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/oom.h> 31 #include <linux/wait.h> 32 #include <linux/mm.h> 33 34 /* 35 * Balloon device works in 4K page units. So each page is pointed to by 36 * multiple balloon pages. All memory counters in this driver are in balloon 37 * page units. 38 */ 39 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 40 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 41 #define OOM_VBALLOON_DEFAULT_PAGES 256 42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 43 44 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES; 45 module_param(oom_pages, int, S_IRUSR | S_IWUSR); 46 MODULE_PARM_DESC(oom_pages, "pages to free on OOM"); 47 48 struct virtio_balloon { 49 struct virtio_device *vdev; 50 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; 51 52 /* The balloon servicing is delegated to a freezable workqueue. */ 53 struct work_struct update_balloon_stats_work; 54 struct work_struct update_balloon_size_work; 55 56 /* Prevent updating balloon when it is being canceled. */ 57 spinlock_t stop_update_lock; 58 bool stop_update; 59 60 /* Waiting for host to ack the pages we released. */ 61 wait_queue_head_t acked; 62 63 /* Number of balloon pages we've told the Host we're not using. */ 64 unsigned int num_pages; 65 /* 66 * The pages we've told the Host we're not using are enqueued 67 * at vb_dev_info->pages list. 68 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 69 * to num_pages above. 70 */ 71 struct balloon_dev_info vb_dev_info; 72 73 /* Synchronize access/update to this struct virtio_balloon elements */ 74 struct mutex balloon_lock; 75 76 /* The array of pfns we tell the Host about. */ 77 unsigned int num_pfns; 78 u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 79 80 /* Memory statistics */ 81 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 82 83 /* To register callback in oom notifier call chain */ 84 struct notifier_block nb; 85 }; 86 87 static struct virtio_device_id id_table[] = { 88 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 89 { 0 }, 90 }; 91 92 static u32 page_to_balloon_pfn(struct page *page) 93 { 94 unsigned long pfn = page_to_pfn(page); 95 96 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 97 /* Convert pfn from Linux page size to balloon page size. */ 98 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 99 } 100 101 static struct page *balloon_pfn_to_page(u32 pfn) 102 { 103 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE); 104 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE); 105 } 106 107 static void balloon_ack(struct virtqueue *vq) 108 { 109 struct virtio_balloon *vb = vq->vdev->priv; 110 111 wake_up(&vb->acked); 112 } 113 114 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 115 { 116 struct scatterlist sg; 117 unsigned int len; 118 119 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 120 121 /* We should always be able to add one buffer to an empty queue. */ 122 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 123 virtqueue_kick(vq); 124 125 /* When host has read buffer, this completes via balloon_ack */ 126 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 127 128 } 129 130 static void set_page_pfns(u32 pfns[], struct page *page) 131 { 132 unsigned int i; 133 134 /* Set balloon pfns pointing at this page. 135 * Note that the first pfn points at start of the page. */ 136 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 137 pfns[i] = page_to_balloon_pfn(page) + i; 138 } 139 140 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) 141 { 142 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 143 unsigned num_allocated_pages; 144 145 /* We can only do one array worth at a time. */ 146 num = min(num, ARRAY_SIZE(vb->pfns)); 147 148 mutex_lock(&vb->balloon_lock); 149 for (vb->num_pfns = 0; vb->num_pfns < num; 150 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 151 struct page *page = balloon_page_enqueue(vb_dev_info); 152 153 if (!page) { 154 dev_info_ratelimited(&vb->vdev->dev, 155 "Out of puff! Can't get %u pages\n", 156 VIRTIO_BALLOON_PAGES_PER_PAGE); 157 /* Sleep for at least 1/5 of a second before retry. */ 158 msleep(200); 159 break; 160 } 161 set_page_pfns(vb->pfns + vb->num_pfns, page); 162 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 163 if (!virtio_has_feature(vb->vdev, 164 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 165 adjust_managed_page_count(page, -1); 166 } 167 168 num_allocated_pages = vb->num_pfns; 169 /* Did we get any? */ 170 if (vb->num_pfns != 0) 171 tell_host(vb, vb->inflate_vq); 172 mutex_unlock(&vb->balloon_lock); 173 174 return num_allocated_pages; 175 } 176 177 static void release_pages_balloon(struct virtio_balloon *vb) 178 { 179 unsigned int i; 180 181 /* Find pfns pointing at start of each page, get pages and free them. */ 182 for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) { 183 struct page *page = balloon_pfn_to_page(vb->pfns[i]); 184 if (!virtio_has_feature(vb->vdev, 185 VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 186 adjust_managed_page_count(page, 1); 187 put_page(page); /* balloon reference */ 188 } 189 } 190 191 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) 192 { 193 unsigned num_freed_pages; 194 struct page *page; 195 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 196 197 /* We can only do one array worth at a time. */ 198 num = min(num, ARRAY_SIZE(vb->pfns)); 199 200 mutex_lock(&vb->balloon_lock); 201 for (vb->num_pfns = 0; vb->num_pfns < num; 202 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 203 page = balloon_page_dequeue(vb_dev_info); 204 if (!page) 205 break; 206 set_page_pfns(vb->pfns + vb->num_pfns, page); 207 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 208 } 209 210 num_freed_pages = vb->num_pfns; 211 /* 212 * Note that if 213 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 214 * is true, we *have* to do it in this order 215 */ 216 if (vb->num_pfns != 0) 217 tell_host(vb, vb->deflate_vq); 218 release_pages_balloon(vb); 219 mutex_unlock(&vb->balloon_lock); 220 return num_freed_pages; 221 } 222 223 static inline void update_stat(struct virtio_balloon *vb, int idx, 224 u16 tag, u64 val) 225 { 226 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 227 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag); 228 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); 229 } 230 231 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 232 233 static void update_balloon_stats(struct virtio_balloon *vb) 234 { 235 unsigned long events[NR_VM_EVENT_ITEMS]; 236 struct sysinfo i; 237 int idx = 0; 238 long available; 239 240 all_vm_events(events); 241 si_meminfo(&i); 242 243 available = si_mem_available(); 244 245 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 246 pages_to_bytes(events[PSWPIN])); 247 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 248 pages_to_bytes(events[PSWPOUT])); 249 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 250 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 251 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 252 pages_to_bytes(i.freeram)); 253 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 254 pages_to_bytes(i.totalram)); 255 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, 256 pages_to_bytes(available)); 257 } 258 259 /* 260 * While most virtqueues communicate guest-initiated requests to the hypervisor, 261 * the stats queue operates in reverse. The driver initializes the virtqueue 262 * with a single buffer. From that point forward, all conversations consist of 263 * a hypervisor request (a call to this function) which directs us to refill 264 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 265 * we delegate the job to a freezable workqueue that will do the actual work via 266 * stats_handle_request(). 267 */ 268 static void stats_request(struct virtqueue *vq) 269 { 270 struct virtio_balloon *vb = vq->vdev->priv; 271 272 spin_lock(&vb->stop_update_lock); 273 if (!vb->stop_update) 274 queue_work(system_freezable_wq, &vb->update_balloon_stats_work); 275 spin_unlock(&vb->stop_update_lock); 276 } 277 278 static void stats_handle_request(struct virtio_balloon *vb) 279 { 280 struct virtqueue *vq; 281 struct scatterlist sg; 282 unsigned int len; 283 284 update_balloon_stats(vb); 285 286 vq = vb->stats_vq; 287 if (!virtqueue_get_buf(vq, &len)) 288 return; 289 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 290 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 291 virtqueue_kick(vq); 292 } 293 294 static void virtballoon_changed(struct virtio_device *vdev) 295 { 296 struct virtio_balloon *vb = vdev->priv; 297 unsigned long flags; 298 299 spin_lock_irqsave(&vb->stop_update_lock, flags); 300 if (!vb->stop_update) 301 queue_work(system_freezable_wq, &vb->update_balloon_size_work); 302 spin_unlock_irqrestore(&vb->stop_update_lock, flags); 303 } 304 305 static inline s64 towards_target(struct virtio_balloon *vb) 306 { 307 s64 target; 308 u32 num_pages; 309 310 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, 311 &num_pages); 312 313 /* Legacy balloon config space is LE, unlike all other devices. */ 314 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 315 num_pages = le32_to_cpu((__force __le32)num_pages); 316 317 target = num_pages; 318 return target - vb->num_pages; 319 } 320 321 static void update_balloon_size(struct virtio_balloon *vb) 322 { 323 u32 actual = vb->num_pages; 324 325 /* Legacy balloon config space is LE, unlike all other devices. */ 326 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) 327 actual = (__force u32)cpu_to_le32(actual); 328 329 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, 330 &actual); 331 } 332 333 /* 334 * virtballoon_oom_notify - release pages when system is under severe 335 * memory pressure (called from out_of_memory()) 336 * @self : notifier block struct 337 * @dummy: not used 338 * @parm : returned - number of freed pages 339 * 340 * The balancing of memory by use of the virtio balloon should not cause 341 * the termination of processes while there are pages in the balloon. 342 * If virtio balloon manages to release some memory, it will make the 343 * system return and retry the allocation that forced the OOM killer 344 * to run. 345 */ 346 static int virtballoon_oom_notify(struct notifier_block *self, 347 unsigned long dummy, void *parm) 348 { 349 struct virtio_balloon *vb; 350 unsigned long *freed; 351 unsigned num_freed_pages; 352 353 vb = container_of(self, struct virtio_balloon, nb); 354 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) 355 return NOTIFY_OK; 356 357 freed = parm; 358 num_freed_pages = leak_balloon(vb, oom_pages); 359 update_balloon_size(vb); 360 *freed += num_freed_pages; 361 362 return NOTIFY_OK; 363 } 364 365 static void update_balloon_stats_func(struct work_struct *work) 366 { 367 struct virtio_balloon *vb; 368 369 vb = container_of(work, struct virtio_balloon, 370 update_balloon_stats_work); 371 stats_handle_request(vb); 372 } 373 374 static void update_balloon_size_func(struct work_struct *work) 375 { 376 struct virtio_balloon *vb; 377 s64 diff; 378 379 vb = container_of(work, struct virtio_balloon, 380 update_balloon_size_work); 381 diff = towards_target(vb); 382 383 if (diff > 0) 384 diff -= fill_balloon(vb, diff); 385 else if (diff < 0) 386 diff += leak_balloon(vb, -diff); 387 update_balloon_size(vb); 388 389 if (diff) 390 queue_work(system_freezable_wq, work); 391 } 392 393 static int init_vqs(struct virtio_balloon *vb) 394 { 395 struct virtqueue *vqs[3]; 396 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 397 static const char * const names[] = { "inflate", "deflate", "stats" }; 398 int err, nvqs; 399 400 /* 401 * We expect two virtqueues: inflate and deflate, and 402 * optionally stat. 403 */ 404 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 405 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names); 406 if (err) 407 return err; 408 409 vb->inflate_vq = vqs[0]; 410 vb->deflate_vq = vqs[1]; 411 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 412 struct scatterlist sg; 413 vb->stats_vq = vqs[2]; 414 415 /* 416 * Prime this virtqueue with one buffer so the hypervisor can 417 * use it to signal us later (it can't be broken yet!). 418 */ 419 sg_init_one(&sg, vb->stats, sizeof vb->stats); 420 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) 421 < 0) 422 BUG(); 423 virtqueue_kick(vb->stats_vq); 424 } 425 return 0; 426 } 427 428 #ifdef CONFIG_BALLOON_COMPACTION 429 /* 430 * virtballoon_migratepage - perform the balloon page migration on behalf of 431 * a compation thread. (called under page lock) 432 * @vb_dev_info: the balloon device 433 * @newpage: page that will replace the isolated page after migration finishes. 434 * @page : the isolated (old) page that is about to be migrated to newpage. 435 * @mode : compaction mode -- not used for balloon page migration. 436 * 437 * After a ballooned page gets isolated by compaction procedures, this is the 438 * function that performs the page migration on behalf of a compaction thread 439 * The page migration for virtio balloon is done in a simple swap fashion which 440 * follows these two macro steps: 441 * 1) insert newpage into vb->pages list and update the host about it; 442 * 2) update the host about the old page removed from vb->pages list; 443 * 444 * This function preforms the balloon page migration task. 445 * Called through balloon_mapping->a_ops->migratepage 446 */ 447 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 448 struct page *newpage, struct page *page, enum migrate_mode mode) 449 { 450 struct virtio_balloon *vb = container_of(vb_dev_info, 451 struct virtio_balloon, vb_dev_info); 452 unsigned long flags; 453 454 /* 455 * In order to avoid lock contention while migrating pages concurrently 456 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 457 * this turn, as it is easier to retry the page migration later. 458 * This also prevents fill_balloon() getting stuck into a mutex 459 * recursion in the case it ends up triggering memory compaction 460 * while it is attempting to inflate the ballon. 461 */ 462 if (!mutex_trylock(&vb->balloon_lock)) 463 return -EAGAIN; 464 465 get_page(newpage); /* balloon reference */ 466 467 /* balloon's page migration 1st step -- inflate "newpage" */ 468 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 469 balloon_page_insert(vb_dev_info, newpage); 470 vb_dev_info->isolated_pages--; 471 __count_vm_event(BALLOON_MIGRATE); 472 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 473 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 474 set_page_pfns(vb->pfns, newpage); 475 tell_host(vb, vb->inflate_vq); 476 477 /* balloon's page migration 2nd step -- deflate "page" */ 478 balloon_page_delete(page); 479 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 480 set_page_pfns(vb->pfns, page); 481 tell_host(vb, vb->deflate_vq); 482 483 mutex_unlock(&vb->balloon_lock); 484 485 put_page(page); /* balloon reference */ 486 487 return MIGRATEPAGE_SUCCESS; 488 } 489 #endif /* CONFIG_BALLOON_COMPACTION */ 490 491 static int virtballoon_probe(struct virtio_device *vdev) 492 { 493 struct virtio_balloon *vb; 494 int err; 495 496 if (!vdev->config->get) { 497 dev_err(&vdev->dev, "%s failure: config access disabled\n", 498 __func__); 499 return -EINVAL; 500 } 501 502 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 503 if (!vb) { 504 err = -ENOMEM; 505 goto out; 506 } 507 508 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); 509 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); 510 spin_lock_init(&vb->stop_update_lock); 511 vb->stop_update = false; 512 vb->num_pages = 0; 513 mutex_init(&vb->balloon_lock); 514 init_waitqueue_head(&vb->acked); 515 vb->vdev = vdev; 516 517 balloon_devinfo_init(&vb->vb_dev_info); 518 #ifdef CONFIG_BALLOON_COMPACTION 519 vb->vb_dev_info.migratepage = virtballoon_migratepage; 520 #endif 521 522 err = init_vqs(vb); 523 if (err) 524 goto out_free_vb; 525 526 vb->nb.notifier_call = virtballoon_oom_notify; 527 vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY; 528 err = register_oom_notifier(&vb->nb); 529 if (err < 0) 530 goto out_oom_notify; 531 532 virtio_device_ready(vdev); 533 534 return 0; 535 536 out_oom_notify: 537 vdev->config->del_vqs(vdev); 538 out_free_vb: 539 kfree(vb); 540 out: 541 return err; 542 } 543 544 static void remove_common(struct virtio_balloon *vb) 545 { 546 /* There might be pages left in the balloon: free them. */ 547 while (vb->num_pages) 548 leak_balloon(vb, vb->num_pages); 549 update_balloon_size(vb); 550 551 /* Now we reset the device so we can clean up the queues. */ 552 vb->vdev->config->reset(vb->vdev); 553 554 vb->vdev->config->del_vqs(vb->vdev); 555 } 556 557 static void virtballoon_remove(struct virtio_device *vdev) 558 { 559 struct virtio_balloon *vb = vdev->priv; 560 561 unregister_oom_notifier(&vb->nb); 562 563 spin_lock_irq(&vb->stop_update_lock); 564 vb->stop_update = true; 565 spin_unlock_irq(&vb->stop_update_lock); 566 cancel_work_sync(&vb->update_balloon_size_work); 567 cancel_work_sync(&vb->update_balloon_stats_work); 568 569 remove_common(vb); 570 kfree(vb); 571 } 572 573 #ifdef CONFIG_PM_SLEEP 574 static int virtballoon_freeze(struct virtio_device *vdev) 575 { 576 struct virtio_balloon *vb = vdev->priv; 577 578 /* 579 * The workqueue is already frozen by the PM core before this 580 * function is called. 581 */ 582 remove_common(vb); 583 return 0; 584 } 585 586 static int virtballoon_restore(struct virtio_device *vdev) 587 { 588 struct virtio_balloon *vb = vdev->priv; 589 int ret; 590 591 ret = init_vqs(vdev->priv); 592 if (ret) 593 return ret; 594 595 virtio_device_ready(vdev); 596 597 if (towards_target(vb)) 598 virtballoon_changed(vdev); 599 update_balloon_size(vb); 600 return 0; 601 } 602 #endif 603 604 static unsigned int features[] = { 605 VIRTIO_BALLOON_F_MUST_TELL_HOST, 606 VIRTIO_BALLOON_F_STATS_VQ, 607 VIRTIO_BALLOON_F_DEFLATE_ON_OOM, 608 }; 609 610 static struct virtio_driver virtio_balloon_driver = { 611 .feature_table = features, 612 .feature_table_size = ARRAY_SIZE(features), 613 .driver.name = KBUILD_MODNAME, 614 .driver.owner = THIS_MODULE, 615 .id_table = id_table, 616 .probe = virtballoon_probe, 617 .remove = virtballoon_remove, 618 .config_changed = virtballoon_changed, 619 #ifdef CONFIG_PM_SLEEP 620 .freeze = virtballoon_freeze, 621 .restore = virtballoon_restore, 622 #endif 623 }; 624 625 module_virtio_driver(virtio_balloon_driver); 626 MODULE_DEVICE_TABLE(virtio, id_table); 627 MODULE_DESCRIPTION("Virtio balloon driver"); 628 MODULE_LICENSE("GPL"); 629