Version:  2.0.40 2.2.26 2.4.37 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 4.2 4.3 4.4 4.5 4.6

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/workqueue.h>
 26 #include <linux/delay.h>
 27 #include <linux/slab.h>
 28 #include <linux/module.h>
 29 #include <linux/balloon_compaction.h>
 30 #include <linux/oom.h>
 31 #include <linux/wait.h>
 32 #include <linux/mm.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         /* The balloon servicing is delegated to a freezable workqueue. */
 53         struct work_struct update_balloon_stats_work;
 54         struct work_struct update_balloon_size_work;
 55 
 56         /* Prevent updating balloon when it is being canceled. */
 57         spinlock_t stop_update_lock;
 58         bool stop_update;
 59 
 60         /* Waiting for host to ack the pages we released. */
 61         wait_queue_head_t acked;
 62 
 63         /* Number of balloon pages we've told the Host we're not using. */
 64         unsigned int num_pages;
 65         /*
 66          * The pages we've told the Host we're not using are enqueued
 67          * at vb_dev_info->pages list.
 68          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 69          * to num_pages above.
 70          */
 71         struct balloon_dev_info vb_dev_info;
 72 
 73         /* Synchronize access/update to this struct virtio_balloon elements */
 74         struct mutex balloon_lock;
 75 
 76         /* The array of pfns we tell the Host about. */
 77         unsigned int num_pfns;
 78         u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 79 
 80         /* Memory statistics */
 81         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 82 
 83         /* To register callback in oom notifier call chain */
 84         struct notifier_block nb;
 85 };
 86 
 87 static struct virtio_device_id id_table[] = {
 88         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 89         { 0 },
 90 };
 91 
 92 static u32 page_to_balloon_pfn(struct page *page)
 93 {
 94         unsigned long pfn = page_to_pfn(page);
 95 
 96         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 97         /* Convert pfn from Linux page size to balloon page size. */
 98         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 99 }
100 
101 static struct page *balloon_pfn_to_page(u32 pfn)
102 {
103         BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
104         return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
105 }
106 
107 static void balloon_ack(struct virtqueue *vq)
108 {
109         struct virtio_balloon *vb = vq->vdev->priv;
110 
111         wake_up(&vb->acked);
112 }
113 
114 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
115 {
116         struct scatterlist sg;
117         unsigned int len;
118 
119         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
120 
121         /* We should always be able to add one buffer to an empty queue. */
122         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
123         virtqueue_kick(vq);
124 
125         /* When host has read buffer, this completes via balloon_ack */
126         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
127 
128 }
129 
130 static void set_page_pfns(u32 pfns[], struct page *page)
131 {
132         unsigned int i;
133 
134         /* Set balloon pfns pointing at this page.
135          * Note that the first pfn points at start of the page. */
136         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
137                 pfns[i] = page_to_balloon_pfn(page) + i;
138 }
139 
140 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
141 {
142         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
143         unsigned num_allocated_pages;
144 
145         /* We can only do one array worth at a time. */
146         num = min(num, ARRAY_SIZE(vb->pfns));
147 
148         mutex_lock(&vb->balloon_lock);
149         for (vb->num_pfns = 0; vb->num_pfns < num;
150              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
151                 struct page *page = balloon_page_enqueue(vb_dev_info);
152 
153                 if (!page) {
154                         dev_info_ratelimited(&vb->vdev->dev,
155                                              "Out of puff! Can't get %u pages\n",
156                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
157                         /* Sleep for at least 1/5 of a second before retry. */
158                         msleep(200);
159                         break;
160                 }
161                 set_page_pfns(vb->pfns + vb->num_pfns, page);
162                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
163                 if (!virtio_has_feature(vb->vdev,
164                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
165                         adjust_managed_page_count(page, -1);
166         }
167 
168         num_allocated_pages = vb->num_pfns;
169         /* Did we get any? */
170         if (vb->num_pfns != 0)
171                 tell_host(vb, vb->inflate_vq);
172         mutex_unlock(&vb->balloon_lock);
173 
174         return num_allocated_pages;
175 }
176 
177 static void release_pages_balloon(struct virtio_balloon *vb)
178 {
179         unsigned int i;
180 
181         /* Find pfns pointing at start of each page, get pages and free them. */
182         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
183                 struct page *page = balloon_pfn_to_page(vb->pfns[i]);
184                 if (!virtio_has_feature(vb->vdev,
185                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
186                         adjust_managed_page_count(page, 1);
187                 put_page(page); /* balloon reference */
188         }
189 }
190 
191 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
192 {
193         unsigned num_freed_pages;
194         struct page *page;
195         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
196 
197         /* We can only do one array worth at a time. */
198         num = min(num, ARRAY_SIZE(vb->pfns));
199 
200         mutex_lock(&vb->balloon_lock);
201         for (vb->num_pfns = 0; vb->num_pfns < num;
202              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
203                 page = balloon_page_dequeue(vb_dev_info);
204                 if (!page)
205                         break;
206                 set_page_pfns(vb->pfns + vb->num_pfns, page);
207                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
208         }
209 
210         num_freed_pages = vb->num_pfns;
211         /*
212          * Note that if
213          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
214          * is true, we *have* to do it in this order
215          */
216         if (vb->num_pfns != 0)
217                 tell_host(vb, vb->deflate_vq);
218         release_pages_balloon(vb);
219         mutex_unlock(&vb->balloon_lock);
220         return num_freed_pages;
221 }
222 
223 static inline void update_stat(struct virtio_balloon *vb, int idx,
224                                u16 tag, u64 val)
225 {
226         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
227         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
228         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
229 }
230 
231 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
232 
233 static void update_balloon_stats(struct virtio_balloon *vb)
234 {
235         unsigned long events[NR_VM_EVENT_ITEMS];
236         struct sysinfo i;
237         int idx = 0;
238         long available;
239 
240         all_vm_events(events);
241         si_meminfo(&i);
242 
243         available = si_mem_available();
244 
245         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
246                                 pages_to_bytes(events[PSWPIN]));
247         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
248                                 pages_to_bytes(events[PSWPOUT]));
249         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
250         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
251         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
252                                 pages_to_bytes(i.freeram));
253         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
254                                 pages_to_bytes(i.totalram));
255         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
256                                 pages_to_bytes(available));
257 }
258 
259 /*
260  * While most virtqueues communicate guest-initiated requests to the hypervisor,
261  * the stats queue operates in reverse.  The driver initializes the virtqueue
262  * with a single buffer.  From that point forward, all conversations consist of
263  * a hypervisor request (a call to this function) which directs us to refill
264  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
265  * we delegate the job to a freezable workqueue that will do the actual work via
266  * stats_handle_request().
267  */
268 static void stats_request(struct virtqueue *vq)
269 {
270         struct virtio_balloon *vb = vq->vdev->priv;
271 
272         spin_lock(&vb->stop_update_lock);
273         if (!vb->stop_update)
274                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
275         spin_unlock(&vb->stop_update_lock);
276 }
277 
278 static void stats_handle_request(struct virtio_balloon *vb)
279 {
280         struct virtqueue *vq;
281         struct scatterlist sg;
282         unsigned int len;
283 
284         update_balloon_stats(vb);
285 
286         vq = vb->stats_vq;
287         if (!virtqueue_get_buf(vq, &len))
288                 return;
289         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
290         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
291         virtqueue_kick(vq);
292 }
293 
294 static void virtballoon_changed(struct virtio_device *vdev)
295 {
296         struct virtio_balloon *vb = vdev->priv;
297         unsigned long flags;
298 
299         spin_lock_irqsave(&vb->stop_update_lock, flags);
300         if (!vb->stop_update)
301                 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
302         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
303 }
304 
305 static inline s64 towards_target(struct virtio_balloon *vb)
306 {
307         s64 target;
308         u32 num_pages;
309 
310         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
311                      &num_pages);
312 
313         /* Legacy balloon config space is LE, unlike all other devices. */
314         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
315                 num_pages = le32_to_cpu((__force __le32)num_pages);
316 
317         target = num_pages;
318         return target - vb->num_pages;
319 }
320 
321 static void update_balloon_size(struct virtio_balloon *vb)
322 {
323         u32 actual = vb->num_pages;
324 
325         /* Legacy balloon config space is LE, unlike all other devices. */
326         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
327                 actual = (__force u32)cpu_to_le32(actual);
328 
329         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
330                       &actual);
331 }
332 
333 /*
334  * virtballoon_oom_notify - release pages when system is under severe
335  *                          memory pressure (called from out_of_memory())
336  * @self : notifier block struct
337  * @dummy: not used
338  * @parm : returned - number of freed pages
339  *
340  * The balancing of memory by use of the virtio balloon should not cause
341  * the termination of processes while there are pages in the balloon.
342  * If virtio balloon manages to release some memory, it will make the
343  * system return and retry the allocation that forced the OOM killer
344  * to run.
345  */
346 static int virtballoon_oom_notify(struct notifier_block *self,
347                                   unsigned long dummy, void *parm)
348 {
349         struct virtio_balloon *vb;
350         unsigned long *freed;
351         unsigned num_freed_pages;
352 
353         vb = container_of(self, struct virtio_balloon, nb);
354         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
355                 return NOTIFY_OK;
356 
357         freed = parm;
358         num_freed_pages = leak_balloon(vb, oom_pages);
359         update_balloon_size(vb);
360         *freed += num_freed_pages;
361 
362         return NOTIFY_OK;
363 }
364 
365 static void update_balloon_stats_func(struct work_struct *work)
366 {
367         struct virtio_balloon *vb;
368 
369         vb = container_of(work, struct virtio_balloon,
370                           update_balloon_stats_work);
371         stats_handle_request(vb);
372 }
373 
374 static void update_balloon_size_func(struct work_struct *work)
375 {
376         struct virtio_balloon *vb;
377         s64 diff;
378 
379         vb = container_of(work, struct virtio_balloon,
380                           update_balloon_size_work);
381         diff = towards_target(vb);
382 
383         if (diff > 0)
384                 diff -= fill_balloon(vb, diff);
385         else if (diff < 0)
386                 diff += leak_balloon(vb, -diff);
387         update_balloon_size(vb);
388 
389         if (diff)
390                 queue_work(system_freezable_wq, work);
391 }
392 
393 static int init_vqs(struct virtio_balloon *vb)
394 {
395         struct virtqueue *vqs[3];
396         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
397         static const char * const names[] = { "inflate", "deflate", "stats" };
398         int err, nvqs;
399 
400         /*
401          * We expect two virtqueues: inflate and deflate, and
402          * optionally stat.
403          */
404         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
405         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
406         if (err)
407                 return err;
408 
409         vb->inflate_vq = vqs[0];
410         vb->deflate_vq = vqs[1];
411         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
412                 struct scatterlist sg;
413                 vb->stats_vq = vqs[2];
414 
415                 /*
416                  * Prime this virtqueue with one buffer so the hypervisor can
417                  * use it to signal us later (it can't be broken yet!).
418                  */
419                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
420                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
421                     < 0)
422                         BUG();
423                 virtqueue_kick(vb->stats_vq);
424         }
425         return 0;
426 }
427 
428 #ifdef CONFIG_BALLOON_COMPACTION
429 /*
430  * virtballoon_migratepage - perform the balloon page migration on behalf of
431  *                           a compation thread.     (called under page lock)
432  * @vb_dev_info: the balloon device
433  * @newpage: page that will replace the isolated page after migration finishes.
434  * @page   : the isolated (old) page that is about to be migrated to newpage.
435  * @mode   : compaction mode -- not used for balloon page migration.
436  *
437  * After a ballooned page gets isolated by compaction procedures, this is the
438  * function that performs the page migration on behalf of a compaction thread
439  * The page migration for virtio balloon is done in a simple swap fashion which
440  * follows these two macro steps:
441  *  1) insert newpage into vb->pages list and update the host about it;
442  *  2) update the host about the old page removed from vb->pages list;
443  *
444  * This function preforms the balloon page migration task.
445  * Called through balloon_mapping->a_ops->migratepage
446  */
447 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
448                 struct page *newpage, struct page *page, enum migrate_mode mode)
449 {
450         struct virtio_balloon *vb = container_of(vb_dev_info,
451                         struct virtio_balloon, vb_dev_info);
452         unsigned long flags;
453 
454         /*
455          * In order to avoid lock contention while migrating pages concurrently
456          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
457          * this turn, as it is easier to retry the page migration later.
458          * This also prevents fill_balloon() getting stuck into a mutex
459          * recursion in the case it ends up triggering memory compaction
460          * while it is attempting to inflate the ballon.
461          */
462         if (!mutex_trylock(&vb->balloon_lock))
463                 return -EAGAIN;
464 
465         get_page(newpage); /* balloon reference */
466 
467         /* balloon's page migration 1st step  -- inflate "newpage" */
468         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
469         balloon_page_insert(vb_dev_info, newpage);
470         vb_dev_info->isolated_pages--;
471         __count_vm_event(BALLOON_MIGRATE);
472         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
473         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
474         set_page_pfns(vb->pfns, newpage);
475         tell_host(vb, vb->inflate_vq);
476 
477         /* balloon's page migration 2nd step -- deflate "page" */
478         balloon_page_delete(page);
479         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
480         set_page_pfns(vb->pfns, page);
481         tell_host(vb, vb->deflate_vq);
482 
483         mutex_unlock(&vb->balloon_lock);
484 
485         put_page(page); /* balloon reference */
486 
487         return MIGRATEPAGE_SUCCESS;
488 }
489 #endif /* CONFIG_BALLOON_COMPACTION */
490 
491 static int virtballoon_probe(struct virtio_device *vdev)
492 {
493         struct virtio_balloon *vb;
494         int err;
495 
496         if (!vdev->config->get) {
497                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
498                         __func__);
499                 return -EINVAL;
500         }
501 
502         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
503         if (!vb) {
504                 err = -ENOMEM;
505                 goto out;
506         }
507 
508         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
509         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
510         spin_lock_init(&vb->stop_update_lock);
511         vb->stop_update = false;
512         vb->num_pages = 0;
513         mutex_init(&vb->balloon_lock);
514         init_waitqueue_head(&vb->acked);
515         vb->vdev = vdev;
516 
517         balloon_devinfo_init(&vb->vb_dev_info);
518 #ifdef CONFIG_BALLOON_COMPACTION
519         vb->vb_dev_info.migratepage = virtballoon_migratepage;
520 #endif
521 
522         err = init_vqs(vb);
523         if (err)
524                 goto out_free_vb;
525 
526         vb->nb.notifier_call = virtballoon_oom_notify;
527         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
528         err = register_oom_notifier(&vb->nb);
529         if (err < 0)
530                 goto out_oom_notify;
531 
532         virtio_device_ready(vdev);
533 
534         return 0;
535 
536 out_oom_notify:
537         vdev->config->del_vqs(vdev);
538 out_free_vb:
539         kfree(vb);
540 out:
541         return err;
542 }
543 
544 static void remove_common(struct virtio_balloon *vb)
545 {
546         /* There might be pages left in the balloon: free them. */
547         while (vb->num_pages)
548                 leak_balloon(vb, vb->num_pages);
549         update_balloon_size(vb);
550 
551         /* Now we reset the device so we can clean up the queues. */
552         vb->vdev->config->reset(vb->vdev);
553 
554         vb->vdev->config->del_vqs(vb->vdev);
555 }
556 
557 static void virtballoon_remove(struct virtio_device *vdev)
558 {
559         struct virtio_balloon *vb = vdev->priv;
560 
561         unregister_oom_notifier(&vb->nb);
562 
563         spin_lock_irq(&vb->stop_update_lock);
564         vb->stop_update = true;
565         spin_unlock_irq(&vb->stop_update_lock);
566         cancel_work_sync(&vb->update_balloon_size_work);
567         cancel_work_sync(&vb->update_balloon_stats_work);
568 
569         remove_common(vb);
570         kfree(vb);
571 }
572 
573 #ifdef CONFIG_PM_SLEEP
574 static int virtballoon_freeze(struct virtio_device *vdev)
575 {
576         struct virtio_balloon *vb = vdev->priv;
577 
578         /*
579          * The workqueue is already frozen by the PM core before this
580          * function is called.
581          */
582         remove_common(vb);
583         return 0;
584 }
585 
586 static int virtballoon_restore(struct virtio_device *vdev)
587 {
588         struct virtio_balloon *vb = vdev->priv;
589         int ret;
590 
591         ret = init_vqs(vdev->priv);
592         if (ret)
593                 return ret;
594 
595         virtio_device_ready(vdev);
596 
597         if (towards_target(vb))
598                 virtballoon_changed(vdev);
599         update_balloon_size(vb);
600         return 0;
601 }
602 #endif
603 
604 static unsigned int features[] = {
605         VIRTIO_BALLOON_F_MUST_TELL_HOST,
606         VIRTIO_BALLOON_F_STATS_VQ,
607         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
608 };
609 
610 static struct virtio_driver virtio_balloon_driver = {
611         .feature_table = features,
612         .feature_table_size = ARRAY_SIZE(features),
613         .driver.name =  KBUILD_MODNAME,
614         .driver.owner = THIS_MODULE,
615         .id_table =     id_table,
616         .probe =        virtballoon_probe,
617         .remove =       virtballoon_remove,
618         .config_changed = virtballoon_changed,
619 #ifdef CONFIG_PM_SLEEP
620         .freeze =       virtballoon_freeze,
621         .restore =      virtballoon_restore,
622 #endif
623 };
624 
625 module_virtio_driver(virtio_balloon_driver);
626 MODULE_DEVICE_TABLE(virtio, id_table);
627 MODULE_DESCRIPTION("Virtio balloon driver");
628 MODULE_LICENSE("GPL");
629 

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