1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Virtio balloon implementation, inspired by Dor Laor and Marcelo 4 * Tosatti's implementations. 5 * 6 * Copyright 2008 Rusty Russell IBM Corporation 7 */ 8 9 #include <linux/virtio.h> 10 #include <linux/virtio_balloon.h> 11 #include <linux/swap.h> 12 #include <linux/workqueue.h> 13 #include <linux/delay.h> 14 #include <linux/slab.h> 15 #include <linux/module.h> 16 #include <linux/balloon_compaction.h> 17 #include <linux/wait.h> 18 #include <linux/mm.h> 19 #include <linux/mount.h> 20 #include <linux/magic.h> 21 #include <linux/pseudo_fs.h> 22 23 /* 24 * Balloon device works in 4K page units. So each page is pointed to by 25 * multiple balloon pages. All memory counters in this driver are in balloon 26 * page units. 27 */ 28 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 29 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 30 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 31 32 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ 33 __GFP_NOMEMALLOC) 34 /* The order of free page blocks to report to host */ 35 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1) 36 /* The size of a free page block in bytes */ 37 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \ 38 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT)) 39 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER) 40 41 #ifdef CONFIG_BALLOON_COMPACTION 42 static struct vfsmount *balloon_mnt; 43 #endif 44 45 enum virtio_balloon_vq { 46 VIRTIO_BALLOON_VQ_INFLATE, 47 VIRTIO_BALLOON_VQ_DEFLATE, 48 VIRTIO_BALLOON_VQ_STATS, 49 VIRTIO_BALLOON_VQ_FREE_PAGE, 50 VIRTIO_BALLOON_VQ_MAX 51 }; 52 53 enum virtio_balloon_config_read { 54 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, 55 }; 56 57 struct virtio_balloon { 58 struct virtio_device *vdev; 59 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; 60 61 /* Balloon's own wq for cpu-intensive work items */ 62 struct workqueue_struct *balloon_wq; 63 /* The free page reporting work item submitted to the balloon wq */ 64 struct work_struct report_free_page_work; 65 66 /* The balloon servicing is delegated to a freezable workqueue. */ 67 struct work_struct update_balloon_stats_work; 68 struct work_struct update_balloon_size_work; 69 70 /* Prevent updating balloon when it is being canceled. */ 71 spinlock_t stop_update_lock; 72 bool stop_update; 73 /* Bitmap to indicate if reading the related config fields are needed */ 74 unsigned long config_read_bitmap; 75 76 /* The list of allocated free pages, waiting to be given back to mm */ 77 struct list_head free_page_list; 78 spinlock_t free_page_list_lock; 79 /* The number of free page blocks on the above list */ 80 unsigned long num_free_page_blocks; 81 /* 82 * The cmd id received from host. 83 * Read it via virtio_balloon_cmd_id_received to get the latest value 84 * sent from host. 85 */ 86 u32 cmd_id_received_cache; 87 /* The cmd id that is actively in use */ 88 __virtio32 cmd_id_active; 89 /* Buffer to store the stop sign */ 90 __virtio32 cmd_id_stop; 91 92 /* Waiting for host to ack the pages we released. */ 93 wait_queue_head_t acked; 94 95 /* Number of balloon pages we've told the Host we're not using. */ 96 unsigned int num_pages; 97 /* 98 * The pages we've told the Host we're not using are enqueued 99 * at vb_dev_info->pages list. 100 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 101 * to num_pages above. 102 */ 103 struct balloon_dev_info vb_dev_info; 104 105 /* Synchronize access/update to this struct virtio_balloon elements */ 106 struct mutex balloon_lock; 107 108 /* The array of pfns we tell the Host about. */ 109 unsigned int num_pfns; 110 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 111 112 /* Memory statistics */ 113 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 114 115 /* To register a shrinker to shrink memory upon memory pressure */ 116 struct shrinker shrinker; 117 }; 118 119 static struct virtio_device_id id_table[] = { 120 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 121 { 0 }, 122 }; 123 124 static u32 page_to_balloon_pfn(struct page *page) 125 { 126 unsigned long pfn = page_to_pfn(page); 127 128 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 129 /* Convert pfn from Linux page size to balloon page size. */ 130 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 131 } 132 133 static void balloon_ack(struct virtqueue *vq) 134 { 135 struct virtio_balloon *vb = vq->vdev->priv; 136 137 wake_up(&vb->acked); 138 } 139 140 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 141 { 142 struct scatterlist sg; 143 unsigned int len; 144 145 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 146 147 /* We should always be able to add one buffer to an empty queue. */ 148 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 149 virtqueue_kick(vq); 150 151 /* When host has read buffer, this completes via balloon_ack */ 152 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 153 154 } 155 156 static void set_page_pfns(struct virtio_balloon *vb, 157 __virtio32 pfns[], struct page *page) 158 { 159 unsigned int i; 160 161 /* 162 * Set balloon pfns pointing at this page. 163 * Note that the first pfn points at start of the page. 164 */ 165 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 166 pfns[i] = cpu_to_virtio32(vb->vdev, 167 page_to_balloon_pfn(page) + i); 168 } 169 170 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) 171 { 172 unsigned num_allocated_pages; 173 unsigned num_pfns; 174 struct page *page; 175 LIST_HEAD(pages); 176 177 /* We can only do one array worth at a time. */ 178 num = min(num, ARRAY_SIZE(vb->pfns)); 179 180 for (num_pfns = 0; num_pfns < num; 181 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 182 struct page *page = balloon_page_alloc(); 183 184 if (!page) { 185 dev_info_ratelimited(&vb->vdev->dev, 186 "Out of puff! Can't get %u pages\n", 187 VIRTIO_BALLOON_PAGES_PER_PAGE); 188 /* Sleep for at least 1/5 of a second before retry. */ 189 msleep(200); 190 break; 191 } 192 193 balloon_page_push(&pages, page); 194 } 195 196 mutex_lock(&vb->balloon_lock); 197 198 vb->num_pfns = 0; 199 200 while ((page = balloon_page_pop(&pages))) { 201 balloon_page_enqueue(&vb->vb_dev_info, page); 202 203 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 204 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 205 if (!virtio_has_feature(vb->vdev, 206 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 207 adjust_managed_page_count(page, -1); 208 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; 209 } 210 211 num_allocated_pages = vb->num_pfns; 212 /* Did we get any? */ 213 if (vb->num_pfns != 0) 214 tell_host(vb, vb->inflate_vq); 215 mutex_unlock(&vb->balloon_lock); 216 217 return num_allocated_pages; 218 } 219 220 static void release_pages_balloon(struct virtio_balloon *vb, 221 struct list_head *pages) 222 { 223 struct page *page, *next; 224 225 list_for_each_entry_safe(page, next, pages, lru) { 226 if (!virtio_has_feature(vb->vdev, 227 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 228 adjust_managed_page_count(page, 1); 229 list_del(&page->lru); 230 put_page(page); /* balloon reference */ 231 } 232 } 233 234 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) 235 { 236 unsigned num_freed_pages; 237 struct page *page; 238 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 239 LIST_HEAD(pages); 240 241 /* We can only do one array worth at a time. */ 242 num = min(num, ARRAY_SIZE(vb->pfns)); 243 244 mutex_lock(&vb->balloon_lock); 245 /* We can't release more pages than taken */ 246 num = min(num, (size_t)vb->num_pages); 247 for (vb->num_pfns = 0; vb->num_pfns < num; 248 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 249 page = balloon_page_dequeue(vb_dev_info); 250 if (!page) 251 break; 252 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 253 list_add(&page->lru, &pages); 254 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 255 } 256 257 num_freed_pages = vb->num_pfns; 258 /* 259 * Note that if 260 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 261 * is true, we *have* to do it in this order 262 */ 263 if (vb->num_pfns != 0) 264 tell_host(vb, vb->deflate_vq); 265 release_pages_balloon(vb, &pages); 266 mutex_unlock(&vb->balloon_lock); 267 return num_freed_pages; 268 } 269 270 static inline void update_stat(struct virtio_balloon *vb, int idx, 271 u16 tag, u64 val) 272 { 273 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 274 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag); 275 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); 276 } 277 278 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 279 280 static unsigned int update_balloon_stats(struct virtio_balloon *vb) 281 { 282 unsigned long events[NR_VM_EVENT_ITEMS]; 283 struct sysinfo i; 284 unsigned int idx = 0; 285 long available; 286 unsigned long caches; 287 288 all_vm_events(events); 289 si_meminfo(&i); 290 291 available = si_mem_available(); 292 caches = global_node_page_state(NR_FILE_PAGES); 293 294 #ifdef CONFIG_VM_EVENT_COUNTERS 295 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 296 pages_to_bytes(events[PSWPIN])); 297 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 298 pages_to_bytes(events[PSWPOUT])); 299 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 300 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 301 #ifdef CONFIG_HUGETLB_PAGE 302 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC, 303 events[HTLB_BUDDY_PGALLOC]); 304 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL, 305 events[HTLB_BUDDY_PGALLOC_FAIL]); 306 #endif 307 #endif 308 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 309 pages_to_bytes(i.freeram)); 310 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 311 pages_to_bytes(i.totalram)); 312 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, 313 pages_to_bytes(available)); 314 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES, 315 pages_to_bytes(caches)); 316 317 return idx; 318 } 319 320 /* 321 * While most virtqueues communicate guest-initiated requests to the hypervisor, 322 * the stats queue operates in reverse. The driver initializes the virtqueue 323 * with a single buffer. From that point forward, all conversations consist of 324 * a hypervisor request (a call to this function) which directs us to refill 325 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 326 * we delegate the job to a freezable workqueue that will do the actual work via 327 * stats_handle_request(). 328 */ 329 static void stats_request(struct virtqueue *vq) 330 { 331 struct virtio_balloon *vb = vq->vdev->priv; 332 333 spin_lock(&vb->stop_update_lock); 334 if (!vb->stop_update) 335 queue_work(system_freezable_wq, &vb->update_balloon_stats_work); 336 spin_unlock(&vb->stop_update_lock); 337 } 338 339 static void stats_handle_request(struct virtio_balloon *vb) 340 { 341 struct virtqueue *vq; 342 struct scatterlist sg; 343 unsigned int len, num_stats; 344 345 num_stats = update_balloon_stats(vb); 346 347 vq = vb->stats_vq; 348 if (!virtqueue_get_buf(vq, &len)) 349 return; 350 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 351 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 352 virtqueue_kick(vq); 353 } 354 355 static inline s64 towards_target(struct virtio_balloon *vb) 356 { 357 s64 target; 358 u32 num_pages; 359 360 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, 361 &num_pages); 362 363 /* Legacy balloon config space is LE, unlike all other devices. */ 364 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 365 num_pages = le32_to_cpu((__force __le32)num_pages); 366 367 target = num_pages; 368 return target - vb->num_pages; 369 } 370 371 /* Gives back @num_to_return blocks of free pages to mm. */ 372 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, 373 unsigned long num_to_return) 374 { 375 struct page *page; 376 unsigned long num_returned; 377 378 spin_lock_irq(&vb->free_page_list_lock); 379 for (num_returned = 0; num_returned < num_to_return; num_returned++) { 380 page = balloon_page_pop(&vb->free_page_list); 381 if (!page) 382 break; 383 free_pages((unsigned long)page_address(page), 384 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 385 } 386 vb->num_free_page_blocks -= num_returned; 387 spin_unlock_irq(&vb->free_page_list_lock); 388 389 return num_returned; 390 } 391 392 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) 393 { 394 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 395 return; 396 397 /* No need to queue the work if the bit was already set. */ 398 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 399 &vb->config_read_bitmap)) 400 return; 401 402 queue_work(vb->balloon_wq, &vb->report_free_page_work); 403 } 404 405 static void virtballoon_changed(struct virtio_device *vdev) 406 { 407 struct virtio_balloon *vb = vdev->priv; 408 unsigned long flags; 409 410 spin_lock_irqsave(&vb->stop_update_lock, flags); 411 if (!vb->stop_update) { 412 queue_work(system_freezable_wq, 413 &vb->update_balloon_size_work); 414 virtio_balloon_queue_free_page_work(vb); 415 } 416 spin_unlock_irqrestore(&vb->stop_update_lock, flags); 417 } 418 419 static void update_balloon_size(struct virtio_balloon *vb) 420 { 421 u32 actual = vb->num_pages; 422 423 /* Legacy balloon config space is LE, unlike all other devices. */ 424 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 425 actual = (__force u32)cpu_to_le32(actual); 426 427 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, 428 &actual); 429 } 430 431 static void update_balloon_stats_func(struct work_struct *work) 432 { 433 struct virtio_balloon *vb; 434 435 vb = container_of(work, struct virtio_balloon, 436 update_balloon_stats_work); 437 stats_handle_request(vb); 438 } 439 440 static void update_balloon_size_func(struct work_struct *work) 441 { 442 struct virtio_balloon *vb; 443 s64 diff; 444 445 vb = container_of(work, struct virtio_balloon, 446 update_balloon_size_work); 447 diff = towards_target(vb); 448 449 if (!diff) 450 return; 451 452 if (diff > 0) 453 diff -= fill_balloon(vb, diff); 454 else 455 diff += leak_balloon(vb, -diff); 456 update_balloon_size(vb); 457 458 if (diff) 459 queue_work(system_freezable_wq, work); 460 } 461 462 static int init_vqs(struct virtio_balloon *vb) 463 { 464 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX]; 465 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX]; 466 const char *names[VIRTIO_BALLOON_VQ_MAX]; 467 int err; 468 469 /* 470 * Inflateq and deflateq are used unconditionally. The names[] 471 * will be NULL if the related feature is not enabled, which will 472 * cause no allocation for the corresponding virtqueue in find_vqs. 473 */ 474 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack; 475 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate"; 476 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack; 477 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; 478 names[VIRTIO_BALLOON_VQ_STATS] = NULL; 479 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 480 481 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 482 names[VIRTIO_BALLOON_VQ_STATS] = "stats"; 483 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request; 484 } 485 486 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 487 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq"; 488 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 489 } 490 491 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, 492 vqs, callbacks, names, NULL, NULL); 493 if (err) 494 return err; 495 496 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; 497 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; 498 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 499 struct scatterlist sg; 500 unsigned int num_stats; 501 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS]; 502 503 /* 504 * Prime this virtqueue with one buffer so the hypervisor can 505 * use it to signal us later (it can't be broken yet!). 506 */ 507 num_stats = update_balloon_stats(vb); 508 509 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 510 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, 511 GFP_KERNEL); 512 if (err) { 513 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n", 514 __func__); 515 return err; 516 } 517 virtqueue_kick(vb->stats_vq); 518 } 519 520 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 521 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; 522 523 return 0; 524 } 525 526 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb) 527 { 528 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 529 &vb->config_read_bitmap)) 530 virtio_cread(vb->vdev, struct virtio_balloon_config, 531 free_page_report_cmd_id, 532 &vb->cmd_id_received_cache); 533 534 return vb->cmd_id_received_cache; 535 } 536 537 static int send_cmd_id_start(struct virtio_balloon *vb) 538 { 539 struct scatterlist sg; 540 struct virtqueue *vq = vb->free_page_vq; 541 int err, unused; 542 543 /* Detach all the used buffers from the vq */ 544 while (virtqueue_get_buf(vq, &unused)) 545 ; 546 547 vb->cmd_id_active = virtio32_to_cpu(vb->vdev, 548 virtio_balloon_cmd_id_received(vb)); 549 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active)); 550 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL); 551 if (!err) 552 virtqueue_kick(vq); 553 return err; 554 } 555 556 static int send_cmd_id_stop(struct virtio_balloon *vb) 557 { 558 struct scatterlist sg; 559 struct virtqueue *vq = vb->free_page_vq; 560 int err, unused; 561 562 /* Detach all the used buffers from the vq */ 563 while (virtqueue_get_buf(vq, &unused)) 564 ; 565 566 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop)); 567 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL); 568 if (!err) 569 virtqueue_kick(vq); 570 return err; 571 } 572 573 static int get_free_page_and_send(struct virtio_balloon *vb) 574 { 575 struct virtqueue *vq = vb->free_page_vq; 576 struct page *page; 577 struct scatterlist sg; 578 int err, unused; 579 void *p; 580 581 /* Detach all the used buffers from the vq */ 582 while (virtqueue_get_buf(vq, &unused)) 583 ; 584 585 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG, 586 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 587 /* 588 * When the allocation returns NULL, it indicates that we have got all 589 * the possible free pages, so return -EINTR to stop. 590 */ 591 if (!page) 592 return -EINTR; 593 594 p = page_address(page); 595 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES); 596 /* There is always 1 entry reserved for the cmd id to use. */ 597 if (vq->num_free > 1) { 598 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL); 599 if (unlikely(err)) { 600 free_pages((unsigned long)p, 601 VIRTIO_BALLOON_HINT_BLOCK_ORDER); 602 return err; 603 } 604 virtqueue_kick(vq); 605 spin_lock_irq(&vb->free_page_list_lock); 606 balloon_page_push(&vb->free_page_list, page); 607 vb->num_free_page_blocks++; 608 spin_unlock_irq(&vb->free_page_list_lock); 609 } else { 610 /* 611 * The vq has no available entry to add this page block, so 612 * just free it. 613 */ 614 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); 615 } 616 617 return 0; 618 } 619 620 static int send_free_pages(struct virtio_balloon *vb) 621 { 622 int err; 623 u32 cmd_id_active; 624 625 while (1) { 626 /* 627 * If a stop id or a new cmd id was just received from host, 628 * stop the reporting. 629 */ 630 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active); 631 if (unlikely(cmd_id_active != 632 virtio_balloon_cmd_id_received(vb))) 633 break; 634 635 /* 636 * The free page blocks are allocated and sent to host one by 637 * one. 638 */ 639 err = get_free_page_and_send(vb); 640 if (err == -EINTR) 641 break; 642 else if (unlikely(err)) 643 return err; 644 } 645 646 return 0; 647 } 648 649 static void virtio_balloon_report_free_page(struct virtio_balloon *vb) 650 { 651 int err; 652 struct device *dev = &vb->vdev->dev; 653 654 /* Start by sending the received cmd id to host with an outbuf. */ 655 err = send_cmd_id_start(vb); 656 if (unlikely(err)) 657 dev_err(dev, "Failed to send a start id, err = %d\n", err); 658 659 err = send_free_pages(vb); 660 if (unlikely(err)) 661 dev_err(dev, "Failed to send a free page, err = %d\n", err); 662 663 /* End by sending a stop id to host with an outbuf. */ 664 err = send_cmd_id_stop(vb); 665 if (unlikely(err)) 666 dev_err(dev, "Failed to send a stop id, err = %d\n", err); 667 } 668 669 static void report_free_page_func(struct work_struct *work) 670 { 671 struct virtio_balloon *vb = container_of(work, struct virtio_balloon, 672 report_free_page_work); 673 u32 cmd_id_received; 674 675 cmd_id_received = virtio_balloon_cmd_id_received(vb); 676 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { 677 /* Pass ULONG_MAX to give back all the free pages */ 678 return_free_pages_to_mm(vb, ULONG_MAX); 679 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && 680 cmd_id_received != 681 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { 682 virtio_balloon_report_free_page(vb); 683 } 684 } 685 686 #ifdef CONFIG_BALLOON_COMPACTION 687 /* 688 * virtballoon_migratepage - perform the balloon page migration on behalf of 689 * a compation thread. (called under page lock) 690 * @vb_dev_info: the balloon device 691 * @newpage: page that will replace the isolated page after migration finishes. 692 * @page : the isolated (old) page that is about to be migrated to newpage. 693 * @mode : compaction mode -- not used for balloon page migration. 694 * 695 * After a ballooned page gets isolated by compaction procedures, this is the 696 * function that performs the page migration on behalf of a compaction thread 697 * The page migration for virtio balloon is done in a simple swap fashion which 698 * follows these two macro steps: 699 * 1) insert newpage into vb->pages list and update the host about it; 700 * 2) update the host about the old page removed from vb->pages list; 701 * 702 * This function preforms the balloon page migration task. 703 * Called through balloon_mapping->a_ops->migratepage 704 */ 705 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 706 struct page *newpage, struct page *page, enum migrate_mode mode) 707 { 708 struct virtio_balloon *vb = container_of(vb_dev_info, 709 struct virtio_balloon, vb_dev_info); 710 unsigned long flags; 711 712 /* 713 * In order to avoid lock contention while migrating pages concurrently 714 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 715 * this turn, as it is easier to retry the page migration later. 716 * This also prevents fill_balloon() getting stuck into a mutex 717 * recursion in the case it ends up triggering memory compaction 718 * while it is attempting to inflate the ballon. 719 */ 720 if (!mutex_trylock(&vb->balloon_lock)) 721 return -EAGAIN; 722 723 get_page(newpage); /* balloon reference */ 724 725 /* 726 * When we migrate a page to a different zone and adjusted the 727 * managed page count when inflating, we have to fixup the count of 728 * both involved zones. 729 */ 730 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) && 731 page_zone(page) != page_zone(newpage)) { 732 adjust_managed_page_count(page, 1); 733 adjust_managed_page_count(newpage, -1); 734 } 735 736 /* balloon's page migration 1st step -- inflate "newpage" */ 737 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 738 balloon_page_insert(vb_dev_info, newpage); 739 vb_dev_info->isolated_pages--; 740 __count_vm_event(BALLOON_MIGRATE); 741 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 742 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 743 set_page_pfns(vb, vb->pfns, newpage); 744 tell_host(vb, vb->inflate_vq); 745 746 /* balloon's page migration 2nd step -- deflate "page" */ 747 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 748 balloon_page_delete(page); 749 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 750 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 751 set_page_pfns(vb, vb->pfns, page); 752 tell_host(vb, vb->deflate_vq); 753 754 mutex_unlock(&vb->balloon_lock); 755 756 put_page(page); /* balloon reference */ 757 758 return MIGRATEPAGE_SUCCESS; 759 } 760 761 static int balloon_init_fs_context(struct fs_context *fc) 762 { 763 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM; 764 } 765 766 static struct file_system_type balloon_fs = { 767 .name = "balloon-kvm", 768 .init_fs_context = balloon_init_fs_context, 769 .kill_sb = kill_anon_super, 770 }; 771 772 #endif /* CONFIG_BALLOON_COMPACTION */ 773 774 static unsigned long shrink_free_pages(struct virtio_balloon *vb, 775 unsigned long pages_to_free) 776 { 777 unsigned long blocks_to_free, blocks_freed; 778 779 pages_to_free = round_up(pages_to_free, 780 VIRTIO_BALLOON_HINT_BLOCK_PAGES); 781 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES; 782 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free); 783 784 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 785 } 786 787 static unsigned long leak_balloon_pages(struct virtio_balloon *vb, 788 unsigned long pages_to_free) 789 { 790 return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) / 791 VIRTIO_BALLOON_PAGES_PER_PAGE; 792 } 793 794 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb, 795 unsigned long pages_to_free) 796 { 797 unsigned long pages_freed = 0; 798 799 /* 800 * One invocation of leak_balloon can deflate at most 801 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it 802 * multiple times to deflate pages till reaching pages_to_free. 803 */ 804 while (vb->num_pages && pages_freed < pages_to_free) 805 pages_freed += leak_balloon_pages(vb, 806 pages_to_free - pages_freed); 807 808 update_balloon_size(vb); 809 810 return pages_freed; 811 } 812 813 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, 814 struct shrink_control *sc) 815 { 816 unsigned long pages_to_free, pages_freed = 0; 817 struct virtio_balloon *vb = container_of(shrinker, 818 struct virtio_balloon, shrinker); 819 820 pages_to_free = sc->nr_to_scan; 821 822 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 823 pages_freed = shrink_free_pages(vb, pages_to_free); 824 825 if (pages_freed >= pages_to_free) 826 return pages_freed; 827 828 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed); 829 830 return pages_freed; 831 } 832 833 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, 834 struct shrink_control *sc) 835 { 836 struct virtio_balloon *vb = container_of(shrinker, 837 struct virtio_balloon, shrinker); 838 unsigned long count; 839 840 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE; 841 count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; 842 843 return count; 844 } 845 846 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) 847 { 848 unregister_shrinker(&vb->shrinker); 849 } 850 851 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) 852 { 853 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan; 854 vb->shrinker.count_objects = virtio_balloon_shrinker_count; 855 vb->shrinker.seeks = DEFAULT_SEEKS; 856 857 return register_shrinker(&vb->shrinker); 858 } 859 860 static int virtballoon_probe(struct virtio_device *vdev) 861 { 862 struct virtio_balloon *vb; 863 __u32 poison_val; 864 int err; 865 866 if (!vdev->config->get) { 867 dev_err(&vdev->dev, "%s failure: config access disabled\n", 868 __func__); 869 return -EINVAL; 870 } 871 872 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL); 873 if (!vb) { 874 err = -ENOMEM; 875 goto out; 876 } 877 878 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); 879 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); 880 spin_lock_init(&vb->stop_update_lock); 881 mutex_init(&vb->balloon_lock); 882 init_waitqueue_head(&vb->acked); 883 vb->vdev = vdev; 884 885 balloon_devinfo_init(&vb->vb_dev_info); 886 887 err = init_vqs(vb); 888 if (err) 889 goto out_free_vb; 890 891 #ifdef CONFIG_BALLOON_COMPACTION 892 balloon_mnt = kern_mount(&balloon_fs); 893 if (IS_ERR(balloon_mnt)) { 894 err = PTR_ERR(balloon_mnt); 895 goto out_del_vqs; 896 } 897 898 vb->vb_dev_info.migratepage = virtballoon_migratepage; 899 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb); 900 if (IS_ERR(vb->vb_dev_info.inode)) { 901 err = PTR_ERR(vb->vb_dev_info.inode); 902 kern_unmount(balloon_mnt); 903 goto out_del_vqs; 904 } 905 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops; 906 #endif 907 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 908 /* 909 * There is always one entry reserved for cmd id, so the ring 910 * size needs to be at least two to report free page hints. 911 */ 912 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) { 913 err = -ENOSPC; 914 goto out_del_vqs; 915 } 916 vb->balloon_wq = alloc_workqueue("balloon-wq", 917 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); 918 if (!vb->balloon_wq) { 919 err = -ENOMEM; 920 goto out_del_vqs; 921 } 922 INIT_WORK(&vb->report_free_page_work, report_free_page_func); 923 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP; 924 vb->cmd_id_active = cpu_to_virtio32(vb->vdev, 925 VIRTIO_BALLOON_CMD_ID_STOP); 926 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev, 927 VIRTIO_BALLOON_CMD_ID_STOP); 928 spin_lock_init(&vb->free_page_list_lock); 929 INIT_LIST_HEAD(&vb->free_page_list); 930 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { 931 memset(&poison_val, PAGE_POISON, sizeof(poison_val)); 932 virtio_cwrite(vb->vdev, struct virtio_balloon_config, 933 poison_val, &poison_val); 934 } 935 } 936 /* 937 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a 938 * shrinker needs to be registered to relieve memory pressure. 939 */ 940 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { 941 err = virtio_balloon_register_shrinker(vb); 942 if (err) 943 goto out_del_balloon_wq; 944 } 945 virtio_device_ready(vdev); 946 947 if (towards_target(vb)) 948 virtballoon_changed(vdev); 949 return 0; 950 951 out_del_balloon_wq: 952 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 953 destroy_workqueue(vb->balloon_wq); 954 out_del_vqs: 955 vdev->config->del_vqs(vdev); 956 out_free_vb: 957 kfree(vb); 958 out: 959 return err; 960 } 961 962 static void remove_common(struct virtio_balloon *vb) 963 { 964 /* There might be pages left in the balloon: free them. */ 965 while (vb->num_pages) 966 leak_balloon(vb, vb->num_pages); 967 update_balloon_size(vb); 968 969 /* Now we reset the device so we can clean up the queues. */ 970 vb->vdev->config->reset(vb->vdev); 971 972 vb->vdev->config->del_vqs(vb->vdev); 973 } 974 975 static void virtballoon_remove(struct virtio_device *vdev) 976 { 977 struct virtio_balloon *vb = vdev->priv; 978 979 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 980 virtio_balloon_unregister_shrinker(vb); 981 spin_lock_irq(&vb->stop_update_lock); 982 vb->stop_update = true; 983 spin_unlock_irq(&vb->stop_update_lock); 984 cancel_work_sync(&vb->update_balloon_size_work); 985 cancel_work_sync(&vb->update_balloon_stats_work); 986 987 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 988 cancel_work_sync(&vb->report_free_page_work); 989 destroy_workqueue(vb->balloon_wq); 990 } 991 992 remove_common(vb); 993 #ifdef CONFIG_BALLOON_COMPACTION 994 if (vb->vb_dev_info.inode) 995 iput(vb->vb_dev_info.inode); 996 997 kern_unmount(balloon_mnt); 998 #endif 999 kfree(vb); 1000 } 1001 1002 #ifdef CONFIG_PM_SLEEP 1003 static int virtballoon_freeze(struct virtio_device *vdev) 1004 { 1005 struct virtio_balloon *vb = vdev->priv; 1006 1007 /* 1008 * The workqueue is already frozen by the PM core before this 1009 * function is called. 1010 */ 1011 remove_common(vb); 1012 return 0; 1013 } 1014 1015 static int virtballoon_restore(struct virtio_device *vdev) 1016 { 1017 struct virtio_balloon *vb = vdev->priv; 1018 int ret; 1019 1020 ret = init_vqs(vdev->priv); 1021 if (ret) 1022 return ret; 1023 1024 virtio_device_ready(vdev); 1025 1026 if (towards_target(vb)) 1027 virtballoon_changed(vdev); 1028 update_balloon_size(vb); 1029 return 0; 1030 } 1031 #endif 1032 1033 static int virtballoon_validate(struct virtio_device *vdev) 1034 { 1035 if (!page_poisoning_enabled()) 1036 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); 1037 1038 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM); 1039 return 0; 1040 } 1041 1042 static unsigned int features[] = { 1043 VIRTIO_BALLOON_F_MUST_TELL_HOST, 1044 VIRTIO_BALLOON_F_STATS_VQ, 1045 VIRTIO_BALLOON_F_DEFLATE_ON_OOM, 1046 VIRTIO_BALLOON_F_FREE_PAGE_HINT, 1047 VIRTIO_BALLOON_F_PAGE_POISON, 1048 }; 1049 1050 static struct virtio_driver virtio_balloon_driver = { 1051 .feature_table = features, 1052 .feature_table_size = ARRAY_SIZE(features), 1053 .driver.name = KBUILD_MODNAME, 1054 .driver.owner = THIS_MODULE, 1055 .id_table = id_table, 1056 .validate = virtballoon_validate, 1057 .probe = virtballoon_probe, 1058 .remove = virtballoon_remove, 1059 .config_changed = virtballoon_changed, 1060 #ifdef CONFIG_PM_SLEEP 1061 .freeze = virtballoon_freeze, 1062 .restore = virtballoon_restore, 1063 #endif 1064 }; 1065 1066 module_virtio_driver(virtio_balloon_driver); 1067 MODULE_DEVICE_TABLE(virtio, id_table); 1068 MODULE_DESCRIPTION("Virtio balloon driver"); 1069 MODULE_LICENSE("GPL"); 1070