_notifier(&vb->nb);
 529         if (err < 0)
 530                 goto out_oom_notify;
 531
 532         virtio_device_ready(vdev);
 533
 534         return 0;
 535
 536 out_oom_notify:
 537         vdev->config->del_vqs(vdev);
 538 out_free_vb:
 539         kfree(vb);
 540 out:
 541         return err;
 542 }
 543
 544 static void remove_common(struct virtio_balloon *vb)
 545 {
 546         /* There might be pages left in the balloon: free them. */
 547         while (vb->num_pages)
 548                 leak_balloon(vb, vb->num_pages);
 549         update_balloon_size(vb);
 550
 551         /* Now we reset the device so we can clean up the queues. */
 552         vb->vdev->config->reset(vb->vdev);
 553
 554         vb->vdev->config->del_vqs(vb->vdev);
 555 }
 556
 557 static void virtballoon_remove(struct virtio_device *vdev)
 558 {
 559         struct virtio_balloon *vb = vdev->priv;
 560
 561         unregister_oom_notifier(&vb->nb);
 562
 563         spin_lock_irq(&vb->stop_update_lock);
 564         vb->stop_update = true;
 565         spin_unlock_irq(&vb->stop_update_lock);
 566         cancel_work_sync(&vb->update_balloon_size_work);
 567         cancel_work_sync(&vb->update_balloon_stats_work);
 568
 569         remove_common(vb);
 570         kfree(vb);
 571 }
 572
 573 #ifdef CONFIG_PM_SLEEP
 574 static int virtballoon_freeze(struct virtio_device *vdev)
 575 {
 576         struct virtio_balloon *vb = vdev->priv;
 577
 578         /*
 579          * The workqueue is already frozen by the PM core before this
 580          * function is called.
 581          */
 582         remove_common(vb);
 583         return 0;
 584 }
 585
 586 static int virtballoon_restore(struct virtio_device *vdev)
 587 {
 588         struct virtio_balloon *vb = vdev->priv;
 589         int ret;
 590
 591         ret = init_vqs(vdev->priv);
 592         if (ret)
 593                 return ret;
 594
 595         virtio_device_ready(vdev);
 596
 597         if (towards_target(vb))
 598                 virtballoon_changed(vdev);
 599         update_balloon_size(vb);
 600         return 0;
 601 }
 602 #endif
 603
 604 static unsigned int features[] = {
 605         VIRTIO_BALLOON_F_MUST_TELL_HOST,
 606         VIRTIO_BALLOON_F_STATS_VQ,
 607         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 608 };
 609
 610 static struct virtio_driver virtio_balloon_driver = {
 611         .feature_table = features,
 612         .feature_table_size = ARRAY_SIZE(features),
 613         .driver.name =  KBUILD_MODNAME,
 614         .driver.owner = THIS_MODULE,
 615         .id_table =     id_table,
 616         .probe =        virtballoon_probe,
 617         .remove =       virtballoon_remove,
 618         .config_changed = virtballoon_changed,
 619 #ifdef CONFIG_PM_SLEEP
 620         .freeze =       virtballoon_freeze,
 621         .restore =      virtballoon_restore,
 622 #endif
 623 };
 624
 625 module_virtio_driver(virtio_balloon_driver);
 626 MODULE_DEVICE_TABLE(virtio, id_table);
 627 MODULE_DESCRIPTION("Virtio balloon driver");
 628 MODULE_LICENSE("GPL");