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         __virtio32 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(struct virtio_balloon *vb,
 131                           __virtio32 pfns[], struct page *page)
 132 {
 133         unsigned int i;
 134
 135         /* Set balloon pfns pointing at this page.
 136          * Note that the first pfn points at start of the page. */
 137         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 138                 pfns[i] = cpu_to_virtio32(vb->vdev,
 139                                           page_to_balloon_pfn(page) + i);
 140 }
 141
 142 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 143 {
 144         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 145         unsigned num_allocated_pages;
 146
 147         /* We can only do one array worth at a time. */
 148         num = min(num, ARRAY_SIZE(vb->pfns));
 149
 150         mutex_lock(&vb->balloon_lock);
 151         for (vb->num_pfns = 0; vb->num_pfns < num;
 152              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 153                 struct page *page = balloon_page_enqueue(vb_dev_info);
 154
 155                 if (!page) {
 156                         dev_info_ratelimited(&vb->vdev->dev,
 157                                              "Out of puff! Can't get %u pages\n",
 158                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 159                         /* Sleep for at least 1/5 of a second before retry. */
 160                         msleep(200);
 161                         break;
 162                 }
 163                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 164                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 165                 if (!virtio_has_feature(vb->vdev,
 166                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 167                         adjust_managed_page_count(page, -1);
 168         }
 169
 170         num_allocated_pages = vb->num_pfns;
 171         /* Did we get any? */
 172         if (vb->num_pfns != 0)
 173                 tell_host(vb, vb->inflate_vq);
 174         mutex_unlock(&vb->balloon_lock);
 175
 176         return num_allocated_pages;
 177 }
 178
 179 static void release_pages_balloon(struct virtio_balloon *vb)
 180 {
 181         unsigned int i;
 182         struct page *page;
 183
 184         /* Find pfns pointing at start of each page, get pages and free them. */
 185         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 186                 page = balloon_pfn_to_page(virtio32_to_cpu(vb->vdev,
 187                                                            vb->pfns[i]));
 188                 if (!virtio_has_feature(vb->vdev,
 189                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 190                         adjust_managed_page_count(page, 1);
 191                 put_page(page); /* balloon reference */
 192         }
 193 }
 194
 195 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 196 {
 197         unsigned num_freed_pages;
 198         struct page *page;
 199         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 200
 201         /* We can only do one array worth at a time. */
 202         num = min(num, ARRAY_SIZE(vb->pfns));
 203
 204         mutex_lock(&vb->balloon_lock);
 205         for (vb->num_pfns = 0; vb->num_pfns < num;
 206              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 207                 page = balloon_page_dequeue(vb_dev_info);
 208                 if (!page)
 209                         break;
 210                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 211                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 212         }
 213
 214         num_freed_pages = vb->num_pfns;
 215         /*
 216          * Note that if
 217          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 218          * is true, we *have* to do it in this order
 219          */
 220         if (vb->num_pfns != 0)
 221                 tell_host(vb, vb->deflate_vq);
 222         release_pages_balloon(vb);
 223         mutex_unlock(&vb->balloon_lock);
 224         return num_freed_pages;
 225 }
 226
 227 static inline void update_stat(struct virtio_balloon *vb, int idx,
 228                                u16 tag, u64 val)
 229 {
 230         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 231         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 232         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 233 }
 234
 235 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 236
 237 static void update_balloon_stats(struct virtio_balloon *vb)
 238 {
 239         unsigned long events[NR_VM_EVENT_ITEMS];
 240         struct sysinfo i;
 241         int idx = 0;
 242         long available;
 243
 244         all_vm_events(events);
 245         si_meminfo(&i);
 246
 247         available = si_mem_available();
 248
 249         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 250                                 pages_to_bytes(events[PSWPIN]));
 251         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 252                                 pages_to_bytes(events[PSWPOUT]));
 253         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 254         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 255         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 256                                 pages_to_bytes(i.freeram));
 257         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 258                                 pages_to_bytes(i.totalram));
 259         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 260                                 pages_to_bytes(available));
 261 }
 262
 263 /*
 264  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 265  * the stats queue operates in reverse.  The driver initializes the virtqueue
 266  * with a single buffer.  From that point forward, all conversations consist of
 267  * a hypervisor request (a call to this function) which directs us to refill
 268  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 269  * we delegate the job to a freezable workqueue that will do the actual work via
 270  * stats_handle_request().
 271  */
 272 static void stats_request(struct virtqueue *vq)
 273 {
 274         struct virtio_balloon *vb = vq->vdev->priv;
 275
 276         spin_lock(&vb->stop_update_lock);
 277         if (!vb->stop_update)
 278                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 279         spin_unlock(&vb->stop_update_lock);
 280 }
 281
 282 static void stats_handle_request(struct virtio_balloon *vb)
 283 {
 284         struct virtqueue *vq;
 285         struct scatterlist sg;
 286         unsigned int len;
 287
 288         update_balloon_stats(vb);
 289
 290         vq = vb->stats_vq;
 291         if (!virtqueue_get_buf(vq, &len))
 292                 return;
 293         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 294         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 295         virtqueue_kick(vq);
 296 }
 297
 298 static void virtballoon_changed(struct virtio_device *vdev)
 299 {
 300         struct virtio_balloon *vb = vdev->priv;
 301         unsigned long flags;
 302
 303         spin_lock_irqsave(&vb->stop_update_lock, flags);
 304         if (!vb->stop_update)
 305                 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
 306         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 307 }
 308
 309 static inline s64 towards_target(struct virtio_balloon *vb)
 310 {
 311         s64 target;
 312         u32 num_pages;
 313
 314         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 315                      &num_pages);
 316
 317         /* Legacy balloon config space is LE, unlike all other devices. */
 318         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 319                 num_pages = le32_to_cpu((__force __le32)num_pages);
 320
 321         target = num_pages;
 322         return target - vb->num_pages;
 323 }
 324
 325 static void update_balloon_size(struct virtio_balloon *vb)
 326 {
 327         u32 actual = vb->num_pages;
 328
 329         /* Legacy balloon config space is LE, unlike all other devices. */
 330         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 331                 actual = (__force u32)cpu_to_le32(actual);
 332
 333         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 334                       &actual);
 335 }
 336
 337 /*
 338  * virtballoon_oom_notify - release pages when system is under severe
 339  *                          memory pressure (called from out_of_memory())
 340  * @self : notifier block struct
 341  * @dummy: not used
 342  * @parm : returned - number of freed pages
 343  *
 344  * The balancing of memory by use of the virtio balloon should not cause
 345  * the termination of processes while there are pages in the balloon.
 346  * If virtio balloon manages to release some memory, it will make the
 347  * system return and retry the allocation that forced the OOM killer
 348  * to run.
 349  */
 350 static int virtballoon_oom_notify(struct notifier_block *self,
 351                                   unsigned long dummy, void *parm)
 352 {
 353         struct virtio_balloon *vb;
 354         unsigned long *freed;
 355         unsigned num_freed_pages;
 356
 357         vb = container_of(self, struct virtio_balloon, nb);
 358         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 359                 return NOTIFY_OK;
 360
 361         freed = parm;
 362         num_freed_pages = leak_balloon(vb, oom_pages);
 363         update_balloon_size(vb);
 364         *freed += num_freed_pages;
 365
 366         return NOTIFY_OK;
 367 }
 368
 369 static void update_balloon_stats_func(struct work_struct *work)
 370 {
 371         struct virtio_balloon *vb;
 372
 373         vb = container_of(work, struct virtio_balloon,
 374                           update_balloon_stats_work);
 375         stats_handle_request(vb);
 376 }
 377
 378 static void update_balloon_size_func(struct work_struct *work)
 379 {
 380         struct virtio_balloon *vb;
 381         s64 diff;
 382
 383         vb = container_of(work, struct virtio_balloon,
 384                           update_balloon_size_work);
 385         diff = towards_target(vb);
 386
 387         if (diff > 0)
 388                 diff -= fill_balloon(vb, diff);
 389         else if (diff < 0)
 390                 diff += leak_balloon(vb, -diff);
 391         update_balloon_size(vb);
 392
 393         if (diff)
 394                 queue_work(system_freezable_wq, work);
 395 }
 396
 397 static int init_vqs(struct virtio_balloon *vb)
 398 {
 399         struct virtqueue *vqs[3];
 400         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
 401         static const char * const names[] = { "inflate", "deflate", "stats" };
 402         int err, nvqs;
 403
 404         /*
 405          * We expect two virtqueues: inflate and deflate, and
 406          * optionally stat.
 407          */
 408         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
 409         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
 410         if (err)
 411                 return err;
 412
 413         vb->inflate_vq = vqs[0];
 414         vb->deflate_vq = vqs[1];
 415         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 416                 struct scatterlist sg;
 417                 vb->stats_vq = vqs[2];
 418
 419                 /*
 420                  * Prime this virtqueue with one buffer so the hypervisor can
 421                  * use it to signal us later (it can't be broken yet!).
 422                  */
 423                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
 424                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
 425                     < 0)
 426                         BUG();
 427                 virtqueue_kick(vb->stats_vq);
 428         }
 429         return 0;
 430 }
 431
 432 #ifdef CONFIG_BALLOON_COMPACTION
 433 /*
 434  * virtballoon_migratepage - perform the balloon page migration on behalf of
 435  *                           a compation thread.     (called under page lock)
 436  * @vb_dev_info: the balloon device
 437  * @newpage: page that will replace the isolated page after migration finishes.
 438  * @page   : the isolated (old) page that is about to be migrated to newpage.
 439  * @mode   : compaction mode -- not used for balloon page migration.
 440  *
 441  * After a ballooned page gets isolated by compaction procedures, this is the
 442  * function that performs the page migration on behalf of a compaction thread
 443  * The page migration for virtio balloon is done in a simple swap fashion which
 444  * follows these two macro steps:
 445  *  1) insert newpage into vb->pages list and update the host about it;
 446  *  2) update the host about the old page removed from vb->pages list;
 447  *
 448  * This function preforms the balloon page migration task.
 449  * Called through balloon_mapping->a_ops->migratepage
 450  */
 451 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 452                 struct page *newpage, struct page *page, enum migrate_mode mode)
 453 {
 454         struct virtio_balloon *vb = container_of(vb_dev_info,
 455                         struct virtio_balloon, vb_dev_info);
 456         unsigned long flags;
 457
 458         /*
 459          * In order to avoid lock contention while migrating pages concurrently
 460          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 461          * this turn, as it is easier to retry the page migration later.
 462          * This also prevents fill_balloon() getting stuck into a mutex
 463          * recursion in the case it ends up triggering memory compaction
 464          * while it is attempting to inflate the ballon.
 465          */
 466         if (!mutex_trylock(&vb->balloon_lock))
 467                 return -EAGAIN;
 468
 469         get_page(newpage); /* balloon reference */
 470
 471         /* balloon's page migration 1st step  -- inflate "newpage" */
 472         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 473         balloon_page_insert(vb_dev_info, newpage);
 474         vb_dev_info->isolated_pages--;
 475         __count_vm_event(BALLOON_MIGRATE);
 476         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 477         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 478         set_page_pfns(vb, vb->pfns, newpage);
 479         tell_host(vb, vb->inflate_vq);
 480
 481         /* balloon's page migration 2nd step -- deflate "page" */
 482         balloon_page_delete(page);
 483         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 484         set_page_pfns(vb, vb->pfns, page);
 485         tell_host(vb, vb->deflate_vq);
 486
 487         mutex_unlock(&vb->balloon_lock);
 488
 489         put_page(page); /* balloon reference */
 490
 491         return MIGRATEPAGE_SUCCESS;
 492 }
 493 #endif /* CONFIG_BALLOON_COMPACTION */
 494
 495 static int virtballoon_probe(struct virtio_device *vdev)
 496 {
 497         struct virtio_balloon *vb;
 498         int err;
 499
 500         if (!vdev->config->get) {
 501                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 502                         __func__);
 503                 return -EINVAL;
 504         }
 505
 506         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 507         if (!vb) {
 508                 err = -ENOMEM;
 509                 goto out;
 510         }
 511
 512         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 513         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 514         spin_lock_init(&vb->stop_update_lock);
 515         vb->stop_update = false;
 516         vb->num_pages = 0;
 517         mutex_init(&vb->balloon_lock);
 518         init_waitqueue_head(&vb->acked);
 519         vb->vdev = vdev;
 520
 521         balloon_devinfo_init(&vb->vb_dev_info);
 522 #ifdef CONFIG_BALLOON_COMPACTION
 523         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 524 #endif
 525
 526         err = init_vqs(vb);
 527         if (err)
 528                 goto out_free_vb;
 529
 530         vb->nb.notifier_call = virtballoon_oom_notify;
 531         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 532         err = register_oom_notifier(&vb->nb);
 533         if (err < 0)
 534                 goto out_oom_notify;
 535
 536         virtio_device_ready(vdev);
 537
 538         return 0;
 539
 540 out_oom_notify:
 541         vdev->config->del_vqs(vdev);
 542 out_free_vb:
 543         kfree(vb);
 544 out:
 545         return err;
 546 }
 547
 548 static void remove_common(struct virtio_balloon *vb)
 549 {
 550         /* There might be pages left in the balloon: free them. */
 551         while (vb->num_pages)
 552                 leak_balloon(vb, vb->num_pages);
 553         update_balloon_size(vb);
 554
 555         /* Now we reset the device so we can clean up the queues. */
 556         vb->vdev->config->reset(vb->vdev);
 557
 558         vb->vdev->config->del_vqs(vb->vdev);
 559 }
 560
 561 static void virtballoon_remove(struct virtio_device *vdev)
 562 {
 563         struct virtio_balloon *vb = vdev->priv;
 564
 565         unregister_oom_notifier(&vb->nb);
 566
 567         spin_lock_irq(&vb->stop_update_lock);
 568         vb->stop_update = true;
 569         spin_unlock_irq(&vb->stop_update_lock);
 570         cancel_work_sync(&vb->update_balloon_size_work);
 571         cancel_work_sync(&vb->update_balloon_stats_work);
 572
 573         remove_common(vb);
 574         kfree(vb);
 575 }
 576
 577 #ifdef CONFIG_PM_SLEEP
 578 static int virtballoon_freeze(struct virtio_device *vdev)
 579 {
 580         struct virtio_balloon *vb = vdev->priv;
 581
 582         /*
 583          * The workqueue is already frozen by the PM core before this
 584          * function is called.
 585          */
 586         remove_common(vb);
 587         return 0;
 588 }
 589
 590 static int virtballoon_restore(struct virtio_device *vdev)
 591 {
 592         struct virtio_balloon *vb = vdev->priv;
 593         int ret;
 594
 595         ret = init_vqs(vdev->priv);
 596         if (ret)
 597                 return ret;
 598
 599         virtio_device_ready(vdev);
 600
 601         if (towards_target(vb))
 602                 virtballoon_changed(vdev);
 603         update_balloon_size(vb);
 604         return 0;
 605 }
 606 #endif
 607
 608 static unsigned int features[] = {
 609         VIRTIO_BALLOON_F_MUST_TELL_HOST,
 610         VIRTIO_BALLOON_F_STATS_VQ,
 611         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 612 };
 613
 614 static struct virtio_driver virtio_balloon_driver = {
 615         .feature_table = features,
 616         .feature_table_size = ARRAY_SIZE(features),
 617         .driver.name =  KBUILD_MODNAME,
 618         .driver.owner = THIS_MODULE,
 619         .id_table =     id_table,
 620         .probe =        virtballoon_probe,
 621         .remove =       virtballoon_remove,
 622         .config_changed = virtballoon_changed,
 623 #ifdef CONFIG_PM_SLEEP
 624         .freeze =       virtballoon_freeze,
 625         .restore =      virtballoon_restore,
 626 #endif
 627 };
 628
 629 module_virtio_driver(virtio_balloon_driver);
 630 MODULE_DEVICE_TABLE(virtio, id_table);
 631 MODULE_DESCRIPTION("Virtio balloon driver");
 632 MODULE_LICENSE("GPL");