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 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 112 virtqueue_kick(vq); 113 114 /* When host has read buffer, this completes via balloon_ack */ 115 wait_event(vb->acked, virtqueue_get_buf(vq, &len)); 116 } 117 118 static void set_page_pfns(u32 pfns[], struct page *page) 119 { 120 unsigned int i; 121 122 /* Set balloon pfns pointing at this page. 123 * Note that the first pfn points at start of the page. */ 124 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) 125 pfns[i] = page_to_balloon_pfn(page) + i; 126 } 127 128 static void fill_balloon(struct virtio_balloon *vb, size_t num) 129 { 130 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 131 132 /* We can only do one array worth at a time. */ 133 num = min(num, ARRAY_SIZE(vb->pfns)); 134 135 mutex_lock(&vb->balloon_lock); 136 for (vb->num_pfns = 0; vb->num_pfns < num; 137 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 138 struct page *page = balloon_page_enqueue(vb_dev_info); 139 140 if (!page) { 141 dev_info_ratelimited(&vb->vdev->dev, 142 "Out of puff! Can't get %u pages\n", 143 VIRTIO_BALLOON_PAGES_PER_PAGE); 144 /* Sleep for at least 1/5 of a second before retry. */ 145 msleep(200); 146 break; 147 } 148 set_page_pfns(vb->pfns + vb->num_pfns, page); 149 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; 150 adjust_managed_page_count(page, -1); 151 } 152 153 /* Did we get any? */ 154 if (vb->num_pfns != 0) 155 tell_host(vb, vb->inflate_vq); 156 mutex_unlock(&vb->balloon_lock); 157 } 158 159 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 160 { 161 unsigned int i; 162 163 /* Find pfns pointing at start of each page, get pages and free them. */ 164 for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) { 165 struct page *page = balloon_pfn_to_page(pfns[i]); 166 adjust_managed_page_count(page, 1); 167 put_page(page); /* balloon reference */ 168 } 169 } 170 171 static void leak_balloon(struct virtio_balloon *vb, size_t num) 172 { 173 struct page *page; 174 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; 175 176 /* We can only do one array worth at a time. */ 177 num = min(num, ARRAY_SIZE(vb->pfns)); 178 179 mutex_lock(&vb->balloon_lock); 180 for (vb->num_pfns = 0; vb->num_pfns < num; 181 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { 182 page = balloon_page_dequeue(vb_dev_info); 183 if (!page) 184 break; 185 set_page_pfns(vb->pfns + vb->num_pfns, page); 186 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; 187 } 188 189 /* 190 * Note that if 191 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 192 * is true, we *have* to do it in this order 193 */ 194 if (vb->num_pfns != 0) 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 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 261 virtqueue_kick(vq); 262 } 263 264 static void virtballoon_changed(struct virtio_device *vdev) 265 { 266 struct virtio_balloon *vb = vdev->priv; 267 268 wake_up(&vb->config_change); 269 } 270 271 static inline s64 towards_target(struct virtio_balloon *vb) 272 { 273 __le32 v; 274 s64 target; 275 276 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v); 277 278 target = le32_to_cpu(v); 279 return target - vb->num_pages; 280 } 281 282 static void update_balloon_size(struct virtio_balloon *vb) 283 { 284 __le32 actual = cpu_to_le32(vb->num_pages); 285 286 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, 287 &actual); 288 } 289 290 static int balloon(void *_vballoon) 291 { 292 struct virtio_balloon *vb = _vballoon; 293 294 set_freezable(); 295 while (!kthread_should_stop()) { 296 s64 diff; 297 298 try_to_freeze(); 299 wait_event_interruptible(vb->config_change, 300 (diff = towards_target(vb)) != 0 301 || vb->need_stats_update 302 || kthread_should_stop() 303 || freezing(current)); 304 if (vb->need_stats_update) 305 stats_handle_request(vb); 306 if (diff > 0) 307 fill_balloon(vb, diff); 308 else if (diff < 0) 309 leak_balloon(vb, -diff); 310 update_balloon_size(vb); 311 312 /* 313 * For large balloon changes, we could spend a lot of time 314 * and always have work to do. Be nice if preempt disabled. 315 */ 316 cond_resched(); 317 } 318 return 0; 319 } 320 321 static int init_vqs(struct virtio_balloon *vb) 322 { 323 struct virtqueue *vqs[3]; 324 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; 325 const char *names[] = { "inflate", "deflate", "stats" }; 326 int err, nvqs; 327 328 /* 329 * We expect two virtqueues: inflate and deflate, and 330 * optionally stat. 331 */ 332 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; 333 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names); 334 if (err) 335 return err; 336 337 vb->inflate_vq = vqs[0]; 338 vb->deflate_vq = vqs[1]; 339 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { 340 struct scatterlist sg; 341 vb->stats_vq = vqs[2]; 342 343 /* 344 * Prime this virtqueue with one buffer so the hypervisor can 345 * use it to signal us later (it can't be broken yet!). 346 */ 347 sg_init_one(&sg, vb->stats, sizeof vb->stats); 348 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) 349 < 0) 350 BUG(); 351 virtqueue_kick(vb->stats_vq); 352 } 353 return 0; 354 } 355 356 #ifdef CONFIG_BALLOON_COMPACTION 357 /* 358 * virtballoon_migratepage - perform the balloon page migration on behalf of 359 * a compation thread. (called under page lock) 360 * @vb_dev_info: the balloon device 361 * @newpage: page that will replace the isolated page after migration finishes. 362 * @page : the isolated (old) page that is about to be migrated to newpage. 363 * @mode : compaction mode -- not used for balloon page migration. 364 * 365 * After a ballooned page gets isolated by compaction procedures, this is the 366 * function that performs the page migration on behalf of a compaction thread 367 * The page migration for virtio balloon is done in a simple swap fashion which 368 * follows these two macro steps: 369 * 1) insert newpage into vb->pages list and update the host about it; 370 * 2) update the host about the old page removed from vb->pages list; 371 * 372 * This function preforms the balloon page migration task. 373 * Called through balloon_mapping->a_ops->migratepage 374 */ 375 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, 376 struct page *newpage, struct page *page, enum migrate_mode mode) 377 { 378 struct virtio_balloon *vb = container_of(vb_dev_info, 379 struct virtio_balloon, vb_dev_info); 380 unsigned long flags; 381 382 /* 383 * In order to avoid lock contention while migrating pages concurrently 384 * to leak_balloon() or fill_balloon() we just give up the balloon_lock 385 * this turn, as it is easier to retry the page migration later. 386 * This also prevents fill_balloon() getting stuck into a mutex 387 * recursion in the case it ends up triggering memory compaction 388 * while it is attempting to inflate the ballon. 389 */ 390 if (!mutex_trylock(&vb->balloon_lock)) 391 return -EAGAIN; 392 393 get_page(newpage); /* balloon reference */ 394 395 /* balloon's page migration 1st step -- inflate "newpage" */ 396 spin_lock_irqsave(&vb_dev_info->pages_lock, flags); 397 balloon_page_insert(vb_dev_info, newpage); 398 vb_dev_info->isolated_pages--; 399 __count_vm_event(BALLOON_MIGRATE); 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 /* balloon's page migration 2nd step -- deflate "page" */ 406 balloon_page_delete(page); 407 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; 408 set_page_pfns(vb->pfns, page); 409 tell_host(vb, vb->deflate_vq); 410 411 mutex_unlock(&vb->balloon_lock); 412 413 put_page(page); /* balloon reference */ 414 415 return MIGRATEPAGE_SUCCESS; 416 } 417 #endif /* CONFIG_BALLOON_COMPACTION */ 418 419 static int virtballoon_probe(struct virtio_device *vdev) 420 { 421 struct virtio_balloon *vb; 422 int err; 423 424 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 425 if (!vb) { 426 err = -ENOMEM; 427 goto out; 428 } 429 430 vb->num_pages = 0; 431 mutex_init(&vb->balloon_lock); 432 init_waitqueue_head(&vb->config_change); 433 init_waitqueue_head(&vb->acked); 434 vb->vdev = vdev; 435 vb->need_stats_update = 0; 436 437 balloon_devinfo_init(&vb->vb_dev_info); 438 #ifdef CONFIG_BALLOON_COMPACTION 439 vb->vb_dev_info.migratepage = virtballoon_migratepage; 440 #endif 441 442 err = init_vqs(vb); 443 if (err) 444 goto out_free_vb; 445 446 vb->thread = kthread_run(balloon, vb, "vballoon"); 447 if (IS_ERR(vb->thread)) { 448 err = PTR_ERR(vb->thread); 449 goto out_del_vqs; 450 } 451 452 return 0; 453 454 out_del_vqs: 455 vdev->config->del_vqs(vdev); 456 out_free_vb: 457 kfree(vb); 458 out: 459 return err; 460 } 461 462 static void remove_common(struct virtio_balloon *vb) 463 { 464 /* There might be pages left in the balloon: free them. */ 465 while (vb->num_pages) 466 leak_balloon(vb, vb->num_pages); 467 update_balloon_size(vb); 468 469 /* Now we reset the device so we can clean up the queues. */ 470 vb->vdev->config->reset(vb->vdev); 471 472 vb->vdev->config->del_vqs(vb->vdev); 473 } 474 475 static void virtballoon_remove(struct virtio_device *vdev) 476 { 477 struct virtio_balloon *vb = vdev->priv; 478 479 kthread_stop(vb->thread); 480 remove_common(vb); 481 kfree(vb); 482 } 483 484 #ifdef CONFIG_PM_SLEEP 485 static int virtballoon_freeze(struct virtio_device *vdev) 486 { 487 struct virtio_balloon *vb = vdev->priv; 488 489 /* 490 * The kthread is already frozen by the PM core before this 491 * function is called. 492 */ 493 494 remove_common(vb); 495 return 0; 496 } 497 498 static int virtballoon_restore(struct virtio_device *vdev) 499 { 500 struct virtio_balloon *vb = vdev->priv; 501 int ret; 502 503 ret = init_vqs(vdev->priv); 504 if (ret) 505 return ret; 506 507 virtio_device_ready(vdev); 508 509 fill_balloon(vb, towards_target(vb)); 510 update_balloon_size(vb); 511 return 0; 512 } 513 #endif 514 515 static unsigned int features[] = { 516 VIRTIO_BALLOON_F_MUST_TELL_HOST, 517 VIRTIO_BALLOON_F_STATS_VQ, 518 }; 519 520 static struct virtio_driver virtio_balloon_driver = { 521 .feature_table = features, 522 .feature_table_size = ARRAY_SIZE(features), 523 .driver.name = KBUILD_MODNAME, 524 .driver.owner = THIS_MODULE, 525 .id_table = id_table, 526 .probe = virtballoon_probe, 527 .remove = virtballoon_remove, 528 .config_changed = virtballoon_changed, 529 #ifdef CONFIG_PM_SLEEP 530 .freeze = virtballoon_freeze, 531 .restore = virtballoon_restore, 532 #endif 533 }; 534 535 module_virtio_driver(virtio_balloon_driver); 536 MODULE_DEVICE_TABLE(virtio, id_table); 537 MODULE_DESCRIPTION("Virtio balloon driver"); 538 MODULE_LICENSE("GPL"); 539