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/wait.h>
  18 #include <linux/mm.h>
  19 #include <linux/mount.h>
  20 #include <linux/magic.h>
  21 #include <linux/pseudo_fs.h>
  22
  23 /*
  24  * Balloon device works in 4K page units.  So each page is pointed to by
  25  * multiple balloon pages.  All memory counters in this driver are in balloon
  26  * page units.
  27  */
  28 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  29 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  30 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  31
  32 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
  33                                              __GFP_NOMEMALLOC)
  34 /* The order of free page blocks to report to host */
  35 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
  36 /* The size of a free page block in bytes */
  37 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
  38         (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
  39 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
  40
  41 #ifdef CONFIG_BALLOON_COMPACTION
  42 static struct vfsmount *balloon_mnt;
  43 #endif
  44
  45 enum virtio_balloon_vq {
  46         VIRTIO_BALLOON_VQ_INFLATE,
  47         VIRTIO_BALLOON_VQ_DEFLATE,
  48         VIRTIO_BALLOON_VQ_STATS,
  49         VIRTIO_BALLOON_VQ_FREE_PAGE,
  50         VIRTIO_BALLOON_VQ_MAX
  51 };
  52
  53 enum virtio_balloon_config_read {
  54         VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
  55 };
  56
  57 struct virtio_balloon {
  58         struct virtio_device *vdev;
  59         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
  60
  61         /* Balloon's own wq for cpu-intensive work items */
  62         struct workqueue_struct *balloon_wq;
  63         /* The free page reporting work item submitted to the balloon wq */
  64         struct work_struct report_free_page_work;
  65
  66         /* The balloon servicing is delegated to a freezable workqueue. */
  67         struct work_struct update_balloon_stats_work;
  68         struct work_struct update_balloon_size_work;
  69
  70         /* Prevent updating balloon when it is being canceled. */
  71         spinlock_t stop_update_lock;
  72         bool stop_update;
  73         /* Bitmap to indicate if reading the related config fields are needed */
  74         unsigned long config_read_bitmap;
  75
  76         /* The list of allocated free pages, waiting to be given back to mm */
  77         struct list_head free_page_list;
  78         spinlock_t free_page_list_lock;
  79         /* The number of free page blocks on the above list */
  80         unsigned long num_free_page_blocks;
  81         /*
  82          * The cmd id received from host.
  83          * Read it via virtio_balloon_cmd_id_received to get the latest value
  84          * sent from host.
  85          */
  86         u32 cmd_id_received_cache;
  87         /* The cmd id that is actively in use */
  88         __virtio32 cmd_id_active;
  89         /* Buffer to store the stop sign */
  90         __virtio32 cmd_id_stop;
  91
  92         /* Waiting for host to ack the pages we released. */
  93         wait_queue_head_t acked;
  94
  95         /* Number of balloon pages we've told the Host we're not using. */
  96         unsigned int num_pages;
  97         /*
  98          * The pages we've told the Host we're not using are enqueued
  99          * at vb_dev_info->pages list.
 100          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 101          * to num_pages above.
 102          */
 103         struct balloon_dev_info vb_dev_info;
 104
 105         /* Synchronize access/update to this struct virtio_balloon elements */
 106         struct mutex balloon_lock;
 107
 108         /* The array of pfns we tell the Host about. */
 109         unsigned int num_pfns;
 110         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 111
 112         /* Memory statistics */
 113         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 114
 115         /* To register a shrinker to shrink memory upon memory pressure */
 116         struct shrinker shrinker;
 117 };
 118
 119 static struct virtio_device_id id_table[] = {
 120         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 121         { 0 },
 122 };
 123
 124 static u32 page_to_balloon_pfn(struct page *page)
 125 {
 126         unsigned long pfn = page_to_pfn(page);
 127
 128         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 129         /* Convert pfn from Linux page size to balloon page size. */
 130         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 131 }
 132
 133 static void balloon_ack(struct virtqueue *vq)
 134 {
 135         struct virtio_balloon *vb = vq->vdev->priv;
 136
 137         wake_up(&vb->acked);
 138 }
 139
 140 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 141 {
 142         struct scatterlist sg;
 143         unsigned int len;
 144
 145         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 146
 147         /* We should always be able to add one buffer to an empty queue. */
 148         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 149         virtqueue_kick(vq);
 150
 151         /* When host has read buffer, this completes via balloon_ack */
 152         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 153
 154 }
 155
 156 static void set_page_pfns(struct virtio_balloon *vb,
 157                           __virtio32 pfns[], struct page *page)
 158 {
 159         unsigned int i;
 160
 161         BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
 162
 163         /*
 164          * Set balloon pfns pointing at this page.
 165          * Note that the first pfn points at start of the page.
 166          */
 167         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 168                 pfns[i] = cpu_to_virtio32(vb->vdev,
 169                                           page_to_balloon_pfn(page) + i);
 170 }
 171
 172 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 173 {
 174         unsigned num_allocated_pages;
 175         unsigned num_pfns;
 176         struct page *page;
 177         LIST_HEAD(pages);
 178
 179         /* We can only do one array worth at a time. */
 180         num = min(num, ARRAY_SIZE(vb->pfns));
 181
 182         for (num_pfns = 0; num_pfns < num;
 183              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 184                 struct page *page = balloon_page_alloc();
 185
 186                 if (!page) {
 187                         dev_info_ratelimited(&vb->vdev->dev,
 188                                              "Out of puff! Can't get %u pages\n",
 189                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 190                         /* Sleep for at least 1/5 of a second before retry. */
 191                         msleep(200);
 192                         break;
 193                 }
 194
 195                 balloon_page_push(&pages, page);
 196         }
 197
 198         mutex_lock(&vb->balloon_lock);
 199
 200         vb->num_pfns = 0;
 201
 202         while ((page = balloon_page_pop(&pages))) {
 203                 balloon_page_enqueue(&vb->vb_dev_info, page);
 204
 205                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 206                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 207                 if (!virtio_has_feature(vb->vdev,
 208                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 209                         adjust_managed_page_count(page, -1);
 210                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
 211         }
 212
 213         num_allocated_pages = vb->num_pfns;
 214         /* Did we get any? */
 215         if (vb->num_pfns != 0)
 216                 tell_host(vb, vb->inflate_vq);
 217         mutex_unlock(&vb->balloon_lock);
 218
 219         return num_allocated_pages;
 220 }
 221
 222 static void release_pages_balloon(struct virtio_balloon *vb,
 223                                  struct list_head *pages)
 224 {
 225         struct page *page, *next;
 226
 227         list_for_each_entry_safe(page, next, pages, lru) {
 228                 if (!virtio_has_feature(vb->vdev,
 229                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 230                         adjust_managed_page_count(page, 1);
 231                 list_del(&page->lru);
 232                 put_page(page); /* balloon reference */
 233         }
 234 }
 235
 236 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 237 {
 238         unsigned num_freed_pages;
 239         struct page *page;
 240         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 241         LIST_HEAD(pages);
 242
 243         /* We can only do one array worth at a time. */
 244         num = min(num, ARRAY_SIZE(vb->pfns));
 245
 246         mutex_lock(&vb->balloon_lock);
 247         /* We can't release more pages than taken */
 248         num = min(num, (size_t)vb->num_pages);
 249         for (vb->num_pfns = 0; vb->num_pfns < num;
 250              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 251                 page = balloon_page_dequeue(vb_dev_info);
 252                 if (!page)
 253                         break;
 254                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 255                 list_add(&page->lru, &pages);
 256                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 257         }
 258
 259         num_freed_pages = vb->num_pfns;
 260         /*
 261          * Note that if
 262          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 263          * is true, we *have* to do it in this order
 264          */
 265         if (vb->num_pfns != 0)
 266                 tell_host(vb, vb->deflate_vq);
 267         release_pages_balloon(vb, &pages);
 268         mutex_unlock(&vb->balloon_lock);
 269         return num_freed_pages;
 270 }
 271
 272 static inline void update_stat(struct virtio_balloon *vb, int idx,
 273                                u16 tag, u64 val)
 274 {
 275         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 276         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 277         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 278 }
 279
 280 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 281
 282 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 283 {
 284         unsigned long events[NR_VM_EVENT_ITEMS];
 285         struct sysinfo i;
 286         unsigned int idx = 0;
 287         long available;
 288         unsigned long caches;
 289
 290         all_vm_events(events);
 291         si_meminfo(&i);
 292
 293         available = si_mem_available();
 294         caches = global_node_page_state(NR_FILE_PAGES);
 295
 296 #ifdef CONFIG_VM_EVENT_COUNTERS
 297         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 298                                 pages_to_bytes(events[PSWPIN]));
 299         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 300                                 pages_to_bytes(events[PSWPOUT]));
 301         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 302         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 303 #ifdef CONFIG_HUGETLB_PAGE
 304         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
 305                     events[HTLB_BUDDY_PGALLOC]);
 306         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
 307                     events[HTLB_BUDDY_PGALLOC_FAIL]);
 308 #endif
 309 #endif
 310         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 311                                 pages_to_bytes(i.freeram));
 312         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 313                                 pages_to_bytes(i.totalram));
 314         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 315                                 pages_to_bytes(available));
 316         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
 317                                 pages_to_bytes(caches));
 318
 319         return idx;
 320 }
 321
 322 /*
 323  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 324  * the stats queue operates in reverse.  The driver initializes the virtqueue
 325  * with a single buffer.  From that point forward, all conversations consist of
 326  * a hypervisor request (a call to this function) which directs us to refill
 327  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 328  * we delegate the job to a freezable workqueue that will do the actual work via
 329  * stats_handle_request().
 330  */
 331 static void stats_request(struct virtqueue *vq)
 332 {
 333         struct virtio_balloon *vb = vq->vdev->priv;
 334
 335         spin_lock(&vb->stop_update_lock);
 336         if (!vb->stop_update)
 337                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 338         spin_unlock(&vb->stop_update_lock);
 339 }
 340
 341 static void stats_handle_request(struct virtio_balloon *vb)
 342 {
 343         struct virtqueue *vq;
 344         struct scatterlist sg;
 345         unsigned int len, num_stats;
 346
 347         num_stats = update_balloon_stats(vb);
 348
 349         vq = vb->stats_vq;
 350         if (!virtqueue_get_buf(vq, &len))
 351                 return;
 352         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 353         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 354         virtqueue_kick(vq);
 355 }
 356
 357 static inline s64 towards_target(struct virtio_balloon *vb)
 358 {
 359         s64 target;
 360         u32 num_pages;
 361
 362         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 363                      &num_pages);
 364
 365         /* Legacy balloon config space is LE, unlike all other devices. */
 366         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 367                 num_pages = le32_to_cpu((__force __le32)num_pages);
 368
 369         target = num_pages;
 370         return target - vb->num_pages;
 371 }
 372
 373 /* Gives back @num_to_return blocks of free pages to mm. */
 374 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 375                                              unsigned long num_to_return)
 376 {
 377         struct page *page;
 378         unsigned long num_returned;
 379
 380         spin_lock_irq(&vb->free_page_list_lock);
 381         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
 382                 page = balloon_page_pop(&vb->free_page_list);
 383                 if (!page)
 384                         break;
 385                 free_pages((unsigned long)page_address(page),
 386                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 387         }
 388         vb->num_free_page_blocks -= num_returned;
 389         spin_unlock_irq(&vb->free_page_list_lock);
 390
 391         return num_returned;
 392 }
 393
 394 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
 395 {
 396         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 397                 return;
 398
 399         /* No need to queue the work if the bit was already set. */
 400         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 401                              &vb->config_read_bitmap))
 402                 return;
 403
 404         queue_work(vb->balloon_wq, &vb->report_free_page_work);
 405 }
 406
 407 static void virtballoon_changed(struct virtio_device *vdev)
 408 {
 409         struct virtio_balloon *vb = vdev->priv;
 410         unsigned long flags;
 411
 412         spin_lock_irqsave(&vb->stop_update_lock, flags);
 413         if (!vb->stop_update) {
 414                 queue_work(system_freezable_wq,
 415                            &vb->update_balloon_size_work);
 416                 virtio_balloon_queue_free_page_work(vb);
 417         }
 418         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 419 }
 420
 421 static void update_balloon_size(struct virtio_balloon *vb)
 422 {
 423         u32 actual = vb->num_pages;
 424
 425         /* Legacy balloon config space is LE, unlike all other devices. */
 426         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 427                 actual = (__force u32)cpu_to_le32(actual);
 428
 429         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 430                       &actual);
 431 }
 432
 433 static void update_balloon_stats_func(struct work_struct *work)
 434 {
 435         struct virtio_balloon *vb;
 436
 437         vb = container_of(work, struct virtio_balloon,
 438                           update_balloon_stats_work);
 439         stats_handle_request(vb);
 440 }
 441
 442 static void update_balloon_size_func(struct work_struct *work)
 443 {
 444         struct virtio_balloon *vb;
 445         s64 diff;
 446
 447         vb = container_of(work, struct virtio_balloon,
 448                           update_balloon_size_work);
 449         diff = towards_target(vb);
 450
 451         if (!diff)
 452                 return;
 453
 454         if (diff > 0)
 455                 diff -= fill_balloon(vb, diff);
 456         else
 457                 diff += leak_balloon(vb, -diff);
 458         update_balloon_size(vb);
 459
 460         if (diff)
 461                 queue_work(system_freezable_wq, work);
 462 }
 463
 464 static int init_vqs(struct virtio_balloon *vb)
 465 {
 466         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 467         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 468         const char *names[VIRTIO_BALLOON_VQ_MAX];
 469         int err;
 470
 471         /*
 472          * Inflateq and deflateq are used unconditionally. The names[]
 473          * will be NULL if the related feature is not enabled, which will
 474          * cause no allocation for the corresponding virtqueue in find_vqs.
 475          */
 476         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
 477         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
 478         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
 479         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 480         callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
 481         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 482         callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 483         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 484
 485         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 486                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
 487                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
 488         }
 489
 490         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 491                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
 492                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 493         }
 494
 495         err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
 496                                          vqs, callbacks, names, NULL, NULL);
 497         if (err)
 498                 return err;
 499
 500         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 501         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 502         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 503                 struct scatterlist sg;
 504                 unsigned int num_stats;
 505                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 506
 507                 /*
 508                  * Prime this virtqueue with one buffer so the hypervisor can
 509                  * use it to signal us later (it can't be broken yet!).
 510                  */
 511                 num_stats = update_balloon_stats(vb);
 512
 513                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
 514                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
 515                                            GFP_KERNEL);
 516                 if (err) {
 517                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
 518                                  __func__);
 519                         return err;
 520                 }
 521                 virtqueue_kick(vb->stats_vq);
 522         }
 523
 524         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 525                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
 526
 527         return 0;
 528 }
 529
 530 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
 531 {
 532         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
 533                                &vb->config_read_bitmap))
 534                 virtio_cread(vb->vdev, struct virtio_balloon_config,
 535                              free_page_report_cmd_id,
 536                              &vb->cmd_id_received_cache);
 537
 538         return vb->cmd_id_received_cache;
 539 }
 540
 541 static int send_cmd_id_start(struct virtio_balloon *vb)
 542 {
 543         struct scatterlist sg;
 544         struct virtqueue *vq = vb->free_page_vq;
 545         int err, unused;
 546
 547         /* Detach all the used buffers from the vq */
 548         while (virtqueue_get_buf(vq, &unused))
 549                 ;
 550
 551         vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
 552                                         virtio_balloon_cmd_id_received(vb));
 553         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
 554         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
 555         if (!err)
 556                 virtqueue_kick(vq);
 557         return err;
 558 }
 559
 560 static int send_cmd_id_stop(struct virtio_balloon *vb)
 561 {
 562         struct scatterlist sg;
 563         struct virtqueue *vq = vb->free_page_vq;
 564         int err, unused;
 565
 566         /* Detach all the used buffers from the vq */
 567         while (virtqueue_get_buf(vq, &unused))
 568                 ;
 569
 570         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
 571         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
 572         if (!err)
 573                 virtqueue_kick(vq);
 574         return err;
 575 }
 576
 577 static int get_free_page_and_send(struct virtio_balloon *vb)
 578 {
 579         struct virtqueue *vq = vb->free_page_vq;
 580         struct page *page;
 581         struct scatterlist sg;
 582         int err, unused;
 583         void *p;
 584
 585         /* Detach all the used buffers from the vq */
 586         while (virtqueue_get_buf(vq, &unused))
 587                 ;
 588
 589         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
 590                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 591         /*
 592          * When the allocation returns NULL, it indicates that we have got all
 593          * the possible free pages, so return -EINTR to stop.
 594          */
 595         if (!page)
 596                 return -EINTR;
 597
 598         p = page_address(page);
 599         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
 600         /* There is always 1 entry reserved for the cmd id to use. */
 601         if (vq->num_free > 1) {
 602                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
 603                 if (unlikely(err)) {
 604                         free_pages((unsigned long)p,
 605                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 606                         return err;
 607                 }
 608                 virtqueue_kick(vq);
 609                 spin_lock_irq(&vb->free_page_list_lock);
 610                 balloon_page_push(&vb->free_page_list, page);
 611                 vb->num_free_page_blocks++;
 612                 spin_unlock_irq(&vb->free_page_list_lock);
 613         } else {
 614                 /*
 615                  * The vq has no available entry to add this page block, so
 616                  * just free it.
 617                  */
 618                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 619         }
 620
 621         return 0;
 622 }
 623
 624 static int send_free_pages(struct virtio_balloon *vb)
 625 {
 626         int err;
 627         u32 cmd_id_active;
 628
 629         while (1) {
 630                 /*
 631                  * If a stop id or a new cmd id was just received from host,
 632                  * stop the reporting.
 633                  */
 634                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
 635                 if (unlikely(cmd_id_active !=
 636                              virtio_balloon_cmd_id_received(vb)))
 637                         break;
 638
 639                 /*
 640                  * The free page blocks are allocated and sent to host one by
 641                  * one.
 642                  */
 643                 err = get_free_page_and_send(vb);
 644                 if (err == -EINTR)
 645                         break;
 646                 else if (unlikely(err))
 647                         return err;
 648         }
 649
 650         return 0;
 651 }
 652
 653 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
 654 {
 655         int err;
 656         struct device *dev = &vb->vdev->dev;
 657
 658         /* Start by sending the received cmd id to host with an outbuf. */
 659         err = send_cmd_id_start(vb);
 660         if (unlikely(err))
 661                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
 662
 663         err = send_free_pages(vb);
 664         if (unlikely(err))
 665                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
 666
 667         /* End by sending a stop id to host with an outbuf. */
 668         err = send_cmd_id_stop(vb);
 669         if (unlikely(err))
 670                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
 671 }
 672
 673 static void report_free_page_func(struct work_struct *work)
 674 {
 675         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
 676                                                  report_free_page_work);
 677         u32 cmd_id_received;
 678
 679         cmd_id_received = virtio_balloon_cmd_id_received(vb);
 680         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
 681                 /* Pass ULONG_MAX to give back all the free pages */
 682                 return_free_pages_to_mm(vb, ULONG_MAX);
 683         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
 684                    cmd_id_received !=
 685                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
 686                 virtio_balloon_report_free_page(vb);
 687         }
 688 }
 689
 690 #ifdef CONFIG_BALLOON_COMPACTION
 691 /*
 692  * virtballoon_migratepage - perform the balloon page migration on behalf of
 693  *                           a compation thread.     (called under page lock)
 694  * @vb_dev_info: the balloon device
 695  * @newpage: page that will replace the isolated page after migration finishes.
 696  * @page   : the isolated (old) page that is about to be migrated to newpage.
 697  * @mode   : compaction mode -- not used for balloon page migration.
 698  *
 699  * After a ballooned page gets isolated by compaction procedures, this is the
 700  * function that performs the page migration on behalf of a compaction thread
 701  * The page migration for virtio balloon is done in a simple swap fashion which
 702  * follows these two macro steps:
 703  *  1) insert newpage into vb->pages list and update the host about it;
 704  *  2) update the host about the old page removed from vb->pages list;
 705  *
 706  * This function preforms the balloon page migration task.
 707  * Called through balloon_mapping->a_ops->migratepage
 708  */
 709 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 710                 struct page *newpage, struct page *page, enum migrate_mode mode)
 711 {
 712         struct virtio_balloon *vb = container_of(vb_dev_info,
 713                         struct virtio_balloon, vb_dev_info);
 714         unsigned long flags;
 715
 716         /*
 717          * In order to avoid lock contention while migrating pages concurrently
 718          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 719          * this turn, as it is easier to retry the page migration later.
 720          * This also prevents fill_balloon() getting stuck into a mutex
 721          * recursion in the case it ends up triggering memory compaction
 722          * while it is attempting to inflate the ballon.
 723          */
 724         if (!mutex_trylock(&vb->balloon_lock))
 725                 return -EAGAIN;
 726
 727         get_page(newpage); /* balloon reference */
 728
 729         /*
 730           * When we migrate a page to a different zone and adjusted the
 731           * managed page count when inflating, we have to fixup the count of
 732           * both involved zones.
 733           */
 734         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
 735             page_zone(page) != page_zone(newpage)) {
 736                 adjust_managed_page_count(page, 1);
 737                 adjust_managed_page_count(newpage, -1);
 738         }
 739
 740         /* balloon's page migration 1st step  -- inflate "newpage" */
 741         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 742         balloon_page_insert(vb_dev_info, newpage);
 743         vb_dev_info->isolated_pages--;
 744         __count_vm_event(BALLOON_MIGRATE);
 745         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 746         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 747         set_page_pfns(vb, vb->pfns, newpage);
 748         tell_host(vb, vb->inflate_vq);
 749
 750         /* balloon's page migration 2nd step -- deflate "page" */
 751         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 752         balloon_page_delete(page);
 753         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 754         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 755         set_page_pfns(vb, vb->pfns, page);
 756         tell_host(vb, vb->deflate_vq);
 757
 758         mutex_unlock(&vb->balloon_lock);
 759
 760         put_page(page); /* balloon reference */
 761
 762         return MIGRATEPAGE_SUCCESS;
 763 }
 764
 765 static int balloon_init_fs_context(struct fs_context *fc)
 766 {
 767         return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
 768 }
 769
 770 static struct file_system_type balloon_fs = {
 771         .name           = "balloon-kvm",
 772         .init_fs_context = balloon_init_fs_context,
 773         .kill_sb        = kill_anon_super,
 774 };
 775
 776 #endif /* CONFIG_BALLOON_COMPACTION */
 777
 778 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 779                                        unsigned long pages_to_free)
 780 {
 781         unsigned long blocks_to_free, blocks_freed;
 782
 783         pages_to_free = round_up(pages_to_free,
 784                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
 785         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 786         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
 787
 788         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 789 }
 790
 791 static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
 792                                           unsigned long pages_to_free)
 793 {
 794         return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
 795                 VIRTIO_BALLOON_PAGES_PER_PAGE;
 796 }
 797
 798 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
 799                                           unsigned long pages_to_free)
 800 {
 801         unsigned long pages_freed = 0;
 802
 803         /*
 804          * One invocation of leak_balloon can deflate at most
 805          * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
 806          * multiple times to deflate pages till reaching pages_to_free.
 807          */
 808         while (vb->num_pages && pages_freed < pages_to_free)
 809                 pages_freed += leak_balloon_pages(vb,
 810                                                   pages_to_free - pages_freed);
 811
 812         update_balloon_size(vb);
 813
 814         return pages_freed;
 815 }
 816
 817 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
 818                                                   struct shrink_control *sc)
 819 {
 820         unsigned long pages_to_free, pages_freed = 0;
 821         struct virtio_balloon *vb = container_of(shrinker,
 822                                         struct virtio_balloon, shrinker);
 823
 824         pages_to_free = sc->nr_to_scan;
 825
 826         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 827                 pages_freed = shrink_free_pages(vb, pages_to_free);
 828
 829         if (pages_freed >= pages_to_free)
 830                 return pages_freed;
 831
 832         pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
 833
 834         return pages_freed;
 835 }
 836
 837 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
 838                                                    struct shrink_control *sc)
 839 {
 840         struct virtio_balloon *vb = container_of(shrinker,
 841                                         struct virtio_balloon, shrinker);
 842         unsigned long count;
 843
 844         count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
 845         count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
 846
 847         return count;
 848 }
 849
 850 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
 851 {
 852         unregister_shrinker(&vb->shrinker);
 853 }
 854
 855 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 856 {
 857         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
 858         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
 859         vb->shrinker.seeks = DEFAULT_SEEKS;
 860
 861         return register_shrinker(&vb->shrinker);
 862 }
 863
 864 static int virtballoon_probe(struct virtio_device *vdev)
 865 {
 866         struct virtio_balloon *vb;
 867         __u32 poison_val;
 868         int err;
 869
 870         if (!vdev->config->get) {
 871                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 872                         __func__);
 873                 return -EINVAL;
 874         }
 875
 876         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 877         if (!vb) {
 878                 err = -ENOMEM;
 879                 goto out;
 880         }
 881
 882         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 883         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 884         spin_lock_init(&vb->stop_update_lock);
 885         mutex_init(&vb->balloon_lock);
 886         init_waitqueue_head(&vb->acked);
 887         vb->vdev = vdev;
 888
 889         balloon_devinfo_init(&vb->vb_dev_info);
 890
 891         err = init_vqs(vb);
 892         if (err)
 893                 goto out_free_vb;
 894
 895 #ifdef CONFIG_BALLOON_COMPACTION
 896         balloon_mnt = kern_mount(&balloon_fs);
 897         if (IS_ERR(balloon_mnt)) {
 898                 err = PTR_ERR(balloon_mnt);
 899                 goto out_del_vqs;
 900         }
 901
 902         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 903         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 904         if (IS_ERR(vb->vb_dev_info.inode)) {
 905                 err = PTR_ERR(vb->vb_dev_info.inode);
 906                 goto out_kern_unmount;
 907         }
 908         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 909 #endif
 910         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 911                 /*
 912                  * There is always one entry reserved for cmd id, so the ring
 913                  * size needs to be at least two to report free page hints.
 914                  */
 915                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 916                         err = -ENOSPC;
 917                         goto out_iput;
 918                 }
 919                 vb->balloon_wq = alloc_workqueue("balloon-wq",
 920                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 921                 if (!vb->balloon_wq) {
 922                         err = -ENOMEM;
 923                         goto out_iput;
 924                 }
 925                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 926                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
 927                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
 928                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 929                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
 930                                                   VIRTIO_BALLOON_CMD_ID_STOP);
 931                 spin_lock_init(&vb->free_page_list_lock);
 932                 INIT_LIST_HEAD(&vb->free_page_list);
 933                 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
 934                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
 935                         virtio_cwrite(vb->vdev, struct virtio_balloon_config,
 936                                       poison_val, &poison_val);
 937                 }
 938         }
 939         /*
 940          * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
 941          * shrinker needs to be registered to relieve memory pressure.
 942          */
 943         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
 944                 err = virtio_balloon_register_shrinker(vb);
 945                 if (err)
 946                         goto out_del_balloon_wq;
 947         }
 948         virtio_device_ready(vdev);
 949
 950         if (towards_target(vb))
 951                 virtballoon_changed(vdev);
 952         return 0;
 953
 954 out_del_balloon_wq:
 955         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 956                 destroy_workqueue(vb->balloon_wq);
 957 out_iput:
 958 #ifdef CONFIG_BALLOON_COMPACTION
 959         iput(vb->vb_dev_info.inode);
 960 out_kern_unmount:
 961         kern_unmount(balloon_mnt);
 962 out_del_vqs:
 963 #endif
 964         vdev->config->del_vqs(vdev);
 965 out_free_vb:
 966         kfree(vb);
 967 out:
 968         return err;
 969 }
 970
 971 static void remove_common(struct virtio_balloon *vb)
 972 {
 973         /* There might be pages left in the balloon: free them. */
 974         while (vb->num_pages)
 975                 leak_balloon(vb, vb->num_pages);
 976         update_balloon_size(vb);
 977
 978         /* There might be free pages that are being reported: release them. */
 979         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 980                 return_free_pages_to_mm(vb, ULONG_MAX);
 981
 982         /* Now we reset the device so we can clean up the queues. */
 983         vb->vdev->config->reset(vb->vdev);
 984
 985         vb->vdev->config->del_vqs(vb->vdev);
 986 }
 987
 988 static void virtballoon_remove(struct virtio_device *vdev)
 989 {
 990         struct virtio_balloon *vb = vdev->priv;
 991
 992         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 993                 virtio_balloon_unregister_shrinker(vb);
 994         spin_lock_irq(&vb->stop_update_lock);
 995         vb->stop_update = true;
 996         spin_unlock_irq(&vb->stop_update_lock);
 997         cancel_work_sync(&vb->update_balloon_size_work);
 998         cancel_work_sync(&vb->update_balloon_stats_work);
 999
1000         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1001                 cancel_work_sync(&vb->report_free_page_work);
1002                 destroy_workqueue(vb->balloon_wq);
1003         }
1004
1005         remove_common(vb);
1006 #ifdef CONFIG_BALLOON_COMPACTION
1007         if (vb->vb_dev_info.inode)
1008                 iput(vb->vb_dev_info.inode);
1009
1010         kern_unmount(balloon_mnt);
1011 #endif
1012         kfree(vb);
1013 }
1014
1015 #ifdef CONFIG_PM_SLEEP
1016 static int virtballoon_freeze(struct virtio_device *vdev)
1017 {
1018         struct virtio_balloon *vb = vdev->priv;
1019
1020         /*
1021          * The workqueue is already frozen by the PM core before this
1022          * function is called.
1023          */
1024         remove_common(vb);
1025         return 0;
1026 }
1027
1028 static int virtballoon_restore(struct virtio_device *vdev)
1029 {
1030         struct virtio_balloon *vb = vdev->priv;
1031         int ret;
1032
1033         ret = init_vqs(vdev->priv);
1034         if (ret)
1035                 return ret;
1036
1037         virtio_device_ready(vdev);
1038
1039         if (towards_target(vb))
1040                 virtballoon_changed(vdev);
1041         update_balloon_size(vb);
1042         return 0;
1043 }
1044 #endif
1045
1046 static int virtballoon_validate(struct virtio_device *vdev)
1047 {
1048         if (!page_poisoning_enabled())
1049                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1050
1051         __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1052         return 0;
1053 }
1054
1055 static unsigned int features[] = {
1056         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1057         VIRTIO_BALLOON_F_STATS_VQ,
1058         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1059         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1060         VIRTIO_BALLOON_F_PAGE_POISON,
1061 };
1062
1063 static struct virtio_driver virtio_balloon_driver = {
1064         .feature_table = features,
1065         .feature_table_size = ARRAY_SIZE(features),
1066         .driver.name =  KBUILD_MODNAME,
1067         .driver.owner = THIS_MODULE,
1068         .id_table =     id_table,
1069         .validate =     virtballoon_validate,
1070         .probe =        virtballoon_probe,
1071         .remove =       virtballoon_remove,
1072         .config_changed = virtballoon_changed,
1073 #ifdef CONFIG_PM_SLEEP
1074         .freeze =       virtballoon_freeze,
1075         .restore =      virtballoon_restore,
1076 #endif
1077 };
1078
1079 module_virtio_driver(virtio_balloon_driver);
1080 MODULE_DEVICE_TABLE(virtio, id_table);
1081 MODULE_DESCRIPTION("Virtio balloon driver");
1082 MODULE_LICENSE("GPL");