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         /*
 399          * Aligned up to guest page size to avoid inflating and deflating
 400          * balloon endlessly.
 401          */
 402         target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
 403         return target - vb->num_pages;
 404 }
 405
 406 /* Gives back @num_to_return blocks of free pages to mm. */
 407 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 408                                              unsigned long num_to_return)
 409 {
 410         struct page *page;
 411         unsigned long num_returned;
 412
 413         spin_lock_irq(&vb->free_page_list_lock);
 414         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 415                 page = balloon_page_pop(&vb->free_page_list);
 416                 if (!page)
 417                         break;
 418                 free_pages((unsigned long)page_address(page),
 419                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 420         }
 421         vb->num_free_page_blocks -= num_returned;
 422         spin_unlock_irq(&vb->free_page_list_lock);
 423
 424         return num_returned;
 425 }
 426
 427 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 428 {
 429         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 430                 return;
 431
 432         /* No need to queue the work if the bit was already set. */
 433         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 434                              &vb->config_read_bitmap))
 435                 return;
 436
 437         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 438 }
 439
 440 static void virtballoon_changed(struct virtio_device *vdev)
 441 {
 442         struct virtio_balloon *vb = vdev->priv;
 443         unsigned long flags;
 444
 445         spin_lock_irqsave(&vb->stop_update_lock, flags);
 446         if (!vb->stop_update) {
 447                 queue_work(system_freezable_wq,
 448                            &vb->update_balloon_size_work);
 449                 virtio_balloon_queue_free_page_work(vb);
 450         }
 451         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 452 }
 453
 454 static void update_balloon_size(struct virtio_balloon *vb)
 455 {
 456         u32 actual = vb->num_pages;
 457
 458         /* Legacy balloon config space is LE, unlike all other devices. */
 459         virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
 460                          &actual);
 461 }
 462
 463 static void update_balloon_stats_func(struct work_struct *work)
 464 {
 465         struct virtio_balloon *vb;
 466
 467         vb = container_of(work, struct virtio_balloon,
 468                           update_balloon_stats_work);
 469         stats_handle_request(vb);
 470 }
 471
 472 static void update_balloon_size_func(struct work_struct *work)
 473 {
 474         struct virtio_balloon *vb;
 475         s64 diff;
 476
 477         vb = container_of(work, struct virtio_balloon,
 478                           update_balloon_size_work);
 479         diff = towards_target(vb);
 480
 481         if (!diff)
 482                 return;
 483
 484         if (diff > 0)
 485                 diff -= fill_balloon(vb, diff);
 486         else
 487                 diff += leak_balloon(vb, -diff);
 488         update_balloon_size(vb);
 489
 490         if (diff)
 491                 queue_work(system_freezable_wq, work);
 492 }
 493
 494 static int init_vqs(struct virtio_balloon *vb)
 495 {
 496         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 497         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 498         const char *names[VIRTIO_BALLOON_VQ_MAX];
 499         int err;
 500
 501         /*
 502          * Inflateq and deflateq are used unconditionally. The names[]
 503          * will be NULL if the related feature is not enabled, which will
 504          * cause no allocation for the corresponding virtqueue in find_vqs.
 505          */
 506         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
 507         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 508         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 509         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 510         callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
 511         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 512         callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 513         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 514         names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
 515
 516         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 517                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
 518                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
 519         }
 520
 521         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 522                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
 523                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 524         }
 525
 526         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 527                 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
 528                 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
 529         }
 530
 531         err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
 532                               callbacks, names, NULL);
 533         if (err)
 534                 return err;
 535
 536         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 537         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 538         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 539                 struct scatterlist sg;
 540                 unsigned int num_stats;
 541                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 542
 543                 /*
 544                  * Prime this virtqueue with one buffer so the hypervisor can
 545                  * use it to signal us later (it can't be broken yet!).
 546                  */
 547                 num_stats = update_balloon_stats(vb);
 548
 549                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 550                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 551                                            GFP_KERNEL);
 552                 if (err) {
 553                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 554                                  __func__);
 555                         return err;
 556                 }
 557                 virtqueue_kick(vb->stats_vq);
 558         }
 559
 560         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 561                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 562
 563         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
 564                 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
 565
 566         return 0;
 567 }
 568
 569 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 570 {
 571         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 572                                &vb->config_read_bitmap)) {
 573                 /* Legacy balloon config space is LE, unlike all other devices. */
 574                 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
 575                                 free_page_hint_cmd_id,
 576                                 &vb->cmd_id_received_cache);
 577         }
 578
 579         return vb->cmd_id_received_cache;
 580 }
 581
 582 static int send_cmd_id_start(struct virtio_balloon *vb)
 583 {
 584         struct scatterlist sg;
 585         struct virtqueue *vq = vb->free_page_vq;
 586         int err, unused;
 587
 588         /* Detach all the used buffers from the vq */
 589         while (virtqueue_get_buf(vq, &unused))
 590                 ;
 591
 592         vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 593                                         virtio_balloon_cmd_id_received(vb));
 594         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 595         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 596         if (!err)
 597                 virtqueue_kick(vq);
 598         return err;
 599 }
 600
 601 static int send_cmd_id_stop(struct virtio_balloon *vb)
 602 {
 603         struct scatterlist sg;
 604         struct virtqueue *vq = vb->free_page_vq;
 605         int err, unused;
 606
 607         /* Detach all the used buffers from the vq */
 608         while (virtqueue_get_buf(vq, &unused))
 609                 ;
 610
 611         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 612         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 613         if (!err)
 614                 virtqueue_kick(vq);
 615         return err;
 616 }
 617
 618 static int get_free_page_and_send(struct virtio_balloon *vb)
 619 {
 620         struct virtqueue *vq = vb->free_page_vq;
 621         struct page *page;
 622         struct scatterlist sg;
 623         int err, unused;
 624         void *p;
 625
 626         /* Detach all the used buffers from the vq */
 627         while (virtqueue_get_buf(vq, &unused))
 628                 ;
 629
 630         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 631                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 632         /*
 633          * When the allocation returns NULL, it indicates that we have got all
 634          * the possible free pages, so return -EINTR to stop.
 635          */
 636         if (!page)
 637                 return -EINTR;
 638
 639         p = page_address(page);
 640         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 641         /* There is always 1 entry reserved for the cmd id to use. */
 642         if (vq->num_free > 1) {
 643                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 644                 if (unlikely(err)) {
 645                         free_pages((unsigned long)p,
 646                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 647                         return err;
 648                 }
 649                 virtqueue_kick(vq);
 650                 spin_lock_irq(&vb->free_page_list_lock);
 651                 balloon_page_push(&vb->free_page_list, page);
 652                 vb->num_free_page_blocks++;
 653                 spin_unlock_irq(&vb->free_page_list_lock);
 654         } else {
 655                 /*
 656                  * The vq has no available entry to add this page block, so
 657                  * just free it.
 658                  */
 659                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 660         }
 661
 662         return 0;
 663 }
 664
 665 static int send_free_pages(struct virtio_balloon *vb)
 666 {
 667         int err;
 668         u32 cmd_id_active;
 669
 670         while (1) {
 671                 /*
 672                  * If a stop id or a new cmd id was just received from host,
 673                  * stop the reporting.
 674                  */
 675                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 676                 if (unlikely(cmd_id_active !=
 677                              virtio_balloon_cmd_id_received(vb)))
 678                         break;
 679
 680                 /*
 681                  * The free page blocks are allocated and sent to host one by
 682                  * one.
 683                  */
 684                 err = get_free_page_and_send(vb);
 685                 if (err == -EINTR)
 686                         break;
 687                 else if (unlikely(err))
 688                         return err;
 689         }
 690
 691         return 0;
 692 }
 693
 694 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 695 {
 696         int err;
 697         struct device *dev = &vb->vdev->dev;
 698
 699         /* Start by sending the received cmd id to host with an outbuf. */
 700         err = send_cmd_id_start(vb);
 701         if (unlikely(err))
 702                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 703
 704         err = send_free_pages(vb);
 705         if (unlikely(err))
 706                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 707
 708         /* End by sending a stop id to host with an outbuf. */
 709         err = send_cmd_id_stop(vb);
 710         if (unlikely(err))
 711                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 712 }
 713
 714 static void report_free_page_func(struct work_struct *work)
 715 {
 716         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 717                                                  report_free_page_work);
 718         u32 cmd_id_received;
 719
 720         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 721         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 722                 /* Pass ULONG_MAX to give back all the free pages */
 723                 return_free_pages_to_mm(vb, ULONG_MAX);
 724         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 725                    cmd_id_received !=
 726                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 727                 virtio_balloon_report_free_page(vb);
 728         }
 729 }
 730
 731 #ifdef CONFIG_BALLOON_COMPACTION
 732 /*
 733  * virtballoon_migratepage - perform the balloon page migration on behalf of
 734  *                           a compaction thread.     (called under page lock)
 735  * @vb_dev_info: the balloon device
 736  * @newpage: page that will replace the isolated page after migration finishes.
 737  * @page   : the isolated (old) page that is about to be migrated to newpage.
 738  * @mode   : compaction mode -- not used for balloon page migration.
 739  *
 740  * After a ballooned page gets isolated by compaction procedures, this is the
 741  * function that performs the page migration on behalf of a compaction thread
 742  * The page migration for virtio balloon is done in a simple swap fashion which
 743  * follows these two macro steps:
 744  *  1) insert newpage into vb->pages list and update the host about it;
 745  *  2) update the host about the old page removed from vb->pages list;
 746  *
 747  * This function preforms the balloon page migration task.
 748  * Called through balloon_mapping->a_ops->migratepage
 749  */
 750 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 751                 struct page *newpage, struct page *page, enum migrate_mode mode)
 752 {
 753         struct virtio_balloon *vb = container_of(vb_dev_info,
 754                         struct virtio_balloon, vb_dev_info);
 755         unsigned long flags;
 756
 757         /*
 758          * In order to avoid lock contention while migrating pages concurrently
 759          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 760          * this turn, as it is easier to retry the page migration later.
 761          * This also prevents fill_balloon() getting stuck into a mutex
 762          * recursion in the case it ends up triggering memory compaction
 763          * while it is attempting to inflate the ballon.
 764          */
 765         if (!mutex_trylock(&vb->balloon_lock))
 766                 return -EAGAIN;
 767
 768         get_page(newpage); /* balloon reference */
 769
 770         /*
 771           * When we migrate a page to a different zone and adjusted the
 772           * managed page count when inflating, we have to fixup the count of
 773           * both involved zones.
 774           */
 775         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 776             page_zone(page) != page_zone(newpage)) {
 777                 adjust_managed_page_count(page, 1);
 778                 adjust_managed_page_count(newpage, -1);
 779         }
 780
 781         /* balloon's page migration 1st step  -- inflate "newpage" */
 782         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 783         balloon_page_insert(vb_dev_info, newpage);
 784         vb_dev_info->isolated_pages--;
 785         __count_vm_event(BALLOON_MIGRATE);
 786         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 787         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 788         set_page_pfns(vb, vb->pfns, newpage);
 789         tell_host(vb, vb->inflate_vq);
 790
 791         /* balloon's page migration 2nd step -- deflate "page" */
 792         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 793         balloon_page_delete(page);
 794         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 795         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 796         set_page_pfns(vb, vb->pfns, page);
 797         tell_host(vb, vb->deflate_vq);
 798
 799         mutex_unlock(&vb->balloon_lock);
 800
 801         put_page(page); /* balloon reference */
 802
 803         return MIGRATEPAGE_SUCCESS;
 804 }
 805 #endif /* CONFIG_BALLOON_COMPACTION */
 806
 807 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 808                                        unsigned long pages_to_free)
 809 {
 810         unsigned long blocks_to_free, blocks_freed;
 811
 812         pages_to_free = round_up(pages_to_free,
 813                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 814         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 815         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 816
 817         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 818 }
 819
 820 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 821                                                   struct shrink_control *sc)
 822 {
 823         struct virtio_balloon *vb = container_of(shrinker,
 824                                         struct virtio_balloon, shrinker);
 825
 826         return shrink_free_pages(vb, sc->nr_to_scan);
 827 }
 828
 829 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 830                                                    struct shrink_control *sc)
 831 {
 832         struct virtio_balloon *vb = container_of(shrinker,
 833                                         struct virtio_balloon, shrinker);
 834
 835         return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 836 }
 837
 838 static int virtio_balloon_oom_notify(struct notifier_block *nb,
 839                                      unsigned long dummy, void *parm)
 840 {
 841         struct virtio_balloon *vb = container_of(nb,
 842                                                  struct virtio_balloon, oom_nb);
 843         unsigned long *freed = parm;
 844
 845         *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
 846                   VIRTIO_BALLOON_PAGES_PER_PAGE;
 847         update_balloon_size(vb);
 848
 849         return NOTIFY_OK;
 850 }
 851
 852 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 853 {
 854         unregister_shrinker(&vb->shrinker);
 855 }
 856
 857 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 858 {
 859         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
 860         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
 861         vb->shrinker.seeks = DEFAULT_SEEKS;
 862
 863         return register_shrinker(&vb->shrinker, "virtio-balloon");
 864 }
 865
 866 static int virtballoon_probe(struct virtio_device *vdev)
 867 {
 868         struct virtio_balloon *vb;
 869         int err;
 870
 871         if (!vdev->config->get) {
 872                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 873                         __func__);
 874                 return -EINVAL;
 875         }
 876
 877         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 878         if (!vb) {
 879                 err = -ENOMEM;
 880                 goto out;
 881         }
 882
 883         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 884         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 885         spin_lock_init(&vb->stop_update_lock);
 886         mutex_init(&vb->balloon_lock);
 887         init_waitqueue_head(&vb->acked);
 888         vb->vdev = vdev;
 889
 890         balloon_devinfo_init(&vb->vb_dev_info);
 891
 892         err = init_vqs(vb);
 893         if (err)
 894                 goto out_free_vb;
 895
 896 #ifdef CONFIG_BALLOON_COMPACTION
 897         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 898 #endif
 899         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 900                 /*
 901                  * There is always one entry reserved for cmd id, so the ring
 902                  * size needs to be at least two to report free page hints.
 903                  */
 904                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 905                         err = -ENOSPC;
 906                         goto out_del_vqs;
 907                 }
 908                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 909                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 910                 if (!vb->balloon_wq) {
 911                         err = -ENOMEM;
 912                         goto out_del_vqs;
 913                 }
 914                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 915                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 916                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 917                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 918                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 919                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 920                 spin_lock_init(&vb->free_page_list_lock);
 921                 INIT_LIST_HEAD(&vb->free_page_list);
 922                 /*
 923                  * We're allowed to reuse any free pages, even if they are
 924                  * still to be processed by the host.
 925                  */
 926                 err = virtio_balloon_register_shrinker(vb);
 927                 if (err)
 928                         goto out_del_balloon_wq;
 929         }
 930
 931         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
 932                 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
 933                 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
 934                 err = register_oom_notifier(&vb->oom_nb);
 935                 if (err < 0)
 936                         goto out_unregister_shrinker;
 937         }
 938
 939         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
 940                 /* Start with poison val of 0 representing general init */
 941                 __u32 poison_val = 0;
 942
 943                 /*
 944                  * Let the hypervisor know that we are expecting a
 945                  * specific value to be written back in balloon pages.
 946                  *
 947                  * If the PAGE_POISON value was larger than a byte we would
 948                  * need to byte swap poison_val here to guarantee it is
 949                  * little-endian. However for now it is a single byte so we
 950                  * can pass it as-is.
 951                  */
 952                 if (!want_init_on_free())
 953                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
 954
 955                 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
 956                                  poison_val, &poison_val);
 957         }
 958
 959         vb->pr_dev_info.report = virtballoon_free_page_report;
 960         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
 961                 unsigned int capacity;
 962
 963                 capacity = virtqueue_get_vring_size(vb->reporting_vq);
 964                 if (capacity < PAGE_REPORTING_CAPACITY) {
 965                         err = -ENOSPC;
 966                         goto out_unregister_oom;
 967                 }
 968
 969                 /*
 970                  * The default page reporting order is @pageblock_order, which
 971                  * corresponds to 512MB in size on ARM64 when 64KB base page
 972                  * size is used. The page reporting won't be triggered if the
 973                  * freeing page can't come up with a free area like that huge.
 974                  * So we specify the page reporting order to 5, corresponding
 975                  * to 2MB. It helps to avoid THP splitting if 4KB base page
 976                  * size is used by host.
 977                  *
 978                  * Ideally, the page reporting order is selected based on the
 979                  * host's base page size. However, it needs more work to report
 980                  * that value. The hard-coded order would be fine currently.
 981                  */
 982 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
 983                 vb->pr_dev_info.order = 5;
 984 #endif
 985
 986                 err = page_reporting_register(&vb->pr_dev_info);
 987                 if (err)
 988                         goto out_unregister_oom;
 989         }
 990
 991         virtio_device_ready(vdev);
 992
 993         if (towards_target(vb))
 994                 virtballoon_changed(vdev);
 995         return 0;
 996
 997 out_unregister_oom:
 998         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 999                 unregister_oom_notifier(&vb->oom_nb);
1000 out_unregister_shrinker:
1001         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1002                 virtio_balloon_unregister_shrinker(vb);
1003 out_del_balloon_wq:
1004         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1005                 destroy_workqueue(vb->balloon_wq);
1006 out_del_vqs:
1007         vdev->config->del_vqs(vdev);
1008 out_free_vb:
1009         kfree(vb);
1010 out:
1011         return err;
1012 }
1013
1014 static void remove_common(struct virtio_balloon *vb)
1015 {
1016         /* There might be pages left in the balloon: free them. */
1017         while (vb->num_pages)
1018                 leak_balloon(vb, vb->num_pages);
1019         update_balloon_size(vb);
1020
1021         /* There might be free pages that are being reported: release them. */
1022         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1023                 return_free_pages_to_mm(vb, ULONG_MAX);
1024
1025         /* Now we reset the device so we can clean up the queues. */
1026         virtio_reset_device(vb->vdev);
1027
1028         vb->vdev->config->del_vqs(vb->vdev);
1029 }
1030
1031 static void virtballoon_remove(struct virtio_device *vdev)
1032 {
1033         struct virtio_balloon *vb = vdev->priv;
1034
1035         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1036                 page_reporting_unregister(&vb->pr_dev_info);
1037         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1038                 unregister_oom_notifier(&vb->oom_nb);
1039         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1040                 virtio_balloon_unregister_shrinker(vb);
1041         spin_lock_irq(&vb->stop_update_lock);
1042         vb->stop_update = true;
1043         spin_unlock_irq(&vb->stop_update_lock);
1044         cancel_work_sync(&vb->update_balloon_size_work);
1045         cancel_work_sync(&vb->update_balloon_stats_work);
1046
1047         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1048                 cancel_work_sync(&vb->report_free_page_work);
1049                 destroy_workqueue(vb->balloon_wq);
1050         }
1051
1052         remove_common(vb);
1053         kfree(vb);
1054 }
1055
1056 #ifdef CONFIG_PM_SLEEP
1057 static int virtballoon_freeze(struct virtio_device *vdev)
1058 {
1059         struct virtio_balloon *vb = vdev->priv;
1060
1061         /*
1062          * The workqueue is already frozen by the PM core before this
1063          * function is called.
1064          */
1065         remove_common(vb);
1066         return 0;
1067 }
1068
1069 static int virtballoon_restore(struct virtio_device *vdev)
1070 {
1071         struct virtio_balloon *vb = vdev->priv;
1072         int ret;
1073
1074         ret = init_vqs(vdev->priv);
1075         if (ret)
1076                 return ret;
1077
1078         virtio_device_ready(vdev);
1079
1080         if (towards_target(vb))
1081                 virtballoon_changed(vdev);
1082         update_balloon_size(vb);
1083         return 0;
1084 }
1085 #endif
1086
1087 static int virtballoon_validate(struct virtio_device *vdev)
1088 {
1089         /*
1090          * Inform the hypervisor that our pages are poisoned or
1091          * initialized. If we cannot do that then we should disable
1092          * page reporting as it could potentially change the contents
1093          * of our free pages.
1094          */
1095         if (!want_init_on_free() && !page_poisoning_enabled_static())
1096                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1097         else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1098                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1099
1100         __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1101         return 0;
1102 }
1103
1104 static unsigned int features[] = {
1105         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1106         VIRTIO_BALLOON_F_STATS_VQ,
1107         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1108         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1109         VIRTIO_BALLOON_F_PAGE_POISON,
1110         VIRTIO_BALLOON_F_REPORTING,
1111 };
1112
1113 static struct virtio_driver virtio_balloon_driver = {
1114         .feature_table = features,
1115         .feature_table_size = ARRAY_SIZE(features),
1116         .driver.name =  KBUILD_MODNAME,
1117         .driver.owner = THIS_MODULE,
1118         .id_table =     id_table,
1119         .validate =     virtballoon_validate,
1120         .probe =        virtballoon_probe,
1121         .remove =       virtballoon_remove,
1122         .config_changed = virtballoon_changed,
1123 #ifdef CONFIG_PM_SLEEP
1124         .freeze =       virtballoon_freeze,
1125         .restore =      virtballoon_restore,
1126 #endif
1127 };
1128
1129 module_virtio_driver(virtio_balloon_driver);
1130 MODULE_DEVICE_TABLE(virtio, id_table);
1131 MODULE_DESCRIPTION("Virtio balloon driver");
1132 MODULE_LICENSE("GPL");