1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Virtio balloon implementation, inspired by Dor Laor and Marcelo 4 * Tosatti's implementations. 5 * 6 * Copyright 2008 Rusty Russell IBM Corporation 7 */ 8 9 #include <linux/virtio.h> 10 #include <linux/virtio_balloon.h> 11 #include <linux/swap.h> 12 #include <linux/workqueue.h> 13 #include <linux/delay.h> 14 #include <linux/slab.h> 15 #include <linux/module.h> 16 #include <linux/balloon_compaction.h> 17 #include <linux/oom.h> 18 #include <linux/wait.h> 19 #include <linux/mm.h> 20 #include <linux/page_reporting.h> 21 22 /* 23 * Balloon device works in 4K page units. So each page is pointed to by 24 * multiple balloon pages. All memory counters in this driver are in balloon 25 * page units. 26 */ 27 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 28 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 29 /* Maximum number of (4k) pages to deflate on OOM notifications. */ 30 #define VIRTIO_BALLOON_OOM_NR_PAGES 256 31 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80 32 33 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ 34 __GFP_NOMEMALLOC) 35 /* The order of free page blocks to report to host */ 36 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER MAX_PAGE_ORDER 37 /* The size of a free page block in bytes */ 38 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \ 39 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT)) 40 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER) 41 42 enum virtio_balloon_vq { 43 VIRTIO_BALLOON_VQ_INFLATE, 44 VIRTIO_BALLOON_VQ_DEFLATE, 45 VIRTIO_BALLOON_VQ_STATS, 46 VIRTIO_BALLOON_VQ_FREE_PAGE, 47 VIRTIO_BALLOON_VQ_REPORTING, 48 VIRTIO_BALLOON_VQ_MAX 49 }; 50 51 enum virtio_balloon_config_read { 52 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, 53 }; 54 55 struct virtio_balloon { 56 struct virtio_device *vdev; 57 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; 58 59 /* Balloon's own wq for cpu-intensive work items */ 60 struct workqueue_struct *balloon_wq; 61 /* The free page reporting work item submitted to the balloon wq */ 62 struct work_struct report_free_page_work; 63 64 /* The balloon servicing is delegated to a freezable workqueue. */ 65 struct work_struct update_balloon_stats_work; 66 struct work_struct update_balloon_size_work; 67 68 /* Prevent updating balloon when it is being canceled. */ 69 spinlock_t stop_update_lock; 70 bool stop_update; 71 /* Bitmap to indicate if reading the related config fields are needed */ 72 unsigned long config_read_bitmap; 73 74 /* The list of allocated free pages, waiting to be given back to mm */ 75 struct list_head free_page_list; 76 spinlock_t free_page_list_lock; 77 /* The number of free page blocks on the above list */ 78 unsigned long num_free_page_blocks; 79 /* 80 * The cmd id received from host. 81 * Read it via virtio_balloon_cmd_id_received to get the latest value 82 * sent from host. 83 */ 84 u32 cmd_id_received_cache; 85 /* The cmd id that is actively in use */ 86 __virtio32 cmd_id_active; 87 /* Buffer to store the stop sign */ 88 __virtio32 cmd_id_stop; 89 90 /* Waiting for host to ack the pages we released. */ 91 wait_queue_head_t acked; 92 93 /* Number of balloon pages we've told the Host we're not using. */ 94 unsigned int num_pages; 95 /* 96 * The pages we've told the Host we're not using are enqueued 97 * at vb_dev_info->pages list. 98 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 99 * to num_pages above. 100 */ 101 struct balloon_dev_info vb_dev_info; 102 103 /* Synchronize access/update to this struct virtio_balloon elements */ 104 struct mutex balloon_lock; 105 106 /* The array of pfns we tell the Host about. */ 107 unsigned int num_pfns; 108 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 109 110 /* Memory statistics */ 111 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 112 113 /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */ 114 struct shrinker *shrinker; 115 116 /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */ 117 struct notifier_block oom_nb; 118 119 /* Free page reporting device */ 120 struct virtqueue *reporting_vq; 121 struct page_reporting_dev_info pr_dev_info; 122 123 /* State for keeping the wakeup_source active while adjusting the balloon */ 124 spinlock_t adjustment_lock; 125 bool adjustment_signal_pending; 126 bool adjustment_in_progress; 127 }; 128 129 static const struct virtio_device_id id_table[] = { 130 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 131 { 0 }, 132 }; 133 134 static u32 page_to_balloon_pfn(struct page *page) 135 { 136 unsigned long pfn = page_to_pfn(page); 137 138 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 139 /* Convert pfn from Linux page size to balloon page size. */ 140 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 141 } 142 143 static void balloon_ack(struct virtqueue *vq) 144 { 145 struct virtio_balloon *vb = vq->vdev->priv; 146 147 wake_up(&vb->acked); 148 } 149 150 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 151 { 152 struct scatterlist sg; 153 unsigned int len; 154 155 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 156 157 /* We should always be able to add one buffer to an empty queue. */ 158 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 159 virtqueue_kick(vq); 160 161 /* When host has read buffer, this completes via balloon_ack */ 162 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 163 164 } 165 166 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, 167 struct scatterlist *sg, unsigned int nents) 168 { 169 struct virtio_balloon *vb = 170 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); 171 struct virtqueue *vq = vb->reporting_vq; 172 unsigned int unused, err; 173 174 /* We should always be able to add these buffers to an empty queue. */ 175 err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN); 176 177 /* 178 * In the extremely unlikely case that something has occurred and we 179 * are able to trigger an error we will simply display a warning 180 * and exit without actually processing the pages. 181 */ 182 if (WARN_ON_ONCE(err)) 183 return err; 184 185 virtqueue_kick(vq); 186 187 /* When host has read buffer, this completes via balloon_ack */ 188 wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); 189 190 return 0; 191 } 192 193 static void set_page_pfns(struct virtio_balloon *vb, 194 __virtio32 pfns[], struct page *page) 195 { 196 unsigned int i; 197 198 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX); 199 200 /* 201 * Set balloon pfns pointing at this page. 202 * Note that the first pfn points at start of the page. 203 */ 204 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 205 pfns[i] = cpu_to_virtio32(vb->vdev, 206 page_to_balloon_pfn(page) + i); 207 } 208 209 static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) 210 { 211 unsigned int num_allocated_pages; 212 unsigned int num_pfns; 213 struct page *page; 214 LIST_HEAD(pages); 215 216 /* We can only do one array worth at a time. */ 217 num = min(num, ARRAY_SIZE(vb->pfns)); 218 219 for (num_pfns = 0; num_pfns < num; 220 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 221 struct page *page = balloon_page_alloc(); 222 223 if (!page) { 224 dev_info_ratelimited(&vb->vdev->dev, 225 "Out of puff! Can't get %u pages\n", 226 VIRTIO_BALLOON_PAGES_PER_PAGE); 227 /* Sleep for at least 1/5 of a second before retry. */ 228 msleep(200); 229 break; 230 } 231 232 balloon_page_push(&pages, page); 233 } 234 235 mutex_lock(&vb->balloon_lock); 236 237 vb->num_pfns = 0; 238 239 while ((page = balloon_page_pop(&pages))) { 240 balloon_page_enqueue(&vb->vb_dev_info, page); 241 242 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 243 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 244 if (!virtio_has_feature(vb->vdev, 245 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 246 adjust_managed_page_count(page, -1); 247 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; 248 } 249 250 num_allocated_pages = vb->num_pfns; 251 /* Did we get any? */ 252 if (vb->num_pfns != 0) 253 tell_host(vb, vb->inflate_vq); 254 mutex_unlock(&vb->balloon_lock); 255 256 return num_allocated_pages; 257 } 258 259 static void release_pages_balloon(struct virtio_balloon *vb, 260 struct list_head *pages) 261 { 262 struct page *page, *next; 263 264 list_for_each_entry_safe(page, next, pages, lru) { 265 if (!virtio_has_feature(vb->vdev, 266 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 267 adjust_managed_page_count(page, 1); 268 list_del(&page->lru); 269 put_page(page); /* balloon reference */ 270 } 271 } 272 273 static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num) 274 { 275 unsigned int num_freed_pages; 276 struct page *page; 277 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 278 LIST_HEAD(pages); 279 280 /* We can only do one array worth at a time. */ 281 num = min(num, ARRAY_SIZE(vb->pfns)); 282 283 mutex_lock(&vb->balloon_lock); 284 /* We can't release more pages than taken */ 285 num = min(num, (size_t)vb->num_pages); 286 for (vb->num_pfns = 0; vb->num_pfns < num; 287 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 288 page = balloon_page_dequeue(vb_dev_info); 289 if (!page) 290 break; 291 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 292 list_add(&page->lru, &pages); 293 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 294 } 295 296 num_freed_pages = vb->num_pfns; 297 /* 298 * Note that if 299 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 300 * is true, we *have* to do it in this order 301 */ 302 if (vb->num_pfns != 0) 303 tell_host(vb, vb->deflate_vq); 304 release_pages_balloon(vb, &pages); 305 mutex_unlock(&vb->balloon_lock); 306 return num_freed_pages; 307 } 308 309 static inline void update_stat(struct virtio_balloon *vb, int idx, 310 u16 tag, u64 val) 311 { 312 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 313 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag); 314 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); 315 } 316 317 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 318 319 static unsigned int update_balloon_stats(struct virtio_balloon *vb) 320 { 321 unsigned long events[NR_VM_EVENT_ITEMS]; 322 struct sysinfo i; 323 unsigned int idx = 0; 324 long available; 325 unsigned long caches; 326 327 all_vm_events(events); 328 si_meminfo(&i); 329 330 available = si_mem_available(); 331 caches = global_node_page_state(NR_FILE_PAGES); 332 333 #ifdef CONFIG_VM_EVENT_COUNTERS 334 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 335 pages_to_bytes(events[PSWPIN])); 336 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 337 pages_to_bytes(events[PSWPOUT])); 338 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 339 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 340 #ifdef CONFIG_HUGETLB_PAGE 341 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC, 342 events[HTLB_BUDDY_PGALLOC]); 343 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL, 344 events[HTLB_BUDDY_PGALLOC_FAIL]); 345 #endif 346 #endif 347 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 348 pages_to_bytes(i.freeram)); 349 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 350 pages_to_bytes(i.totalram)); 351 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, 352 pages_to_bytes(available)); 353 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES, 354 pages_to_bytes(caches)); 355 356 return idx; 357 } 358 359 /* 360 * While most virtqueues communicate guest-initiated requests to the hypervisor, 361 * the stats queue operates in reverse. The driver initializes the virtqueue 362 * with a single buffer. From that point forward, all conversations consist of 363 * a hypervisor request (a call to this function) which directs us to refill 364 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 365 * we delegate the job to a freezable workqueue that will do the actual work via 366 * stats_handle_request(). 367 */ 368 static void stats_request(struct virtqueue *vq) 369 { 370 struct virtio_balloon *vb = vq->vdev->priv; 371 372 spin_lock(&vb->stop_update_lock); 373 if (!vb->stop_update) 374 queue_work(system_freezable_wq, &vb->update_balloon_stats_work); 375 spin_unlock(&vb->stop_update_lock); 376 } 377 378 static void stats_handle_request(struct virtio_balloon *vb) 379 { 380 struct virtqueue *vq; 381 struct scatterlist sg; 382 unsigned int len, num_stats; 383 384 num_stats = update_balloon_stats(vb); 385 386 vq = vb->stats_vq; 387 if (!virtqueue_get_buf(vq, &len)) 388 return; 389 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 390 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 391 virtqueue_kick(vq); 392 } 393 394 static inline s64 towards_target(struct virtio_balloon *vb) 395 { 396 s64 target; 397 u32 num_pages; 398 399 /* Legacy balloon config space is LE, unlike all other devices. */ 400 virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages, 401 &num_pages); 402 403 /* 404 * Aligned up to guest page size to avoid inflating and deflating 405 * balloon endlessly. 406 */ 407 target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE); 408 return target - vb->num_pages; 409 } 410 411 /* Gives back @num_to_return blocks of free pages to mm. */ 412 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, 413 unsigned long num_to_return) 414 { 415 struct page *page; 416 unsigned long num_returned; 417 418 spin_lock_irq(&vb->free_page_list_lock); 419 for (num_returned = 0; num_returned < num_to_return; num_returned++) { 420 page = balloon_page_pop(&vb->free_page_list); 421 if (!page) 422 break; 423 free_pages((unsigned long)page_address(page), 424 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 425 } 426 vb->num_free_page_blocks -= num_returned; 427 spin_unlock_irq(&vb->free_page_list_lock); 428 429 return num_returned; 430 } 431 432 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) 433 { 434 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 435 return; 436 437 /* No need to queue the work if the bit was already set. */ 438 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 439 &vb->config_read_bitmap)) 440 return; 441 442 queue_work(vb->balloon_wq, &vb->report_free_page_work); 443 } 444 445 static void start_update_balloon_size(struct virtio_balloon *vb) 446 { 447 unsigned long flags; 448 449 spin_lock_irqsave(&vb->adjustment_lock, flags); 450 vb->adjustment_signal_pending = true; 451 if (!vb->adjustment_in_progress) { 452 vb->adjustment_in_progress = true; 453 pm_stay_awake(vb->vdev->dev.parent); 454 } 455 spin_unlock_irqrestore(&vb->adjustment_lock, flags); 456 457 queue_work(system_freezable_wq, &vb->update_balloon_size_work); 458 } 459 460 static void end_update_balloon_size(struct virtio_balloon *vb) 461 { 462 spin_lock_irq(&vb->adjustment_lock); 463 if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) { 464 vb->adjustment_in_progress = false; 465 pm_relax(vb->vdev->dev.parent); 466 } 467 spin_unlock_irq(&vb->adjustment_lock); 468 } 469 470 static void virtballoon_changed(struct virtio_device *vdev) 471 { 472 struct virtio_balloon *vb = vdev->priv; 473 unsigned long flags; 474 475 spin_lock_irqsave(&vb->stop_update_lock, flags); 476 if (!vb->stop_update) { 477 start_update_balloon_size(vb); 478 virtio_balloon_queue_free_page_work(vb); 479 } 480 spin_unlock_irqrestore(&vb->stop_update_lock, flags); 481 } 482 483 static void update_balloon_size(struct virtio_balloon *vb) 484 { 485 u32 actual = vb->num_pages; 486 487 /* Legacy balloon config space is LE, unlike all other devices. */ 488 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual, 489 &actual); 490 } 491 492 static void update_balloon_stats_func(struct work_struct *work) 493 { 494 struct virtio_balloon *vb; 495 496 vb = container_of(work, struct virtio_balloon, 497 update_balloon_stats_work); 498 stats_handle_request(vb); 499 } 500 501 static void update_balloon_size_func(struct work_struct *work) 502 { 503 struct virtio_balloon *vb; 504 s64 diff; 505 506 vb = container_of(work, struct virtio_balloon, 507 update_balloon_size_work); 508 509 spin_lock_irq(&vb->adjustment_lock); 510 vb->adjustment_signal_pending = false; 511 spin_unlock_irq(&vb->adjustment_lock); 512 513 diff = towards_target(vb); 514 515 if (diff) { 516 if (diff > 0) 517 diff -= fill_balloon(vb, diff); 518 else 519 diff += leak_balloon(vb, -diff); 520 update_balloon_size(vb); 521 } 522 523 if (diff) 524 queue_work(system_freezable_wq, work); 525 else 526 end_update_balloon_size(vb); 527 } 528 529 static int init_vqs(struct virtio_balloon *vb) 530 { 531 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX]; 532 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX]; 533 const char *names[VIRTIO_BALLOON_VQ_MAX]; 534 int err; 535 536 /* 537 * Inflateq and deflateq are used unconditionally. The names[] 538 * will be NULL if the related feature is not enabled, which will 539 * cause no allocation for the corresponding virtqueue in find_vqs. 540 */ 541 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack; 542 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate"; 543 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack; 544 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; 545 callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL; 546 names[VIRTIO_BALLOON_VQ_STATS] = NULL; 547 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 548 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 549 names[VIRTIO_BALLOON_VQ_REPORTING] = NULL; 550 551 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 552 names[VIRTIO_BALLOON_VQ_STATS] = "stats"; 553 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request; 554 } 555 556 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 557 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq"; 558 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 559 } 560 561 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { 562 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq"; 563 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack; 564 } 565 566 err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs, 567 callbacks, names, NULL); 568 if (err) 569 return err; 570 571 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; 572 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; 573 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 574 struct scatterlist sg; 575 unsigned int num_stats; 576 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS]; 577 578 /* 579 * Prime this virtqueue with one buffer so the hypervisor can 580 * use it to signal us later (it can't be broken yet!). 581 */ 582 num_stats = update_balloon_stats(vb); 583 584 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 585 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, 586 GFP_KERNEL); 587 if (err) { 588 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n", 589 __func__); 590 return err; 591 } 592 virtqueue_kick(vb->stats_vq); 593 } 594 595 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 596 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; 597 598 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) 599 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING]; 600 601 return 0; 602 } 603 604 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb) 605 { 606 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 607 &vb->config_read_bitmap)) { 608 /* Legacy balloon config space is LE, unlike all other devices. */ 609 virtio_cread_le(vb->vdev, struct virtio_balloon_config, 610 free_page_hint_cmd_id, 611 &vb->cmd_id_received_cache); 612 } 613 614 return vb->cmd_id_received_cache; 615 } 616 617 static int send_cmd_id_start(struct virtio_balloon *vb) 618 { 619 struct scatterlist sg; 620 struct virtqueue *vq = vb->free_page_vq; 621 int err, unused; 622 623 /* Detach all the used buffers from the vq */ 624 while (virtqueue_get_buf(vq, &unused)) 625 ; 626 627 vb->cmd_id_active = cpu_to_virtio32(vb->vdev, 628 virtio_balloon_cmd_id_received(vb)); 629 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active)); 630 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL); 631 if (!err) 632 virtqueue_kick(vq); 633 return err; 634 } 635 636 static int send_cmd_id_stop(struct virtio_balloon *vb) 637 { 638 struct scatterlist sg; 639 struct virtqueue *vq = vb->free_page_vq; 640 int err, unused; 641 642 /* Detach all the used buffers from the vq */ 643 while (virtqueue_get_buf(vq, &unused)) 644 ; 645 646 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop)); 647 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL); 648 if (!err) 649 virtqueue_kick(vq); 650 return err; 651 } 652 653 static int get_free_page_and_send(struct virtio_balloon *vb) 654 { 655 struct virtqueue *vq = vb->free_page_vq; 656 struct page *page; 657 struct scatterlist sg; 658 int err, unused; 659 void *p; 660 661 /* Detach all the used buffers from the vq */ 662 while (virtqueue_get_buf(vq, &unused)) 663 ; 664 665 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG, 666 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 667 /* 668 * When the allocation returns NULL, it indicates that we have got all 669 * the possible free pages, so return -EINTR to stop. 670 */ 671 if (!page) 672 return -EINTR; 673 674 p = page_address(page); 675 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES); 676 /* There is always 1 entry reserved for the cmd id to use. */ 677 if (vq->num_free > 1) { 678 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL); 679 if (unlikely(err)) { 680 free_pages((unsigned long)p, 681 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 682 return err; 683 } 684 virtqueue_kick(vq); 685 spin_lock_irq(&vb->free_page_list_lock); 686 balloon_page_push(&vb->free_page_list, page); 687 vb->num_free_page_blocks++; 688 spin_unlock_irq(&vb->free_page_list_lock); 689 } else { 690 /* 691 * The vq has no available entry to add this page block, so 692 * just free it. 693 */ 694 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); 695 } 696 697 return 0; 698 } 699 700 static int send_free_pages(struct virtio_balloon *vb) 701 { 702 int err; 703 u32 cmd_id_active; 704 705 while (1) { 706 /* 707 * If a stop id or a new cmd id was just received from host, 708 * stop the reporting. 709 */ 710 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active); 711 if (unlikely(cmd_id_active != 712 virtio_balloon_cmd_id_received(vb))) 713 break; 714 715 /* 716 * The free page blocks are allocated and sent to host one by 717 * one. 718 */ 719 err = get_free_page_and_send(vb); 720 if (err == -EINTR) 721 break; 722 else if (unlikely(err)) 723 return err; 724 } 725 726 return 0; 727 } 728 729 static void virtio_balloon_report_free_page(struct virtio_balloon *vb) 730 { 731 int err; 732 struct device *dev = &vb->vdev->dev; 733 734 /* Start by sending the received cmd id to host with an outbuf. */ 735 err = send_cmd_id_start(vb); 736 if (unlikely(err)) 737 dev_err(dev, "Failed to send a start id, err = %d\n", err); 738 739 err = send_free_pages(vb); 740 if (unlikely(err)) 741 dev_err(dev, "Failed to send a free page, err = %d\n", err); 742 743 /* End by sending a stop id to host with an outbuf. */ 744 err = send_cmd_id_stop(vb); 745 if (unlikely(err)) 746 dev_err(dev, "Failed to send a stop id, err = %d\n", err); 747 } 748 749 static void report_free_page_func(struct work_struct *work) 750 { 751 struct virtio_balloon *vb = container_of(work, struct virtio_balloon, 752 report_free_page_work); 753 u32 cmd_id_received; 754 755 cmd_id_received = virtio_balloon_cmd_id_received(vb); 756 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { 757 /* Pass ULONG_MAX to give back all the free pages */ 758 return_free_pages_to_mm(vb, ULONG_MAX); 759 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && 760 cmd_id_received != 761 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { 762 virtio_balloon_report_free_page(vb); 763 } 764 } 765 766 #ifdef CONFIG_BALLOON_COMPACTION 767 /* 768 * virtballoon_migratepage - perform the balloon page migration on behalf of 769 * a compaction thread. (called under page lock) 770 * @vb_dev_info: the balloon device 771 * @newpage: page that will replace the isolated page after migration finishes. 772 * @page : the isolated (old) page that is about to be migrated to newpage. 773 * @mode : compaction mode -- not used for balloon page migration. 774 * 775 * After a ballooned page gets isolated by compaction procedures, this is the 776 * function that performs the page migration on behalf of a compaction thread 777 * The page migration for virtio balloon is done in a simple swap fashion which 778 * follows these two macro steps: 779 * 1) insert newpage into vb->pages list and update the host about it; 780 * 2) update the host about the old page removed from vb->pages list; 781 * 782 * This function preforms the balloon page migration task. 783 * Called through movable_operations->migrate_page 784 */ 785 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 786 struct page *newpage, struct page *page, enum migrate_mode mode) 787 { 788 struct virtio_balloon *vb = container_of(vb_dev_info, 789 struct virtio_balloon, vb_dev_info); 790 unsigned long flags; 791 792 /* 793 * In order to avoid lock contention while migrating pages concurrently 794 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 795 * this turn, as it is easier to retry the page migration later. 796 * This also prevents fill_balloon() getting stuck into a mutex 797 * recursion in the case it ends up triggering memory compaction 798 * while it is attempting to inflate the ballon. 799 */ 800 if (!mutex_trylock(&vb->balloon_lock)) 801 return -EAGAIN; 802 803 get_page(newpage); /* balloon reference */ 804 805 /* 806 * When we migrate a page to a different zone and adjusted the 807 * managed page count when inflating, we have to fixup the count of 808 * both involved zones. 809 */ 810 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) && 811 page_zone(page) != page_zone(newpage)) { 812 adjust_managed_page_count(page, 1); 813 adjust_managed_page_count(newpage, -1); 814 } 815 816 /* balloon's page migration 1st step -- inflate "newpage" */ 817 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 818 balloon_page_insert(vb_dev_info, newpage); 819 vb_dev_info->isolated_pages--; 820 __count_vm_event(BALLOON_MIGRATE); 821 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 822 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 823 set_page_pfns(vb, vb->pfns, newpage); 824 tell_host(vb, vb->inflate_vq); 825 826 /* balloon's page migration 2nd step -- deflate "page" */ 827 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 828 balloon_page_delete(page); 829 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 830 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 831 set_page_pfns(vb, vb->pfns, page); 832 tell_host(vb, vb->deflate_vq); 833 834 mutex_unlock(&vb->balloon_lock); 835 836 put_page(page); /* balloon reference */ 837 838 return MIGRATEPAGE_SUCCESS; 839 } 840 #endif /* CONFIG_BALLOON_COMPACTION */ 841 842 static unsigned long shrink_free_pages(struct virtio_balloon *vb, 843 unsigned long pages_to_free) 844 { 845 unsigned long blocks_to_free, blocks_freed; 846 847 pages_to_free = round_up(pages_to_free, 848 VIRTIO_BALLOON_HINT_BLOCK_PAGES); 849 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES; 850 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free); 851 852 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 853 } 854 855 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, 856 struct shrink_control *sc) 857 { 858 struct virtio_balloon *vb = shrinker->private_data; 859 860 return shrink_free_pages(vb, sc->nr_to_scan); 861 } 862 863 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, 864 struct shrink_control *sc) 865 { 866 struct virtio_balloon *vb = shrinker->private_data; 867 868 return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 869 } 870 871 static int virtio_balloon_oom_notify(struct notifier_block *nb, 872 unsigned long dummy, void *parm) 873 { 874 struct virtio_balloon *vb = container_of(nb, 875 struct virtio_balloon, oom_nb); 876 unsigned long *freed = parm; 877 878 *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) / 879 VIRTIO_BALLOON_PAGES_PER_PAGE; 880 update_balloon_size(vb); 881 882 return NOTIFY_OK; 883 } 884 885 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) 886 { 887 shrinker_free(vb->shrinker); 888 } 889 890 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) 891 { 892 vb->shrinker = shrinker_alloc(0, "virtio-balloon"); 893 if (!vb->shrinker) 894 return -ENOMEM; 895 896 vb->shrinker->scan_objects = virtio_balloon_shrinker_scan; 897 vb->shrinker->count_objects = virtio_balloon_shrinker_count; 898 vb->shrinker->private_data = vb; 899 900 shrinker_register(vb->shrinker); 901 902 return 0; 903 } 904 905 static int virtballoon_probe(struct virtio_device *vdev) 906 { 907 struct virtio_balloon *vb; 908 int err; 909 910 if (!vdev->config->get) { 911 dev_err(&vdev->dev, "%s failure: config access disabled\n", 912 __func__); 913 return -EINVAL; 914 } 915 916 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL); 917 if (!vb) { 918 err = -ENOMEM; 919 goto out; 920 } 921 922 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); 923 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); 924 spin_lock_init(&vb->stop_update_lock); 925 mutex_init(&vb->balloon_lock); 926 init_waitqueue_head(&vb->acked); 927 vb->vdev = vdev; 928 929 balloon_devinfo_init(&vb->vb_dev_info); 930 931 err = init_vqs(vb); 932 if (err) 933 goto out_free_vb; 934 935 #ifdef CONFIG_BALLOON_COMPACTION 936 vb->vb_dev_info.migratepage = virtballoon_migratepage; 937 #endif 938 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 939 /* 940 * There is always one entry reserved for cmd id, so the ring 941 * size needs to be at least two to report free page hints. 942 */ 943 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) { 944 err = -ENOSPC; 945 goto out_del_vqs; 946 } 947 vb->balloon_wq = alloc_workqueue("balloon-wq", 948 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); 949 if (!vb->balloon_wq) { 950 err = -ENOMEM; 951 goto out_del_vqs; 952 } 953 INIT_WORK(&vb->report_free_page_work, report_free_page_func); 954 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP; 955 vb->cmd_id_active = cpu_to_virtio32(vb->vdev, 956 VIRTIO_BALLOON_CMD_ID_STOP); 957 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev, 958 VIRTIO_BALLOON_CMD_ID_STOP); 959 spin_lock_init(&vb->free_page_list_lock); 960 INIT_LIST_HEAD(&vb->free_page_list); 961 /* 962 * We're allowed to reuse any free pages, even if they are 963 * still to be processed by the host. 964 */ 965 err = virtio_balloon_register_shrinker(vb); 966 if (err) 967 goto out_del_balloon_wq; 968 } 969 970 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { 971 vb->oom_nb.notifier_call = virtio_balloon_oom_notify; 972 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY; 973 err = register_oom_notifier(&vb->oom_nb); 974 if (err < 0) 975 goto out_unregister_shrinker; 976 } 977 978 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { 979 /* Start with poison val of 0 representing general init */ 980 __u32 poison_val = 0; 981 982 /* 983 * Let the hypervisor know that we are expecting a 984 * specific value to be written back in balloon pages. 985 * 986 * If the PAGE_POISON value was larger than a byte we would 987 * need to byte swap poison_val here to guarantee it is 988 * little-endian. However for now it is a single byte so we 989 * can pass it as-is. 990 */ 991 if (!want_init_on_free()) 992 memset(&poison_val, PAGE_POISON, sizeof(poison_val)); 993 994 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, 995 poison_val, &poison_val); 996 } 997 998 vb->pr_dev_info.report = virtballoon_free_page_report; 999 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { 1000 unsigned int capacity; 1001 1002 capacity = virtqueue_get_vring_size(vb->reporting_vq); 1003 if (capacity < PAGE_REPORTING_CAPACITY) { 1004 err = -ENOSPC; 1005 goto out_unregister_oom; 1006 } 1007 1008 /* 1009 * The default page reporting order is @pageblock_order, which 1010 * corresponds to 512MB in size on ARM64 when 64KB base page 1011 * size is used. The page reporting won't be triggered if the 1012 * freeing page can't come up with a free area like that huge. 1013 * So we specify the page reporting order to 5, corresponding 1014 * to 2MB. It helps to avoid THP splitting if 4KB base page 1015 * size is used by host. 1016 * 1017 * Ideally, the page reporting order is selected based on the 1018 * host's base page size. However, it needs more work to report 1019 * that value. The hard-coded order would be fine currently. 1020 */ 1021 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES) 1022 vb->pr_dev_info.order = 5; 1023 #endif 1024 1025 err = page_reporting_register(&vb->pr_dev_info); 1026 if (err) 1027 goto out_unregister_oom; 1028 } 1029 1030 spin_lock_init(&vb->adjustment_lock); 1031 1032 virtio_device_ready(vdev); 1033 1034 if (towards_target(vb)) 1035 virtballoon_changed(vdev); 1036 return 0; 1037 1038 out_unregister_oom: 1039 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 1040 unregister_oom_notifier(&vb->oom_nb); 1041 out_unregister_shrinker: 1042 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1043 virtio_balloon_unregister_shrinker(vb); 1044 out_del_balloon_wq: 1045 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1046 destroy_workqueue(vb->balloon_wq); 1047 out_del_vqs: 1048 vdev->config->del_vqs(vdev); 1049 out_free_vb: 1050 kfree(vb); 1051 out: 1052 return err; 1053 } 1054 1055 static void remove_common(struct virtio_balloon *vb) 1056 { 1057 /* There might be pages left in the balloon: free them. */ 1058 while (vb->num_pages) 1059 leak_balloon(vb, vb->num_pages); 1060 update_balloon_size(vb); 1061 1062 /* There might be free pages that are being reported: release them. */ 1063 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1064 return_free_pages_to_mm(vb, ULONG_MAX); 1065 1066 /* Now we reset the device so we can clean up the queues. */ 1067 virtio_reset_device(vb->vdev); 1068 1069 vb->vdev->config->del_vqs(vb->vdev); 1070 } 1071 1072 static void virtballoon_remove(struct virtio_device *vdev) 1073 { 1074 struct virtio_balloon *vb = vdev->priv; 1075 1076 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) 1077 page_reporting_unregister(&vb->pr_dev_info); 1078 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 1079 unregister_oom_notifier(&vb->oom_nb); 1080 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1081 virtio_balloon_unregister_shrinker(vb); 1082 spin_lock_irq(&vb->stop_update_lock); 1083 vb->stop_update = true; 1084 spin_unlock_irq(&vb->stop_update_lock); 1085 cancel_work_sync(&vb->update_balloon_size_work); 1086 cancel_work_sync(&vb->update_balloon_stats_work); 1087 1088 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 1089 cancel_work_sync(&vb->report_free_page_work); 1090 destroy_workqueue(vb->balloon_wq); 1091 } 1092 1093 remove_common(vb); 1094 kfree(vb); 1095 } 1096 1097 #ifdef CONFIG_PM_SLEEP 1098 static int virtballoon_freeze(struct virtio_device *vdev) 1099 { 1100 struct virtio_balloon *vb = vdev->priv; 1101 1102 /* 1103 * The workqueue is already frozen by the PM core before this 1104 * function is called. 1105 */ 1106 remove_common(vb); 1107 return 0; 1108 } 1109 1110 static int virtballoon_restore(struct virtio_device *vdev) 1111 { 1112 struct virtio_balloon *vb = vdev->priv; 1113 int ret; 1114 1115 ret = init_vqs(vdev->priv); 1116 if (ret) 1117 return ret; 1118 1119 virtio_device_ready(vdev); 1120 1121 if (towards_target(vb)) 1122 virtballoon_changed(vdev); 1123 update_balloon_size(vb); 1124 return 0; 1125 } 1126 #endif 1127 1128 static int virtballoon_validate(struct virtio_device *vdev) 1129 { 1130 /* 1131 * Inform the hypervisor that our pages are poisoned or 1132 * initialized. If we cannot do that then we should disable 1133 * page reporting as it could potentially change the contents 1134 * of our free pages. 1135 */ 1136 if (!want_init_on_free() && !page_poisoning_enabled_static()) 1137 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); 1138 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) 1139 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); 1140 1141 __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM); 1142 return 0; 1143 } 1144 1145 static unsigned int features[] = { 1146 VIRTIO_BALLOON_F_MUST_TELL_HOST, 1147 VIRTIO_BALLOON_F_STATS_VQ, 1148 VIRTIO_BALLOON_F_DEFLATE_ON_OOM, 1149 VIRTIO_BALLOON_F_FREE_PAGE_HINT, 1150 VIRTIO_BALLOON_F_PAGE_POISON, 1151 VIRTIO_BALLOON_F_REPORTING, 1152 }; 1153 1154 static struct virtio_driver virtio_balloon_driver = { 1155 .feature_table = features, 1156 .feature_table_size = ARRAY_SIZE(features), 1157 .driver.name = KBUILD_MODNAME, 1158 .driver.owner = THIS_MODULE, 1159 .id_table = id_table, 1160 .validate = virtballoon_validate, 1161 .probe = virtballoon_probe, 1162 .remove = virtballoon_remove, 1163 .config_changed = virtballoon_changed, 1164 #ifdef CONFIG_PM_SLEEP 1165 .freeze = virtballoon_freeze, 1166 .restore = virtballoon_restore, 1167 #endif 1168 }; 1169 1170 module_virtio_driver(virtio_balloon_driver); 1171 MODULE_DEVICE_TABLE(virtio, id_table); 1172 MODULE_DESCRIPTION("Virtio balloon driver"); 1173 MODULE_LICENSE("GPL"); 1174