drivers/virtio/virtio_balloon.c

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