Version:  2.0.40 2.2.26 2.4.37 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 3.18 3.19 4.0 4.1

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 #include <linux/oom.h>
 32 #include <linux/wait.h>
 33 
 34 /*
 35  * Balloon device works in 4K page units.  So each page is pointed to by
 36  * multiple balloon pages.  All memory counters in this driver are in balloon
 37  * page units.
 38  */
 39 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
 40 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
 41 #define OOM_VBALLOON_DEFAULT_PAGES 256
 42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
 43 
 44 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
 45 module_param(oom_pages, int, S_IRUSR | S_IWUSR);
 46 MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
 47 
 48 struct virtio_balloon {
 49         struct virtio_device *vdev;
 50         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
 51 
 52         /* Where the ballooning thread waits for config to change. */
 53         wait_queue_head_t config_change;
 54 
 55         /* The thread servicing the balloon. */
 56         struct task_struct *thread;
 57 
 58         /* Waiting for host to ack the pages we released. */
 59         wait_queue_head_t acked;
 60 
 61         /* Number of balloon pages we've told the Host we're not using. */
 62         unsigned int num_pages;
 63         /*
 64          * The pages we've told the Host we're not using are enqueued
 65          * at vb_dev_info->pages list.
 66          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 67          * to num_pages above.
 68          */
 69         struct balloon_dev_info vb_dev_info;
 70 
 71         /* Synchronize access/update to this struct virtio_balloon elements */
 72         struct mutex balloon_lock;
 73 
 74         /* The array of pfns we tell the Host about. */
 75         unsigned int num_pfns;
 76         u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 77 
 78         /* Memory statistics */
 79         int need_stats_update;
 80         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 81 
 82         /* To register callback in oom notifier call chain */
 83         struct notifier_block nb;
 84 };
 85 
 86 static struct virtio_device_id id_table[] = {
 87         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 88         { 0 },
 89 };
 90 
 91 static u32 page_to_balloon_pfn(struct page *page)
 92 {
 93         unsigned long pfn = page_to_pfn(page);
 94 
 95         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 96         /* Convert pfn from Linux page size to balloon page size. */
 97         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 98 }
 99 
100 static struct page *balloon_pfn_to_page(u32 pfn)
101 {
102         BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
103         return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
104 }
105 
106 static void balloon_ack(struct virtqueue *vq)
107 {
108         struct virtio_balloon *vb = vq->vdev->priv;
109 
110         wake_up(&vb->acked);
111 }
112 
113 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
114 {
115         struct scatterlist sg;
116         unsigned int len;
117 
118         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
119 
120         /* We should always be able to add one buffer to an empty queue. */
121         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
122         virtqueue_kick(vq);
123 
124         /* When host has read buffer, this completes via balloon_ack */
125         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
126 }
127 
128 static void set_page_pfns(u32 pfns[], struct page *page)
129 {
130         unsigned int i;
131 
132         /* Set balloon pfns pointing at this page.
133          * Note that the first pfn points at start of the page. */
134         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
135                 pfns[i] = page_to_balloon_pfn(page) + i;
136 }
137 
138 static void fill_balloon(struct virtio_balloon *vb, size_t num)
139 {
140         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
141 
142         /* We can only do one array worth at a time. */
143         num = min(num, ARRAY_SIZE(vb->pfns));
144 
145         mutex_lock(&vb->balloon_lock);
146         for (vb->num_pfns = 0; vb->num_pfns < num;
147              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
148                 struct page *page = balloon_page_enqueue(vb_dev_info);
149 
150                 if (!page) {
151                         dev_info_ratelimited(&vb->vdev->dev,
152                                              "Out of puff! Can't get %u pages\n",
153                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
154                         /* Sleep for at least 1/5 of a second before retry. */
155                         msleep(200);
156                         break;
157                 }
158                 set_page_pfns(vb->pfns + vb->num_pfns, page);
159                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
160                 adjust_managed_page_count(page, -1);
161         }
162 
163         /* Did we get any? */
164         if (vb->num_pfns != 0)
165                 tell_host(vb, vb->inflate_vq);
166         mutex_unlock(&vb->balloon_lock);
167 }
168 
169 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
170 {
171         unsigned int i;
172 
173         /* Find pfns pointing at start of each page, get pages and free them. */
174         for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
175                 struct page *page = balloon_pfn_to_page(pfns[i]);
176                 adjust_managed_page_count(page, 1);
177                 put_page(page); /* balloon reference */
178         }
179 }
180 
181 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
182 {
183         unsigned num_freed_pages;
184         struct page *page;
185         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
186 
187         /* We can only do one array worth at a time. */
188         num = min(num, ARRAY_SIZE(vb->pfns));
189 
190         mutex_lock(&vb->balloon_lock);
191         for (vb->num_pfns = 0; vb->num_pfns < num;
192              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
193                 page = balloon_page_dequeue(vb_dev_info);
194                 if (!page)
195                         break;
196                 set_page_pfns(vb->pfns + vb->num_pfns, page);
197                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
198         }
199 
200         num_freed_pages = vb->num_pfns;
201         /*
202          * Note that if
203          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
204          * is true, we *have* to do it in this order
205          */
206         if (vb->num_pfns != 0)
207                 tell_host(vb, vb->deflate_vq);
208         mutex_unlock(&vb->balloon_lock);
209         release_pages_by_pfn(vb->pfns, vb->num_pfns);
210         return num_freed_pages;
211 }
212 
213 static inline void update_stat(struct virtio_balloon *vb, int idx,
214                                u16 tag, u64 val)
215 {
216         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
217         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
218         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
219 }
220 
221 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
222 
223 static void update_balloon_stats(struct virtio_balloon *vb)
224 {
225         unsigned long events[NR_VM_EVENT_ITEMS];
226         struct sysinfo i;
227         int idx = 0;
228 
229         all_vm_events(events);
230         si_meminfo(&i);
231 
232         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
233                                 pages_to_bytes(events[PSWPIN]));
234         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
235                                 pages_to_bytes(events[PSWPOUT]));
236         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
237         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
238         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
239                                 pages_to_bytes(i.freeram));
240         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
241                                 pages_to_bytes(i.totalram));
242 }
243 
244 /*
245  * While most virtqueues communicate guest-initiated requests to the hypervisor,
246  * the stats queue operates in reverse.  The driver initializes the virtqueue
247  * with a single buffer.  From that point forward, all conversations consist of
248  * a hypervisor request (a call to this function) which directs us to refill
249  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
250  * we notify our kthread which does the actual work via stats_handle_request().
251  */
252 static void stats_request(struct virtqueue *vq)
253 {
254         struct virtio_balloon *vb = vq->vdev->priv;
255 
256         vb->need_stats_update = 1;
257         wake_up(&vb->config_change);
258 }
259 
260 static void stats_handle_request(struct virtio_balloon *vb)
261 {
262         struct virtqueue *vq;
263         struct scatterlist sg;
264         unsigned int len;
265 
266         vb->need_stats_update = 0;
267         update_balloon_stats(vb);
268 
269         vq = vb->stats_vq;
270         if (!virtqueue_get_buf(vq, &len))
271                 return;
272         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
273         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
274         virtqueue_kick(vq);
275 }
276 
277 static void virtballoon_changed(struct virtio_device *vdev)
278 {
279         struct virtio_balloon *vb = vdev->priv;
280 
281         wake_up(&vb->config_change);
282 }
283 
284 static inline s64 towards_target(struct virtio_balloon *vb)
285 {
286         s64 target;
287         u32 num_pages;
288 
289         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
290                      &num_pages);
291 
292         /* Legacy balloon config space is LE, unlike all other devices. */
293         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
294                 num_pages = le32_to_cpu((__force __le32)num_pages);
295 
296         target = num_pages;
297         return target - vb->num_pages;
298 }
299 
300 static void update_balloon_size(struct virtio_balloon *vb)
301 {
302         u32 actual = vb->num_pages;
303 
304         /* Legacy balloon config space is LE, unlike all other devices. */
305         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
306                 actual = (__force u32)cpu_to_le32(actual);
307 
308         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
309                       &actual);
310 }
311 
312 /*
313  * virtballoon_oom_notify - release pages when system is under severe
314  *                          memory pressure (called from out_of_memory())
315  * @self : notifier block struct
316  * @dummy: not used
317  * @parm : returned - number of freed pages
318  *
319  * The balancing of memory by use of the virtio balloon should not cause
320  * the termination of processes while there are pages in the balloon.
321  * If virtio balloon manages to release some memory, it will make the
322  * system return and retry the allocation that forced the OOM killer
323  * to run.
324  */
325 static int virtballoon_oom_notify(struct notifier_block *self,
326                                   unsigned long dummy, void *parm)
327 {
328         struct virtio_balloon *vb;
329         unsigned long *freed;
330         unsigned num_freed_pages;
331 
332         vb = container_of(self, struct virtio_balloon, nb);
333         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
334                 return NOTIFY_OK;
335 
336         freed = parm;
337         num_freed_pages = leak_balloon(vb, oom_pages);
338         update_balloon_size(vb);
339         *freed += num_freed_pages;
340 
341         return NOTIFY_OK;
342 }
343 
344 static int balloon(void *_vballoon)
345 {
346         struct virtio_balloon *vb = _vballoon;
347         DEFINE_WAIT_FUNC(wait, woken_wake_function);
348 
349         set_freezable();
350         while (!kthread_should_stop()) {
351                 s64 diff;
352 
353                 try_to_freeze();
354 
355                 add_wait_queue(&vb->config_change, &wait);
356                 for (;;) {
357                         if ((diff = towards_target(vb)) != 0 ||
358                             vb->need_stats_update ||
359                             kthread_should_stop() ||
360                             freezing(current))
361                                 break;
362                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
363                 }
364                 remove_wait_queue(&vb->config_change, &wait);
365 
366                 if (vb->need_stats_update)
367                         stats_handle_request(vb);
368                 if (diff > 0)
369                         fill_balloon(vb, diff);
370                 else if (diff < 0)
371                         leak_balloon(vb, -diff);
372                 update_balloon_size(vb);
373 
374                 /*
375                  * For large balloon changes, we could spend a lot of time
376                  * and always have work to do.  Be nice if preempt disabled.
377                  */
378                 cond_resched();
379         }
380         return 0;
381 }
382 
383 static int init_vqs(struct virtio_balloon *vb)
384 {
385         struct virtqueue *vqs[3];
386         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
387         const char *names[] = { "inflate", "deflate", "stats" };
388         int err, nvqs;
389 
390         /*
391          * We expect two virtqueues: inflate and deflate, and
392          * optionally stat.
393          */
394         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
395         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
396         if (err)
397                 return err;
398 
399         vb->inflate_vq = vqs[0];
400         vb->deflate_vq = vqs[1];
401         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
402                 struct scatterlist sg;
403                 vb->stats_vq = vqs[2];
404 
405                 /*
406                  * Prime this virtqueue with one buffer so the hypervisor can
407                  * use it to signal us later (it can't be broken yet!).
408                  */
409                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
410                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
411                     < 0)
412                         BUG();
413                 virtqueue_kick(vb->stats_vq);
414         }
415         return 0;
416 }
417 
418 #ifdef CONFIG_BALLOON_COMPACTION
419 /*
420  * virtballoon_migratepage - perform the balloon page migration on behalf of
421  *                           a compation thread.     (called under page lock)
422  * @vb_dev_info: the balloon device
423  * @newpage: page that will replace the isolated page after migration finishes.
424  * @page   : the isolated (old) page that is about to be migrated to newpage.
425  * @mode   : compaction mode -- not used for balloon page migration.
426  *
427  * After a ballooned page gets isolated by compaction procedures, this is the
428  * function that performs the page migration on behalf of a compaction thread
429  * The page migration for virtio balloon is done in a simple swap fashion which
430  * follows these two macro steps:
431  *  1) insert newpage into vb->pages list and update the host about it;
432  *  2) update the host about the old page removed from vb->pages list;
433  *
434  * This function preforms the balloon page migration task.
435  * Called through balloon_mapping->a_ops->migratepage
436  */
437 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
438                 struct page *newpage, struct page *page, enum migrate_mode mode)
439 {
440         struct virtio_balloon *vb = container_of(vb_dev_info,
441                         struct virtio_balloon, vb_dev_info);
442         unsigned long flags;
443 
444         /*
445          * In order to avoid lock contention while migrating pages concurrently
446          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
447          * this turn, as it is easier to retry the page migration later.
448          * This also prevents fill_balloon() getting stuck into a mutex
449          * recursion in the case it ends up triggering memory compaction
450          * while it is attempting to inflate the ballon.
451          */
452         if (!mutex_trylock(&vb->balloon_lock))
453                 return -EAGAIN;
454 
455         get_page(newpage); /* balloon reference */
456 
457         /* balloon's page migration 1st step  -- inflate "newpage" */
458         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
459         balloon_page_insert(vb_dev_info, newpage);
460         vb_dev_info->isolated_pages--;
461         __count_vm_event(BALLOON_MIGRATE);
462         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
463         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
464         set_page_pfns(vb->pfns, newpage);
465         tell_host(vb, vb->inflate_vq);
466 
467         /* balloon's page migration 2nd step -- deflate "page" */
468         balloon_page_delete(page);
469         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
470         set_page_pfns(vb->pfns, page);
471         tell_host(vb, vb->deflate_vq);
472 
473         mutex_unlock(&vb->balloon_lock);
474 
475         put_page(page); /* balloon reference */
476 
477         return MIGRATEPAGE_SUCCESS;
478 }
479 #endif /* CONFIG_BALLOON_COMPACTION */
480 
481 static int virtballoon_probe(struct virtio_device *vdev)
482 {
483         struct virtio_balloon *vb;
484         int err;
485 
486         if (!vdev->config->get) {
487                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
488                         __func__);
489                 return -EINVAL;
490         }
491 
492         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
493         if (!vb) {
494                 err = -ENOMEM;
495                 goto out;
496         }
497 
498         vb->num_pages = 0;
499         mutex_init(&vb->balloon_lock);
500         init_waitqueue_head(&vb->config_change);
501         init_waitqueue_head(&vb->acked);
502         vb->vdev = vdev;
503         vb->need_stats_update = 0;
504 
505         balloon_devinfo_init(&vb->vb_dev_info);
506 #ifdef CONFIG_BALLOON_COMPACTION
507         vb->vb_dev_info.migratepage = virtballoon_migratepage;
508 #endif
509 
510         err = init_vqs(vb);
511         if (err)
512                 goto out_free_vb;
513 
514         vb->nb.notifier_call = virtballoon_oom_notify;
515         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
516         err = register_oom_notifier(&vb->nb);
517         if (err < 0)
518                 goto out_oom_notify;
519 
520         virtio_device_ready(vdev);
521 
522         vb->thread = kthread_run(balloon, vb, "vballoon");
523         if (IS_ERR(vb->thread)) {
524                 err = PTR_ERR(vb->thread);
525                 goto out_del_vqs;
526         }
527 
528         return 0;
529 
530 out_del_vqs:
531         unregister_oom_notifier(&vb->nb);
532 out_oom_notify:
533         vdev->config->del_vqs(vdev);
534 out_free_vb:
535         kfree(vb);
536 out:
537         return err;
538 }
539 
540 static void remove_common(struct virtio_balloon *vb)
541 {
542         /* There might be pages left in the balloon: free them. */
543         while (vb->num_pages)
544                 leak_balloon(vb, vb->num_pages);
545         update_balloon_size(vb);
546 
547         /* Now we reset the device so we can clean up the queues. */
548         vb->vdev->config->reset(vb->vdev);
549 
550         vb->vdev->config->del_vqs(vb->vdev);
551 }
552 
553 static void virtballoon_remove(struct virtio_device *vdev)
554 {
555         struct virtio_balloon *vb = vdev->priv;
556 
557         unregister_oom_notifier(&vb->nb);
558         kthread_stop(vb->thread);
559         remove_common(vb);
560         kfree(vb);
561 }
562 
563 #ifdef CONFIG_PM_SLEEP
564 static int virtballoon_freeze(struct virtio_device *vdev)
565 {
566         struct virtio_balloon *vb = vdev->priv;
567 
568         /*
569          * The kthread is already frozen by the PM core before this
570          * function is called.
571          */
572 
573         remove_common(vb);
574         return 0;
575 }
576 
577 static int virtballoon_restore(struct virtio_device *vdev)
578 {
579         struct virtio_balloon *vb = vdev->priv;
580         int ret;
581 
582         ret = init_vqs(vdev->priv);
583         if (ret)
584                 return ret;
585 
586         virtio_device_ready(vdev);
587 
588         fill_balloon(vb, towards_target(vb));
589         update_balloon_size(vb);
590         return 0;
591 }
592 #endif
593 
594 static unsigned int features[] = {
595         VIRTIO_BALLOON_F_MUST_TELL_HOST,
596         VIRTIO_BALLOON_F_STATS_VQ,
597         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
598 };
599 
600 static struct virtio_driver virtio_balloon_driver = {
601         .feature_table = features,
602         .feature_table_size = ARRAY_SIZE(features),
603         .driver.name =  KBUILD_MODNAME,
604         .driver.owner = THIS_MODULE,
605         .id_table =     id_table,
606         .probe =        virtballoon_probe,
607         .remove =       virtballoon_remove,
608         .config_changed = virtballoon_changed,
609 #ifdef CONFIG_PM_SLEEP
610         .freeze =       virtballoon_freeze,
611         .restore =      virtballoon_restore,
612 #endif
613 };
614 
615 module_virtio_driver(virtio_balloon_driver);
616 MODULE_DEVICE_TABLE(virtio, id_table);
617 MODULE_DESCRIPTION("Virtio balloon driver");
618 MODULE_LICENSE("GPL");
619 

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