Version:  2.0.40 2.2.26 2.4.37 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 4.7

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         __virtio32 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(struct virtio_balloon *vb,
131                           __virtio32 pfns[], struct page *page)
132 {
133         unsigned int i;
134 
135         /* Set balloon pfns pointing at this page.
136          * Note that the first pfn points at start of the page. */
137         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
138                 pfns[i] = cpu_to_virtio32(vb->vdev,
139                                           page_to_balloon_pfn(page) + i);
140 }
141 
142 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
143 {
144         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
145         unsigned num_allocated_pages;
146 
147         /* We can only do one array worth at a time. */
148         num = min(num, ARRAY_SIZE(vb->pfns));
149 
150         mutex_lock(&vb->balloon_lock);
151         for (vb->num_pfns = 0; vb->num_pfns < num;
152              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
153                 struct page *page = balloon_page_enqueue(vb_dev_info);
154 
155                 if (!page) {
156                         dev_info_ratelimited(&vb->vdev->dev,
157                                              "Out of puff! Can't get %u pages\n",
158                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
159                         /* Sleep for at least 1/5 of a second before retry. */
160                         msleep(200);
161                         break;
162                 }
163                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
164                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
165                 if (!virtio_has_feature(vb->vdev,
166                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
167                         adjust_managed_page_count(page, -1);
168         }
169 
170         num_allocated_pages = vb->num_pfns;
171         /* Did we get any? */
172         if (vb->num_pfns != 0)
173                 tell_host(vb, vb->inflate_vq);
174         mutex_unlock(&vb->balloon_lock);
175 
176         return num_allocated_pages;
177 }
178 
179 static void release_pages_balloon(struct virtio_balloon *vb)
180 {
181         unsigned int i;
182         struct page *page;
183 
184         /* Find pfns pointing at start of each page, get pages and free them. */
185         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
186                 page = balloon_pfn_to_page(virtio32_to_cpu(vb->vdev,
187                                                            vb->pfns[i]));
188                 if (!virtio_has_feature(vb->vdev,
189                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
190                         adjust_managed_page_count(page, 1);
191                 put_page(page); /* balloon reference */
192         }
193 }
194 
195 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
196 {
197         unsigned num_freed_pages;
198         struct page *page;
199         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
200 
201         /* We can only do one array worth at a time. */
202         num = min(num, ARRAY_SIZE(vb->pfns));
203 
204         mutex_lock(&vb->balloon_lock);
205         for (vb->num_pfns = 0; vb->num_pfns < num;
206              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
207                 page = balloon_page_dequeue(vb_dev_info);
208                 if (!page)
209                         break;
210                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
211                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
212         }
213 
214         num_freed_pages = vb->num_pfns;
215         /*
216          * Note that if
217          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
218          * is true, we *have* to do it in this order
219          */
220         if (vb->num_pfns != 0)
221                 tell_host(vb, vb->deflate_vq);
222         release_pages_balloon(vb);
223         mutex_unlock(&vb->balloon_lock);
224         return num_freed_pages;
225 }
226 
227 static inline void update_stat(struct virtio_balloon *vb, int idx,
228                                u16 tag, u64 val)
229 {
230         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
231         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
232         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
233 }
234 
235 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
236 
237 static void update_balloon_stats(struct virtio_balloon *vb)
238 {
239         unsigned long events[NR_VM_EVENT_ITEMS];
240         struct sysinfo i;
241         int idx = 0;
242         long available;
243 
244         all_vm_events(events);
245         si_meminfo(&i);
246 
247         available = si_mem_available();
248 
249         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
250                                 pages_to_bytes(events[PSWPIN]));
251         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
252                                 pages_to_bytes(events[PSWPOUT]));
253         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
254         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
255         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
256                                 pages_to_bytes(i.freeram));
257         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
258                                 pages_to_bytes(i.totalram));
259         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
260                                 pages_to_bytes(available));
261 }
262 
263 /*
264  * While most virtqueues communicate guest-initiated requests to the hypervisor,
265  * the stats queue operates in reverse.  The driver initializes the virtqueue
266  * with a single buffer.  From that point forward, all conversations consist of
267  * a hypervisor request (a call to this function) which directs us to refill
268  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
269  * we delegate the job to a freezable workqueue that will do the actual work via
270  * stats_handle_request().
271  */
272 static void stats_request(struct virtqueue *vq)
273 {
274         struct virtio_balloon *vb = vq->vdev->priv;
275 
276         spin_lock(&vb->stop_update_lock);
277         if (!vb->stop_update)
278                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
279         spin_unlock(&vb->stop_update_lock);
280 }
281 
282 static void stats_handle_request(struct virtio_balloon *vb)
283 {
284         struct virtqueue *vq;
285         struct scatterlist sg;
286         unsigned int len;
287 
288         update_balloon_stats(vb);
289 
290         vq = vb->stats_vq;
291         if (!virtqueue_get_buf(vq, &len))
292                 return;
293         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
294         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
295         virtqueue_kick(vq);
296 }
297 
298 static void virtballoon_changed(struct virtio_device *vdev)
299 {
300         struct virtio_balloon *vb = vdev->priv;
301         unsigned long flags;
302 
303         spin_lock_irqsave(&vb->stop_update_lock, flags);
304         if (!vb->stop_update)
305                 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
306         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
307 }
308 
309 static inline s64 towards_target(struct virtio_balloon *vb)
310 {
311         s64 target;
312         u32 num_pages;
313 
314         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
315                      &num_pages);
316 
317         /* Legacy balloon config space is LE, unlike all other devices. */
318         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
319                 num_pages = le32_to_cpu((__force __le32)num_pages);
320 
321         target = num_pages;
322         return target - vb->num_pages;
323 }
324 
325 static void update_balloon_size(struct virtio_balloon *vb)
326 {
327         u32 actual = vb->num_pages;
328 
329         /* Legacy balloon config space is LE, unlike all other devices. */
330         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
331                 actual = (__force u32)cpu_to_le32(actual);
332 
333         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
334                       &actual);
335 }
336 
337 /*
338  * virtballoon_oom_notify - release pages when system is under severe
339  *                          memory pressure (called from out_of_memory())
340  * @self : notifier block struct
341  * @dummy: not used
342  * @parm : returned - number of freed pages
343  *
344  * The balancing of memory by use of the virtio balloon should not cause
345  * the termination of processes while there are pages in the balloon.
346  * If virtio balloon manages to release some memory, it will make the
347  * system return and retry the allocation that forced the OOM killer
348  * to run.
349  */
350 static int virtballoon_oom_notify(struct notifier_block *self,
351                                   unsigned long dummy, void *parm)
352 {
353         struct virtio_balloon *vb;
354         unsigned long *freed;
355         unsigned num_freed_pages;
356 
357         vb = container_of(self, struct virtio_balloon, nb);
358         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
359                 return NOTIFY_OK;
360 
361         freed = parm;
362         num_freed_pages = leak_balloon(vb, oom_pages);
363         update_balloon_size(vb);
364         *freed += num_freed_pages;
365 
366         return NOTIFY_OK;
367 }
368 
369 static void update_balloon_stats_func(struct work_struct *work)
370 {
371         struct virtio_balloon *vb;
372 
373         vb = container_of(work, struct virtio_balloon,
374                           update_balloon_stats_work);
375         stats_handle_request(vb);
376 }
377 
378 static void update_balloon_size_func(struct work_struct *work)
379 {
380         struct virtio_balloon *vb;
381         s64 diff;
382 
383         vb = container_of(work, struct virtio_balloon,
384                           update_balloon_size_work);
385         diff = towards_target(vb);
386 
387         if (diff > 0)
388                 diff -= fill_balloon(vb, diff);
389         else if (diff < 0)
390                 diff += leak_balloon(vb, -diff);
391         update_balloon_size(vb);
392 
393         if (diff)
394                 queue_work(system_freezable_wq, work);
395 }
396 
397 static int init_vqs(struct virtio_balloon *vb)
398 {
399         struct virtqueue *vqs[3];
400         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
401         static const char * const names[] = { "inflate", "deflate", "stats" };
402         int err, nvqs;
403 
404         /*
405          * We expect two virtqueues: inflate and deflate, and
406          * optionally stat.
407          */
408         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
409         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
410         if (err)
411                 return err;
412 
413         vb->inflate_vq = vqs[0];
414         vb->deflate_vq = vqs[1];
415         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
416                 struct scatterlist sg;
417                 vb->stats_vq = vqs[2];
418 
419                 /*
420                  * Prime this virtqueue with one buffer so the hypervisor can
421                  * use it to signal us later (it can't be broken yet!).
422                  */
423                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
424                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
425                     < 0)
426                         BUG();
427                 virtqueue_kick(vb->stats_vq);
428         }
429         return 0;
430 }
431 
432 #ifdef CONFIG_BALLOON_COMPACTION
433 /*
434  * virtballoon_migratepage - perform the balloon page migration on behalf of
435  *                           a compation thread.     (called under page lock)
436  * @vb_dev_info: the balloon device
437  * @newpage: page that will replace the isolated page after migration finishes.
438  * @page   : the isolated (old) page that is about to be migrated to newpage.
439  * @mode   : compaction mode -- not used for balloon page migration.
440  *
441  * After a ballooned page gets isolated by compaction procedures, this is the
442  * function that performs the page migration on behalf of a compaction thread
443  * The page migration for virtio balloon is done in a simple swap fashion which
444  * follows these two macro steps:
445  *  1) insert newpage into vb->pages list and update the host about it;
446  *  2) update the host about the old page removed from vb->pages list;
447  *
448  * This function preforms the balloon page migration task.
449  * Called through balloon_mapping->a_ops->migratepage
450  */
451 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
452                 struct page *newpage, struct page *page, enum migrate_mode mode)
453 {
454         struct virtio_balloon *vb = container_of(vb_dev_info,
455                         struct virtio_balloon, vb_dev_info);
456         unsigned long flags;
457 
458         /*
459          * In order to avoid lock contention while migrating pages concurrently
460          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
461          * this turn, as it is easier to retry the page migration later.
462          * This also prevents fill_balloon() getting stuck into a mutex
463          * recursion in the case it ends up triggering memory compaction
464          * while it is attempting to inflate the ballon.
465          */
466         if (!mutex_trylock(&vb->balloon_lock))
467                 return -EAGAIN;
468 
469         get_page(newpage); /* balloon reference */
470 
471         /* balloon's page migration 1st step  -- inflate "newpage" */
472         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
473         balloon_page_insert(vb_dev_info, newpage);
474         vb_dev_info->isolated_pages--;
475         __count_vm_event(BALLOON_MIGRATE);
476         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
477         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
478         set_page_pfns(vb, vb->pfns, newpage);
479         tell_host(vb, vb->inflate_vq);
480 
481         /* balloon's page migration 2nd step -- deflate "page" */
482         balloon_page_delete(page);
483         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
484         set_page_pfns(vb, vb->pfns, page);
485         tell_host(vb, vb->deflate_vq);
486 
487         mutex_unlock(&vb->balloon_lock);
488 
489         put_page(page); /* balloon reference */
490 
491         return MIGRATEPAGE_SUCCESS;
492 }
493 #endif /* CONFIG_BALLOON_COMPACTION */
494 
495 static int virtballoon_probe(struct virtio_device *vdev)
496 {
497         struct virtio_balloon *vb;
498         int err;
499 
500         if (!vdev->config->get) {
501                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
502                         __func__);
503                 return -EINVAL;
504         }
505 
506         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
507         if (!vb) {
508                 err = -ENOMEM;
509                 goto out;
510         }
511 
512         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
513         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
514         spin_lock_init(&vb->stop_update_lock);
515         vb->stop_update = false;
516         vb->num_pages = 0;
517         mutex_init(&vb->balloon_lock);
518         init_waitqueue_head(&vb->acked);
519         vb->vdev = vdev;
520 
521         balloon_devinfo_init(&vb->vb_dev_info);
522 #ifdef CONFIG_BALLOON_COMPACTION
523         vb->vb_dev_info.migratepage = virtballoon_migratepage;
524 #endif
525 
526         err = init_vqs(vb);
527         if (err)
528                 goto out_free_vb;
529 
530         vb->nb.notifier_call = virtballoon_oom_notify;
531         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
532         err = register_oom_notifier(&vb->nb);
533         if (err < 0)
534                 goto out_oom_notify;
535 
536         virtio_device_ready(vdev);
537 
538         return 0;
539 
540 out_oom_notify:
541         vdev->config->del_vqs(vdev);
542 out_free_vb:
543         kfree(vb);
544 out:
545         return err;
546 }
547 
548 static void remove_common(struct virtio_balloon *vb)
549 {
550         /* There might be pages left in the balloon: free them. */
551         while (vb->num_pages)
552                 leak_balloon(vb, vb->num_pages);
553         update_balloon_size(vb);
554 
555         /* Now we reset the device so we can clean up the queues. */
556         vb->vdev->config->reset(vb->vdev);
557 
558         vb->vdev->config->del_vqs(vb->vdev);
559 }
560 
561 static void virtballoon_remove(struct virtio_device *vdev)
562 {
563         struct virtio_balloon *vb = vdev->priv;
564 
565         unregister_oom_notifier(&vb->nb);
566 
567         spin_lock_irq(&vb->stop_update_lock);
568         vb->stop_update = true;
569         spin_unlock_irq(&vb->stop_update_lock);
570         cancel_work_sync(&vb->update_balloon_size_work);
571         cancel_work_sync(&vb->update_balloon_stats_work);
572 
573         remove_common(vb);
574         kfree(vb);
575 }
576 
577 #ifdef CONFIG_PM_SLEEP
578 static int virtballoon_freeze(struct virtio_device *vdev)
579 {
580         struct virtio_balloon *vb = vdev->priv;
581 
582         /*
583          * The workqueue is already frozen by the PM core before this
584          * function is called.
585          */
586         remove_common(vb);
587         return 0;
588 }
589 
590 static int virtballoon_restore(struct virtio_device *vdev)
591 {
592         struct virtio_balloon *vb = vdev->priv;
593         int ret;
594 
595         ret = init_vqs(vdev->priv);
596         if (ret)
597                 return ret;
598 
599         virtio_device_ready(vdev);
600 
601         if (towards_target(vb))
602                 virtballoon_changed(vdev);
603         update_balloon_size(vb);
604         return 0;
605 }
606 #endif
607 
608 static unsigned int features[] = {
609         VIRTIO_BALLOON_F_MUST_TELL_HOST,
610         VIRTIO_BALLOON_F_STATS_VQ,
611         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
612 };
613 
614 static struct virtio_driver virtio_balloon_driver = {
615         .feature_table = features,
616         .feature_table_size = ARRAY_SIZE(features),
617         .driver.name =  KBUILD_MODNAME,
618         .driver.owner = THIS_MODULE,
619         .id_table =     id_table,
620         .probe =        virtballoon_probe,
621         .remove =       virtballoon_remove,
622         .config_changed = virtballoon_changed,
623 #ifdef CONFIG_PM_SLEEP
624         .freeze =       virtballoon_freeze,
625         .restore =      virtballoon_restore,
626 #endif
627 };
628 
629 module_virtio_driver(virtio_balloon_driver);
630 MODULE_DEVICE_TABLE(virtio, id_table);
631 MODULE_DESCRIPTION("Virtio balloon driver");
632 MODULE_LICENSE("GPL");
633 

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