aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/virtio/virtio_balloon.c
blob: 797e1c79a104864ff5c87c2e887c02eb2fe1db89 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
/*
 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
 * Tosatti's implementations.
 *
 *  Copyright 2008 Rusty Russell IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <linux/virtio.h>
#include <linux/virtio_balloon.h>
#include <linux/swap.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>

/*
 * Balloon device works in 4K page units.  So each page is pointed to by
 * multiple balloon pages.  All memory counters in this driver are in balloon
 * page units.
 */
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256

struct virtio_balloon
{
	struct virtio_device *vdev;
	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;

	/* Where the ballooning thread waits for config to change. */
	wait_queue_head_t config_change;

	/* The thread servicing the balloon. */
	struct task_struct *thread;

	/* Waiting for host to ack the pages we released. */
	wait_queue_head_t acked;

	/* Number of balloon pages we've told the Host we're not using. */
	unsigned int num_pages;
	/*
	 * The pages we've told the Host we're not using are enqueued
	 * at vb_dev_info->pages list.
	 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
	 * to num_pages above.
	 */
	struct balloon_dev_info *vb_dev_info;

	/* Synchronize access/update to this struct virtio_balloon elements */
	struct mutex balloon_lock;

	/* The array of pfns we tell the Host about. */
	unsigned int num_pfns;
	u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];

	/* Memory statistics */
	int need_stats_update;
	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
};

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

static u32 page_to_balloon_pfn(struct page *page)
{
	unsigned long pfn = page_to_pfn(page);

	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
	/* Convert pfn from Linux page size to balloon page size. */
	return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
}

static struct page *balloon_pfn_to_page(u32 pfn)
{
	BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
	return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
}

static void balloon_ack(struct virtqueue *vq)
{
	struct virtio_balloon *vb = vq->vdev->priv;

	wake_up(&vb->acked);
}

static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
{
	struct scatterlist sg;
	unsigned int len;

	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);

	/* We should always be able to add one buffer to an empty queue. */
	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
		BUG();
	virtqueue_kick(vq);

	/* When host has read buffer, this completes via balloon_ack */
	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
}

static void set_page_pfns(u32 pfns[], struct page *page)
{
	unsigned int i;

	/* Set balloon pfns pointing at this page.
	 * Note that the first pfn points at start of the page. */
	for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
		pfns[i] = page_to_balloon_pfn(page) + i;
}

static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;

	/* We can only do one array worth at a time. */
	num = min(num, ARRAY_SIZE(vb->pfns));

	mutex_lock(&vb->balloon_lock);
	for (vb->num_pfns = 0; vb->num_pfns < num;
	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		struct page *page = balloon_page_enqueue(vb_dev_info);

		if (!page) {
			dev_info_ratelimited(&vb->vdev->dev,
					     "Out of puff! Can't get %u pages\n",
					     VIRTIO_BALLOON_PAGES_PER_PAGE);
			/* Sleep for at least 1/5 of a second before retry. */
			msleep(200);
			break;
		}
		set_page_pfns(vb->pfns + vb->num_pfns, page);
		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
		totalram_pages--;
	}

	/* Did we get any? */
	if (vb->num_pfns != 0)
		tell_host(vb, vb->inflate_vq);
	mutex_unlock(&vb->balloon_lock);
}

static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
{
	unsigned int i;

	/* Find pfns pointing at start of each page, get pages and free them. */
	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		balloon_page_free(balloon_pfn_to_page(pfns[i]));
		totalram_pages++;
	}
}

static void leak_balloon(struct virtio_balloon *vb, size_t num)
{
	struct page *page;
	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;

	/* We can only do one array worth at a time. */
	num = min(num, ARRAY_SIZE(vb->pfns));

	mutex_lock(&vb->balloon_lock);
	for (vb->num_pfns = 0; vb->num_pfns < num;
	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		page = balloon_page_dequeue(vb_dev_info);
		if (!page)
			break;
		set_page_pfns(vb->pfns + vb->num_pfns, page);
		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
	}

	/*
	 * Note that if
	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
	 * is true, we *have* to do it in this order
	 */
	tell_host(vb, vb->deflate_vq);
	mutex_unlock(&vb->balloon_lock);
	release_pages_by_pfn(vb->pfns, vb->num_pfns);
}

static inline void update_stat(struct virtio_balloon *vb, int idx,
			       u16 tag, u64 val)
{
	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	vb->stats[idx].tag = tag;
	vb->stats[idx].val = val;
}

#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)

static void update_balloon_stats(struct virtio_balloon *vb)
{
	unsigned long events[NR_VM_EVENT_ITEMS];
	struct sysinfo i;
	int idx = 0;

	all_vm_events(events);
	si_meminfo(&i);

	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
				pages_to_bytes(events[PSWPIN]));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
				pages_to_bytes(events[PSWPOUT]));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
				pages_to_bytes(i.freeram));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
				pages_to_bytes(i.totalram));
}

/*
 * While most virtqueues communicate guest-initiated requests to the hypervisor,
 * the stats queue operates in reverse.  The driver initializes the virtqueue
 * with a single buffer.  From that point forward, all conversations consist of
 * a hypervisor request (a call to this function) which directs us to refill
 * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 * we notify our kthread which does the actual work via stats_handle_request().
 */
static void stats_request(struct virtqueue *vq)
{
	struct virtio_balloon *vb = vq->vdev->priv;

	vb->need_stats_update = 1;
	wake_up(&vb->config_change);
}

static void stats_handle_request(struct virtio_balloon *vb)
{
	struct virtqueue *vq;
	struct scatterlist sg;
	unsigned int len;

	vb->need_stats_update = 0;
	update_balloon_stats(vb);

	vq = vb->stats_vq;
	if (!virtqueue_get_buf(vq, &len))
		return;
	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
		BUG();
	virtqueue_kick(vq);
}

static void virtballoon_changed(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	wake_up(&vb->config_change);
}

static inline s64 towards_target(struct virtio_balloon *vb)
{
	__le32 v;
	s64 target;

	vb->vdev->config->get(vb->vdev,
			      offsetof(struct virtio_balloon_config, num_pages),
			      &v, sizeof(v));
	target = le32_to_cpu(v);
	return target - vb->num_pages;
}

static void update_balloon_size(struct virtio_balloon *vb)
{
	__le32 actual = cpu_to_le32(vb->num_pages);

	vb->vdev->config->set(vb->vdev,
			      offsetof(struct virtio_balloon_config, actual),
			      &actual, sizeof(actual));
}

static int balloon(void *_vballoon)
{
	struct virtio_balloon *vb = _vballoon;

	set_freezable();
	while (!kthread_should_stop()) {
		s64 diff;

		try_to_freeze();
		wait_event_interruptible(vb->config_change,
					 (diff = towards_target(vb)) != 0
					 || vb->need_stats_update
					 || kthread_should_stop()
					 || freezing(current));
		if (vb->need_stats_update)
			stats_handle_request(vb);
		if (diff > 0)
			fill_balloon(vb, diff);
		else if (diff < 0)
			leak_balloon(vb, -diff);
		update_balloon_size(vb);
	}
	return 0;
}

static int init_vqs(struct virtio_balloon *vb)
{
	struct virtqueue *vqs[3];
	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
	const char *names[] = { "inflate", "deflate", "stats" };
	int err, nvqs;

	/*
	 * We expect two virtqueues: inflate and deflate, and
	 * optionally stat.
	 */
	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
	if (err)
		return err;

	vb->inflate_vq = vqs[0];
	vb->deflate_vq = vqs[1];
	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
		struct scatterlist sg;
		vb->stats_vq = vqs[2];

		/*
		 * Prime this virtqueue with one buffer so the hypervisor can
		 * use it to signal us later.
		 */
		sg_init_one(&sg, vb->stats, sizeof vb->stats);
		if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
		    < 0)
			BUG();
		virtqueue_kick(vb->stats_vq);
	}
	return 0;
}

static const struct address_space_operations virtio_balloon_aops;
#ifdef CONFIG_BALLOON_COMPACTION
/*
 * virtballoon_migratepage - perform the balloon page migration on behalf of
 *			     a compation thread.     (called under page lock)
 * @mapping: the page->mapping which will be assigned to the new migrated page.
 * @newpage: page that will replace the isolated page after migration finishes.
 * @page   : the isolated (old) page that is about to be migrated to newpage.
 * @mode   : compaction mode -- not used for balloon page migration.
 *
 * After a ballooned page gets isolated by compaction procedures, this is the
 * function that performs the page migration on behalf of a compaction thread
 * The page migration for virtio balloon is done in a simple swap fashion which
 * follows these two macro steps:
 *  1) insert newpage into vb->pages list and update the host about it;
 *  2) update the host about the old page removed from vb->pages list;
 *
 * This function preforms the balloon page migration task.
 * Called through balloon_mapping->a_ops->migratepage
 */
int virtballoon_migratepage(struct address_space *mapping,
		struct page *newpage, struct page *page, enum migrate_mode mode)
{
	struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
	struct virtio_balloon *vb;
	unsigned long flags;

	BUG_ON(!vb_dev_info);

	vb = vb_dev_info->balloon_device;

	/*
	 * In order to avoid lock contention while migrating pages concurrently
	 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
	 * this turn, as it is easier to retry the page migration later.
	 * This also prevents fill_balloon() getting stuck into a mutex
	 * recursion in the case it ends up triggering memory compaction
	 * while it is attempting to inflate the ballon.
	 */
	if (!mutex_trylock(&vb->balloon_lock))
		return -EAGAIN;

	/* balloon's page migration 1st step  -- inflate "newpage" */
	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
	balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
	vb_dev_info->isolated_pages--;
	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
	set_page_pfns(vb->pfns, newpage);
	tell_host(vb, vb->inflate_vq);

	/*
	 * balloon's page migration 2nd step -- deflate "page"
	 *
	 * It's safe to delete page->lru here because this page is at
	 * an isolated migration list, and this step is expected to happen here
	 */
	balloon_page_delete(page);
	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
	set_page_pfns(vb->pfns, page);
	tell_host(vb, vb->deflate_vq);

	mutex_unlock(&vb->balloon_lock);

	return MIGRATEPAGE_BALLOON_SUCCESS;
}

/* define the balloon_mapping->a_ops callback to allow balloon page migration */
static const struct address_space_operations virtio_balloon_aops = {
			.migratepage = virtballoon_migratepage,
};
#endif /* CONFIG_BALLOON_COMPACTION */

static int virtballoon_probe(struct virtio_device *vdev)
{
	struct virtio_balloon *vb;
	struct address_space *vb_mapping;
	struct balloon_dev_info *vb_devinfo;
	int err;

	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	if (!vb) {
		err = -ENOMEM;
		goto out;
	}

	vb->num_pages = 0;
	mutex_init(&vb->balloon_lock);
	init_waitqueue_head(&vb->config_change);
	init_waitqueue_head(&vb->acked);
	vb->vdev = vdev;
	vb->need_stats_update = 0;

	vb_devinfo = balloon_devinfo_alloc(vb);
	if (IS_ERR(vb_devinfo)) {
		err = PTR_ERR(vb_devinfo);
		goto out_free_vb;
	}

	vb_mapping = balloon_mapping_alloc(vb_devinfo,
					   (balloon_compaction_check()) ?
					   &virtio_balloon_aops : NULL);
	if (IS_ERR(vb_mapping)) {
		/*
		 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
		 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
		 */
		err = PTR_ERR(vb_mapping);
		if (err != -EOPNOTSUPP)
			goto out_free_vb_devinfo;
	}

	vb->vb_dev_info = vb_devinfo;

	err = init_vqs(vb);
	if (err)
		goto out_free_vb_mapping;

	vb->thread = kthread_run(balloon, vb, "vballoon");
	if (IS_ERR(vb->thread)) {
		err = PTR_ERR(vb->thread);
		goto out_del_vqs;
	}

	return 0;

out_del_vqs:
	vdev->config->del_vqs(vdev);
out_free_vb_mapping:
	balloon_mapping_free(vb_mapping);
out_free_vb_devinfo:
	balloon_devinfo_free(vb_devinfo);
out_free_vb:
	kfree(vb);
out:
	return err;
}

static void remove_common(struct virtio_balloon *vb)
{
	/* There might be pages left in the balloon: free them. */
	while (vb->num_pages)
		leak_balloon(vb, vb->num_pages);
	update_balloon_size(vb);

	/* Now we reset the device so we can clean up the queues. */
	vb->vdev->config->reset(vb->vdev);

	vb->vdev->config->del_vqs(vb->vdev);
}

static void virtballoon_remove(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	kthread_stop(vb->thread);
	remove_common(vb);
	balloon_mapping_free(vb->vb_dev_info->mapping);
	balloon_devinfo_free(vb->vb_dev_info);
	kfree(vb);
}

#ifdef CONFIG_PM
static int virtballoon_freeze(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	/*
	 * The kthread is already frozen by the PM core before this
	 * function is called.
	 */

	remove_common(vb);
	return 0;
}

static int virtballoon_restore(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;
	int ret;

	ret = init_vqs(vdev->priv);
	if (ret)
		return ret;

	fill_balloon(vb, towards_target(vb));
	update_balloon_size(vb);
	return 0;
}
#endif

static unsigned int features[] = {
	VIRTIO_BALLOON_F_MUST_TELL_HOST,
	VIRTIO_BALLOON_F_STATS_VQ,
};

static struct virtio_driver virtio_balloon_driver = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name =	KBUILD_MODNAME,
	.driver.owner =	THIS_MODULE,
	.id_table =	id_table,
	.probe =	virtballoon_probe,
	.remove =	virtballoon_remove,
	.config_changed = virtballoon_changed,
#ifdef CONFIG_PM
	.freeze	=	virtballoon_freeze,
	.restore =	virtballoon_restore,
#endif
};

static int __init init(void)
{
	return register_virtio_driver(&virtio_balloon_driver);
}

static void __exit fini(void)
{
	unregister_virtio_driver(&virtio_balloon_driver);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio balloon driver");
MODULE_LICENSE("GPL");