Version:  2.0.40 2.2.26 2.4.37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17

Linux/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 #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                 balloon_page_free(page);
167                 adjust_managed_page_count(page, 1);
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 static const struct address_space_operations virtio_balloon_aops;
357 #ifdef CONFIG_BALLOON_COMPACTION
358 /*
359  * virtballoon_migratepage - perform the balloon page migration on behalf of
360  *                           a compation thread.     (called under page lock)
361  * @mapping: the page->mapping which will be assigned to the new migrated page.
362  * @newpage: page that will replace the isolated page after migration finishes.
363  * @page   : the isolated (old) page that is about to be migrated to newpage.
364  * @mode   : compaction mode -- not used for balloon page migration.
365  *
366  * After a ballooned page gets isolated by compaction procedures, this is the
367  * function that performs the page migration on behalf of a compaction thread
368  * The page migration for virtio balloon is done in a simple swap fashion which
369  * follows these two macro steps:
370  *  1) insert newpage into vb->pages list and update the host about it;
371  *  2) update the host about the old page removed from vb->pages list;
372  *
373  * This function preforms the balloon page migration task.
374  * Called through balloon_mapping->a_ops->migratepage
375  */
376 static int virtballoon_migratepage(struct address_space *mapping,
377                 struct page *newpage, struct page *page, enum migrate_mode mode)
378 {
379         struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
380         struct virtio_balloon *vb;
381         unsigned long flags;
382 
383         BUG_ON(!vb_dev_info);
384 
385         vb = vb_dev_info->balloon_device;
386 
387         /*
388          * In order to avoid lock contention while migrating pages concurrently
389          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
390          * this turn, as it is easier to retry the page migration later.
391          * This also prevents fill_balloon() getting stuck into a mutex
392          * recursion in the case it ends up triggering memory compaction
393          * while it is attempting to inflate the ballon.
394          */
395         if (!mutex_trylock(&vb->balloon_lock))
396                 return -EAGAIN;
397 
398         /* balloon's page migration 1st step  -- inflate "newpage" */
399         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
400         balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
401         vb_dev_info->isolated_pages--;
402         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
403         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
404         set_page_pfns(vb->pfns, newpage);
405         tell_host(vb, vb->inflate_vq);
406 
407         /*
408          * balloon's page migration 2nd step -- deflate "page"
409          *
410          * It's safe to delete page->lru here because this page is at
411          * an isolated migration list, and this step is expected to happen here
412          */
413         balloon_page_delete(page);
414         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
415         set_page_pfns(vb->pfns, page);
416         tell_host(vb, vb->deflate_vq);
417 
418         mutex_unlock(&vb->balloon_lock);
419 
420         return MIGRATEPAGE_BALLOON_SUCCESS;
421 }
422 
423 /* define the balloon_mapping->a_ops callback to allow balloon page migration */
424 static const struct address_space_operations virtio_balloon_aops = {
425                         .migratepage = virtballoon_migratepage,
426 };
427 #endif /* CONFIG_BALLOON_COMPACTION */
428 
429 static int virtballoon_probe(struct virtio_device *vdev)
430 {
431         struct virtio_balloon *vb;
432         struct address_space *vb_mapping;
433         struct balloon_dev_info *vb_devinfo;
434         int err;
435 
436         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
437         if (!vb) {
438                 err = -ENOMEM;
439                 goto out;
440         }
441 
442         vb->num_pages = 0;
443         mutex_init(&vb->balloon_lock);
444         init_waitqueue_head(&vb->config_change);
445         init_waitqueue_head(&vb->acked);
446         vb->vdev = vdev;
447         vb->need_stats_update = 0;
448 
449         vb_devinfo = balloon_devinfo_alloc(vb);
450         if (IS_ERR(vb_devinfo)) {
451                 err = PTR_ERR(vb_devinfo);
452                 goto out_free_vb;
453         }
454 
455         vb_mapping = balloon_mapping_alloc(vb_devinfo,
456                                            (balloon_compaction_check()) ?
457                                            &virtio_balloon_aops : NULL);
458         if (IS_ERR(vb_mapping)) {
459                 /*
460                  * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
461                  * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
462                  */
463                 err = PTR_ERR(vb_mapping);
464                 if (err != -EOPNOTSUPP)
465                         goto out_free_vb_devinfo;
466         }
467 
468         vb->vb_dev_info = vb_devinfo;
469 
470         err = init_vqs(vb);
471         if (err)
472                 goto out_free_vb_mapping;
473 
474         vb->thread = kthread_run(balloon, vb, "vballoon");
475         if (IS_ERR(vb->thread)) {
476                 err = PTR_ERR(vb->thread);
477                 goto out_del_vqs;
478         }
479 
480         return 0;
481 
482 out_del_vqs:
483         vdev->config->del_vqs(vdev);
484 out_free_vb_mapping:
485         balloon_mapping_free(vb_mapping);
486 out_free_vb_devinfo:
487         balloon_devinfo_free(vb_devinfo);
488 out_free_vb:
489         kfree(vb);
490 out:
491         return err;
492 }
493 
494 static void remove_common(struct virtio_balloon *vb)
495 {
496         /* There might be pages left in the balloon: free them. */
497         while (vb->num_pages)
498                 leak_balloon(vb, vb->num_pages);
499         update_balloon_size(vb);
500 
501         /* Now we reset the device so we can clean up the queues. */
502         vb->vdev->config->reset(vb->vdev);
503 
504         vb->vdev->config->del_vqs(vb->vdev);
505 }
506 
507 static void virtballoon_remove(struct virtio_device *vdev)
508 {
509         struct virtio_balloon *vb = vdev->priv;
510 
511         kthread_stop(vb->thread);
512         remove_common(vb);
513         balloon_mapping_free(vb->vb_dev_info->mapping);
514         balloon_devinfo_free(vb->vb_dev_info);
515         kfree(vb);
516 }
517 
518 #ifdef CONFIG_PM_SLEEP
519 static int virtballoon_freeze(struct virtio_device *vdev)
520 {
521         struct virtio_balloon *vb = vdev->priv;
522 
523         /*
524          * The kthread is already frozen by the PM core before this
525          * function is called.
526          */
527 
528         remove_common(vb);
529         return 0;
530 }
531 
532 static int virtballoon_restore(struct virtio_device *vdev)
533 {
534         struct virtio_balloon *vb = vdev->priv;
535         int ret;
536 
537         ret = init_vqs(vdev->priv);
538         if (ret)
539                 return ret;
540 
541         fill_balloon(vb, towards_target(vb));
542         update_balloon_size(vb);
543         return 0;
544 }
545 #endif
546 
547 static unsigned int features[] = {
548         VIRTIO_BALLOON_F_MUST_TELL_HOST,
549         VIRTIO_BALLOON_F_STATS_VQ,
550 };
551 
552 static struct virtio_driver virtio_balloon_driver = {
553         .feature_table = features,
554         .feature_table_size = ARRAY_SIZE(features),
555         .driver.name =  KBUILD_MODNAME,
556         .driver.owner = THIS_MODULE,
557         .id_table =     id_table,
558         .probe =        virtballoon_probe,
559         .remove =       virtballoon_remove,
560         .config_changed = virtballoon_changed,
561 #ifdef CONFIG_PM_SLEEP
562         .freeze =       virtballoon_freeze,
563         .restore =      virtballoon_restore,
564 #endif
565 };
566 
567 module_virtio_driver(virtio_balloon_driver);
568 MODULE_DEVICE_TABLE(virtio, id_table);
569 MODULE_DESCRIPTION("Virtio balloon driver");
570 MODULE_LICENSE("GPL");
571 

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