drivers/virtio/virtio_balloon.c

   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
  31 struct virtio_balloon
  32 {
  33         struct virtio_device *vdev;
  34         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  35
  36         /* Where the ballooning thread waits for config to change. */
  37         wait_queue_head_t config_change;
  38
  39         /* The thread servicing the balloon. */
  40         struct task_struct *thread;
  41
  42         /* Waiting for host to ack the pages we released. */
  43         struct completion acked;
  44
  45         /* The pages we've told the Host we're not using. */
  46         unsigned int num_pages;
  47         struct list_head pages;
  48
  49         /* The array of pfns we tell the Host about. */
  50         unsigned int num_pfns;
  51         u32 pfns[256];
  52
  53         /* Memory statistics */
  54         int need_stats_update;
  55         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
  56 };
  57
  58 static struct virtio_device_id id_table[] = {
  59         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
  60         { 0 },
  61 };
  62
  63 static u32 page_to_balloon_pfn(struct page *page)
  64 {
  65         unsigned long pfn = page_to_pfn(page);
  66
  67         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
  68         /* Convert pfn from Linux page size to balloon page size. */
  69         return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
  70 }
  71
  72 static void balloon_ack(struct virtqueue *vq)
  73 {
  74         struct virtio_balloon *vb;
  75         unsigned int len;
  76
  77         vb = virtqueue_get_buf(vq, &len);
  78         if (vb)
  79                 complete(&vb->acked);
  80 }
  81
  82 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
  83 {
  84         struct scatterlist sg;
  85
  86         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
  87
  88         init_completion(&vb->acked);
  89
  90         /* We should always be able to add one buffer to an empty queue. */
  91         if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
  92                 BUG();
  93         virtqueue_kick(vq);
  94
  95         /* When host has read buffer, this completes via balloon_ack */
  96         wait_for_completion(&vb->acked);
  97 }
  98
  99 static void fill_balloon(struct virtio_balloon *vb, size_t num)
 100 {
 101         /* We can only do one array worth at a time. */
 102         num = min(num, ARRAY_SIZE(vb->pfns));
 103
 104         for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
 105                 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
 106                                         __GFP_NOMEMALLOC | __GFP_NOWARN);
 107                 if (!page) {
 108                         if (printk_ratelimit())
 109                                 dev_printk(KERN_INFO, &vb->vdev->dev,
 110                                            "Out of puff! Can't get %zu pages\n",
 111                                            num);
 112                         /* Sleep for at least 1/5 of a second before retry. */
 113                         msleep(200);
 114                         break;
 115                 }
 116                 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
 117                 totalram_pages--;
 118                 vb->num_pages++;
 119                 list_add(&page->lru, &vb->pages);
 120         }
 121
 122         /* Didn't get any?  Oh well. */
 123         if (vb->num_pfns == 0)
 124                 return;
 125
 126         tell_host(vb, vb->inflate_vq);
 127 }
 128
 129 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
 130 {
 131         unsigned int i;
 132
 133         for (i = 0; i < num; i++) {
 134                 __free_page(pfn_to_page(pfns[i]));
 135                 totalram_pages++;
 136         }
 137 }
 138
 139 static void leak_balloon(struct virtio_balloon *vb, size_t num)
 140 {
 141         struct page *page;
 142
 143         /* We can only do one array worth at a time. */
 144         num = min(num, ARRAY_SIZE(vb->pfns));
 145
 146         for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
 147                 page = list_first_entry(&vb->pages, struct page, lru);
 148                 list_del(&page->lru);
 149                 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
 150                 vb->num_pages--;
 151         }
 152
 153         /*
 154          * Note that if
 155          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 156          * is true, we *have* to do it in this order
 157          */
 158         tell_host(vb, vb->deflate_vq);
 159         release_pages_by_pfn(vb->pfns, vb->num_pfns);
 160 }
 161
 162 static inline void update_stat(struct virtio_balloon *vb, int idx,
 163                                u16 tag, u64 val)
 164 {
 165         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 166         vb->stats[idx].tag = tag;
 167         vb->stats[idx].val = val;
 168 }
 169
 170 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 171
 172 static void update_balloon_stats(struct virtio_balloon *vb)
 173 {
 174         unsigned long events[NR_VM_EVENT_ITEMS];
 175         struct sysinfo i;
 176         int idx = 0;
 177
 178         all_vm_events(events);
 179         si_meminfo(&i);
 180
 181         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 182                                 pages_to_bytes(events[PSWPIN]));
 183         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 184                                 pages_to_bytes(events[PSWPOUT]));
 185         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 186         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 187         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 188                                 pages_to_bytes(i.freeram));
 189         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 190                                 pages_to_bytes(i.totalram));
 191 }
 192
 193 /*
 194  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 195  * the stats queue operates in reverse.  The driver initializes the virtqueue
 196  * with a single buffer.  From that point forward, all conversations consist of
 197  * a hypervisor request (a call to this function) which directs us to refill
 198  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 199  * we notify our kthread which does the actual work via stats_handle_request().
 200  */
 201 static void stats_request(struct virtqueue *vq)
 202 {
 203         struct virtio_balloon *vb;
 204         unsigned int len;
 205
 206         vb = virtqueue_get_buf(vq, &len);
 207         if (!vb)
 208                 return;
 209         vb->need_stats_update = 1;
 210         wake_up(&vb->config_change);
 211 }
 212
 213 static void stats_handle_request(struct virtio_balloon *vb)
 214 {
 215         struct virtqueue *vq;
 216         struct scatterlist sg;
 217
 218         vb->need_stats_update = 0;
 219         update_balloon_stats(vb);
 220
 221         vq = vb->stats_vq;
 222         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 223         if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
 224                 BUG();
 225         virtqueue_kick(vq);
 226 }
 227
 228 static void virtballoon_changed(struct virtio_device *vdev)
 229 {
 230         struct virtio_balloon *vb = vdev->priv;
 231
 232         wake_up(&vb->config_change);
 233 }
 234
 235 static inline s64 towards_target(struct virtio_balloon *vb)
 236 {
 237         u32 v;
 238         vb->vdev->config->get(vb->vdev,
 239                               offsetof(struct virtio_balloon_config, num_pages),
 240                               &v, sizeof(v));
 241         return (s64)v - vb->num_pages;
 242 }
 243
 244 static void update_balloon_size(struct virtio_balloon *vb)
 245 {
 246         __le32 actual = cpu_to_le32(vb->num_pages);
 247
 248         vb->vdev->config->set(vb->vdev,
 249                               offsetof(struct virtio_balloon_config, actual),
 250                               &actual, sizeof(actual));
 251 }
 252
 253 static int balloon(void *_vballoon)
 254 {
 255         struct virtio_balloon *vb = _vballoon;
 256
 257         set_freezable();
 258         while (!kthread_should_stop()) {
 259                 s64 diff;
 260
 261                 try_to_freeze();
 262                 wait_event_interruptible(vb->config_change,
 263                                          (diff = towards_target(vb)) != 0
 264                                          || vb->need_stats_update
 265                                          || kthread_should_stop()
 266                                          || freezing(current));
 267                 if (vb->need_stats_update)
 268                         stats_handle_request(vb);
 269                 if (diff > 0)
 270                         fill_balloon(vb, diff);
 271                 else if (diff < 0)
 272                         leak_balloon(vb, -diff);
 273                 update_balloon_size(vb);
 274         }
 275         return 0;
 276 }
 277
 278 static int init_vqs(struct virtio_balloon *vb)
 279 {
 280         struct virtqueue *vqs[3];
 281         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
 282         const char *names[] = { "inflate", "deflate", "stats" };
 283         int err, nvqs;
 284
 285         /*
 286          * We expect two virtqueues: inflate and deflate, and
 287          * optionally stat.
 288          */
 289         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
 290         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
 291         if (err)
 292                 return err;
 293
 294         vb->inflate_vq = vqs[0];
 295         vb->deflate_vq = vqs[1];
 296         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 297                 struct scatterlist sg;
 298                 vb->stats_vq = vqs[2];
 299
 300                 /*
 301                  * Prime this virtqueue with one buffer so the hypervisor can
 302                  * use it to signal us later.
 303                  */
 304                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
 305                 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
 306                     < 0)
 307                         BUG();
 308                 virtqueue_kick(vb->stats_vq);
 309         }
 310         return 0;
 311 }
 312
 313 static int virtballoon_probe(struct virtio_device *vdev)
 314 {
 315         struct virtio_balloon *vb;
 316         int err;
 317
 318         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 319         if (!vb) {
 320                 err = -ENOMEM;
 321                 goto out;
 322         }
 323
 324         INIT_LIST_HEAD(&vb->pages);
 325         vb->num_pages = 0;
 326         init_waitqueue_head(&vb->config_change);
 327         vb->vdev = vdev;
 328         vb->need_stats_update = 0;
 329
 330         err = init_vqs(vb);
 331         if (err)
 332                 goto out_free_vb;
 333
 334         vb->thread = kthread_run(balloon, vb, "vballoon");
 335         if (IS_ERR(vb->thread)) {
 336                 err = PTR_ERR(vb->thread);
 337                 goto out_del_vqs;
 338         }
 339
 340         return 0;
 341
 342 out_del_vqs:
 343         vdev->config->del_vqs(vdev);
 344 out_free_vb:
 345         kfree(vb);
 346 out:
 347         return err;
 348 }
 349
 350 static void __devexit virtballoon_remove(struct virtio_device *vdev)
 351 {
 352         struct virtio_balloon *vb = vdev->priv;
 353
 354         kthread_stop(vb->thread);
 355
 356         /* There might be pages left in the balloon: free them. */
 357         while (vb->num_pages)
 358                 leak_balloon(vb, vb->num_pages);
 359
 360         /* Now we reset the device so we can clean up the queues. */
 361         vdev->config->reset(vdev);
 362
 363         vdev->config->del_vqs(vdev);
 364         kfree(vb);
 365 }
 366
 367 #ifdef CONFIG_PM
 368 static int virtballoon_freeze(struct virtio_device *vdev)
 369 {
 370         struct virtio_balloon *vb = vdev->priv;
 371
 372         /*
 373          * The kthread is already frozen by the PM core before this
 374          * function is called.
 375          */
 376
 377         while (vb->num_pages)
 378                 leak_balloon(vb, vb->num_pages);
 379         update_balloon_size(vb);
 380
 381         /* Ensure we don't get any more requests from the host */
 382         vdev->config->reset(vdev);
 383         vdev->config->del_vqs(vdev);
 384         return 0;
 385 }
 386
 387 static int restore_common(struct virtio_device *vdev)
 388 {
 389         struct virtio_balloon *vb = vdev->priv;
 390         int ret;
 391
 392         ret = init_vqs(vdev->priv);
 393         if (ret)
 394                 return ret;
 395
 396         fill_balloon(vb, towards_target(vb));
 397         update_balloon_size(vb);
 398         return 0;
 399 }
 400
 401 static int virtballoon_thaw(struct virtio_device *vdev)
 402 {
 403         return restore_common(vdev);
 404 }
 405
 406 static int virtballoon_restore(struct virtio_device *vdev)
 407 {
 408         struct virtio_balloon *vb = vdev->priv;
 409
 410         /*
 411          * If a request wasn't complete at the time of freezing, this
 412          * could have been set.
 413          */
 414         vb->need_stats_update = 0;
 415
 416         return restore_common(vdev);
 417 }
 418 #endif
 419
 420 static unsigned int features[] = {
 421         VIRTIO_BALLOON_F_MUST_TELL_HOST,
 422         VIRTIO_BALLOON_F_STATS_VQ,
 423 };
 424
 425 static struct virtio_driver virtio_balloon_driver = {
 426         .feature_table = features,
 427         .feature_table_size = ARRAY_SIZE(features),
 428         .driver.name =  KBUILD_MODNAME,
 429         .driver.owner = THIS_MODULE,
 430         .id_table =     id_table,
 431         .probe =        virtballoon_probe,
 432         .remove =       __devexit_p(virtballoon_remove),
 433         .config_changed = virtballoon_changed,
 434 #ifdef CONFIG_PM
 435         .freeze =       virtballoon_freeze,
 436         .restore =      virtballoon_restore,
 437         .thaw =         virtballoon_thaw,
 438 #endif
 439 };
 440
 441 static int __init init(void)
 442 {
 443         return register_virtio_driver(&virtio_balloon_driver);
 444 }
 445
 446 static void __exit fini(void)
 447 {
 448         unregister_virtio_driver(&virtio_balloon_driver);
 449 }
 450 module_init(init);
 451 module_exit(fini);
 452
 453 MODULE_DEVICE_TABLE(virtio, id_table);
 454 MODULE_DESCRIPTION("Virtio balloon driver");
 455 MODULE_LICENSE("GPL");