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