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 42enum 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 51enum virtio_balloon_config_read { 52 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, 53}; 54 55struct 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 124static const struct virtio_device_id id_table[] = { 125 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 126 { 0 }, 127}; 128 129static 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 138static void balloon_ack(struct virtqueue *vq) 139{ 140 struct virtio_balloon *vb = vq->vdev->priv; 141 142 wake_up(&vb->acked); 143} 144 145static 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 161static 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 188static 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 204static 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 254static 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 268static 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 304static 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 314static 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 */ 363static 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 373static 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 389static 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. */ 407static 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 427static 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 440static 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 454static 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 463static 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 472static 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 494static 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 569static 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 582static 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 601static 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 618static 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 665static 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 694static 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 714static 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 */ 750static 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 807static 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 820static 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 829static 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 838static 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 852static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) 853{ 854 unregister_shrinker(&vb->shrinker); 855} 856 857static 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 866static 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 997out_unregister_oom: 998 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 999 unregister_oom_notifier(&vb->oom_nb); 1000out_unregister_shrinker: 1001 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1002 virtio_balloon_unregister_shrinker(vb); 1003out_del_balloon_wq: 1004 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1005 destroy_workqueue(vb->balloon_wq); 1006out_del_vqs: 1007 vdev->config->del_vqs(vdev); 1008out_free_vb: 1009 kfree(vb); 1010out: 1011 return err; 1012} 1013 1014static 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 1031static 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 1057static 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 1069static 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 1087static 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 1104static 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 1113static 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 1129module_virtio_driver(virtio_balloon_driver); 1130MODULE_DEVICE_TABLE(virtio, id_table); 1131MODULE_DESCRIPTION("Virtio balloon driver"); 1132MODULE_LICENSE("GPL"); 1133