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