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[linux.git] / drivers / virtio / virtio_balloon.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
4  * Tosatti's implementations.
5  *
6  *  Copyright 2008 Rusty Russell IBM Corporation
7  */
8
9 #include <linux/virtio.h>
10 #include <linux/virtio_balloon.h>
11 #include <linux/swap.h>
12 #include <linux/workqueue.h>
13 #include <linux/delay.h>
14 #include <linux/slab.h>
15 #include <linux/module.h>
16 #include <linux/balloon_compaction.h>
17 #include <linux/oom.h>
18 #include <linux/wait.h>
19 #include <linux/mm.h>
20 #include <linux/page_reporting.h>
21
22 /*
23  * Balloon device works in 4K page units.  So each page is pointed to by
24  * multiple balloon pages.  All memory counters in this driver are in balloon
25  * page units.
26  */
27 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
28 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
29 /* Maximum number of (4k) pages to deflate on OOM notifications. */
30 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
31 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
32
33 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
34                                              __GFP_NOMEMALLOC)
35 /* The order of free page blocks to report to host */
36 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER MAX_PAGE_ORDER
37 /* The size of a free page block in bytes */
38 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
39         (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
40 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
41
42 enum virtio_balloon_vq {
43         VIRTIO_BALLOON_VQ_INFLATE,
44         VIRTIO_BALLOON_VQ_DEFLATE,
45         VIRTIO_BALLOON_VQ_STATS,
46         VIRTIO_BALLOON_VQ_FREE_PAGE,
47         VIRTIO_BALLOON_VQ_REPORTING,
48         VIRTIO_BALLOON_VQ_MAX
49 };
50
51 enum virtio_balloon_config_read {
52         VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
53 };
54
55 struct virtio_balloon {
56         struct virtio_device *vdev;
57         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
58
59         /* Balloon's own wq for cpu-intensive work items */
60         struct workqueue_struct *balloon_wq;
61         /* The free page reporting work item submitted to the balloon wq */
62         struct work_struct report_free_page_work;
63
64         /* The balloon servicing is delegated to a freezable workqueue. */
65         struct work_struct update_balloon_stats_work;
66         struct work_struct update_balloon_size_work;
67
68         /* Prevent updating balloon when it is being canceled. */
69         spinlock_t stop_update_lock;
70         bool stop_update;
71         /* Bitmap to indicate if reading the related config fields are needed */
72         unsigned long config_read_bitmap;
73
74         /* The list of allocated free pages, waiting to be given back to mm */
75         struct list_head free_page_list;
76         spinlock_t free_page_list_lock;
77         /* The number of free page blocks on the above list */
78         unsigned long num_free_page_blocks;
79         /*
80          * The cmd id received from host.
81          * Read it via virtio_balloon_cmd_id_received to get the latest value
82          * sent from host.
83          */
84         u32 cmd_id_received_cache;
85         /* The cmd id that is actively in use */
86         __virtio32 cmd_id_active;
87         /* Buffer to store the stop sign */
88         __virtio32 cmd_id_stop;
89
90         /* Waiting for host to ack the pages we released. */
91         wait_queue_head_t acked;
92
93         /* Number of balloon pages we've told the Host we're not using. */
94         unsigned int num_pages;
95         /*
96          * The pages we've told the Host we're not using are enqueued
97          * at vb_dev_info->pages list.
98          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
99          * to num_pages above.
100          */
101         struct balloon_dev_info vb_dev_info;
102
103         /* Synchronize access/update to this struct virtio_balloon elements */
104         struct mutex balloon_lock;
105
106         /* The array of pfns we tell the Host about. */
107         unsigned int num_pfns;
108         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
109
110         /* Memory statistics */
111         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
112
113         /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
114         struct shrinker *shrinker;
115
116         /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
117         struct notifier_block oom_nb;
118
119         /* Free page reporting device */
120         struct virtqueue *reporting_vq;
121         struct page_reporting_dev_info pr_dev_info;
122
123         /* State for keeping the wakeup_source active while adjusting the balloon */
124         spinlock_t wakeup_lock;
125         bool processing_wakeup_event;
126         u32 wakeup_signal_mask;
127 };
128
129 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST (1 << 0)
130 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS (1 << 1)
131
132 static const struct virtio_device_id id_table[] = {
133         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
134         { 0 },
135 };
136
137 static u32 page_to_balloon_pfn(struct page *page)
138 {
139         unsigned long pfn = page_to_pfn(page);
140
141         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
142         /* Convert pfn from Linux page size to balloon page size. */
143         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
144 }
145
146 static void start_wakeup_event(struct virtio_balloon *vb, u32 mask)
147 {
148         unsigned long flags;
149
150         spin_lock_irqsave(&vb->wakeup_lock, flags);
151         vb->wakeup_signal_mask |= mask;
152         if (!vb->processing_wakeup_event) {
153                 vb->processing_wakeup_event = true;
154                 pm_stay_awake(&vb->vdev->dev);
155         }
156         spin_unlock_irqrestore(&vb->wakeup_lock, flags);
157 }
158
159 static void process_wakeup_event(struct virtio_balloon *vb, u32 mask)
160 {
161         spin_lock_irq(&vb->wakeup_lock);
162         vb->wakeup_signal_mask &= ~mask;
163         spin_unlock_irq(&vb->wakeup_lock);
164 }
165
166 static void finish_wakeup_event(struct virtio_balloon *vb)
167 {
168         spin_lock_irq(&vb->wakeup_lock);
169         if (!vb->wakeup_signal_mask && vb->processing_wakeup_event) {
170                 vb->processing_wakeup_event = false;
171                 pm_relax(&vb->vdev->dev);
172         }
173         spin_unlock_irq(&vb->wakeup_lock);
174 }
175
176 static void balloon_ack(struct virtqueue *vq)
177 {
178         struct virtio_balloon *vb = vq->vdev->priv;
179
180         wake_up(&vb->acked);
181 }
182
183 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
184 {
185         struct scatterlist sg;
186         unsigned int len;
187
188         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
189
190         /* We should always be able to add one buffer to an empty queue. */
191         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
192         virtqueue_kick(vq);
193
194         /* When host has read buffer, this completes via balloon_ack */
195         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
196
197 }
198
199 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
200                                    struct scatterlist *sg, unsigned int nents)
201 {
202         struct virtio_balloon *vb =
203                 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
204         struct virtqueue *vq = vb->reporting_vq;
205         unsigned int unused, err;
206
207         /* We should always be able to add these buffers to an empty queue. */
208         err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
209
210         /*
211          * In the extremely unlikely case that something has occurred and we
212          * are able to trigger an error we will simply display a warning
213          * and exit without actually processing the pages.
214          */
215         if (WARN_ON_ONCE(err))
216                 return err;
217
218         virtqueue_kick(vq);
219
220         /* When host has read buffer, this completes via balloon_ack */
221         wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
222
223         return 0;
224 }
225
226 static void set_page_pfns(struct virtio_balloon *vb,
227                           __virtio32 pfns[], struct page *page)
228 {
229         unsigned int i;
230
231         BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
232
233         /*
234          * Set balloon pfns pointing at this page.
235          * Note that the first pfn points at start of the page.
236          */
237         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
238                 pfns[i] = cpu_to_virtio32(vb->vdev,
239                                           page_to_balloon_pfn(page) + i);
240 }
241
242 static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
243 {
244         unsigned int num_allocated_pages;
245         unsigned int num_pfns;
246         struct page *page;
247         LIST_HEAD(pages);
248
249         /* We can only do one array worth at a time. */
250         num = min(num, ARRAY_SIZE(vb->pfns));
251
252         for (num_pfns = 0; num_pfns < num;
253              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
254                 struct page *page = balloon_page_alloc();
255
256                 if (!page) {
257                         dev_info_ratelimited(&vb->vdev->dev,
258                                              "Out of puff! Can't get %u pages\n",
259                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
260                         /* Sleep for at least 1/5 of a second before retry. */
261                         msleep(200);
262                         break;
263                 }
264
265                 balloon_page_push(&pages, page);
266         }
267
268         mutex_lock(&vb->balloon_lock);
269
270         vb->num_pfns = 0;
271
272         while ((page = balloon_page_pop(&pages))) {
273                 balloon_page_enqueue(&vb->vb_dev_info, page);
274
275                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
276                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
277                 if (!virtio_has_feature(vb->vdev,
278                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
279                         adjust_managed_page_count(page, -1);
280                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
281         }
282
283         num_allocated_pages = vb->num_pfns;
284         /* Did we get any? */
285         if (vb->num_pfns != 0)
286                 tell_host(vb, vb->inflate_vq);
287         mutex_unlock(&vb->balloon_lock);
288
289         return num_allocated_pages;
290 }
291
292 static void release_pages_balloon(struct virtio_balloon *vb,
293                                  struct list_head *pages)
294 {
295         struct page *page, *next;
296
297         list_for_each_entry_safe(page, next, pages, lru) {
298                 if (!virtio_has_feature(vb->vdev,
299                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
300                         adjust_managed_page_count(page, 1);
301                 list_del(&page->lru);
302                 put_page(page); /* balloon reference */
303         }
304 }
305
306 static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num)
307 {
308         unsigned int num_freed_pages;
309         struct page *page;
310         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
311         LIST_HEAD(pages);
312
313         /* We can only do one array worth at a time. */
314         num = min(num, ARRAY_SIZE(vb->pfns));
315
316         mutex_lock(&vb->balloon_lock);
317         /* We can't release more pages than taken */
318         num = min(num, (size_t)vb->num_pages);
319         for (vb->num_pfns = 0; vb->num_pfns < num;
320              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
321                 page = balloon_page_dequeue(vb_dev_info);
322                 if (!page)
323                         break;
324                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
325                 list_add(&page->lru, &pages);
326                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
327         }
328
329         num_freed_pages = vb->num_pfns;
330         /*
331          * Note that if
332          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
333          * is true, we *have* to do it in this order
334          */
335         if (vb->num_pfns != 0)
336                 tell_host(vb, vb->deflate_vq);
337         release_pages_balloon(vb, &pages);
338         mutex_unlock(&vb->balloon_lock);
339         return num_freed_pages;
340 }
341
342 static inline void update_stat(struct virtio_balloon *vb, int idx,
343                                u16 tag, u64 val)
344 {
345         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
346         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
347         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
348 }
349
350 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
351
352 #ifdef CONFIG_VM_EVENT_COUNTERS
353 /* Return the number of entries filled by vm events */
354 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
355 {
356         unsigned long events[NR_VM_EVENT_ITEMS];
357         unsigned int idx = 0;
358
359         all_vm_events(events);
360         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
361                     pages_to_bytes(events[PSWPIN]));
362         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
363                     pages_to_bytes(events[PSWPOUT]));
364         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
365         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
366
367 #ifdef CONFIG_HUGETLB_PAGE
368         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
369                     events[HTLB_BUDDY_PGALLOC]);
370         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
371                     events[HTLB_BUDDY_PGALLOC_FAIL]);
372 #endif /* CONFIG_HUGETLB_PAGE */
373
374         return idx;
375 }
376 #else /* CONFIG_VM_EVENT_COUNTERS */
377 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
378 {
379         return 0;
380 }
381 #endif /* CONFIG_VM_EVENT_COUNTERS */
382
383 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
384 {
385         struct sysinfo i;
386         unsigned int idx;
387         long available;
388         unsigned long caches;
389
390         idx = update_balloon_vm_stats(vb);
391
392         si_meminfo(&i);
393         available = si_mem_available();
394         caches = global_node_page_state(NR_FILE_PAGES);
395         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
396                                 pages_to_bytes(i.freeram));
397         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
398                                 pages_to_bytes(i.totalram));
399         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
400                                 pages_to_bytes(available));
401         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
402                                 pages_to_bytes(caches));
403
404         return idx;
405 }
406
407 /*
408  * While most virtqueues communicate guest-initiated requests to the hypervisor,
409  * the stats queue operates in reverse.  The driver initializes the virtqueue
410  * with a single buffer.  From that point forward, all conversations consist of
411  * a hypervisor request (a call to this function) which directs us to refill
412  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
413  * we delegate the job to a freezable workqueue that will do the actual work via
414  * stats_handle_request().
415  */
416 static void stats_request(struct virtqueue *vq)
417 {
418         struct virtio_balloon *vb = vq->vdev->priv;
419
420         spin_lock(&vb->stop_update_lock);
421         if (!vb->stop_update) {
422                 start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
423                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
424         }
425         spin_unlock(&vb->stop_update_lock);
426 }
427
428 static void stats_handle_request(struct virtio_balloon *vb)
429 {
430         struct virtqueue *vq;
431         struct scatterlist sg;
432         unsigned int len, num_stats;
433
434         num_stats = update_balloon_stats(vb);
435
436         vq = vb->stats_vq;
437         if (!virtqueue_get_buf(vq, &len))
438                 return;
439         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
440         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
441         virtqueue_kick(vq);
442 }
443
444 static inline s64 towards_target(struct virtio_balloon *vb)
445 {
446         s64 target;
447         u32 num_pages;
448
449         /* Legacy balloon config space is LE, unlike all other devices. */
450         virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
451                         &num_pages);
452
453         /*
454          * Aligned up to guest page size to avoid inflating and deflating
455          * balloon endlessly.
456          */
457         target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
458         return target - vb->num_pages;
459 }
460
461 /* Gives back @num_to_return blocks of free pages to mm. */
462 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
463                                              unsigned long num_to_return)
464 {
465         struct page *page;
466         unsigned long num_returned;
467
468         spin_lock_irq(&vb->free_page_list_lock);
469         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
470                 page = balloon_page_pop(&vb->free_page_list);
471                 if (!page)
472                         break;
473                 free_pages((unsigned long)page_address(page),
474                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
475         }
476         vb->num_free_page_blocks -= num_returned;
477         spin_unlock_irq(&vb->free_page_list_lock);
478
479         return num_returned;
480 }
481
482 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
483 {
484         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
485                 return;
486
487         /* No need to queue the work if the bit was already set. */
488         if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
489                              &vb->config_read_bitmap))
490                 return;
491
492         queue_work(vb->balloon_wq, &vb->report_free_page_work);
493 }
494
495 static void start_update_balloon_size(struct virtio_balloon *vb)
496 {
497         start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
498         queue_work(system_freezable_wq, &vb->update_balloon_size_work);
499 }
500
501 static void virtballoon_changed(struct virtio_device *vdev)
502 {
503         struct virtio_balloon *vb = vdev->priv;
504         unsigned long flags;
505
506         spin_lock_irqsave(&vb->stop_update_lock, flags);
507         if (!vb->stop_update) {
508                 start_update_balloon_size(vb);
509                 virtio_balloon_queue_free_page_work(vb);
510         }
511         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
512 }
513
514 static void update_balloon_size(struct virtio_balloon *vb)
515 {
516         u32 actual = vb->num_pages;
517
518         /* Legacy balloon config space is LE, unlike all other devices. */
519         virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
520                          &actual);
521 }
522
523 static void update_balloon_stats_func(struct work_struct *work)
524 {
525         struct virtio_balloon *vb;
526
527         vb = container_of(work, struct virtio_balloon,
528                           update_balloon_stats_work);
529
530         process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
531         stats_handle_request(vb);
532         finish_wakeup_event(vb);
533 }
534
535 static void update_balloon_size_func(struct work_struct *work)
536 {
537         struct virtio_balloon *vb;
538         s64 diff;
539
540         vb = container_of(work, struct virtio_balloon,
541                           update_balloon_size_work);
542
543         process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
544
545         diff = towards_target(vb);
546
547         if (diff) {
548                 if (diff > 0)
549                         diff -= fill_balloon(vb, diff);
550                 else
551                         diff += leak_balloon(vb, -diff);
552                 update_balloon_size(vb);
553         }
554
555         if (diff)
556                 queue_work(system_freezable_wq, work);
557         else
558                 finish_wakeup_event(vb);
559 }
560
561 static int init_vqs(struct virtio_balloon *vb)
562 {
563         struct virtqueue_info vqs_info[VIRTIO_BALLOON_VQ_MAX] = {};
564         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
565         int err;
566
567         /*
568          * Inflateq and deflateq are used unconditionally. The names[]
569          * will be NULL if the related feature is not enabled, which will
570          * cause no allocation for the corresponding virtqueue in find_vqs.
571          */
572         vqs_info[VIRTIO_BALLOON_VQ_INFLATE].callback = balloon_ack;
573         vqs_info[VIRTIO_BALLOON_VQ_INFLATE].name = "inflate";
574         vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].callback = balloon_ack;
575         vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].name = "deflate";
576
577         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
578                 vqs_info[VIRTIO_BALLOON_VQ_STATS].name = "stats";
579                 vqs_info[VIRTIO_BALLOON_VQ_STATS].callback = stats_request;
580         }
581
582         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
583                 vqs_info[VIRTIO_BALLOON_VQ_FREE_PAGE].name = "free_page_vq";
584
585         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
586                 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].name = "reporting_vq";
587                 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].callback = balloon_ack;
588         }
589
590         err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
591                               vqs_info, NULL);
592         if (err)
593                 return err;
594
595         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
596         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
597         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
598                 struct scatterlist sg;
599                 unsigned int num_stats;
600                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
601
602                 /*
603                  * Prime this virtqueue with one buffer so the hypervisor can
604                  * use it to signal us later (it can't be broken yet!).
605                  */
606                 num_stats = update_balloon_stats(vb);
607
608                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
609                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
610                                            GFP_KERNEL);
611                 if (err) {
612                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
613                                  __func__);
614                         return err;
615                 }
616                 virtqueue_kick(vb->stats_vq);
617         }
618
619         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
620                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
621
622         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
623                 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
624
625         return 0;
626 }
627
628 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
629 {
630         if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
631                                &vb->config_read_bitmap)) {
632                 /* Legacy balloon config space is LE, unlike all other devices. */
633                 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
634                                 free_page_hint_cmd_id,
635                                 &vb->cmd_id_received_cache);
636         }
637
638         return vb->cmd_id_received_cache;
639 }
640
641 static int send_cmd_id_start(struct virtio_balloon *vb)
642 {
643         struct scatterlist sg;
644         struct virtqueue *vq = vb->free_page_vq;
645         int err, unused;
646
647         /* Detach all the used buffers from the vq */
648         while (virtqueue_get_buf(vq, &unused))
649                 ;
650
651         vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
652                                         virtio_balloon_cmd_id_received(vb));
653         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
654         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
655         if (!err)
656                 virtqueue_kick(vq);
657         return err;
658 }
659
660 static int send_cmd_id_stop(struct virtio_balloon *vb)
661 {
662         struct scatterlist sg;
663         struct virtqueue *vq = vb->free_page_vq;
664         int err, unused;
665
666         /* Detach all the used buffers from the vq */
667         while (virtqueue_get_buf(vq, &unused))
668                 ;
669
670         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
671         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
672         if (!err)
673                 virtqueue_kick(vq);
674         return err;
675 }
676
677 static int get_free_page_and_send(struct virtio_balloon *vb)
678 {
679         struct virtqueue *vq = vb->free_page_vq;
680         struct page *page;
681         struct scatterlist sg;
682         int err, unused;
683         void *p;
684
685         /* Detach all the used buffers from the vq */
686         while (virtqueue_get_buf(vq, &unused))
687                 ;
688
689         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
690                            VIRTIO_BALLOON_HINT_BLOCK_ORDER);
691         /*
692          * When the allocation returns NULL, it indicates that we have got all
693          * the possible free pages, so return -EINTR to stop.
694          */
695         if (!page)
696                 return -EINTR;
697
698         p = page_address(page);
699         sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
700         /* There is always 1 entry reserved for the cmd id to use. */
701         if (vq->num_free > 1) {
702                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
703                 if (unlikely(err)) {
704                         free_pages((unsigned long)p,
705                                    VIRTIO_BALLOON_HINT_BLOCK_ORDER);
706                         return err;
707                 }
708                 virtqueue_kick(vq);
709                 spin_lock_irq(&vb->free_page_list_lock);
710                 balloon_page_push(&vb->free_page_list, page);
711                 vb->num_free_page_blocks++;
712                 spin_unlock_irq(&vb->free_page_list_lock);
713         } else {
714                 /*
715                  * The vq has no available entry to add this page block, so
716                  * just free it.
717                  */
718                 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
719         }
720
721         return 0;
722 }
723
724 static int send_free_pages(struct virtio_balloon *vb)
725 {
726         int err;
727         u32 cmd_id_active;
728
729         while (1) {
730                 /*
731                  * If a stop id or a new cmd id was just received from host,
732                  * stop the reporting.
733                  */
734                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
735                 if (unlikely(cmd_id_active !=
736                              virtio_balloon_cmd_id_received(vb)))
737                         break;
738
739                 /*
740                  * The free page blocks are allocated and sent to host one by
741                  * one.
742                  */
743                 err = get_free_page_and_send(vb);
744                 if (err == -EINTR)
745                         break;
746                 else if (unlikely(err))
747                         return err;
748         }
749
750         return 0;
751 }
752
753 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
754 {
755         int err;
756         struct device *dev = &vb->vdev->dev;
757
758         /* Start by sending the received cmd id to host with an outbuf. */
759         err = send_cmd_id_start(vb);
760         if (unlikely(err))
761                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
762
763         err = send_free_pages(vb);
764         if (unlikely(err))
765                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
766
767         /* End by sending a stop id to host with an outbuf. */
768         err = send_cmd_id_stop(vb);
769         if (unlikely(err))
770                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
771 }
772
773 static void report_free_page_func(struct work_struct *work)
774 {
775         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
776                                                  report_free_page_work);
777         u32 cmd_id_received;
778
779         cmd_id_received = virtio_balloon_cmd_id_received(vb);
780         if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
781                 /* Pass ULONG_MAX to give back all the free pages */
782                 return_free_pages_to_mm(vb, ULONG_MAX);
783         } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
784                    cmd_id_received !=
785                    virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
786                 virtio_balloon_report_free_page(vb);
787         }
788 }
789
790 #ifdef CONFIG_BALLOON_COMPACTION
791 /*
792  * virtballoon_migratepage - perform the balloon page migration on behalf of
793  *                           a compaction thread.     (called under page lock)
794  * @vb_dev_info: the balloon device
795  * @newpage: page that will replace the isolated page after migration finishes.
796  * @page   : the isolated (old) page that is about to be migrated to newpage.
797  * @mode   : compaction mode -- not used for balloon page migration.
798  *
799  * After a ballooned page gets isolated by compaction procedures, this is the
800  * function that performs the page migration on behalf of a compaction thread
801  * The page migration for virtio balloon is done in a simple swap fashion which
802  * follows these two macro steps:
803  *  1) insert newpage into vb->pages list and update the host about it;
804  *  2) update the host about the old page removed from vb->pages list;
805  *
806  * This function preforms the balloon page migration task.
807  * Called through movable_operations->migrate_page
808  */
809 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
810                 struct page *newpage, struct page *page, enum migrate_mode mode)
811 {
812         struct virtio_balloon *vb = container_of(vb_dev_info,
813                         struct virtio_balloon, vb_dev_info);
814         unsigned long flags;
815
816         /*
817          * In order to avoid lock contention while migrating pages concurrently
818          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
819          * this turn, as it is easier to retry the page migration later.
820          * This also prevents fill_balloon() getting stuck into a mutex
821          * recursion in the case it ends up triggering memory compaction
822          * while it is attempting to inflate the ballon.
823          */
824         if (!mutex_trylock(&vb->balloon_lock))
825                 return -EAGAIN;
826
827         get_page(newpage); /* balloon reference */
828
829         /*
830           * When we migrate a page to a different zone and adjusted the
831           * managed page count when inflating, we have to fixup the count of
832           * both involved zones.
833           */
834         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
835             page_zone(page) != page_zone(newpage)) {
836                 adjust_managed_page_count(page, 1);
837                 adjust_managed_page_count(newpage, -1);
838         }
839
840         /* balloon's page migration 1st step  -- inflate "newpage" */
841         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
842         balloon_page_insert(vb_dev_info, newpage);
843         vb_dev_info->isolated_pages--;
844         __count_vm_event(BALLOON_MIGRATE);
845         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
846         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
847         set_page_pfns(vb, vb->pfns, newpage);
848         tell_host(vb, vb->inflate_vq);
849
850         /* balloon's page migration 2nd step -- deflate "page" */
851         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
852         balloon_page_delete(page);
853         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
854         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
855         set_page_pfns(vb, vb->pfns, page);
856         tell_host(vb, vb->deflate_vq);
857
858         mutex_unlock(&vb->balloon_lock);
859
860         put_page(page); /* balloon reference */
861
862         return MIGRATEPAGE_SUCCESS;
863 }
864 #endif /* CONFIG_BALLOON_COMPACTION */
865
866 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
867                                        unsigned long pages_to_free)
868 {
869         unsigned long blocks_to_free, blocks_freed;
870
871         pages_to_free = round_up(pages_to_free,
872                                  VIRTIO_BALLOON_HINT_BLOCK_PAGES);
873         blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
874         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
875
876         return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
877 }
878
879 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
880                                                   struct shrink_control *sc)
881 {
882         struct virtio_balloon *vb = shrinker->private_data;
883
884         return shrink_free_pages(vb, sc->nr_to_scan);
885 }
886
887 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
888                                                    struct shrink_control *sc)
889 {
890         struct virtio_balloon *vb = shrinker->private_data;
891
892         return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
893 }
894
895 static int virtio_balloon_oom_notify(struct notifier_block *nb,
896                                      unsigned long dummy, void *parm)
897 {
898         struct virtio_balloon *vb = container_of(nb,
899                                                  struct virtio_balloon, oom_nb);
900         unsigned long *freed = parm;
901
902         *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
903                   VIRTIO_BALLOON_PAGES_PER_PAGE;
904         update_balloon_size(vb);
905
906         return NOTIFY_OK;
907 }
908
909 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
910 {
911         shrinker_free(vb->shrinker);
912 }
913
914 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
915 {
916         vb->shrinker = shrinker_alloc(0, "virtio-balloon");
917         if (!vb->shrinker)
918                 return -ENOMEM;
919
920         vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
921         vb->shrinker->count_objects = virtio_balloon_shrinker_count;
922         vb->shrinker->private_data = vb;
923
924         shrinker_register(vb->shrinker);
925
926         return 0;
927 }
928
929 static int virtballoon_probe(struct virtio_device *vdev)
930 {
931         struct virtio_balloon *vb;
932         int err;
933
934         if (!vdev->config->get) {
935                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
936                         __func__);
937                 return -EINVAL;
938         }
939
940         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
941         if (!vb) {
942                 err = -ENOMEM;
943                 goto out;
944         }
945
946         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
947         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
948         spin_lock_init(&vb->stop_update_lock);
949         mutex_init(&vb->balloon_lock);
950         init_waitqueue_head(&vb->acked);
951         vb->vdev = vdev;
952
953         balloon_devinfo_init(&vb->vb_dev_info);
954
955         err = init_vqs(vb);
956         if (err)
957                 goto out_free_vb;
958
959 #ifdef CONFIG_BALLOON_COMPACTION
960         vb->vb_dev_info.migratepage = virtballoon_migratepage;
961 #endif
962         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
963                 /*
964                  * There is always one entry reserved for cmd id, so the ring
965                  * size needs to be at least two to report free page hints.
966                  */
967                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
968                         err = -ENOSPC;
969                         goto out_del_vqs;
970                 }
971                 vb->balloon_wq = alloc_workqueue("balloon-wq",
972                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
973                 if (!vb->balloon_wq) {
974                         err = -ENOMEM;
975                         goto out_del_vqs;
976                 }
977                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
978                 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
979                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
980                                                   VIRTIO_BALLOON_CMD_ID_STOP);
981                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
982                                                   VIRTIO_BALLOON_CMD_ID_STOP);
983                 spin_lock_init(&vb->free_page_list_lock);
984                 INIT_LIST_HEAD(&vb->free_page_list);
985                 /*
986                  * We're allowed to reuse any free pages, even if they are
987                  * still to be processed by the host.
988                  */
989                 err = virtio_balloon_register_shrinker(vb);
990                 if (err)
991                         goto out_del_balloon_wq;
992         }
993
994         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
995                 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
996                 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
997                 err = register_oom_notifier(&vb->oom_nb);
998                 if (err < 0)
999                         goto out_unregister_shrinker;
1000         }
1001
1002         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
1003                 /* Start with poison val of 0 representing general init */
1004                 __u32 poison_val = 0;
1005
1006                 /*
1007                  * Let the hypervisor know that we are expecting a
1008                  * specific value to be written back in balloon pages.
1009                  *
1010                  * If the PAGE_POISON value was larger than a byte we would
1011                  * need to byte swap poison_val here to guarantee it is
1012                  * little-endian. However for now it is a single byte so we
1013                  * can pass it as-is.
1014                  */
1015                 if (!want_init_on_free())
1016                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
1017
1018                 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
1019                                  poison_val, &poison_val);
1020         }
1021
1022         vb->pr_dev_info.report = virtballoon_free_page_report;
1023         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
1024                 unsigned int capacity;
1025
1026                 capacity = virtqueue_get_vring_size(vb->reporting_vq);
1027                 if (capacity < PAGE_REPORTING_CAPACITY) {
1028                         err = -ENOSPC;
1029                         goto out_unregister_oom;
1030                 }
1031
1032                 /*
1033                  * The default page reporting order is @pageblock_order, which
1034                  * corresponds to 512MB in size on ARM64 when 64KB base page
1035                  * size is used. The page reporting won't be triggered if the
1036                  * freeing page can't come up with a free area like that huge.
1037                  * So we specify the page reporting order to 5, corresponding
1038                  * to 2MB. It helps to avoid THP splitting if 4KB base page
1039                  * size is used by host.
1040                  *
1041                  * Ideally, the page reporting order is selected based on the
1042                  * host's base page size. However, it needs more work to report
1043                  * that value. The hard-coded order would be fine currently.
1044                  */
1045 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
1046                 vb->pr_dev_info.order = 5;
1047 #endif
1048
1049                 err = page_reporting_register(&vb->pr_dev_info);
1050                 if (err)
1051                         goto out_unregister_oom;
1052         }
1053
1054         spin_lock_init(&vb->wakeup_lock);
1055
1056         /*
1057          * The virtio balloon itself can't wake up the device, but it is
1058          * responsible for processing wakeup events passed up from the transport
1059          * layer. Wakeup sources don't support nesting/chaining calls, so we use
1060          * our own wakeup source to ensure wakeup events are properly handled
1061          * without trampling on the transport layer's wakeup source.
1062          */
1063         device_set_wakeup_capable(&vb->vdev->dev, true);
1064
1065         virtio_device_ready(vdev);
1066
1067         if (towards_target(vb))
1068                 virtballoon_changed(vdev);
1069         return 0;
1070
1071 out_unregister_oom:
1072         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1073                 unregister_oom_notifier(&vb->oom_nb);
1074 out_unregister_shrinker:
1075         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1076                 virtio_balloon_unregister_shrinker(vb);
1077 out_del_balloon_wq:
1078         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1079                 destroy_workqueue(vb->balloon_wq);
1080 out_del_vqs:
1081         vdev->config->del_vqs(vdev);
1082 out_free_vb:
1083         kfree(vb);
1084 out:
1085         return err;
1086 }
1087
1088 static void remove_common(struct virtio_balloon *vb)
1089 {
1090         /* There might be pages left in the balloon: free them. */
1091         while (vb->num_pages)
1092                 leak_balloon(vb, vb->num_pages);
1093         update_balloon_size(vb);
1094
1095         /* There might be free pages that are being reported: release them. */
1096         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1097                 return_free_pages_to_mm(vb, ULONG_MAX);
1098
1099         /* Now we reset the device so we can clean up the queues. */
1100         virtio_reset_device(vb->vdev);
1101
1102         vb->vdev->config->del_vqs(vb->vdev);
1103 }
1104
1105 static void virtballoon_remove(struct virtio_device *vdev)
1106 {
1107         struct virtio_balloon *vb = vdev->priv;
1108
1109         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1110                 page_reporting_unregister(&vb->pr_dev_info);
1111         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1112                 unregister_oom_notifier(&vb->oom_nb);
1113         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1114                 virtio_balloon_unregister_shrinker(vb);
1115         spin_lock_irq(&vb->stop_update_lock);
1116         vb->stop_update = true;
1117         spin_unlock_irq(&vb->stop_update_lock);
1118         cancel_work_sync(&vb->update_balloon_size_work);
1119         cancel_work_sync(&vb->update_balloon_stats_work);
1120
1121         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1122                 cancel_work_sync(&vb->report_free_page_work);
1123                 destroy_workqueue(vb->balloon_wq);
1124         }
1125
1126         remove_common(vb);
1127         kfree(vb);
1128 }
1129
1130 #ifdef CONFIG_PM_SLEEP
1131 static int virtballoon_freeze(struct virtio_device *vdev)
1132 {
1133         struct virtio_balloon *vb = vdev->priv;
1134
1135         /*
1136          * The workqueue is already frozen by the PM core before this
1137          * function is called.
1138          */
1139         remove_common(vb);
1140         return 0;
1141 }
1142
1143 static int virtballoon_restore(struct virtio_device *vdev)
1144 {
1145         struct virtio_balloon *vb = vdev->priv;
1146         int ret;
1147
1148         ret = init_vqs(vdev->priv);
1149         if (ret)
1150                 return ret;
1151
1152         virtio_device_ready(vdev);
1153
1154         if (towards_target(vb))
1155                 virtballoon_changed(vdev);
1156         update_balloon_size(vb);
1157         return 0;
1158 }
1159 #endif
1160
1161 static int virtballoon_validate(struct virtio_device *vdev)
1162 {
1163         /*
1164          * Inform the hypervisor that our pages are poisoned or
1165          * initialized. If we cannot do that then we should disable
1166          * page reporting as it could potentially change the contents
1167          * of our free pages.
1168          */
1169         if (!want_init_on_free() && !page_poisoning_enabled_static())
1170                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1171         else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1172                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1173
1174         __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1175         return 0;
1176 }
1177
1178 static unsigned int features[] = {
1179         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1180         VIRTIO_BALLOON_F_STATS_VQ,
1181         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1182         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1183         VIRTIO_BALLOON_F_PAGE_POISON,
1184         VIRTIO_BALLOON_F_REPORTING,
1185 };
1186
1187 static struct virtio_driver virtio_balloon_driver = {
1188         .feature_table = features,
1189         .feature_table_size = ARRAY_SIZE(features),
1190         .driver.name =  KBUILD_MODNAME,
1191         .id_table =     id_table,
1192         .validate =     virtballoon_validate,
1193         .probe =        virtballoon_probe,
1194         .remove =       virtballoon_remove,
1195         .config_changed = virtballoon_changed,
1196 #ifdef CONFIG_PM_SLEEP
1197         .freeze =       virtballoon_freeze,
1198         .restore =      virtballoon_restore,
1199 #endif
1200 };
1201
1202 module_virtio_driver(virtio_balloon_driver);
1203 MODULE_DEVICE_TABLE(virtio, id_table);
1204 MODULE_DESCRIPTION("Virtio balloon driver");
1205 MODULE_LICENSE("GPL");
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