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/kthread.h> 26 #include <linux/freezer.h> 27 #include <linux/delay.h> 28 #include <linux/slab.h> 29 #include <linux/module.h> 30 #include <linux/balloon_compaction.h> 31 32 /* 33 * Balloon device works in 4K page units. So each page is pointed to by 34 * multiple balloon pages. All memory counters in this driver are in balloon 35 * page units. 36 */ 37 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) 38 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 39 40 struct virtio_balloon 41 { 42 struct virtio_device *vdev; 43 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; 44 45 /* Where the ballooning thread waits for config to change. */ 46 wait_queue_head_t config_change; 47 48 /* The thread servicing the balloon. */ 49 struct task_struct *thread; 50 51 /* Waiting for host to ack the pages we released. */ 52 wait_queue_head_t acked; 53 54 /* Number of balloon pages we've told the Host we're not using. */ 55 unsigned int num_pages; 56 /* 57 * The pages we've told the Host we're not using are enqueued 58 * at vb_dev_info->pages list. 59 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE 60 * to num_pages above. 61 */ 62 struct balloon_dev_info *vb_dev_info; 63 64 /* Synchronize access/update to this struct virtio_balloon elements */ 65 struct mutex balloon_lock; 66 67 /* The array of pfns we tell the Host about. */ 68 unsigned int num_pfns; 69 u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; 70 71 /* Memory statistics */ 72 int need_stats_update; 73 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; 74 }; 75 76 static struct virtio_device_id id_table[] = { 77 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 78 { 0 }, 79 }; 80 81 static u32 page_to_balloon_pfn(struct page *page) 82 { 83 unsigned long pfn = page_to_pfn(page); 84 85 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 86 /* Convert pfn from Linux page size to balloon page size. */ 87 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; 88 } 89 90 static struct page *balloon_pfn_to_page(u32 pfn) 91 { 92 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE); 93 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE); 94 } 95 96 static void balloon_ack(struct virtqueue *vq) 97 { 98 struct virtio_balloon *vb = vq->vdev->priv; 99 100 wake_up(&vb->acked); 101 } 102 103 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 104 { 105 struct scatterlist sg; 106 unsigned int len; 107 108 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 109 110 /* We should always be able to add one buffer to an empty queue. */ 111 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0) 112 BUG(); 113 virtqueue_kick(vq); 114 115 /* When host has read buffer, this completes via balloon_ack */ 116 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 117 } 118 119 static void set_page_pfns(u32 pfns[], struct page *page) 120 { 121 unsigned int i; 122 123 /* Set balloon pfns pointing at this page. 124 * Note that the first pfn points at start of the page. */ 125 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 126 pfns[i] = page_to_balloon_pfn(page) + i; 127 } 128 129 static void fill_balloon(struct virtio_balloon *vb, size_t num) 130 { 131 struct balloon_dev_info *vb_dev_info = vb->vb_dev_info; 132 133 /* We can only do one array worth at a time. */ 134 num = min(num, ARRAY_SIZE(vb->pfns)); 135 136 mutex_lock(&vb->balloon_lock); 137 for (vb->num_pfns = 0; vb->num_pfns < num; 138 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 139 struct page *page = balloon_page_enqueue(vb_dev_info); 140 141 if (!page) { 142 if (printk_ratelimit()) 143 dev_printk(KERN_INFO, &vb->vdev->dev, 144 "Out of puff! Can't get %u pages\n", 145 VIRTIO_BALLOON_PAGES_PER_PAGE); 146 /* Sleep for at least 1/5 of a second before retry. */ 147 msleep(200); 148 break; 149 } 150 set_page_pfns(vb->pfns + vb->num_pfns, page); 151 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 152 totalram_pages--; 153 } 154 155 /* Did we get any? */ 156 if (vb->num_pfns != 0) 157 tell_host(vb, vb->inflate_vq); 158 mutex_unlock(&vb->balloon_lock); 159 } 160 161 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 162 { 163 unsigned int i; 164 165 /* Find pfns pointing at start of each page, get pages and free them. */ 166 for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) { 167 balloon_page_free(balloon_pfn_to_page(pfns[i])); 168 totalram_pages++; 169 } 170 } 171 172 static void leak_balloon(struct virtio_balloon *vb, size_t num) 173 { 174 struct page *page; 175 struct balloon_dev_info *vb_dev_info = vb->vb_dev_info; 176 177 /* We can only do one array worth at a time. */ 178 num = min(num, ARRAY_SIZE(vb->pfns)); 179 180 mutex_lock(&vb->balloon_lock); 181 for (vb->num_pfns = 0; vb->num_pfns < num; 182 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 183 page = balloon_page_dequeue(vb_dev_info); 184 if (!page) 185 break; 186 set_page_pfns(vb->pfns + vb->num_pfns, page); 187 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 188 } 189 190 /* 191 * Note that if 192 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 193 * is true, we *have* to do it in this order 194 */ 195 tell_host(vb, vb->deflate_vq); 196 mutex_unlock(&vb->balloon_lock); 197 release_pages_by_pfn(vb->pfns, vb->num_pfns); 198 } 199 200 static inline void update_stat(struct virtio_balloon *vb, int idx, 201 u16 tag, u64 val) 202 { 203 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 204 vb->stats[idx].tag = tag; 205 vb->stats[idx].val = val; 206 } 207 208 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 209 210 static void update_balloon_stats(struct virtio_balloon *vb) 211 { 212 unsigned long events[NR_VM_EVENT_ITEMS]; 213 struct sysinfo i; 214 int idx = 0; 215 216 all_vm_events(events); 217 si_meminfo(&i); 218 219 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 220 pages_to_bytes(events[PSWPIN])); 221 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 222 pages_to_bytes(events[PSWPOUT])); 223 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 224 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 225 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 226 pages_to_bytes(i.freeram)); 227 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 228 pages_to_bytes(i.totalram)); 229 } 230 231 /* 232 * While most virtqueues communicate guest-initiated requests to the hypervisor, 233 * the stats queue operates in reverse. The driver initializes the virtqueue 234 * with a single buffer. From that point forward, all conversations consist of 235 * a hypervisor request (a call to this function) which directs us to refill 236 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 237 * we notify our kthread which does the actual work via stats_handle_request(). 238 */ 239 static void stats_request(struct virtqueue *vq) 240 { 241 struct virtio_balloon *vb = vq->vdev->priv; 242 243 vb->need_stats_update = 1; 244 wake_up(&vb->config_change); 245 } 246 247 static void stats_handle_request(struct virtio_balloon *vb) 248 { 249 struct virtqueue *vq; 250 struct scatterlist sg; 251 unsigned int len; 252 253 vb->need_stats_update = 0; 254 update_balloon_stats(vb); 255 256 vq = vb->stats_vq; 257 if (!virtqueue_get_buf(vq, &len)) 258 return; 259 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 260 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0) 261 BUG(); 262 virtqueue_kick(vq); 263 } 264 265 static void virtballoon_changed(struct virtio_device *vdev) 266 { 267 struct virtio_balloon *vb = vdev->priv; 268 269 wake_up(&vb->config_change); 270 } 271 272 static inline s64 towards_target(struct virtio_balloon *vb) 273 { 274 __le32 v; 275 s64 target; 276 277 vb->vdev->config->get(vb->vdev, 278 offsetof(struct virtio_balloon_config, num_pages), 279 &v, sizeof(v)); 280 target = le32_to_cpu(v); 281 return target - vb->num_pages; 282 } 283 284 static void update_balloon_size(struct virtio_balloon *vb) 285 { 286 __le32 actual = cpu_to_le32(vb->num_pages); 287 288 vb->vdev->config->set(vb->vdev, 289 offsetof(struct virtio_balloon_config, actual), 290 &actual, sizeof(actual)); 291 } 292 293 static int balloon(void *_vballoon) 294 { 295 struct virtio_balloon *vb = _vballoon; 296 297 set_freezable(); 298 while (!kthread_should_stop()) { 299 s64 diff; 300 301 try_to_freeze(); 302 wait_event_interruptible(vb->config_change, 303 (diff = towards_target(vb)) != 0 304 || vb->need_stats_update 305 || kthread_should_stop() 306 || freezing(current)); 307 if (vb->need_stats_update) 308 stats_handle_request(vb); 309 if (diff > 0) 310 fill_balloon(vb, diff); 311 else if (diff < 0) 312 leak_balloon(vb, -diff); 313 update_balloon_size(vb); 314 } 315 return 0; 316 } 317 318 static int init_vqs(struct virtio_balloon *vb) 319 { 320 struct virtqueue *vqs[3]; 321 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 322 const char *names[] = { "inflate", "deflate", "stats" }; 323 int err, nvqs; 324 325 /* 326 * We expect two virtqueues: inflate and deflate, and 327 * optionally stat. 328 */ 329 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 330 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names); 331 if (err) 332 return err; 333 334 vb->inflate_vq = vqs[0]; 335 vb->deflate_vq = vqs[1]; 336 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 337 struct scatterlist sg; 338 vb->stats_vq = vqs[2]; 339 340 /* 341 * Prime this virtqueue with one buffer so the hypervisor can 342 * use it to signal us later. 343 */ 344 sg_init_one(&sg, vb->stats, sizeof vb->stats); 345 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL) 346 < 0) 347 BUG(); 348 virtqueue_kick(vb->stats_vq); 349 } 350 return 0; 351 } 352 353 static const struct address_space_operations virtio_balloon_aops; 354 #ifdef CONFIG_BALLOON_COMPACTION 355 /* 356 * virtballoon_migratepage - perform the balloon page migration on behalf of 357 * a compation thread. (called under page lock) 358 * @mapping: the page->mapping which will be assigned to the new migrated page. 359 * @newpage: page that will replace the isolated page after migration finishes. 360 * @page : the isolated (old) page that is about to be migrated to newpage. 361 * @mode : compaction mode -- not used for balloon page migration. 362 * 363 * After a ballooned page gets isolated by compaction procedures, this is the 364 * function that performs the page migration on behalf of a compaction thread 365 * The page migration for virtio balloon is done in a simple swap fashion which 366 * follows these two macro steps: 367 * 1) insert newpage into vb->pages list and update the host about it; 368 * 2) update the host about the old page removed from vb->pages list; 369 * 370 * This function preforms the balloon page migration task. 371 * Called through balloon_mapping->a_ops->migratepage 372 */ 373 int virtballoon_migratepage(struct address_space *mapping, 374 struct page *newpage, struct page *page, enum migrate_mode mode) 375 { 376 struct balloon_dev_info *vb_dev_info = balloon_page_device(page); 377 struct virtio_balloon *vb; 378 unsigned long flags; 379 380 BUG_ON(!vb_dev_info); 381 382 vb = vb_dev_info->balloon_device; 383 384 /* 385 * In order to avoid lock contention while migrating pages concurrently 386 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 387 * this turn, as it is easier to retry the page migration later. 388 * This also prevents fill_balloon() getting stuck into a mutex 389 * recursion in the case it ends up triggering memory compaction 390 * while it is attempting to inflate the ballon. 391 */ 392 if (!mutex_trylock(&vb->balloon_lock)) 393 return -EAGAIN; 394 395 /* balloon's page migration 1st step -- inflate "newpage" */ 396 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 397 balloon_page_insert(newpage, mapping, &vb_dev_info->pages); 398 vb_dev_info->isolated_pages--; 399 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 400 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 401 set_page_pfns(vb->pfns, newpage); 402 tell_host(vb, vb->inflate_vq); 403 404 /* 405 * balloon's page migration 2nd step -- deflate "page" 406 * 407 * It's safe to delete page->lru here because this page is at 408 * an isolated migration list, and this step is expected to happen here 409 */ 410 balloon_page_delete(page); 411 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 412 set_page_pfns(vb->pfns, page); 413 tell_host(vb, vb->deflate_vq); 414 415 mutex_unlock(&vb->balloon_lock); 416 417 return MIGRATEPAGE_BALLOON_SUCCESS; 418 } 419 420 /* define the balloon_mapping->a_ops callback to allow balloon page migration */ 421 static const struct address_space_operations virtio_balloon_aops = { 422 .migratepage = virtballoon_migratepage, 423 }; 424 #endif /* CONFIG_BALLOON_COMPACTION */ 425 426 static int virtballoon_probe(struct virtio_device *vdev) 427 { 428 struct virtio_balloon *vb; 429 struct address_space *vb_mapping; 430 struct balloon_dev_info *vb_devinfo; 431 int err; 432 433 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 434 if (!vb) { 435 err = -ENOMEM; 436 goto out; 437 } 438 439 vb->num_pages = 0; 440 mutex_init(&vb->balloon_lock); 441 init_waitqueue_head(&vb->config_change); 442 init_waitqueue_head(&vb->acked); 443 vb->vdev = vdev; 444 vb->need_stats_update = 0; 445 446 vb_devinfo = balloon_devinfo_alloc(vb); 447 if (IS_ERR(vb_devinfo)) { 448 err = PTR_ERR(vb_devinfo); 449 goto out_free_vb; 450 } 451 452 vb_mapping = balloon_mapping_alloc(vb_devinfo, 453 (balloon_compaction_check()) ? 454 &virtio_balloon_aops : NULL); 455 if (IS_ERR(vb_mapping)) { 456 /* 457 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP 458 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off. 459 */ 460 err = PTR_ERR(vb_mapping); 461 if (err != -EOPNOTSUPP) 462 goto out_free_vb_devinfo; 463 } 464 465 vb->vb_dev_info = vb_devinfo; 466 467 err = init_vqs(vb); 468 if (err) 469 goto out_free_vb_mapping; 470 471 vb->thread = kthread_run(balloon, vb, "vballoon"); 472 if (IS_ERR(vb->thread)) { 473 err = PTR_ERR(vb->thread); 474 goto out_del_vqs; 475 } 476 477 return 0; 478 479 out_del_vqs: 480 vdev->config->del_vqs(vdev); 481 out_free_vb_mapping: 482 balloon_mapping_free(vb_mapping); 483 out_free_vb_devinfo: 484 balloon_devinfo_free(vb_devinfo); 485 out_free_vb: 486 kfree(vb); 487 out: 488 return err; 489 } 490 491 static void remove_common(struct virtio_balloon *vb) 492 { 493 /* There might be pages left in the balloon: free them. */ 494 while (vb->num_pages) 495 leak_balloon(vb, vb->num_pages); 496 update_balloon_size(vb); 497 498 /* Now we reset the device so we can clean up the queues. */ 499 vb->vdev->config->reset(vb->vdev); 500 501 vb->vdev->config->del_vqs(vb->vdev); 502 } 503 504 static void __devexit virtballoon_remove(struct virtio_device *vdev) 505 { 506 struct virtio_balloon *vb = vdev->priv; 507 508 kthread_stop(vb->thread); 509 remove_common(vb); 510 balloon_mapping_free(vb->vb_dev_info->mapping); 511 balloon_devinfo_free(vb->vb_dev_info); 512 kfree(vb); 513 } 514 515 #ifdef CONFIG_PM 516 static int virtballoon_freeze(struct virtio_device *vdev) 517 { 518 struct virtio_balloon *vb = vdev->priv; 519 520 /* 521 * The kthread is already frozen by the PM core before this 522 * function is called. 523 */ 524 525 remove_common(vb); 526 return 0; 527 } 528 529 static int virtballoon_restore(struct virtio_device *vdev) 530 { 531 struct virtio_balloon *vb = vdev->priv; 532 int ret; 533 534 ret = init_vqs(vdev->priv); 535 if (ret) 536 return ret; 537 538 fill_balloon(vb, towards_target(vb)); 539 update_balloon_size(vb); 540 return 0; 541 } 542 #endif 543 544 static unsigned int features[] = { 545 VIRTIO_BALLOON_F_MUST_TELL_HOST, 546 VIRTIO_BALLOON_F_STATS_VQ, 547 }; 548 549 static struct virtio_driver virtio_balloon_driver = { 550 .feature_table = features, 551 .feature_table_size = ARRAY_SIZE(features), 552 .driver.name = KBUILD_MODNAME, 553 .driver.owner = THIS_MODULE, 554 .id_table = id_table, 555 .probe = virtballoon_probe, 556 .remove = __devexit_p(virtballoon_remove), 557 .config_changed = virtballoon_changed, 558 #ifdef CONFIG_PM 559 .freeze = virtballoon_freeze, 560 .restore = virtballoon_restore, 561 #endif 562 }; 563 564 static int __init init(void) 565 { 566 return register_virtio_driver(&virtio_balloon_driver); 567 } 568 569 static void __exit fini(void) 570 { 571 unregister_virtio_driver(&virtio_balloon_driver); 572 } 573 module_init(init); 574 module_exit(fini); 575 576 MODULE_DEVICE_TABLE(virtio, id_table); 577 MODULE_DESCRIPTION("Virtio balloon driver"); 578 MODULE_LICENSE("GPL"); 579