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 const 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         /* Legacy balloon config space is LE, unlike all other devices. */
 402         virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
 403                         &num_pages);
 404
 405         target = num_pages;
 406         return target - vb->num_pages;
 407 }
 408
 409 /* Gives back @num_to_return blocks of free pages to mm. */
 410 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 411                                              unsigned long num_to_return)
 412 {
 413         struct page *page;
 414         unsigned long num_returned;
 415
 416         spin_lock_irq(&vb->free_page_list_lock);
 417         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 418                 page = balloon_page_pop(&vb->free_page_list);
 419                 if (!page)
 420                         break;
 421                 free_pages((unsigned long)page_address(page),
 422                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 423         }
 424         vb->num_free_page_blocks -= num_returned;
 425         spin_unlock_irq(&vb->free_page_list_lock);
 426
 427         return num_returned;
 428 }
 429
 430 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 431 {
 432         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 433                 return;
 434
 435         /* No need to queue the work if the bit was already set. */
 436         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 437                              &vb->config_read_bitmap))
 438                 return;
 439
 440         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 441 }
 442
 443 static void virtballoon_changed(struct virtio_device *vdev)
 444 {
 445         struct virtio_balloon *vb = vdev->priv;
 446         unsigned long flags;
 447
 448         spin_lock_irqsave(&vb->stop_update_lock, flags);
 449         if (!vb->stop_update) {
 450                 queue_work(system_freezable_wq,
 451                            &vb->update_balloon_size_work);
 452                 virtio_balloon_queue_free_page_work(vb);
 453         }
 454         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 455 }
 456
 457 static void update_balloon_size(struct virtio_balloon *vb)
 458 {
 459         u32 actual = vb->num_pages;
 460
 461         /* Legacy balloon config space is LE, unlike all other devices. */
 462         virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
 463                          &actual);
 464 }
 465
 466 static void update_balloon_stats_func(struct work_struct *work)
 467 {
 468         struct virtio_balloon *vb;
 469
 470         vb = container_of(work, struct virtio_balloon,
 471                           update_balloon_stats_work);
 472         stats_handle_request(vb);
 473 }
 474
 475 static void update_balloon_size_func(struct work_struct *work)
 476 {
 477         struct virtio_balloon *vb;
 478         s64 diff;
 479
 480         vb = container_of(work, struct virtio_balloon,
 481                           update_balloon_size_work);
 482         diff = towards_target(vb);
 483
 484         if (!diff)
 485                 return;
 486
 487         if (diff > 0)
 488                 diff -= fill_balloon(vb, diff);
 489         else
 490                 diff += leak_balloon(vb, -diff);
 491         update_balloon_size(vb);
 492
 493         if (diff)
 494                 queue_work(system_freezable_wq, work);
 495 }
 496
 497 static int init_vqs(struct virtio_balloon *vb)
 498 {
 499         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 500         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 501         const char *names[VIRTIO_BALLOON_VQ_MAX];
 502         int err;
 503
 504         /*
 505          * Inflateq and deflateq are used unconditionally. The names[]
 506          * will be NULL if the related feature is not enabled, which will
 507          * cause no allocation for the corresponding virtqueue in find_vqs.
 508          */
 509         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
 510         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 511         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 512         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 513         callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
 514         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 515         callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 516         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 517         names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
 518
 519         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 520                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
 521                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
 522         }
 523
 524         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 525                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
 526                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 527         }
 528
 529         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 530                 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
 531                 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
 532         }
 533
 534         err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
 535                               callbacks, names, NULL);
 536         if (err)
 537                 return err;
 538
 539         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 540         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 541         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 542                 struct scatterlist sg;
 543                 unsigned int num_stats;
 544                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 545
 546                 /*
 547                  * Prime this virtqueue with one buffer so the hypervisor can
 548                  * use it to signal us later (it can't be broken yet!).
 549                  */
 550                 num_stats = update_balloon_stats(vb);
 551
 552                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 553                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 554                                            GFP_KERNEL);
 555                 if (err) {
 556                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 557                                  __func__);
 558                         return err;
 559                 }
 560                 virtqueue_kick(vb->stats_vq);
 561         }
 562
 563         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 564                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 565
 566         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
 567                 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
 568
 569         return 0;
 570 }
 571
 572 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 573 {
 574         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 575                                &vb->config_read_bitmap)) {
 576                 /* Legacy balloon config space is LE, unlike all other devices. */
 577                 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
 578                                 free_page_hint_cmd_id,
 579                                 &vb->cmd_id_received_cache);
 580         }
 581
 582         return vb->cmd_id_received_cache;
 583 }
 584
 585 static int send_cmd_id_start(struct virtio_balloon *vb)
 586 {
 587         struct scatterlist sg;
 588         struct virtqueue *vq = vb->free_page_vq;
 589         int err, unused;
 590
 591         /* Detach all the used buffers from the vq */
 592         while (virtqueue_get_buf(vq, &unused))
 593                 ;
 594
 595         vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 596                                         virtio_balloon_cmd_id_received(vb));
 597         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 598         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 599         if (!err)
 600                 virtqueue_kick(vq);
 601         return err;
 602 }
 603
 604 static int send_cmd_id_stop(struct virtio_balloon *vb)
 605 {
 606         struct scatterlist sg;
 607         struct virtqueue *vq = vb->free_page_vq;
 608         int err, unused;
 609
 610         /* Detach all the used buffers from the vq */
 611         while (virtqueue_get_buf(vq, &unused))
 612                 ;
 613
 614         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 615         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 616         if (!err)
 617                 virtqueue_kick(vq);
 618         return err;
 619 }
 620
 621 static int get_free_page_and_send(struct virtio_balloon *vb)
 622 {
 623         struct virtqueue *vq = vb->free_page_vq;
 624         struct page *page;
 625         struct scatterlist sg;
 626         int err, unused;
 627         void *p;
 628
 629         /* Detach all the used buffers from the vq */
 630         while (virtqueue_get_buf(vq, &unused))
 631                 ;
 632
 633         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 634                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 635         /*
 636          * When the allocation returns NULL, it indicates that we have got all
 637          * the possible free pages, so return -EINTR to stop.
 638          */
 639         if (!page)
 640                 return -EINTR;
 641
 642         p = page_address(page);
 643         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 644         /* There is always 1 entry reserved for the cmd id to use. */
 645         if (vq->num_free > 1) {
 646                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 647                 if (unlikely(err)) {
 648                         free_pages((unsigned long)p,
 649                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 650                         return err;
 651                 }
 652                 virtqueue_kick(vq);
 653                 spin_lock_irq(&vb->free_page_list_lock);
 654                 balloon_page_push(&vb->free_page_list, page);
 655                 vb->num_free_page_blocks++;
 656                 spin_unlock_irq(&vb->free_page_list_lock);
 657         } else {
 658                 /*
 659                  * The vq has no available entry to add this page block, so
 660                  * just free it.
 661                  */
 662                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 663         }
 664
 665         return 0;
 666 }
 667
 668 static int send_free_pages(struct virtio_balloon *vb)
 669 {
 670         int err;
 671         u32 cmd_id_active;
 672
 673         while (1) {
 674                 /*
 675                  * If a stop id or a new cmd id was just received from host,
 676                  * stop the reporting.
 677                  */
 678                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 679                 if (unlikely(cmd_id_active !=
 680                              virtio_balloon_cmd_id_received(vb)))
 681                         break;
 682
 683                 /*
 684                  * The free page blocks are allocated and sent to host one by
 685                  * one.
 686                  */
 687                 err = get_free_page_and_send(vb);
 688                 if (err == -EINTR)
 689                         break;
 690                 else if (unlikely(err))
 691                         return err;
 692         }
 693
 694         return 0;
 695 }
 696
 697 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 698 {
 699         int err;
 700         struct device *dev = &vb->vdev->dev;
 701
 702         /* Start by sending the received cmd id to host with an outbuf. */
 703         err = send_cmd_id_start(vb);
 704         if (unlikely(err))
 705                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 706
 707         err = send_free_pages(vb);
 708         if (unlikely(err))
 709                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 710
 711         /* End by sending a stop id to host with an outbuf. */
 712         err = send_cmd_id_stop(vb);
 713         if (unlikely(err))
 714                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 715 }
 716
 717 static void report_free_page_func(struct work_struct *work)
 718 {
 719         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 720                                                  report_free_page_work);
 721         u32 cmd_id_received;
 722
 723         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 724         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 725                 /* Pass ULONG_MAX to give back all the free pages */
 726                 return_free_pages_to_mm(vb, ULONG_MAX);
 727         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 728                    cmd_id_received !=
 729                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 730                 virtio_balloon_report_free_page(vb);
 731         }
 732 }
 733
 734 #ifdef CONFIG_BALLOON_COMPACTION
 735 /*
 736  * virtballoon_migratepage - perform the balloon page migration on behalf of
 737  *                           a compaction thread.     (called under page lock)
 738  * @vb_dev_info: the balloon device
 739  * @newpage: page that will replace the isolated page after migration finishes.
 740  * @page   : the isolated (old) page that is about to be migrated to newpage.
 741  * @mode   : compaction mode -- not used for balloon page migration.
 742  *
 743  * After a ballooned page gets isolated by compaction procedures, this is the
 744  * function that performs the page migration on behalf of a compaction thread
 745  * The page migration for virtio balloon is done in a simple swap fashion which
 746  * follows these two macro steps:
 747  *  1) insert newpage into vb->pages list and update the host about it;
 748  *  2) update the host about the old page removed from vb->pages list;
 749  *
 750  * This function preforms the balloon page migration task.
 751  * Called through balloon_mapping->a_ops->migratepage
 752  */
 753 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 754                 struct page *newpage, struct page *page, enum migrate_mode mode)
 755 {
 756         struct virtio_balloon *vb = container_of(vb_dev_info,
 757                         struct virtio_balloon, vb_dev_info);
 758         unsigned long flags;
 759
 760         /*
 761          * In order to avoid lock contention while migrating pages concurrently
 762          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 763          * this turn, as it is easier to retry the page migration later.
 764          * This also prevents fill_balloon() getting stuck into a mutex
 765          * recursion in the case it ends up triggering memory compaction
 766          * while it is attempting to inflate the ballon.
 767          */
 768         if (!mutex_trylock(&vb->balloon_lock))
 769                 return -EAGAIN;
 770
 771         get_page(newpage); /* balloon reference */
 772
 773         /*
 774           * When we migrate a page to a different zone and adjusted the
 775           * managed page count when inflating, we have to fixup the count of
 776           * both involved zones.
 777           */
 778         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 779             page_zone(page) != page_zone(newpage)) {
 780                 adjust_managed_page_count(page, 1);
 781                 adjust_managed_page_count(newpage, -1);
 782         }
 783
 784         /* balloon's page migration 1st step  -- inflate "newpage" */
 785         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 786         balloon_page_insert(vb_dev_info, newpage);
 787         vb_dev_info->isolated_pages--;
 788         __count_vm_event(BALLOON_MIGRATE);
 789         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 790         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 791         set_page_pfns(vb, vb->pfns, newpage);
 792         tell_host(vb, vb->inflate_vq);
 793
 794         /* balloon's page migration 2nd step -- deflate "page" */
 795         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 796         balloon_page_delete(page);
 797         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 798         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 799         set_page_pfns(vb, vb->pfns, page);
 800         tell_host(vb, vb->deflate_vq);
 801
 802         mutex_unlock(&vb->balloon_lock);
 803
 804         put_page(page); /* balloon reference */
 805
 806         return MIGRATEPAGE_SUCCESS;
 807 }
 808
 809 static int balloon_init_fs_context(struct fs_context *fc)
 810 {
 811         return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
 812 }
 813
 814 static struct file_system_type balloon_fs = {
 815         .name           = "balloon-kvm",
 816         .init_fs_context = balloon_init_fs_context,
 817         .kill_sb        = kill_anon_super,
 818 };
 819
 820 #endif /* CONFIG_BALLOON_COMPACTION */
 821
 822 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 823                                        unsigned long pages_to_free)
 824 {
 825         unsigned long blocks_to_free, blocks_freed;
 826
 827         pages_to_free = round_up(pages_to_free,
 828                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 829         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 830         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 831
 832         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 833 }
 834
 835 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 836                                                   struct shrink_control *sc)
 837 {
 838         struct virtio_balloon *vb = container_of(shrinker,
 839                                         struct virtio_balloon, shrinker);
 840
 841         return shrink_free_pages(vb, sc->nr_to_scan);
 842 }
 843
 844 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 845                                                    struct shrink_control *sc)
 846 {
 847         struct virtio_balloon *vb = container_of(shrinker,
 848                                         struct virtio_balloon, shrinker);
 849
 850         return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 851 }
 852
 853 static int virtio_balloon_oom_notify(struct notifier_block *nb,
 854                                      unsigned long dummy, void *parm)
 855 {
 856         struct virtio_balloon *vb = container_of(nb,
 857                                                  struct virtio_balloon, oom_nb);
 858         unsigned long *freed = parm;
 859
 860         *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
 861                   VIRTIO_BALLOON_PAGES_PER_PAGE;
 862         update_balloon_size(vb);
 863
 864         return NOTIFY_OK;
 865 }
 866
 867 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 868 {
 869         unregister_shrinker(&vb->shrinker);
 870 }
 871
 872 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 873 {
 874         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
 875         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
 876         vb->shrinker.seeks = DEFAULT_SEEKS;
 877
 878         return register_shrinker(&vb->shrinker);
 879 }
 880
 881 static int virtballoon_probe(struct virtio_device *vdev)
 882 {
 883         struct virtio_balloon *vb;
 884         int err;
 885
 886         if (!vdev->config->get) {
 887                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 888                         __func__);
 889                 return -EINVAL;
 890         }
 891
 892         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 893         if (!vb) {
 894                 err = -ENOMEM;
 895                 goto out;
 896         }
 897
 898         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 899         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 900         spin_lock_init(&vb->stop_update_lock);
 901         mutex_init(&vb->balloon_lock);
 902         init_waitqueue_head(&vb->acked);
 903         vb->vdev = vdev;
 904
 905         balloon_devinfo_init(&vb->vb_dev_info);
 906
 907         err = init_vqs(vb);
 908         if (err)
 909                 goto out_free_vb;
 910
 911 #ifdef CONFIG_BALLOON_COMPACTION
 912         balloon_mnt = kern_mount(&balloon_fs);
 913         if (IS_ERR(balloon_mnt)) {
 914                 err = PTR_ERR(balloon_mnt);
 915                 goto out_del_vqs;
 916         }
 917
 918         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 919         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 920         if (IS_ERR(vb->vb_dev_info.inode)) {
 921                 err = PTR_ERR(vb->vb_dev_info.inode);
 922                 goto out_kern_unmount;
 923         }
 924         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 925 #endif
 926         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 927                 /*
 928                  * There is always one entry reserved for cmd id, so the ring
 929                  * size needs to be at least two to report free page hints.
 930                  */
 931                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 932                         err = -ENOSPC;
 933                         goto out_iput;
 934                 }
 935                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 936                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 937                 if (!vb->balloon_wq) {
 938                         err = -ENOMEM;
 939                         goto out_iput;
 940                 }
 941                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 942                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 943                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 944                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 945                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 946                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 947                 spin_lock_init(&vb->free_page_list_lock);
 948                 INIT_LIST_HEAD(&vb->free_page_list);
 949                 /*
 950                  * We're allowed to reuse any free pages, even if they are
 951                  * still to be processed by the host.
 952                  */
 953                 err = virtio_balloon_register_shrinker(vb);
 954                 if (err)
 955                         goto out_del_balloon_wq;
 956         }
 957
 958         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
 959                 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
 960                 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
 961                 err = register_oom_notifier(&vb->oom_nb);
 962                 if (err < 0)
 963                         goto out_unregister_shrinker;
 964         }
 965
 966         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
 967                 /* Start with poison val of 0 representing general init */
 968                 __u32 poison_val = 0;
 969
 970                 /*
 971                  * Let the hypervisor know that we are expecting a
 972                  * specific value to be written back in balloon pages.
 973                  *
 974                  * If the PAGE_POISON value was larger than a byte we would
 975                  * need to byte swap poison_val here to guarantee it is
 976                  * little-endian. However for now it is a single byte so we
 977                  * can pass it as-is.
 978                  */
 979                 if (!want_init_on_free())
 980                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
 981
 982                 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
 983                                  poison_val, &poison_val);
 984         }
 985
 986         vb->pr_dev_info.report = virtballoon_free_page_report;
 987         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 988                 unsigned int capacity;
 989
 990                 capacity = virtqueue_get_vring_size(vb->reporting_vq);
 991                 if (capacity < PAGE_REPORTING_CAPACITY) {
 992                         err = -ENOSPC;
 993                         goto out_unregister_oom;
 994                 }
 995
 996                 /*
 997                  * The default page reporting order is @pageblock_order, which
 998                  * corresponds to 512MB in size on ARM64 when 64KB base page
 999                  * size is used. The page reporting won't be triggered if the
1000                  * freeing page can't come up with a free area like that huge.
1001                  * So we specify the page reporting order to 5, corresponding
1002                  * to 2MB. It helps to avoid THP splitting if 4KB base page
1003                  * size is used by host.
1004                  *
1005                  * Ideally, the page reporting order is selected based on the
1006                  * host's base page size. However, it needs more work to report
1007                  * that value. The hard-coded order would be fine currently.
1008                  */
1009 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
1010                 vb->pr_dev_info.order = 5;
1011 #endif
1012
1013                 err = page_reporting_register(&vb->pr_dev_info);
1014                 if (err)
1015                         goto out_unregister_oom;
1016         }
1017
1018         virtio_device_ready(vdev);
1019
1020         if (towards_target(vb))
1021                 virtballoon_changed(vdev);
1022         return 0;
1023
1024 out_unregister_oom:
1025         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1026                 unregister_oom_notifier(&vb->oom_nb);
1027 out_unregister_shrinker:
1028         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1029                 virtio_balloon_unregister_shrinker(vb);
1030 out_del_balloon_wq:
1031         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1032                 destroy_workqueue(vb->balloon_wq);
1033 out_iput:
1034 #ifdef CONFIG_BALLOON_COMPACTION
1035         iput(vb->vb_dev_info.inode);
1036 out_kern_unmount:
1037         kern_unmount(balloon_mnt);
1038 out_del_vqs:
1039 #endif
1040         vdev->config->del_vqs(vdev);
1041 out_free_vb:
1042         kfree(vb);
1043 out:
1044         return err;
1045 }
1046
1047 static void remove_common(struct virtio_balloon *vb)
1048 {
1049         /* There might be pages left in the balloon: free them. */
1050         while (vb->num_pages)
1051                 leak_balloon(vb, vb->num_pages);
1052         update_balloon_size(vb);
1053
1054         /* There might be free pages that are being reported: release them. */
1055         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1056                 return_free_pages_to_mm(vb, ULONG_MAX);
1057
1058         /* Now we reset the device so we can clean up the queues. */
1059         vb->vdev->config->reset(vb->vdev);
1060
1061         vb->vdev->config->del_vqs(vb->vdev);
1062 }
1063
1064 static void virtballoon_remove(struct virtio_device *vdev)
1065 {
1066         struct virtio_balloon *vb = vdev->priv;
1067
1068         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1069                 page_reporting_unregister(&vb->pr_dev_info);
1070         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1071                 unregister_oom_notifier(&vb->oom_nb);
1072         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1073                 virtio_balloon_unregister_shrinker(vb);
1074         spin_lock_irq(&vb->stop_update_lock);
1075         vb->stop_update = true;
1076         spin_unlock_irq(&vb->stop_update_lock);
1077         cancel_work_sync(&vb->update_balloon_size_work);
1078         cancel_work_sync(&vb->update_balloon_stats_work);
1079
1080         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1081                 cancel_work_sync(&vb->report_free_page_work);
1082                 destroy_workqueue(vb->balloon_wq);
1083         }
1084
1085         remove_common(vb);
1086 #ifdef CONFIG_BALLOON_COMPACTION
1087         if (vb->vb_dev_info.inode)
1088                 iput(vb->vb_dev_info.inode);
1089
1090         kern_unmount(balloon_mnt);
1091 #endif
1092         kfree(vb);
1093 }
1094
1095 #ifdef CONFIG_PM_SLEEP
1096 static int virtballoon_freeze(struct virtio_device *vdev)
1097 {
1098         struct virtio_balloon *vb = vdev->priv;
1099
1100         /*
1101          * The workqueue is already frozen by the PM core before this
1102          * function is called.
1103          */
1104         remove_common(vb);
1105         return 0;
1106 }
1107
1108 static int virtballoon_restore(struct virtio_device *vdev)
1109 {
1110         struct virtio_balloon *vb = vdev->priv;
1111         int ret;
1112
1113         ret = init_vqs(vdev->priv);
1114         if (ret)
1115                 return ret;
1116
1117         virtio_device_ready(vdev);
1118
1119         if (towards_target(vb))
1120                 virtballoon_changed(vdev);
1121         update_balloon_size(vb);
1122         return 0;
1123 }
1124 #endif
1125
1126 static int virtballoon_validate(struct virtio_device *vdev)
1127 {
1128         /*
1129          * Inform the hypervisor that our pages are poisoned or
1130          * initialized. If we cannot do that then we should disable
1131          * page reporting as it could potentially change the contents
1132          * of our free pages.
1133          */
1134         if (!want_init_on_free() && !page_poisoning_enabled_static())
1135                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1136         else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1137                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1138
1139         __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1140         return 0;
1141 }
1142
1143 static unsigned int features[] = {
1144         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1145         VIRTIO_BALLOON_F_STATS_VQ,
1146         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1147         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1148         VIRTIO_BALLOON_F_PAGE_POISON,
1149         VIRTIO_BALLOON_F_REPORTING,
1150 };
1151
1152 static struct virtio_driver virtio_balloon_driver = {
1153         .feature_table = features,
1154         .feature_table_size = ARRAY_SIZE(features),
1155         .driver.name =  KBUILD_MODNAME,
1156         .driver.owner = THIS_MODULE,
1157         .id_table =     id_table,
1158         .validate =     virtballoon_validate,
1159         .probe =        virtballoon_probe,
1160         .remove =       virtballoon_remove,
1161         .config_changed = virtballoon_changed,
1162 #ifdef CONFIG_PM_SLEEP
1163         .freeze =       virtballoon_freeze,
1164         .restore =      virtballoon_restore,
1165 #endif
1166 };
1167
1168 module_virtio_driver(virtio_balloon_driver);
1169 MODULE_DEVICE_TABLE(virtio, id_table);
1170 MODULE_DESCRIPTION("Virtio balloon driver");
1171 MODULE_LICENSE("GPL");