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_outbuf(vq, &sg, 1, 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 dev_info_ratelimited(&vb->vdev->dev, 143 "Out of puff! Can't get %u pages\n", 144 VIRTIO_BALLOON_PAGES_PER_PAGE); 145 /* Sleep for at least 1/5 of a second before retry. */ 146 msleep(200); 147 break; 148 } 149 set_page_pfns(vb->pfns + vb->num_pfns, page); 150 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 151 adjust_managed_page_count(page, -1); 152 } 153 154 /* Did we get any? */ 155 if (vb->num_pfns != 0) 156 tell_host(vb, vb->inflate_vq); 157 mutex_unlock(&vb->balloon_lock); 158 } 159 160 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 161 { 162 unsigned int i; 163 164 /* Find pfns pointing at start of each page, get pages and free them. */ 165 for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) { 166 struct page *page = balloon_pfn_to_page(pfns[i]); 167 balloon_page_free(page); 168 adjust_managed_page_count(page, 1); 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 if (vb->num_pfns != 0) 196 tell_host(vb, vb->deflate_vq); 197 mutex_unlock(&vb->balloon_lock); 198 release_pages_by_pfn(vb->pfns, vb->num_pfns); 199 } 200 201 static inline void update_stat(struct virtio_balloon *vb, int idx, 202 u16 tag, u64 val) 203 { 204 BUG_ON(idx >= VIRTIO_BALLOON_S_NR); 205 vb->stats[idx].tag = tag; 206 vb->stats[idx].val = val; 207 } 208 209 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) 210 211 static void update_balloon_stats(struct virtio_balloon *vb) 212 { 213 unsigned long events[NR_VM_EVENT_ITEMS]; 214 struct sysinfo i; 215 int idx = 0; 216 217 all_vm_events(events); 218 si_meminfo(&i); 219 220 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, 221 pages_to_bytes(events[PSWPIN])); 222 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, 223 pages_to_bytes(events[PSWPOUT])); 224 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); 225 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); 226 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, 227 pages_to_bytes(i.freeram)); 228 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, 229 pages_to_bytes(i.totalram)); 230 } 231 232 /* 233 * While most virtqueues communicate guest-initiated requests to the hypervisor, 234 * the stats queue operates in reverse. The driver initializes the virtqueue 235 * with a single buffer. From that point forward, all conversations consist of 236 * a hypervisor request (a call to this function) which directs us to refill 237 * the virtqueue with a fresh stats buffer. Since stats collection can sleep, 238 * we notify our kthread which does the actual work via stats_handle_request(). 239 */ 240 static void stats_request(struct virtqueue *vq) 241 { 242 struct virtio_balloon *vb = vq->vdev->priv; 243 244 vb->need_stats_update = 1; 245 wake_up(&vb->config_change); 246 } 247 248 static void stats_handle_request(struct virtio_balloon *vb) 249 { 250 struct virtqueue *vq; 251 struct scatterlist sg; 252 unsigned int len; 253 254 vb->need_stats_update = 0; 255 update_balloon_stats(vb); 256 257 vq = vb->stats_vq; 258 if (!virtqueue_get_buf(vq, &len)) 259 return; 260 sg_init_one(&sg, vb->stats, sizeof(vb->stats)); 261 if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0) 262 BUG(); 263 virtqueue_kick(vq); 264 } 265 266 static void virtballoon_changed(struct virtio_device *vdev) 267 { 268 struct virtio_balloon *vb = vdev->priv; 269 270 wake_up(&vb->config_change); 271 } 272 273 static inline s64 towards_target(struct virtio_balloon *vb) 274 { 275 __le32 v; 276 s64 target; 277 278 vb->vdev->config->get(vb->vdev, 279 offsetof(struct virtio_balloon_config, num_pages), 280 &v, sizeof(v)); 281 target = le32_to_cpu(v); 282 return target - vb->num_pages; 283 } 284 285 static void update_balloon_size(struct virtio_balloon *vb) 286 { 287 __le32 actual = cpu_to_le32(vb->num_pages); 288 289 vb->vdev->config->set(vb->vdev, 290 offsetof(struct virtio_balloon_config, actual), 291 &actual, sizeof(actual)); 292 } 293 294 static int balloon(void *_vballoon) 295 { 296 struct virtio_balloon *vb = _vballoon; 297 298 set_freezable(); 299 while (!kthread_should_stop()) { 300 s64 diff; 301 302 try_to_freeze(); 303 wait_event_interruptible(vb->config_change, 304 (diff = towards_target(vb)) != 0 305 || vb->need_stats_update 306 || kthread_should_stop() 307 || freezing(current)); 308 if (vb->need_stats_update) 309 stats_handle_request(vb); 310 if (diff > 0) 311 fill_balloon(vb, diff); 312 else if (diff < 0) 313 leak_balloon(vb, -diff); 314 update_balloon_size(vb); 315 } 316 return 0; 317 } 318 319 static int init_vqs(struct virtio_balloon *vb) 320 { 321 struct virtqueue *vqs[3]; 322 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 323 const char *names[] = { "inflate", "deflate", "stats" }; 324 int err, nvqs; 325 326 /* 327 * We expect two virtqueues: inflate and deflate, and 328 * optionally stat. 329 */ 330 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 331 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names); 332 if (err) 333 return err; 334 335 vb->inflate_vq = vqs[0]; 336 vb->deflate_vq = vqs[1]; 337 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 338 struct scatterlist sg; 339 vb->stats_vq = vqs[2]; 340 341 /* 342 * Prime this virtqueue with one buffer so the hypervisor can 343 * use it to signal us later. 344 */ 345 sg_init_one(&sg, vb->stats, sizeof vb->stats); 346 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) 347 < 0) 348 BUG(); 349 virtqueue_kick(vb->stats_vq); 350 } 351 return 0; 352 } 353 354 static const struct address_space_operations virtio_balloon_aops; 355 #ifdef CONFIG_BALLOON_COMPACTION 356 /* 357 * virtballoon_migratepage - perform the balloon page migration on behalf of 358 * a compation thread. (called under page lock) 359 * @mapping: the page->mapping which will be assigned to the new migrated page. 360 * @newpage: page that will replace the isolated page after migration finishes. 361 * @page : the isolated (old) page that is about to be migrated to newpage. 362 * @mode : compaction mode -- not used for balloon page migration. 363 * 364 * After a ballooned page gets isolated by compaction procedures, this is the 365 * function that performs the page migration on behalf of a compaction thread 366 * The page migration for virtio balloon is done in a simple swap fashion which 367 * follows these two macro steps: 368 * 1) insert newpage into vb->pages list and update the host about it; 369 * 2) update the host about the old page removed from vb->pages list; 370 * 371 * This function preforms the balloon page migration task. 372 * Called through balloon_mapping->a_ops->migratepage 373 */ 374 int virtballoon_migratepage(struct address_space *mapping, 375 struct page *newpage, struct page *page, enum migrate_mode mode) 376 { 377 struct balloon_dev_info *vb_dev_info = balloon_page_device(page); 378 struct virtio_balloon *vb; 379 unsigned long flags; 380 381 BUG_ON(!vb_dev_info); 382 383 vb = vb_dev_info->balloon_device; 384 385 /* 386 * In order to avoid lock contention while migrating pages concurrently 387 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 388 * this turn, as it is easier to retry the page migration later. 389 * This also prevents fill_balloon() getting stuck into a mutex 390 * recursion in the case it ends up triggering memory compaction 391 * while it is attempting to inflate the ballon. 392 */ 393 if (!mutex_trylock(&vb->balloon_lock)) 394 return -EAGAIN; 395 396 /* balloon's page migration 1st step -- inflate "newpage" */ 397 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 398 balloon_page_insert(newpage, mapping, &vb_dev_info->pages); 399 vb_dev_info->isolated_pages--; 400 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); 401 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 402 set_page_pfns(vb->pfns, newpage); 403 tell_host(vb, vb->inflate_vq); 404 405 /* 406 * balloon's page migration 2nd step -- deflate "page" 407 * 408 * It's safe to delete page->lru here because this page is at 409 * an isolated migration list, and this step is expected to happen here 410 */ 411 balloon_page_delete(page); 412 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 413 set_page_pfns(vb->pfns, page); 414 tell_host(vb, vb->deflate_vq); 415 416 mutex_unlock(&vb->balloon_lock); 417 418 return MIGRATEPAGE_BALLOON_SUCCESS; 419 } 420 421 /* define the balloon_mapping->a_ops callback to allow balloon page migration */ 422 static const struct address_space_operations virtio_balloon_aops = { 423 .migratepage = virtballoon_migratepage, 424 }; 425 #endif /* CONFIG_BALLOON_COMPACTION */ 426 427 static int virtballoon_probe(struct virtio_device *vdev) 428 { 429 struct virtio_balloon *vb; 430 struct address_space *vb_mapping; 431 struct balloon_dev_info *vb_devinfo; 432 int err; 433 434 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 435 if (!vb) { 436 err = -ENOMEM; 437 goto out; 438 } 439 440 vb->num_pages = 0; 441 mutex_init(&vb->balloon_lock); 442 init_waitqueue_head(&vb->config_change); 443 init_waitqueue_head(&vb->acked); 444 vb->vdev = vdev; 445 vb->need_stats_update = 0; 446 447 vb_devinfo = balloon_devinfo_alloc(vb); 448 if (IS_ERR(vb_devinfo)) { 449 err = PTR_ERR(vb_devinfo); 450 goto out_free_vb; 451 } 452 453 vb_mapping = balloon_mapping_alloc(vb_devinfo, 454 (balloon_compaction_check()) ? 455 &virtio_balloon_aops : NULL); 456 if (IS_ERR(vb_mapping)) { 457 /* 458 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP 459 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off. 460 */ 461 err = PTR_ERR(vb_mapping); 462 if (err != -EOPNOTSUPP) 463 goto out_free_vb_devinfo; 464 } 465 466 vb->vb_dev_info = vb_devinfo; 467 468 err = init_vqs(vb); 469 if (err) 470 goto out_free_vb_mapping; 471 472 vb->thread = kthread_run(balloon, vb, "vballoon"); 473 if (IS_ERR(vb->thread)) { 474 err = PTR_ERR(vb->thread); 475 goto out_del_vqs; 476 } 477 478 return 0; 479 480 out_del_vqs: 481 vdev->config->del_vqs(vdev); 482 out_free_vb_mapping: 483 balloon_mapping_free(vb_mapping); 484 out_free_vb_devinfo: 485 balloon_devinfo_free(vb_devinfo); 486 out_free_vb: 487 kfree(vb); 488 out: 489 return err; 490 } 491 492 static void remove_common(struct virtio_balloon *vb) 493 { 494 /* There might be pages left in the balloon: free them. */ 495 while (vb->num_pages) 496 leak_balloon(vb, vb->num_pages); 497 update_balloon_size(vb); 498 499 /* Now we reset the device so we can clean up the queues. */ 500 vb->vdev->config->reset(vb->vdev); 501 502 vb->vdev->config->del_vqs(vb->vdev); 503 } 504 505 static void virtballoon_remove(struct virtio_device *vdev) 506 { 507 struct virtio_balloon *vb = vdev->priv; 508 509 kthread_stop(vb->thread); 510 remove_common(vb); 511 balloon_mapping_free(vb->vb_dev_info->mapping); 512 balloon_devinfo_free(vb->vb_dev_info); 513 kfree(vb); 514 } 515 516 #ifdef CONFIG_PM 517 static int virtballoon_freeze(struct virtio_device *vdev) 518 { 519 struct virtio_balloon *vb = vdev->priv; 520 521 /* 522 * The kthread is already frozen by the PM core before this 523 * function is called. 524 */ 525 526 remove_common(vb); 527 return 0; 528 } 529 530 static int virtballoon_restore(struct virtio_device *vdev) 531 { 532 struct virtio_balloon *vb = vdev->priv; 533 int ret; 534 535 ret = init_vqs(vdev->priv); 536 if (ret) 537 return ret; 538 539 fill_balloon(vb, towards_target(vb)); 540 update_balloon_size(vb); 541 return 0; 542 } 543 #endif 544 545 static unsigned int features[] = { 546 VIRTIO_BALLOON_F_MUST_TELL_HOST, 547 VIRTIO_BALLOON_F_STATS_VQ, 548 }; 549 550 static struct virtio_driver virtio_balloon_driver = { 551 .feature_table = features, 552 .feature_table_size = ARRAY_SIZE(features), 553 .driver.name = KBUILD_MODNAME, 554 .driver.owner = THIS_MODULE, 555 .id_table = id_table, 556 .probe = virtballoon_probe, 557 .remove = virtballoon_remove, 558 .config_changed = virtballoon_changed, 559 #ifdef CONFIG_PM 560 .freeze = virtballoon_freeze, 561 .restore = virtballoon_restore, 562 #endif 563 }; 564 565 module_virtio_driver(virtio_balloon_driver); 566 MODULE_DEVICE_TABLE(virtio, id_table); 567 MODULE_DESCRIPTION("Virtio balloon driver"); 568 MODULE_LICENSE("GPL"); 569