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/mount.h> 21 #include <linux/magic.h> 22 #include <linux/pseudo_fs.h> 23 #include <linux/page_reporting.h> 24 25 /* 26 * Balloon device works in 4K page units. So each page is pointed to by 27 * multiple balloon pages. All memory counters in this driver are in balloon 28 * page units. 29 */ 30 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 31 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 32 /* Maximum number of (4k) pages to deflate on OOM notifications. */ 33 #define VIRTIO_BALLOON_OOM_NR_PAGES 256 34 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80 35 36 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ 37 __GFP_NOMEMALLOC) 38 /* The order of free page blocks to report to host */ 39 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1) 40 /* The size of a free page block in bytes */ 41 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \ 42 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT)) 43 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER) 44 45 #ifdef CONFIG_BALLOON_COMPACTION 46 static struct vfsmount *balloon_mnt; 47 #endif 48 49 enum virtio_balloon_vq { 50 VIRTIO_BALLOON_VQ_INFLATE, 51 VIRTIO_BALLOON_VQ_DEFLATE, 52 VIRTIO_BALLOON_VQ_STATS, 53 VIRTIO_BALLOON_VQ_FREE_PAGE, 54 VIRTIO_BALLOON_VQ_REPORTING, 55 VIRTIO_BALLOON_VQ_MAX 56 }; 57 58 enum virtio_balloon_config_read { 59 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, 60 }; 61 62 struct virtio_balloon { 63 struct virtio_device *vdev; 64 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; 65 66 /* Balloon's own wq for cpu-intensive work items */ 67 struct workqueue_struct *balloon_wq; 68 /* The free page reporting work item submitted to the balloon wq */ 69 struct work_struct report_free_page_work; 70 71 /* The balloon servicing is delegated to a freezable workqueue. */ 72 struct work_struct update_balloon_stats_work; 73 struct work_struct update_balloon_size_work; 74 75 /* Prevent updating balloon when it is being canceled. */ 76 spinlock_t stop_update_lock; 77 bool stop_update; 78 /* Bitmap to indicate if reading the related config fields are needed */ 79 unsigned long config_read_bitmap; 80 81 /* The list of allocated free pages, waiting to be given back to mm */ 82 struct list_head free_page_list; 83 spinlock_t free_page_list_lock; 84 /* The number of free page blocks on the above list */ 85 unsigned long num_free_page_blocks; 86 /* 87 * The cmd id received from host. 88 * Read it via virtio_balloon_cmd_id_received to get the latest value 89 * sent from host. 90 */ 91 u32 cmd_id_received_cache; 92 /* The cmd id that is actively in use */ 93 __virtio32 cmd_id_active; 94 /* Buffer to store the stop sign */ 95 __virtio32 cmd_id_stop; 96 97 /* Waiting for host to ack the pages we released. */ 98 wait_queue_head_t acked; 99 100 /* Number of balloon pages we've told the Host we're not using. */ 101 unsigned int num_pages; 102 /* 103 * The pages we've told the Host we're not using are enqueued 104 * at vb_dev_info->pages list. 105 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 106 * to num_pages above. 107 */ 108 struct balloon_dev_info vb_dev_info; 109 110 /* Synchronize access/update to this struct virtio_balloon elements */ 111 struct mutex balloon_lock; 112 113 /* The array of pfns we tell the Host about. */ 114 unsigned int num_pfns; 115 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 116 117 /* Memory statistics */ 118 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 119 120 /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */ 121 struct shrinker shrinker; 122 123 /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */ 124 struct notifier_block oom_nb; 125 126 /* Free page reporting device */ 127 struct virtqueue *reporting_vq; 128 struct page_reporting_dev_info pr_dev_info; 129 }; 130 131 static struct virtio_device_id id_table[] = { 132 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 133 { 0 }, 134 }; 135 136 static u32 page_to_balloon_pfn(struct page *page) 137 { 138 unsigned long pfn = page_to_pfn(page); 139 140 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 141 /* Convert pfn from Linux page size to balloon page size. */ 142 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 143 } 144 145 static void balloon_ack(struct virtqueue *vq) 146 { 147 struct virtio_balloon *vb = vq->vdev->priv; 148 149 wake_up(&vb->acked); 150 } 151 152 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 153 { 154 struct scatterlist sg; 155 unsigned int len; 156 157 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 158 159 /* We should always be able to add one buffer to an empty queue. */ 160 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 161 virtqueue_kick(vq); 162 163 /* When host has read buffer, this completes via balloon_ack */ 164 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 165 166 } 167 168 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, 169 struct scatterlist *sg, unsigned int nents) 170 { 171 struct virtio_balloon *vb = 172 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); 173 struct virtqueue *vq = vb->reporting_vq; 174 unsigned int unused, err; 175 176 /* We should always be able to add these buffers to an empty queue. */ 177 err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN); 178 179 /* 180 * In the extremely unlikely case that something has occurred and we 181 * are able to trigger an error we will simply display a warning 182 * and exit without actually processing the pages. 183 */ 184 if (WARN_ON_ONCE(err)) 185 return err; 186 187 virtqueue_kick(vq); 188 189 /* When host has read buffer, this completes via balloon_ack */ 190 wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); 191 192 return 0; 193 } 194 195 static void set_page_pfns(struct virtio_balloon *vb, 196 __virtio32 pfns[], struct page *page) 197 { 198 unsigned int i; 199 200 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX); 201 202 /* 203 * Set balloon pfns pointing at this page. 204 * Note that the first pfn points at start of the page. 205 */ 206 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 207 pfns[i] = cpu_to_virtio32(vb->vdev, 208 page_to_balloon_pfn(page) + i); 209 } 210 211 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) 212 { 213 unsigned num_allocated_pages; 214 unsigned num_pfns; 215 struct page *page; 216 LIST_HEAD(pages); 217 218 /* We can only do one array worth at a time. */ 219 num = min(num, ARRAY_SIZE(vb->pfns)); 220 221 for (num_pfns = 0; num_pfns < num; 222 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 223 struct page *page = balloon_page_alloc(); 224 225 if (!page) { 226 dev_info_ratelimited(&vb->vdev->dev, 227 "Out of puff! Can't get %u pages\n", 228 VIRTIO_BALLOON_PAGES_PER_PAGE); 229 /* Sleep for at least 1/5 of a second before retry. */ 230 msleep(200); 231 break; 232 } 233 234 balloon_page_push(&pages, page); 235 } 236 237 mutex_lock(&vb->balloon_lock); 238 239 vb->num_pfns = 0; 240 241 while ((page = balloon_page_pop(&pages))) { 242 balloon_page_enqueue(&vb->vb_dev_info, page); 243 244 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 245 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 246 if (!virtio_has_feature(vb->vdev, 247 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 248 adjust_managed_page_count(page, -1); 249 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; 250 } 251 252 num_allocated_pages = vb->num_pfns; 253 /* Did we get any? */ 254 if (vb->num_pfns != 0) 255 tell_host(vb, vb->inflate_vq); 256 mutex_unlock(&vb->balloon_lock); 257 258 return num_allocated_pages; 259 } 260 261 static void release_pages_balloon(struct virtio_balloon *vb, 262 struct list_head *pages) 263 { 264 struct page *page, *next; 265 266 list_for_each_entry_safe(page, next, pages, lru) { 267 if (!virtio_has_feature(vb->vdev, 268 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 269 adjust_managed_page_count(page, 1); 270 list_del(&page->lru); 271 put_page(page); /* balloon reference */ 272 } 273 } 274 275 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) 276 { 277 unsigned num_freed_pages; 278 struct page *page; 279 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 280 LIST_HEAD(pages); 281 282 /* We can only do one array worth at a time. */ 283 num = min(num, ARRAY_SIZE(vb->pfns)); 284 285 mutex_lock(&vb->balloon_lock); 286 /* We can't release more pages than taken */ 287 num = min(num, (size_t)vb->num_pages); 288 for (vb->num_pfns = 0; vb->num_pfns < num; 289 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 290 page = balloon_page_dequeue(vb_dev_info); 291 if (!page) 292 break; 293 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 294 list_add(&page->lru, &pages); 295 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 296 } 297 298 num_freed_pages = vb->num_pfns; 299 /* 300 * Note that if 301 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 302 * is true, we *have* to do it in this order 303 */ 304 if (vb->num_pfns != 0) 305 tell_host(vb, vb->deflate_vq); 306 release_pages_balloon(vb, &pages); 307 mutex_unlock(&vb->balloon_lock); 308 return num_freed_pages; 309 } 310 311 static inline void update_stat(struct virtio_balloon *vb, int idx, 312 u16 tag, u64 val) 313 { 314 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 315 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag); 316 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); 317 } 318 319 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 320 321 static unsigned int update_balloon_stats(struct virtio_balloon *vb) 322 { 323 unsigned long events[NR_VM_EVENT_ITEMS]; 324 struct sysinfo i; 325 unsigned int idx = 0; 326 long available; 327 unsigned long caches; 328 329 all_vm_events(events); 330 si_meminfo(&i); 331 332 available = si_mem_available(); 333 caches = global_node_page_state(NR_FILE_PAGES); 334 335 #ifdef CONFIG_VM_EVENT_COUNTERS 336 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 337 pages_to_bytes(events[PSWPIN])); 338 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 339 pages_to_bytes(events[PSWPOUT])); 340 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 341 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 342 #ifdef CONFIG_HUGETLB_PAGE 343 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC, 344 events[HTLB_BUDDY_PGALLOC]); 345 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL, 346 events[HTLB_BUDDY_PGALLOC_FAIL]); 347 #endif 348 #endif 349 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 350 pages_to_bytes(i.freeram)); 351 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 352 pages_to_bytes(i.totalram)); 353 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, 354 pages_to_bytes(available)); 355 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES, 356 pages_to_bytes(caches)); 357 358 return idx; 359 } 360 361 /* 362 * While most virtqueues communicate guest-initiated requests to the hypervisor, 363 * the stats queue operates in reverse. The driver initializes the virtqueue 364 * with a single buffer. From that point forward, all conversations consist of 365 * a hypervisor request (a call to this function) which directs us to refill 366 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 367 * we delegate the job to a freezable workqueue that will do the actual work via 368 * stats_handle_request(). 369 */ 370 static void stats_request(struct virtqueue *vq) 371 { 372 struct virtio_balloon *vb = vq->vdev->priv; 373 374 spin_lock(&vb->stop_update_lock); 375 if (!vb->stop_update) 376 queue_work(system_freezable_wq, &vb->update_balloon_stats_work); 377 spin_unlock(&vb->stop_update_lock); 378 } 379 380 static void stats_handle_request(struct virtio_balloon *vb) 381 { 382 struct virtqueue *vq; 383 struct scatterlist sg; 384 unsigned int len, num_stats; 385 386 num_stats = update_balloon_stats(vb); 387 388 vq = vb->stats_vq; 389 if (!virtqueue_get_buf(vq, &len)) 390 return; 391 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 392 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 393 virtqueue_kick(vq); 394 } 395 396 static inline s64 towards_target(struct virtio_balloon *vb) 397 { 398 s64 target; 399 u32 num_pages; 400 401 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, 402 &num_pages); 403 404 /* Legacy balloon config space is LE, unlike all other devices. */ 405 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 406 num_pages = le32_to_cpu((__force __le32)num_pages); 407 408 target = num_pages; 409 return target - vb->num_pages; 410 } 411 412 /* Gives back @num_to_return blocks of free pages to mm. */ 413 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, 414 unsigned long num_to_return) 415 { 416 struct page *page; 417 unsigned long num_returned; 418 419 spin_lock_irq(&vb->free_page_list_lock); 420 for (num_returned = 0; num_returned < num_to_return; num_returned++) { 421 page = balloon_page_pop(&vb->free_page_list); 422 if (!page) 423 break; 424 free_pages((unsigned long)page_address(page), 425 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 426 } 427 vb->num_free_page_blocks -= num_returned; 428 spin_unlock_irq(&vb->free_page_list_lock); 429 430 return num_returned; 431 } 432 433 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) 434 { 435 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 436 return; 437 438 /* No need to queue the work if the bit was already set. */ 439 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 440 &vb->config_read_bitmap)) 441 return; 442 443 queue_work(vb->balloon_wq, &vb->report_free_page_work); 444 } 445 446 static void virtballoon_changed(struct virtio_device *vdev) 447 { 448 struct virtio_balloon *vb = vdev->priv; 449 unsigned long flags; 450 451 spin_lock_irqsave(&vb->stop_update_lock, flags); 452 if (!vb->stop_update) { 453 queue_work(system_freezable_wq, 454 &vb->update_balloon_size_work); 455 virtio_balloon_queue_free_page_work(vb); 456 } 457 spin_unlock_irqrestore(&vb->stop_update_lock, flags); 458 } 459 460 static void update_balloon_size(struct virtio_balloon *vb) 461 { 462 u32 actual = vb->num_pages; 463 464 /* Legacy balloon config space is LE, unlike all other devices. */ 465 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 466 actual = (__force u32)cpu_to_le32(actual); 467 468 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, 469 &actual); 470 } 471 472 static void update_balloon_stats_func(struct work_struct *work) 473 { 474 struct virtio_balloon *vb; 475 476 vb = container_of(work, struct virtio_balloon, 477 update_balloon_stats_work); 478 stats_handle_request(vb); 479 } 480 481 static void update_balloon_size_func(struct work_struct *work) 482 { 483 struct virtio_balloon *vb; 484 s64 diff; 485 486 vb = container_of(work, struct virtio_balloon, 487 update_balloon_size_work); 488 diff = towards_target(vb); 489 490 if (!diff) 491 return; 492 493 if (diff > 0) 494 diff -= fill_balloon(vb, diff); 495 else 496 diff += leak_balloon(vb, -diff); 497 update_balloon_size(vb); 498 499 if (diff) 500 queue_work(system_freezable_wq, work); 501 } 502 503 static int init_vqs(struct virtio_balloon *vb) 504 { 505 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX]; 506 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX]; 507 const char *names[VIRTIO_BALLOON_VQ_MAX]; 508 int err; 509 510 /* 511 * Inflateq and deflateq are used unconditionally. The names[] 512 * will be NULL if the related feature is not enabled, which will 513 * cause no allocation for the corresponding virtqueue in find_vqs. 514 */ 515 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack; 516 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate"; 517 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack; 518 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; 519 callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL; 520 names[VIRTIO_BALLOON_VQ_STATS] = NULL; 521 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 522 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 523 names[VIRTIO_BALLOON_VQ_REPORTING] = NULL; 524 525 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 526 names[VIRTIO_BALLOON_VQ_STATS] = "stats"; 527 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request; 528 } 529 530 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 531 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq"; 532 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 533 } 534 535 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { 536 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq"; 537 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack; 538 } 539 540 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, 541 vqs, callbacks, names, NULL, NULL); 542 if (err) 543 return err; 544 545 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; 546 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; 547 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 548 struct scatterlist sg; 549 unsigned int num_stats; 550 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS]; 551 552 /* 553 * Prime this virtqueue with one buffer so the hypervisor can 554 * use it to signal us later (it can't be broken yet!). 555 */ 556 num_stats = update_balloon_stats(vb); 557 558 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 559 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, 560 GFP_KERNEL); 561 if (err) { 562 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n", 563 __func__); 564 return err; 565 } 566 virtqueue_kick(vb->stats_vq); 567 } 568 569 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 570 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; 571 572 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) 573 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING]; 574 575 return 0; 576 } 577 578 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb) 579 { 580 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 581 &vb->config_read_bitmap)) 582 virtio_cread(vb->vdev, struct virtio_balloon_config, 583 free_page_hint_cmd_id, 584 &vb->cmd_id_received_cache); 585 586 return vb->cmd_id_received_cache; 587 } 588 589 static int send_cmd_id_start(struct virtio_balloon *vb) 590 { 591 struct scatterlist sg; 592 struct virtqueue *vq = vb->free_page_vq; 593 int err, unused; 594 595 /* Detach all the used buffers from the vq */ 596 while (virtqueue_get_buf(vq, &unused)) 597 ; 598 599 vb->cmd_id_active = virtio32_to_cpu(vb->vdev, 600 virtio_balloon_cmd_id_received(vb)); 601 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active)); 602 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL); 603 if (!err) 604 virtqueue_kick(vq); 605 return err; 606 } 607 608 static int send_cmd_id_stop(struct virtio_balloon *vb) 609 { 610 struct scatterlist sg; 611 struct virtqueue *vq = vb->free_page_vq; 612 int err, unused; 613 614 /* Detach all the used buffers from the vq */ 615 while (virtqueue_get_buf(vq, &unused)) 616 ; 617 618 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop)); 619 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL); 620 if (!err) 621 virtqueue_kick(vq); 622 return err; 623 } 624 625 static int get_free_page_and_send(struct virtio_balloon *vb) 626 { 627 struct virtqueue *vq = vb->free_page_vq; 628 struct page *page; 629 struct scatterlist sg; 630 int err, unused; 631 void *p; 632 633 /* Detach all the used buffers from the vq */ 634 while (virtqueue_get_buf(vq, &unused)) 635 ; 636 637 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG, 638 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 639 /* 640 * When the allocation returns NULL, it indicates that we have got all 641 * the possible free pages, so return -EINTR to stop. 642 */ 643 if (!page) 644 return -EINTR; 645 646 p = page_address(page); 647 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES); 648 /* There is always 1 entry reserved for the cmd id to use. */ 649 if (vq->num_free > 1) { 650 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL); 651 if (unlikely(err)) { 652 free_pages((unsigned long)p, 653 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 654 return err; 655 } 656 virtqueue_kick(vq); 657 spin_lock_irq(&vb->free_page_list_lock); 658 balloon_page_push(&vb->free_page_list, page); 659 vb->num_free_page_blocks++; 660 spin_unlock_irq(&vb->free_page_list_lock); 661 } else { 662 /* 663 * The vq has no available entry to add this page block, so 664 * just free it. 665 */ 666 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); 667 } 668 669 return 0; 670 } 671 672 static int send_free_pages(struct virtio_balloon *vb) 673 { 674 int err; 675 u32 cmd_id_active; 676 677 while (1) { 678 /* 679 * If a stop id or a new cmd id was just received from host, 680 * stop the reporting. 681 */ 682 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active); 683 if (unlikely(cmd_id_active != 684 virtio_balloon_cmd_id_received(vb))) 685 break; 686 687 /* 688 * The free page blocks are allocated and sent to host one by 689 * one. 690 */ 691 err = get_free_page_and_send(vb); 692 if (err == -EINTR) 693 break; 694 else if (unlikely(err)) 695 return err; 696 } 697 698 return 0; 699 } 700 701 static void virtio_balloon_report_free_page(struct virtio_balloon *vb) 702 { 703 int err; 704 struct device *dev = &vb->vdev->dev; 705 706 /* Start by sending the received cmd id to host with an outbuf. */ 707 err = send_cmd_id_start(vb); 708 if (unlikely(err)) 709 dev_err(dev, "Failed to send a start id, err = %d\n", err); 710 711 err = send_free_pages(vb); 712 if (unlikely(err)) 713 dev_err(dev, "Failed to send a free page, err = %d\n", err); 714 715 /* End by sending a stop id to host with an outbuf. */ 716 err = send_cmd_id_stop(vb); 717 if (unlikely(err)) 718 dev_err(dev, "Failed to send a stop id, err = %d\n", err); 719 } 720 721 static void report_free_page_func(struct work_struct *work) 722 { 723 struct virtio_balloon *vb = container_of(work, struct virtio_balloon, 724 report_free_page_work); 725 u32 cmd_id_received; 726 727 cmd_id_received = virtio_balloon_cmd_id_received(vb); 728 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { 729 /* Pass ULONG_MAX to give back all the free pages */ 730 return_free_pages_to_mm(vb, ULONG_MAX); 731 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && 732 cmd_id_received != 733 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { 734 virtio_balloon_report_free_page(vb); 735 } 736 } 737 738 #ifdef CONFIG_BALLOON_COMPACTION 739 /* 740 * virtballoon_migratepage - perform the balloon page migration on behalf of 741 * a compation thread. (called under page lock) 742 * @vb_dev_info: the balloon device 743 * @newpage: page that will replace the isolated page after migration finishes. 744 * @page : the isolated (old) page that is about to be migrated to newpage. 745 * @mode : compaction mode -- not used for balloon page migration. 746 * 747 * After a ballooned page gets isolated by compaction procedures, this is the 748 * function that performs the page migration on behalf of a compaction thread 749 * The page migration for virtio balloon is done in a simple swap fashion which 750 * follows these two macro steps: 751 * 1) insert newpage into vb->pages list and update the host about it; 752 * 2) update the host about the old page removed from vb->pages list; 753 * 754 * This function preforms the balloon page migration task. 755 * Called through balloon_mapping->a_ops->migratepage 756 */ 757 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 758 struct page *newpage, struct page *page, enum migrate_mode mode) 759 { 760 struct virtio_balloon *vb = container_of(vb_dev_info, 761 struct virtio_balloon, vb_dev_info); 762 unsigned long flags; 763 764 /* 765 * In order to avoid lock contention while migrating pages concurrently 766 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 767 * this turn, as it is easier to retry the page migration later. 768 * This also prevents fill_balloon() getting stuck into a mutex 769 * recursion in the case it ends up triggering memory compaction 770 * while it is attempting to inflate the ballon. 771 */ 772 if (!mutex_trylock(&vb->balloon_lock)) 773 return -EAGAIN; 774 775 get_page(newpage); /* balloon reference */ 776 777 /* 778 * When we migrate a page to a different zone and adjusted the 779 * managed page count when inflating, we have to fixup the count of 780 * both involved zones. 781 */ 782 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) && 783 page_zone(page) != page_zone(newpage)) { 784 adjust_managed_page_count(page, 1); 785 adjust_managed_page_count(newpage, -1); 786 } 787 788 /* balloon's page migration 1st step -- inflate "newpage" */ 789 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 790 balloon_page_insert(vb_dev_info, newpage); 791 vb_dev_info->isolated_pages--; 792 __count_vm_event(BALLOON_MIGRATE); 793 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 794 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 795 set_page_pfns(vb, vb->pfns, newpage); 796 tell_host(vb, vb->inflate_vq); 797 798 /* balloon's page migration 2nd step -- deflate "page" */ 799 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 800 balloon_page_delete(page); 801 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 802 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 803 set_page_pfns(vb, vb->pfns, page); 804 tell_host(vb, vb->deflate_vq); 805 806 mutex_unlock(&vb->balloon_lock); 807 808 put_page(page); /* balloon reference */ 809 810 return MIGRATEPAGE_SUCCESS; 811 } 812 813 static int balloon_init_fs_context(struct fs_context *fc) 814 { 815 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM; 816 } 817 818 static struct file_system_type balloon_fs = { 819 .name = "balloon-kvm", 820 .init_fs_context = balloon_init_fs_context, 821 .kill_sb = kill_anon_super, 822 }; 823 824 #endif /* CONFIG_BALLOON_COMPACTION */ 825 826 static unsigned long shrink_free_pages(struct virtio_balloon *vb, 827 unsigned long pages_to_free) 828 { 829 unsigned long blocks_to_free, blocks_freed; 830 831 pages_to_free = round_up(pages_to_free, 832 VIRTIO_BALLOON_HINT_BLOCK_PAGES); 833 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES; 834 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free); 835 836 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 837 } 838 839 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, 840 struct shrink_control *sc) 841 { 842 struct virtio_balloon *vb = container_of(shrinker, 843 struct virtio_balloon, shrinker); 844 845 return shrink_free_pages(vb, sc->nr_to_scan); 846 } 847 848 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, 849 struct shrink_control *sc) 850 { 851 struct virtio_balloon *vb = container_of(shrinker, 852 struct virtio_balloon, shrinker); 853 854 return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 855 } 856 857 static int virtio_balloon_oom_notify(struct notifier_block *nb, 858 unsigned long dummy, void *parm) 859 { 860 struct virtio_balloon *vb = container_of(nb, 861 struct virtio_balloon, oom_nb); 862 unsigned long *freed = parm; 863 864 *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) / 865 VIRTIO_BALLOON_PAGES_PER_PAGE; 866 update_balloon_size(vb); 867 868 return NOTIFY_OK; 869 } 870 871 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) 872 { 873 unregister_shrinker(&vb->shrinker); 874 } 875 876 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) 877 { 878 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan; 879 vb->shrinker.count_objects = virtio_balloon_shrinker_count; 880 vb->shrinker.seeks = DEFAULT_SEEKS; 881 882 return register_shrinker(&vb->shrinker); 883 } 884 885 static int virtballoon_probe(struct virtio_device *vdev) 886 { 887 struct virtio_balloon *vb; 888 int err; 889 890 if (!vdev->config->get) { 891 dev_err(&vdev->dev, "%s failure: config access disabled\n", 892 __func__); 893 return -EINVAL; 894 } 895 896 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL); 897 if (!vb) { 898 err = -ENOMEM; 899 goto out; 900 } 901 902 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); 903 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); 904 spin_lock_init(&vb->stop_update_lock); 905 mutex_init(&vb->balloon_lock); 906 init_waitqueue_head(&vb->acked); 907 vb->vdev = vdev; 908 909 balloon_devinfo_init(&vb->vb_dev_info); 910 911 err = init_vqs(vb); 912 if (err) 913 goto out_free_vb; 914 915 #ifdef CONFIG_BALLOON_COMPACTION 916 balloon_mnt = kern_mount(&balloon_fs); 917 if (IS_ERR(balloon_mnt)) { 918 err = PTR_ERR(balloon_mnt); 919 goto out_del_vqs; 920 } 921 922 vb->vb_dev_info.migratepage = virtballoon_migratepage; 923 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb); 924 if (IS_ERR(vb->vb_dev_info.inode)) { 925 err = PTR_ERR(vb->vb_dev_info.inode); 926 goto out_kern_unmount; 927 } 928 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops; 929 #endif 930 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 931 /* 932 * There is always one entry reserved for cmd id, so the ring 933 * size needs to be at least two to report free page hints. 934 */ 935 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) { 936 err = -ENOSPC; 937 goto out_iput; 938 } 939 vb->balloon_wq = alloc_workqueue("balloon-wq", 940 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); 941 if (!vb->balloon_wq) { 942 err = -ENOMEM; 943 goto out_iput; 944 } 945 INIT_WORK(&vb->report_free_page_work, report_free_page_func); 946 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP; 947 vb->cmd_id_active = cpu_to_virtio32(vb->vdev, 948 VIRTIO_BALLOON_CMD_ID_STOP); 949 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev, 950 VIRTIO_BALLOON_CMD_ID_STOP); 951 spin_lock_init(&vb->free_page_list_lock); 952 INIT_LIST_HEAD(&vb->free_page_list); 953 /* 954 * We're allowed to reuse any free pages, even if they are 955 * still to be processed by the host. 956 */ 957 err = virtio_balloon_register_shrinker(vb); 958 if (err) 959 goto out_del_balloon_wq; 960 } 961 962 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { 963 vb->oom_nb.notifier_call = virtio_balloon_oom_notify; 964 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY; 965 err = register_oom_notifier(&vb->oom_nb); 966 if (err < 0) 967 goto out_unregister_shrinker; 968 } 969 970 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { 971 /* Start with poison val of 0 representing general init */ 972 __u32 poison_val = 0; 973 974 /* 975 * Let the hypervisor know that we are expecting a 976 * specific value to be written back in balloon pages. 977 */ 978 if (!want_init_on_free()) 979 memset(&poison_val, PAGE_POISON, sizeof(poison_val)); 980 981 virtio_cwrite(vb->vdev, struct virtio_balloon_config, 982 poison_val, &poison_val); 983 } 984 985 vb->pr_dev_info.report = virtballoon_free_page_report; 986 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { 987 unsigned int capacity; 988 989 capacity = virtqueue_get_vring_size(vb->reporting_vq); 990 if (capacity < PAGE_REPORTING_CAPACITY) { 991 err = -ENOSPC; 992 goto out_unregister_oom; 993 } 994 995 err = page_reporting_register(&vb->pr_dev_info); 996 if (err) 997 goto out_unregister_oom; 998 } 999 1000 virtio_device_ready(vdev); 1001 1002 if (towards_target(vb)) 1003 virtballoon_changed(vdev); 1004 return 0; 1005 1006 out_unregister_oom: 1007 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 1008 unregister_oom_notifier(&vb->oom_nb); 1009 out_unregister_shrinker: 1010 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1011 virtio_balloon_unregister_shrinker(vb); 1012 out_del_balloon_wq: 1013 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1014 destroy_workqueue(vb->balloon_wq); 1015 out_iput: 1016 #ifdef CONFIG_BALLOON_COMPACTION 1017 iput(vb->vb_dev_info.inode); 1018 out_kern_unmount: 1019 kern_unmount(balloon_mnt); 1020 out_del_vqs: 1021 #endif 1022 vdev->config->del_vqs(vdev); 1023 out_free_vb: 1024 kfree(vb); 1025 out: 1026 return err; 1027 } 1028 1029 static void remove_common(struct virtio_balloon *vb) 1030 { 1031 /* There might be pages left in the balloon: free them. */ 1032 while (vb->num_pages) 1033 leak_balloon(vb, vb->num_pages); 1034 update_balloon_size(vb); 1035 1036 /* There might be free pages that are being reported: release them. */ 1037 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1038 return_free_pages_to_mm(vb, ULONG_MAX); 1039 1040 /* Now we reset the device so we can clean up the queues. */ 1041 vb->vdev->config->reset(vb->vdev); 1042 1043 vb->vdev->config->del_vqs(vb->vdev); 1044 } 1045 1046 static void virtballoon_remove(struct virtio_device *vdev) 1047 { 1048 struct virtio_balloon *vb = vdev->priv; 1049 1050 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) 1051 page_reporting_unregister(&vb->pr_dev_info); 1052 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 1053 unregister_oom_notifier(&vb->oom_nb); 1054 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 1055 virtio_balloon_unregister_shrinker(vb); 1056 spin_lock_irq(&vb->stop_update_lock); 1057 vb->stop_update = true; 1058 spin_unlock_irq(&vb->stop_update_lock); 1059 cancel_work_sync(&vb->update_balloon_size_work); 1060 cancel_work_sync(&vb->update_balloon_stats_work); 1061 1062 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 1063 cancel_work_sync(&vb->report_free_page_work); 1064 destroy_workqueue(vb->balloon_wq); 1065 } 1066 1067 remove_common(vb); 1068 #ifdef CONFIG_BALLOON_COMPACTION 1069 if (vb->vb_dev_info.inode) 1070 iput(vb->vb_dev_info.inode); 1071 1072 kern_unmount(balloon_mnt); 1073 #endif 1074 kfree(vb); 1075 } 1076 1077 #ifdef CONFIG_PM_SLEEP 1078 static int virtballoon_freeze(struct virtio_device *vdev) 1079 { 1080 struct virtio_balloon *vb = vdev->priv; 1081 1082 /* 1083 * The workqueue is already frozen by the PM core before this 1084 * function is called. 1085 */ 1086 remove_common(vb); 1087 return 0; 1088 } 1089 1090 static int virtballoon_restore(struct virtio_device *vdev) 1091 { 1092 struct virtio_balloon *vb = vdev->priv; 1093 int ret; 1094 1095 ret = init_vqs(vdev->priv); 1096 if (ret) 1097 return ret; 1098 1099 virtio_device_ready(vdev); 1100 1101 if (towards_target(vb)) 1102 virtballoon_changed(vdev); 1103 update_balloon_size(vb); 1104 return 0; 1105 } 1106 #endif 1107 1108 static int virtballoon_validate(struct virtio_device *vdev) 1109 { 1110 /* 1111 * Inform the hypervisor that our pages are poisoned or 1112 * initialized. If we cannot do that then we should disable 1113 * page reporting as it could potentially change the contents 1114 * of our free pages. 1115 */ 1116 if (!want_init_on_free() && 1117 (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || 1118 !page_poisoning_enabled())) 1119 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); 1120 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) 1121 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); 1122 1123 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM); 1124 return 0; 1125 } 1126 1127 static unsigned int features[] = { 1128 VIRTIO_BALLOON_F_MUST_TELL_HOST, 1129 VIRTIO_BALLOON_F_STATS_VQ, 1130 VIRTIO_BALLOON_F_DEFLATE_ON_OOM, 1131 VIRTIO_BALLOON_F_FREE_PAGE_HINT, 1132 VIRTIO_BALLOON_F_PAGE_POISON, 1133 VIRTIO_BALLOON_F_REPORTING, 1134 }; 1135 1136 static struct virtio_driver virtio_balloon_driver = { 1137 .feature_table = features, 1138 .feature_table_size = ARRAY_SIZE(features), 1139 .driver.name = KBUILD_MODNAME, 1140 .driver.owner = THIS_MODULE, 1141 .id_table = id_table, 1142 .validate = virtballoon_validate, 1143 .probe = virtballoon_probe, 1144 .remove = virtballoon_remove, 1145 .config_changed = virtballoon_changed, 1146 #ifdef CONFIG_PM_SLEEP 1147 .freeze = virtballoon_freeze, 1148 .restore = virtballoon_restore, 1149 #endif 1150 }; 1151 1152 module_virtio_driver(virtio_balloon_driver); 1153 MODULE_DEVICE_TABLE(virtio, id_table); 1154 MODULE_DESCRIPTION("Virtio balloon driver"); 1155 MODULE_LICENSE("GPL"); 1156