1 /* 2 * Virtio balloon implementation, inspired by Dor Laor and Marcelo 3 * Tosatti's implementations. 4 * 5 * Copyright 2008 Rusty Russell IBM Corporation 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22 #include <linux/virtio.h> 23 #include <linux/virtio_balloon.h> 24 #include <linux/swap.h> 25 #include <linux/workqueue.h> 26 #include <linux/delay.h> 27 #include <linux/slab.h> 28 #include <linux/module.h> 29 #include <linux/balloon_compaction.h> 30 #include <linux/wait.h> 31 #include <linux/mm.h> 32 #include <linux/mount.h> 33 #include <linux/magic.h> 34 35 /* 36 * Balloon device works in 4K page units. So each page is pointed to by 37 * multiple balloon pages. All memory counters in this driver are in balloon 38 * page units. 39 */ 40 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 41 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 43 44 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ 45 __GFP_NOMEMALLOC) 46 /* The order of free page blocks to report to host */ 47 #define VIRTIO_BALLOON_FREE_PAGE_ORDER (MAX_ORDER - 1) 48 /* The size of a free page block in bytes */ 49 #define VIRTIO_BALLOON_FREE_PAGE_SIZE \ 50 (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT)) 51 52 #ifdef CONFIG_BALLOON_COMPACTION 53 static struct vfsmount *balloon_mnt; 54 #endif 55 56 enum virtio_balloon_vq { 57 VIRTIO_BALLOON_VQ_INFLATE, 58 VIRTIO_BALLOON_VQ_DEFLATE, 59 VIRTIO_BALLOON_VQ_STATS, 60 VIRTIO_BALLOON_VQ_FREE_PAGE, 61 VIRTIO_BALLOON_VQ_MAX 62 }; 63 64 enum virtio_balloon_config_read { 65 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, 66 }; 67 68 struct virtio_balloon { 69 struct virtio_device *vdev; 70 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; 71 72 /* Balloon's own wq for cpu-intensive work items */ 73 struct workqueue_struct *balloon_wq; 74 /* The free page reporting work item submitted to the balloon wq */ 75 struct work_struct report_free_page_work; 76 77 /* The balloon servicing is delegated to a freezable workqueue. */ 78 struct work_struct update_balloon_stats_work; 79 struct work_struct update_balloon_size_work; 80 81 /* Prevent updating balloon when it is being canceled. */ 82 spinlock_t stop_update_lock; 83 bool stop_update; 84 /* Bitmap to indicate if reading the related config fields are needed */ 85 unsigned long config_read_bitmap; 86 87 /* The list of allocated free pages, waiting to be given back to mm */ 88 struct list_head free_page_list; 89 spinlock_t free_page_list_lock; 90 /* The number of free page blocks on the above list */ 91 unsigned long num_free_page_blocks; 92 /* 93 * The cmd id received from host. 94 * Read it via virtio_balloon_cmd_id_received to get the latest value 95 * sent from host. 96 */ 97 u32 cmd_id_received_cache; 98 /* The cmd id that is actively in use */ 99 __virtio32 cmd_id_active; 100 /* Buffer to store the stop sign */ 101 __virtio32 cmd_id_stop; 102 103 /* Waiting for host to ack the pages we released. */ 104 wait_queue_head_t acked; 105 106 /* Number of balloon pages we've told the Host we're not using. */ 107 unsigned int num_pages; 108 /* 109 * The pages we've told the Host we're not using are enqueued 110 * at vb_dev_info->pages list. 111 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 112 * to num_pages above. 113 */ 114 struct balloon_dev_info vb_dev_info; 115 116 /* Synchronize access/update to this struct virtio_balloon elements */ 117 struct mutex balloon_lock; 118 119 /* The array of pfns we tell the Host about. */ 120 unsigned int num_pfns; 121 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 122 123 /* Memory statistics */ 124 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 125 126 /* To register a shrinker to shrink memory upon memory pressure */ 127 struct shrinker shrinker; 128 }; 129 130 static struct virtio_device_id id_table[] = { 131 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 132 { 0 }, 133 }; 134 135 static u32 page_to_balloon_pfn(struct page *page) 136 { 137 unsigned long pfn = page_to_pfn(page); 138 139 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 140 /* Convert pfn from Linux page size to balloon page size. */ 141 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 142 } 143 144 static void balloon_ack(struct virtqueue *vq) 145 { 146 struct virtio_balloon *vb = vq->vdev->priv; 147 148 wake_up(&vb->acked); 149 } 150 151 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 152 { 153 struct scatterlist sg; 154 unsigned int len; 155 156 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 157 158 /* We should always be able to add one buffer to an empty queue. */ 159 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 160 virtqueue_kick(vq); 161 162 /* When host has read buffer, this completes via balloon_ack */ 163 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 164 165 } 166 167 static void set_page_pfns(struct virtio_balloon *vb, 168 __virtio32 pfns[], struct page *page) 169 { 170 unsigned int i; 171 172 /* 173 * Set balloon pfns pointing at this page. 174 * Note that the first pfn points at start of the page. 175 */ 176 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 177 pfns[i] = cpu_to_virtio32(vb->vdev, 178 page_to_balloon_pfn(page) + i); 179 } 180 181 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) 182 { 183 unsigned num_allocated_pages; 184 unsigned num_pfns; 185 struct page *page; 186 LIST_HEAD(pages); 187 188 /* We can only do one array worth at a time. */ 189 num = min(num, ARRAY_SIZE(vb->pfns)); 190 191 for (num_pfns = 0; num_pfns < num; 192 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 193 struct page *page = balloon_page_alloc(); 194 195 if (!page) { 196 dev_info_ratelimited(&vb->vdev->dev, 197 "Out of puff! Can't get %u pages\n", 198 VIRTIO_BALLOON_PAGES_PER_PAGE); 199 /* Sleep for at least 1/5 of a second before retry. */ 200 msleep(200); 201 break; 202 } 203 204 balloon_page_push(&pages, page); 205 } 206 207 mutex_lock(&vb->balloon_lock); 208 209 vb->num_pfns = 0; 210 211 while ((page = balloon_page_pop(&pages))) { 212 balloon_page_enqueue(&vb->vb_dev_info, page); 213 214 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 215 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 216 if (!virtio_has_feature(vb->vdev, 217 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 218 adjust_managed_page_count(page, -1); 219 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; 220 } 221 222 num_allocated_pages = vb->num_pfns; 223 /* Did we get any? */ 224 if (vb->num_pfns != 0) 225 tell_host(vb, vb->inflate_vq); 226 mutex_unlock(&vb->balloon_lock); 227 228 return num_allocated_pages; 229 } 230 231 static void release_pages_balloon(struct virtio_balloon *vb, 232 struct list_head *pages) 233 { 234 struct page *page, *next; 235 236 list_for_each_entry_safe(page, next, pages, lru) { 237 if (!virtio_has_feature(vb->vdev, 238 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 239 adjust_managed_page_count(page, 1); 240 list_del(&page->lru); 241 put_page(page); /* balloon reference */ 242 } 243 } 244 245 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) 246 { 247 unsigned num_freed_pages; 248 struct page *page; 249 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 250 LIST_HEAD(pages); 251 252 /* We can only do one array worth at a time. */ 253 num = min(num, ARRAY_SIZE(vb->pfns)); 254 255 mutex_lock(&vb->balloon_lock); 256 /* We can't release more pages than taken */ 257 num = min(num, (size_t)vb->num_pages); 258 for (vb->num_pfns = 0; vb->num_pfns < num; 259 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 260 page = balloon_page_dequeue(vb_dev_info); 261 if (!page) 262 break; 263 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); 264 list_add(&page->lru, &pages); 265 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 266 } 267 268 num_freed_pages = vb->num_pfns; 269 /* 270 * Note that if 271 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 272 * is true, we *have* to do it in this order 273 */ 274 if (vb->num_pfns != 0) 275 tell_host(vb, vb->deflate_vq); 276 release_pages_balloon(vb, &pages); 277 mutex_unlock(&vb->balloon_lock); 278 return num_freed_pages; 279 } 280 281 static inline void update_stat(struct virtio_balloon *vb, int idx, 282 u16 tag, u64 val) 283 { 284 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 285 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag); 286 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); 287 } 288 289 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 290 291 static unsigned int update_balloon_stats(struct virtio_balloon *vb) 292 { 293 unsigned long events[NR_VM_EVENT_ITEMS]; 294 struct sysinfo i; 295 unsigned int idx = 0; 296 long available; 297 unsigned long caches; 298 299 all_vm_events(events); 300 si_meminfo(&i); 301 302 available = si_mem_available(); 303 caches = global_node_page_state(NR_FILE_PAGES); 304 305 #ifdef CONFIG_VM_EVENT_COUNTERS 306 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 307 pages_to_bytes(events[PSWPIN])); 308 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 309 pages_to_bytes(events[PSWPOUT])); 310 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 311 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 312 #ifdef CONFIG_HUGETLB_PAGE 313 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC, 314 events[HTLB_BUDDY_PGALLOC]); 315 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL, 316 events[HTLB_BUDDY_PGALLOC_FAIL]); 317 #endif 318 #endif 319 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 320 pages_to_bytes(i.freeram)); 321 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 322 pages_to_bytes(i.totalram)); 323 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, 324 pages_to_bytes(available)); 325 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES, 326 pages_to_bytes(caches)); 327 328 return idx; 329 } 330 331 /* 332 * While most virtqueues communicate guest-initiated requests to the hypervisor, 333 * the stats queue operates in reverse. The driver initializes the virtqueue 334 * with a single buffer. From that point forward, all conversations consist of 335 * a hypervisor request (a call to this function) which directs us to refill 336 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 337 * we delegate the job to a freezable workqueue that will do the actual work via 338 * stats_handle_request(). 339 */ 340 static void stats_request(struct virtqueue *vq) 341 { 342 struct virtio_balloon *vb = vq->vdev->priv; 343 344 spin_lock(&vb->stop_update_lock); 345 if (!vb->stop_update) 346 queue_work(system_freezable_wq, &vb->update_balloon_stats_work); 347 spin_unlock(&vb->stop_update_lock); 348 } 349 350 static void stats_handle_request(struct virtio_balloon *vb) 351 { 352 struct virtqueue *vq; 353 struct scatterlist sg; 354 unsigned int len, num_stats; 355 356 num_stats = update_balloon_stats(vb); 357 358 vq = vb->stats_vq; 359 if (!virtqueue_get_buf(vq, &len)) 360 return; 361 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 362 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 363 virtqueue_kick(vq); 364 } 365 366 static inline s64 towards_target(struct virtio_balloon *vb) 367 { 368 s64 target; 369 u32 num_pages; 370 371 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, 372 &num_pages); 373 374 /* Legacy balloon config space is LE, unlike all other devices. */ 375 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 376 num_pages = le32_to_cpu((__force __le32)num_pages); 377 378 target = num_pages; 379 return target - vb->num_pages; 380 } 381 382 /* Gives back @num_to_return blocks of free pages to mm. */ 383 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, 384 unsigned long num_to_return) 385 { 386 struct page *page; 387 unsigned long num_returned; 388 389 spin_lock_irq(&vb->free_page_list_lock); 390 for (num_returned = 0; num_returned < num_to_return; num_returned++) { 391 page = balloon_page_pop(&vb->free_page_list); 392 if (!page) 393 break; 394 free_pages((unsigned long)page_address(page), 395 VIRTIO_BALLOON_FREE_PAGE_ORDER); 396 } 397 vb->num_free_page_blocks -= num_returned; 398 spin_unlock_irq(&vb->free_page_list_lock); 399 400 return num_returned; 401 } 402 403 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) 404 { 405 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 406 return; 407 408 /* No need to queue the work if the bit was already set. */ 409 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 410 &vb->config_read_bitmap)) 411 return; 412 413 queue_work(vb->balloon_wq, &vb->report_free_page_work); 414 } 415 416 static void virtballoon_changed(struct virtio_device *vdev) 417 { 418 struct virtio_balloon *vb = vdev->priv; 419 unsigned long flags; 420 421 spin_lock_irqsave(&vb->stop_update_lock, flags); 422 if (!vb->stop_update) { 423 queue_work(system_freezable_wq, 424 &vb->update_balloon_size_work); 425 virtio_balloon_queue_free_page_work(vb); 426 } 427 spin_unlock_irqrestore(&vb->stop_update_lock, flags); 428 } 429 430 static void update_balloon_size(struct virtio_balloon *vb) 431 { 432 u32 actual = vb->num_pages; 433 434 /* Legacy balloon config space is LE, unlike all other devices. */ 435 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 436 actual = (__force u32)cpu_to_le32(actual); 437 438 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, 439 &actual); 440 } 441 442 static void update_balloon_stats_func(struct work_struct *work) 443 { 444 struct virtio_balloon *vb; 445 446 vb = container_of(work, struct virtio_balloon, 447 update_balloon_stats_work); 448 stats_handle_request(vb); 449 } 450 451 static void update_balloon_size_func(struct work_struct *work) 452 { 453 struct virtio_balloon *vb; 454 s64 diff; 455 456 vb = container_of(work, struct virtio_balloon, 457 update_balloon_size_work); 458 diff = towards_target(vb); 459 460 if (diff > 0) 461 diff -= fill_balloon(vb, diff); 462 else if (diff < 0) 463 diff += leak_balloon(vb, -diff); 464 update_balloon_size(vb); 465 466 if (diff) 467 queue_work(system_freezable_wq, work); 468 } 469 470 static int init_vqs(struct virtio_balloon *vb) 471 { 472 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX]; 473 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX]; 474 const char *names[VIRTIO_BALLOON_VQ_MAX]; 475 int err; 476 477 /* 478 * Inflateq and deflateq are used unconditionally. The names[] 479 * will be NULL if the related feature is not enabled, which will 480 * cause no allocation for the corresponding virtqueue in find_vqs. 481 */ 482 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack; 483 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate"; 484 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack; 485 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; 486 names[VIRTIO_BALLOON_VQ_STATS] = NULL; 487 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 488 489 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 490 names[VIRTIO_BALLOON_VQ_STATS] = "stats"; 491 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request; 492 } 493 494 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 495 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq"; 496 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; 497 } 498 499 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, 500 vqs, callbacks, names, NULL, NULL); 501 if (err) 502 return err; 503 504 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; 505 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; 506 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 507 struct scatterlist sg; 508 unsigned int num_stats; 509 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS]; 510 511 /* 512 * Prime this virtqueue with one buffer so the hypervisor can 513 * use it to signal us later (it can't be broken yet!). 514 */ 515 num_stats = update_balloon_stats(vb); 516 517 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); 518 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, 519 GFP_KERNEL); 520 if (err) { 521 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n", 522 __func__); 523 return err; 524 } 525 virtqueue_kick(vb->stats_vq); 526 } 527 528 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 529 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; 530 531 return 0; 532 } 533 534 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb) 535 { 536 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, 537 &vb->config_read_bitmap)) 538 virtio_cread(vb->vdev, struct virtio_balloon_config, 539 free_page_report_cmd_id, 540 &vb->cmd_id_received_cache); 541 542 return vb->cmd_id_received_cache; 543 } 544 545 static int send_cmd_id_start(struct virtio_balloon *vb) 546 { 547 struct scatterlist sg; 548 struct virtqueue *vq = vb->free_page_vq; 549 int err, unused; 550 551 /* Detach all the used buffers from the vq */ 552 while (virtqueue_get_buf(vq, &unused)) 553 ; 554 555 vb->cmd_id_active = virtio32_to_cpu(vb->vdev, 556 virtio_balloon_cmd_id_received(vb)); 557 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active)); 558 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL); 559 if (!err) 560 virtqueue_kick(vq); 561 return err; 562 } 563 564 static int send_cmd_id_stop(struct virtio_balloon *vb) 565 { 566 struct scatterlist sg; 567 struct virtqueue *vq = vb->free_page_vq; 568 int err, unused; 569 570 /* Detach all the used buffers from the vq */ 571 while (virtqueue_get_buf(vq, &unused)) 572 ; 573 574 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop)); 575 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL); 576 if (!err) 577 virtqueue_kick(vq); 578 return err; 579 } 580 581 static int get_free_page_and_send(struct virtio_balloon *vb) 582 { 583 struct virtqueue *vq = vb->free_page_vq; 584 struct page *page; 585 struct scatterlist sg; 586 int err, unused; 587 void *p; 588 589 /* Detach all the used buffers from the vq */ 590 while (virtqueue_get_buf(vq, &unused)) 591 ; 592 593 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG, 594 VIRTIO_BALLOON_FREE_PAGE_ORDER); 595 /* 596 * When the allocation returns NULL, it indicates that we have got all 597 * the possible free pages, so return -EINTR to stop. 598 */ 599 if (!page) 600 return -EINTR; 601 602 p = page_address(page); 603 sg_init_one(&sg, p, VIRTIO_BALLOON_FREE_PAGE_SIZE); 604 /* There is always 1 entry reserved for the cmd id to use. */ 605 if (vq->num_free > 1) { 606 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL); 607 if (unlikely(err)) { 608 free_pages((unsigned long)p, 609 VIRTIO_BALLOON_FREE_PAGE_ORDER); 610 return err; 611 } 612 virtqueue_kick(vq); 613 spin_lock_irq(&vb->free_page_list_lock); 614 balloon_page_push(&vb->free_page_list, page); 615 vb->num_free_page_blocks++; 616 spin_unlock_irq(&vb->free_page_list_lock); 617 } else { 618 /* 619 * The vq has no available entry to add this page block, so 620 * just free it. 621 */ 622 free_pages((unsigned long)p, VIRTIO_BALLOON_FREE_PAGE_ORDER); 623 } 624 625 return 0; 626 } 627 628 static int send_free_pages(struct virtio_balloon *vb) 629 { 630 int err; 631 u32 cmd_id_active; 632 633 while (1) { 634 /* 635 * If a stop id or a new cmd id was just received from host, 636 * stop the reporting. 637 */ 638 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active); 639 if (unlikely(cmd_id_active != 640 virtio_balloon_cmd_id_received(vb))) 641 break; 642 643 /* 644 * The free page blocks are allocated and sent to host one by 645 * one. 646 */ 647 err = get_free_page_and_send(vb); 648 if (err == -EINTR) 649 break; 650 else if (unlikely(err)) 651 return err; 652 } 653 654 return 0; 655 } 656 657 static void virtio_balloon_report_free_page(struct virtio_balloon *vb) 658 { 659 int err; 660 struct device *dev = &vb->vdev->dev; 661 662 /* Start by sending the received cmd id to host with an outbuf. */ 663 err = send_cmd_id_start(vb); 664 if (unlikely(err)) 665 dev_err(dev, "Failed to send a start id, err = %d\n", err); 666 667 err = send_free_pages(vb); 668 if (unlikely(err)) 669 dev_err(dev, "Failed to send a free page, err = %d\n", err); 670 671 /* End by sending a stop id to host with an outbuf. */ 672 err = send_cmd_id_stop(vb); 673 if (unlikely(err)) 674 dev_err(dev, "Failed to send a stop id, err = %d\n", err); 675 } 676 677 static void report_free_page_func(struct work_struct *work) 678 { 679 struct virtio_balloon *vb = container_of(work, struct virtio_balloon, 680 report_free_page_work); 681 u32 cmd_id_received; 682 683 cmd_id_received = virtio_balloon_cmd_id_received(vb); 684 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { 685 /* Pass ULONG_MAX to give back all the free pages */ 686 return_free_pages_to_mm(vb, ULONG_MAX); 687 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && 688 cmd_id_received != 689 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { 690 virtio_balloon_report_free_page(vb); 691 } 692 } 693 694 #ifdef CONFIG_BALLOON_COMPACTION 695 /* 696 * virtballoon_migratepage - perform the balloon page migration on behalf of 697 * a compation thread. (called under page lock) 698 * @vb_dev_info: the balloon device 699 * @newpage: page that will replace the isolated page after migration finishes. 700 * @page : the isolated (old) page that is about to be migrated to newpage. 701 * @mode : compaction mode -- not used for balloon page migration. 702 * 703 * After a ballooned page gets isolated by compaction procedures, this is the 704 * function that performs the page migration on behalf of a compaction thread 705 * The page migration for virtio balloon is done in a simple swap fashion which 706 * follows these two macro steps: 707 * 1) insert newpage into vb->pages list and update the host about it; 708 * 2) update the host about the old page removed from vb->pages list; 709 * 710 * This function preforms the balloon page migration task. 711 * Called through balloon_mapping->a_ops->migratepage 712 */ 713 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 714 struct page *newpage, struct page *page, enum migrate_mode mode) 715 { 716 struct virtio_balloon *vb = container_of(vb_dev_info, 717 struct virtio_balloon, vb_dev_info); 718 unsigned long flags; 719 720 /* 721 * In order to avoid lock contention while migrating pages concurrently 722 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 723 * this turn, as it is easier to retry the page migration later. 724 * This also prevents fill_balloon() getting stuck into a mutex 725 * recursion in the case it ends up triggering memory compaction 726 * while it is attempting to inflate the ballon. 727 */ 728 if (!mutex_trylock(&vb->balloon_lock)) 729 return -EAGAIN; 730 731 get_page(newpage); /* balloon reference */ 732 733 /* balloon's page migration 1st step -- inflate "newpage" */ 734 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 735 balloon_page_insert(vb_dev_info, newpage); 736 vb_dev_info->isolated_pages--; 737 __count_vm_event(BALLOON_MIGRATE); 738 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 739 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 740 set_page_pfns(vb, vb->pfns, newpage); 741 tell_host(vb, vb->inflate_vq); 742 743 /* balloon's page migration 2nd step -- deflate "page" */ 744 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 745 balloon_page_delete(page); 746 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 747 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 748 set_page_pfns(vb, vb->pfns, page); 749 tell_host(vb, vb->deflate_vq); 750 751 mutex_unlock(&vb->balloon_lock); 752 753 put_page(page); /* balloon reference */ 754 755 return MIGRATEPAGE_SUCCESS; 756 } 757 758 static struct dentry *balloon_mount(struct file_system_type *fs_type, 759 int flags, const char *dev_name, void *data) 760 { 761 static const struct dentry_operations ops = { 762 .d_dname = simple_dname, 763 }; 764 765 return mount_pseudo(fs_type, "balloon-kvm:", NULL, &ops, 766 BALLOON_KVM_MAGIC); 767 } 768 769 static struct file_system_type balloon_fs = { 770 .name = "balloon-kvm", 771 .mount = balloon_mount, 772 .kill_sb = kill_anon_super, 773 }; 774 775 #endif /* CONFIG_BALLOON_COMPACTION */ 776 777 static unsigned long shrink_free_pages(struct virtio_balloon *vb, 778 unsigned long pages_to_free) 779 { 780 unsigned long blocks_to_free, blocks_freed; 781 782 pages_to_free = round_up(pages_to_free, 783 1 << VIRTIO_BALLOON_FREE_PAGE_ORDER); 784 blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER; 785 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free); 786 787 return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER; 788 } 789 790 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb, 791 unsigned long pages_to_free) 792 { 793 unsigned long pages_freed = 0; 794 795 /* 796 * One invocation of leak_balloon can deflate at most 797 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it 798 * multiple times to deflate pages till reaching pages_to_free. 799 */ 800 while (vb->num_pages && pages_to_free) { 801 pages_freed += leak_balloon(vb, pages_to_free) / 802 VIRTIO_BALLOON_PAGES_PER_PAGE; 803 pages_to_free -= pages_freed; 804 } 805 update_balloon_size(vb); 806 807 return pages_freed; 808 } 809 810 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, 811 struct shrink_control *sc) 812 { 813 unsigned long pages_to_free, pages_freed = 0; 814 struct virtio_balloon *vb = container_of(shrinker, 815 struct virtio_balloon, shrinker); 816 817 pages_to_free = sc->nr_to_scan * VIRTIO_BALLOON_PAGES_PER_PAGE; 818 819 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 820 pages_freed = shrink_free_pages(vb, pages_to_free); 821 822 if (pages_freed >= pages_to_free) 823 return pages_freed; 824 825 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed); 826 827 return pages_freed; 828 } 829 830 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, 831 struct shrink_control *sc) 832 { 833 struct virtio_balloon *vb = container_of(shrinker, 834 struct virtio_balloon, shrinker); 835 unsigned long count; 836 837 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE; 838 count += vb->num_free_page_blocks >> VIRTIO_BALLOON_FREE_PAGE_ORDER; 839 840 return count; 841 } 842 843 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) 844 { 845 unregister_shrinker(&vb->shrinker); 846 } 847 848 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) 849 { 850 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan; 851 vb->shrinker.count_objects = virtio_balloon_shrinker_count; 852 vb->shrinker.seeks = DEFAULT_SEEKS; 853 854 return register_shrinker(&vb->shrinker); 855 } 856 857 static int virtballoon_probe(struct virtio_device *vdev) 858 { 859 struct virtio_balloon *vb; 860 __u32 poison_val; 861 int err; 862 863 if (!vdev->config->get) { 864 dev_err(&vdev->dev, "%s failure: config access disabled\n", 865 __func__); 866 return -EINVAL; 867 } 868 869 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL); 870 if (!vb) { 871 err = -ENOMEM; 872 goto out; 873 } 874 875 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); 876 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); 877 spin_lock_init(&vb->stop_update_lock); 878 mutex_init(&vb->balloon_lock); 879 init_waitqueue_head(&vb->acked); 880 vb->vdev = vdev; 881 882 balloon_devinfo_init(&vb->vb_dev_info); 883 884 err = init_vqs(vb); 885 if (err) 886 goto out_free_vb; 887 888 #ifdef CONFIG_BALLOON_COMPACTION 889 balloon_mnt = kern_mount(&balloon_fs); 890 if (IS_ERR(balloon_mnt)) { 891 err = PTR_ERR(balloon_mnt); 892 goto out_del_vqs; 893 } 894 895 vb->vb_dev_info.migratepage = virtballoon_migratepage; 896 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb); 897 if (IS_ERR(vb->vb_dev_info.inode)) { 898 err = PTR_ERR(vb->vb_dev_info.inode); 899 kern_unmount(balloon_mnt); 900 goto out_del_vqs; 901 } 902 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops; 903 #endif 904 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 905 /* 906 * There is always one entry reserved for cmd id, so the ring 907 * size needs to be at least two to report free page hints. 908 */ 909 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) { 910 err = -ENOSPC; 911 goto out_del_vqs; 912 } 913 vb->balloon_wq = alloc_workqueue("balloon-wq", 914 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); 915 if (!vb->balloon_wq) { 916 err = -ENOMEM; 917 goto out_del_vqs; 918 } 919 INIT_WORK(&vb->report_free_page_work, report_free_page_func); 920 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP; 921 vb->cmd_id_active = cpu_to_virtio32(vb->vdev, 922 VIRTIO_BALLOON_CMD_ID_STOP); 923 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev, 924 VIRTIO_BALLOON_CMD_ID_STOP); 925 vb->num_free_page_blocks = 0; 926 spin_lock_init(&vb->free_page_list_lock); 927 INIT_LIST_HEAD(&vb->free_page_list); 928 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { 929 memset(&poison_val, PAGE_POISON, sizeof(poison_val)); 930 virtio_cwrite(vb->vdev, struct virtio_balloon_config, 931 poison_val, &poison_val); 932 } 933 } 934 /* 935 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a 936 * shrinker needs to be registered to relieve memory pressure. 937 */ 938 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { 939 err = virtio_balloon_register_shrinker(vb); 940 if (err) 941 goto out_del_balloon_wq; 942 } 943 virtio_device_ready(vdev); 944 945 if (towards_target(vb)) 946 virtballoon_changed(vdev); 947 return 0; 948 949 out_del_balloon_wq: 950 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) 951 destroy_workqueue(vb->balloon_wq); 952 out_del_vqs: 953 vdev->config->del_vqs(vdev); 954 out_free_vb: 955 kfree(vb); 956 out: 957 return err; 958 } 959 960 static void remove_common(struct virtio_balloon *vb) 961 { 962 /* There might be pages left in the balloon: free them. */ 963 while (vb->num_pages) 964 leak_balloon(vb, vb->num_pages); 965 update_balloon_size(vb); 966 967 /* Now we reset the device so we can clean up the queues. */ 968 vb->vdev->config->reset(vb->vdev); 969 970 vb->vdev->config->del_vqs(vb->vdev); 971 } 972 973 static void virtballoon_remove(struct virtio_device *vdev) 974 { 975 struct virtio_balloon *vb = vdev->priv; 976 977 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 978 virtio_balloon_unregister_shrinker(vb); 979 spin_lock_irq(&vb->stop_update_lock); 980 vb->stop_update = true; 981 spin_unlock_irq(&vb->stop_update_lock); 982 cancel_work_sync(&vb->update_balloon_size_work); 983 cancel_work_sync(&vb->update_balloon_stats_work); 984 985 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { 986 cancel_work_sync(&vb->report_free_page_work); 987 destroy_workqueue(vb->balloon_wq); 988 } 989 990 remove_common(vb); 991 #ifdef CONFIG_BALLOON_COMPACTION 992 if (vb->vb_dev_info.inode) 993 iput(vb->vb_dev_info.inode); 994 995 kern_unmount(balloon_mnt); 996 #endif 997 kfree(vb); 998 } 999 1000 #ifdef CONFIG_PM_SLEEP 1001 static int virtballoon_freeze(struct virtio_device *vdev) 1002 { 1003 struct virtio_balloon *vb = vdev->priv; 1004 1005 /* 1006 * The workqueue is already frozen by the PM core before this 1007 * function is called. 1008 */ 1009 remove_common(vb); 1010 return 0; 1011 } 1012 1013 static int virtballoon_restore(struct virtio_device *vdev) 1014 { 1015 struct virtio_balloon *vb = vdev->priv; 1016 int ret; 1017 1018 ret = init_vqs(vdev->priv); 1019 if (ret) 1020 return ret; 1021 1022 virtio_device_ready(vdev); 1023 1024 if (towards_target(vb)) 1025 virtballoon_changed(vdev); 1026 update_balloon_size(vb); 1027 return 0; 1028 } 1029 #endif 1030 1031 static int virtballoon_validate(struct virtio_device *vdev) 1032 { 1033 if (!page_poisoning_enabled()) 1034 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); 1035 1036 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM); 1037 return 0; 1038 } 1039 1040 static unsigned int features[] = { 1041 VIRTIO_BALLOON_F_MUST_TELL_HOST, 1042 VIRTIO_BALLOON_F_STATS_VQ, 1043 VIRTIO_BALLOON_F_DEFLATE_ON_OOM, 1044 VIRTIO_BALLOON_F_FREE_PAGE_HINT, 1045 VIRTIO_BALLOON_F_PAGE_POISON, 1046 }; 1047 1048 static struct virtio_driver virtio_balloon_driver = { 1049 .feature_table = features, 1050 .feature_table_size = ARRAY_SIZE(features), 1051 .driver.name = KBUILD_MODNAME, 1052 .driver.owner = THIS_MODULE, 1053 .id_table = id_table, 1054 .validate = virtballoon_validate, 1055 .probe = virtballoon_probe, 1056 .remove = virtballoon_remove, 1057 .config_changed = virtballoon_changed, 1058 #ifdef CONFIG_PM_SLEEP 1059 .freeze = virtballoon_freeze, 1060 .restore = virtballoon_restore, 1061 #endif 1062 }; 1063 1064 module_virtio_driver(virtio_balloon_driver); 1065 MODULE_DEVICE_TABLE(virtio, id_table); 1066 MODULE_DESCRIPTION("Virtio balloon driver"); 1067 MODULE_LICENSE("GPL"); 1068