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1/*
2 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
3 * Tosatti's implementations.
4 *
5 * Copyright 2008 Rusty Russell IBM Corporation
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include <linux/virtio.h>
23#include <linux/virtio_balloon.h>
24#include <linux/swap.h>
25#include <linux/workqueue.h>
26#include <linux/delay.h>
27#include <linux/slab.h>
28#include <linux/module.h>
29#include <linux/balloon_compaction.h>
30#include <linux/oom.h>
31#include <linux/wait.h>
32#include <linux/mm.h>
33
34/*
35 * Balloon device works in 4K page units. So each page is pointed to by
36 * multiple balloon pages. All memory counters in this driver are in balloon
37 * page units.
38 */
39#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
40#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
41#define OOM_VBALLOON_DEFAULT_PAGES 256
42#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
43
44static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
45module_param(oom_pages, int, S_IRUSR | S_IWUSR);
46MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
47
48struct virtio_balloon {
49 struct virtio_device *vdev;
50 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
51
52 /* The balloon servicing is delegated to a freezable workqueue. */
53 struct work_struct update_balloon_stats_work;
54 struct work_struct update_balloon_size_work;
55
56 /* Prevent updating balloon when it is being canceled. */
57 spinlock_t stop_update_lock;
58 bool stop_update;
59
60 /* Waiting for host to ack the pages we released. */
61 wait_queue_head_t acked;
62
63 /* Number of balloon pages we've told the Host we're not using. */
64 unsigned int num_pages;
65 /*
66 * The pages we've told the Host we're not using are enqueued
67 * at vb_dev_info->pages list.
68 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
69 * to num_pages above.
70 */
71 struct balloon_dev_info vb_dev_info;
72
73 /* Synchronize access/update to this struct virtio_balloon elements */
74 struct mutex balloon_lock;
75
76 /* The array of pfns we tell the Host about. */
77 unsigned int num_pfns;
78 u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
79
80 /* Memory statistics */
81 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
82
83 /* To register callback in oom notifier call chain */
84 struct notifier_block nb;
85};
86
87static struct virtio_device_id id_table[] = {
88 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
89 { 0 },
90};
91
92static u32 page_to_balloon_pfn(struct page *page)
93{
94 unsigned long pfn = page_to_pfn(page);
95
96 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
97 /* Convert pfn from Linux page size to balloon page size. */
98 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
99}
100
101static struct page *balloon_pfn_to_page(u32 pfn)
102{
103 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
104 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
105}
106
107static void balloon_ack(struct virtqueue *vq)
108{
109 struct virtio_balloon *vb = vq->vdev->priv;
110
111 wake_up(&vb->acked);
112}
113
114static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
115{
116 struct scatterlist sg;
117 unsigned int len;
118
119 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
120
121 /* We should always be able to add one buffer to an empty queue. */
122 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
123 virtqueue_kick(vq);
124
125 /* When host has read buffer, this completes via balloon_ack */
126 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
127
128}
129
130static void set_page_pfns(u32 pfns[], struct page *page)
131{
132 unsigned int i;
133
134 /* Set balloon pfns pointing at this page.
135 * Note that the first pfn points at start of the page. */
136 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
137 pfns[i] = page_to_balloon_pfn(page) + i;
138}
139
140static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
141{
142 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
143 unsigned num_allocated_pages;
144
145 /* We can only do one array worth at a time. */
146 num = min(num, ARRAY_SIZE(vb->pfns));
147
148 mutex_lock(&vb->balloon_lock);
149 for (vb->num_pfns = 0; vb->num_pfns < num;
150 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
151 struct page *page = balloon_page_enqueue(vb_dev_info);
152
153 if (!page) {
154 dev_info_ratelimited(&vb->vdev->dev,
155 "Out of puff! Can't get %u pages\n",
156 VIRTIO_BALLOON_PAGES_PER_PAGE);
157 /* Sleep for at least 1/5 of a second before retry. */
158 msleep(200);
159 break;
160 }
161 set_page_pfns(vb->pfns + vb->num_pfns, page);
162 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
163 if (!virtio_has_feature(vb->vdev,
164 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
165 adjust_managed_page_count(page, -1);
166 }
167
168 num_allocated_pages = vb->num_pfns;
169 /* Did we get any? */
170 if (vb->num_pfns != 0)
171 tell_host(vb, vb->inflate_vq);
172 mutex_unlock(&vb->balloon_lock);
173
174 return num_allocated_pages;
175}
176
177static void release_pages_balloon(struct virtio_balloon *vb)
178{
179 unsigned int i;
180
181 /* Find pfns pointing at start of each page, get pages and free them. */
182 for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
183 struct page *page = balloon_pfn_to_page(vb->pfns[i]);
184 if (!virtio_has_feature(vb->vdev,
185 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
186 adjust_managed_page_count(page, 1);
187 put_page(page); /* balloon reference */
188 }
189}
190
191static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
192{
193 unsigned num_freed_pages;
194 struct page *page;
195 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
196
197 /* We can only do one array worth at a time. */
198 num = min(num, ARRAY_SIZE(vb->pfns));
199
200 mutex_lock(&vb->balloon_lock);
201 for (vb->num_pfns = 0; vb->num_pfns < num;
202 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
203 page = balloon_page_dequeue(vb_dev_info);
204 if (!page)
205 break;
206 set_page_pfns(vb->pfns + vb->num_pfns, page);
207 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
208 }
209
210 num_freed_pages = vb->num_pfns;
211 /*
212 * Note that if
213 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
214 * is true, we *have* to do it in this order
215 */
216 if (vb->num_pfns != 0)
217 tell_host(vb, vb->deflate_vq);
218 release_pages_balloon(vb);
219 mutex_unlock(&vb->balloon_lock);
220 return num_freed_pages;
221}
222
223static inline void update_stat(struct virtio_balloon *vb, int idx,
224 u16 tag, u64 val)
225{
226 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
227 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
228 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
229}
230
231#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
232
233static void update_balloon_stats(struct virtio_balloon *vb)
234{
235 unsigned long events[NR_VM_EVENT_ITEMS];
236 struct sysinfo i;
237 int idx = 0;
238 long available;
239
240 all_vm_events(events);
241 si_meminfo(&i);
242
243 available = si_mem_available();
244
245 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
246 pages_to_bytes(events[PSWPIN]));
247 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
248 pages_to_bytes(events[PSWPOUT]));
249 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
250 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
251 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
252 pages_to_bytes(i.freeram));
253 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
254 pages_to_bytes(i.totalram));
255 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
256 pages_to_bytes(available));
257}
258
259/*
260 * While most virtqueues communicate guest-initiated requests to the hypervisor,
261 * the stats queue operates in reverse. The driver initializes the virtqueue
262 * with a single buffer. From that point forward, all conversations consist of
263 * a hypervisor request (a call to this function) which directs us to refill
264 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
265 * we delegate the job to a freezable workqueue that will do the actual work via
266 * stats_handle_request().
267 */
268static void stats_request(struct virtqueue *vq)
269{
270 struct virtio_balloon *vb = vq->vdev->priv;
271
272 spin_lock(&vb->stop_update_lock);
273 if (!vb->stop_update)
274 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
275 spin_unlock(&vb->stop_update_lock);
276}
277
278static void stats_handle_request(struct virtio_balloon *vb)
279{
280 struct virtqueue *vq;
281 struct scatterlist sg;
282 unsigned int len;
283
284 update_balloon_stats(vb);
285
286 vq = vb->stats_vq;
287 if (!virtqueue_get_buf(vq, &len))
288 return;
289 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
290 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
291 virtqueue_kick(vq);
292}
293
294static void virtballoon_changed(struct virtio_device *vdev)
295{
296 struct virtio_balloon *vb = vdev->priv;
297 unsigned long flags;
298
299 spin_lock_irqsave(&vb->stop_update_lock, flags);
300 if (!vb->stop_update)
301 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
302 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
303}
304
305static inline s64 towards_target(struct virtio_balloon *vb)
306{
307 s64 target;
308 u32 num_pages;
309
310 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
311 &num_pages);
312
313 /* Legacy balloon config space is LE, unlike all other devices. */
314 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
315 num_pages = le32_to_cpu((__force __le32)num_pages);
316
317 target = num_pages;
318 return target - vb->num_pages;
319}
320
321static void update_balloon_size(struct virtio_balloon *vb)
322{
323 u32 actual = vb->num_pages;
324
325 /* Legacy balloon config space is LE, unlike all other devices. */
326 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
327 actual = (__force u32)cpu_to_le32(actual);
328
329 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
330 &actual);
331}
332
333/*
334 * virtballoon_oom_notify - release pages when system is under severe
335 * memory pressure (called from out_of_memory())
336 * @self : notifier block struct
337 * @dummy: not used
338 * @parm : returned - number of freed pages
339 *
340 * The balancing of memory by use of the virtio balloon should not cause
341 * the termination of processes while there are pages in the balloon.
342 * If virtio balloon manages to release some memory, it will make the
343 * system return and retry the allocation that forced the OOM killer
344 * to run.
345 */
346static int virtballoon_oom_notify(struct notifier_block *self,
347 unsigned long dummy, void *parm)
348{
349 struct virtio_balloon *vb;
350 unsigned long *freed;
351 unsigned num_freed_pages;
352
353 vb = container_of(self, struct virtio_balloon, nb);
354 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
355 return NOTIFY_OK;
356
357 freed = parm;
358 num_freed_pages = leak_balloon(vb, oom_pages);
359 update_balloon_size(vb);
360 *freed += num_freed_pages;
361
362 return NOTIFY_OK;
363}
364
365static void update_balloon_stats_func(struct work_struct *work)
366{
367 struct virtio_balloon *vb;
368
369 vb = container_of(work, struct virtio_balloon,
370 update_balloon_stats_work);
371 stats_handle_request(vb);
372}
373
374static void update_balloon_size_func(struct work_struct *work)
375{
376 struct virtio_balloon *vb;
377 s64 diff;
378
379 vb = container_of(work, struct virtio_balloon,
380 update_balloon_size_work);
381 diff = towards_target(vb);
382
383 if (diff > 0)
384 diff -= fill_balloon(vb, diff);
385 else if (diff < 0)
386 diff += leak_balloon(vb, -diff);
387 update_balloon_size(vb);
388
389 if (diff)
390 queue_work(system_freezable_wq, work);
391}
392
393static int init_vqs(struct virtio_balloon *vb)
394{
395 struct virtqueue *vqs[3];
396 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
397 static const char * const names[] = { "inflate", "deflate", "stats" };
398 int err, nvqs;
399
400 /*
401 * We expect two virtqueues: inflate and deflate, and
402 * optionally stat.
403 */
404 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
405 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
406 if (err)
407 return err;
408
409 vb->inflate_vq = vqs[0];
410 vb->deflate_vq = vqs[1];
411 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
412 struct scatterlist sg;
413 vb->stats_vq = vqs[2];
414
415 /*
416 * Prime this virtqueue with one buffer so the hypervisor can
417 * use it to signal us later (it can't be broken yet!).
418 */
419 sg_init_one(&sg, vb->stats, sizeof vb->stats);
420 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
421 < 0)
422 BUG();
423 virtqueue_kick(vb->stats_vq);
424 }
425 return 0;
426}
427
428#ifdef CONFIG_BALLOON_COMPACTION
429/*
430 * virtballoon_migratepage - perform the balloon page migration on behalf of
431 * a compation thread. (called under page lock)
432 * @vb_dev_info: the balloon device
433 * @newpage: page that will replace the isolated page after migration finishes.
434 * @page : the isolated (old) page that is about to be migrated to newpage.
435 * @mode : compaction mode -- not used for balloon page migration.
436 *
437 * After a ballooned page gets isolated by compaction procedures, this is the
438 * function that performs the page migration on behalf of a compaction thread
439 * The page migration for virtio balloon is done in a simple swap fashion which
440 * follows these two macro steps:
441 * 1) insert newpage into vb->pages list and update the host about it;
442 * 2) update the host about the old page removed from vb->pages list;
443 *
444 * This function preforms the balloon page migration task.
445 * Called through balloon_mapping->a_ops->migratepage
446 */
447static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
448 struct page *newpage, struct page *page, enum migrate_mode mode)
449{
450 struct virtio_balloon *vb = container_of(vb_dev_info,
451 struct virtio_balloon, vb_dev_info);
452 unsigned long flags;
453
454 /*
455 * In order to avoid lock contention while migrating pages concurrently
456 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
457 * this turn, as it is easier to retry the page migration later.
458 * This also prevents fill_balloon() getting stuck into a mutex
459 * recursion in the case it ends up triggering memory compaction
460 * while it is attempting to inflate the ballon.
461 */
462 if (!mutex_trylock(&vb->balloon_lock))
463 return -EAGAIN;
464
465 get_page(newpage); /* balloon reference */
466
467 /* balloon's page migration 1st step -- inflate "newpage" */
468 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
469 balloon_page_insert(vb_dev_info, newpage);
470 vb_dev_info->isolated_pages--;
471 __count_vm_event(BALLOON_MIGRATE);
472 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
473 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
474 set_page_pfns(vb->pfns, newpage);
475 tell_host(vb, vb->inflate_vq);
476
477 /* balloon's page migration 2nd step -- deflate "page" */
478 balloon_page_delete(page);
479 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
480 set_page_pfns(vb->pfns, page);
481 tell_host(vb, vb->deflate_vq);
482
483 mutex_unlock(&vb->balloon_lock);
484
485 put_page(page); /* balloon reference */
486
487 return MIGRATEPAGE_SUCCESS;
488}
489#endif /* CONFIG_BALLOON_COMPACTION */
490
491static int virtballoon_probe(struct virtio_device *vdev)
492{
493 struct virtio_balloon *vb;
494 int err;
495
496 if (!vdev->config->get) {
497 dev_err(&vdev->dev, "%s failure: config access disabled\n",
498 __func__);
499 return -EINVAL;
500 }
501
502 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
503 if (!vb) {
504 err = -ENOMEM;
505 goto out;
506 }
507
508 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
509 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
510 spin_lock_init(&vb->stop_update_lock);
511 vb->stop_update = false;
512 vb->num_pages = 0;
513 mutex_init(&vb->balloon_lock);
514 init_waitqueue_head(&vb->acked);
515 vb->vdev = vdev;
516
517 balloon_devinfo_init(&vb->vb_dev_info);
518#ifdef CONFIG_BALLOON_COMPACTION
519 vb->vb_dev_info.migratepage = virtballoon_migratepage;
520#endif
521
522 err = init_vqs(vb);
523 if (err)
524 goto out_free_vb;
525
526 vb->nb.notifier_call = virtballoon_oom_notify;
527 vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
528 err = register_oom_notifier(&vb->nb);
529 if (err < 0)
530 goto out_oom_notify;
531
532 virtio_device_ready(vdev);
533
534 return 0;
535
536out_oom_notify:
537 vdev->config->del_vqs(vdev);
538out_free_vb:
539 kfree(vb);
540out:
541 return err;
542}
543
544static void remove_common(struct virtio_balloon *vb)
545{
546 /* There might be pages left in the balloon: free them. */
547 while (vb->num_pages)
548 leak_balloon(vb, vb->num_pages);
549 update_balloon_size(vb);
550
551 /* Now we reset the device so we can clean up the queues. */
552 vb->vdev->config->reset(vb->vdev);
553
554 vb->vdev->config->del_vqs(vb->vdev);
555}
556
557static void virtballoon_remove(struct virtio_device *vdev)
558{
559 struct virtio_balloon *vb = vdev->priv;
560
561 unregister_oom_notifier(&vb->nb);
562
563 spin_lock_irq(&vb->stop_update_lock);
564 vb->stop_update = true;
565 spin_unlock_irq(&vb->stop_update_lock);
566 cancel_work_sync(&vb->update_balloon_size_work);
567 cancel_work_sync(&vb->update_balloon_stats_work);
568
569 remove_common(vb);
570 kfree(vb);
571}
572
573#ifdef CONFIG_PM_SLEEP
574static int virtballoon_freeze(struct virtio_device *vdev)
575{
576 struct virtio_balloon *vb = vdev->priv;
577
578 /*
579 * The workqueue is already frozen by the PM core before this
580 * function is called.
581 */
582 remove_common(vb);
583 return 0;
584}
585
586static int virtballoon_restore(struct virtio_device *vdev)
587{
588 struct virtio_balloon *vb = vdev->priv;
589 int ret;
590
591 ret = init_vqs(vdev->priv);
592 if (ret)
593 return ret;
594
595 virtio_device_ready(vdev);
596
597 if (towards_target(vb))
598 virtballoon_changed(vdev);
599 update_balloon_size(vb);
600 return 0;
601}
602#endif
603
604static unsigned int features[] = {
605 VIRTIO_BALLOON_F_MUST_TELL_HOST,
606 VIRTIO_BALLOON_F_STATS_VQ,
607 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
608};
609
610static struct virtio_driver virtio_balloon_driver = {
611 .feature_table = features,
612 .feature_table_size = ARRAY_SIZE(features),
613 .driver.name = KBUILD_MODNAME,
614 .driver.owner = THIS_MODULE,
615 .id_table = id_table,
616 .probe = virtballoon_probe,
617 .remove = virtballoon_remove,
618 .config_changed = virtballoon_changed,
619#ifdef CONFIG_PM_SLEEP
620 .freeze = virtballoon_freeze,
621 .restore = virtballoon_restore,
622#endif
623};
624
625module_virtio_driver(virtio_balloon_driver);
626MODULE_DEVICE_TABLE(virtio, id_table);
627MODULE_DESCRIPTION("Virtio balloon driver");
628MODULE_LICENSE("GPL");
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
46static struct vfsmount *balloon_mnt;
47#endif
48
49enum 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
58enum virtio_balloon_config_read {
59 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
60};
61
62struct 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
131static struct virtio_device_id id_table[] = {
132 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
133 { 0 },
134};
135
136static 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
145static void balloon_ack(struct virtqueue *vq)
146{
147 struct virtio_balloon *vb = vq->vdev->priv;
148
149 wake_up(&vb->acked);
150}
151
152static 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
168static 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
195static 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
211static 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
261static 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
275static 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
311static 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
321static 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 */
370static 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
380static 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
396static 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. */
410static 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
430static 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
443static 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
457static 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
466static 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
475static 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
497static 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
572static 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
585static 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
604static 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
621static 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
668static 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
697static 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
717static 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 compation 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 */
753static 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
809static int balloon_init_fs_context(struct fs_context *fc)
810{
811 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
812}
813
814static 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
822static 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
835static 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
844static 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
853static 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
867static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
868{
869 unregister_shrinker(&vb->shrinker);
870}
871
872static 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
881static 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 err = page_reporting_register(&vb->pr_dev_info);
997 if (err)
998 goto out_unregister_oom;
999 }
1000
1001 virtio_device_ready(vdev);
1002
1003 if (towards_target(vb))
1004 virtballoon_changed(vdev);
1005 return 0;
1006
1007out_unregister_oom:
1008 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1009 unregister_oom_notifier(&vb->oom_nb);
1010out_unregister_shrinker:
1011 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1012 virtio_balloon_unregister_shrinker(vb);
1013out_del_balloon_wq:
1014 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1015 destroy_workqueue(vb->balloon_wq);
1016out_iput:
1017#ifdef CONFIG_BALLOON_COMPACTION
1018 iput(vb->vb_dev_info.inode);
1019out_kern_unmount:
1020 kern_unmount(balloon_mnt);
1021out_del_vqs:
1022#endif
1023 vdev->config->del_vqs(vdev);
1024out_free_vb:
1025 kfree(vb);
1026out:
1027 return err;
1028}
1029
1030static void remove_common(struct virtio_balloon *vb)
1031{
1032 /* There might be pages left in the balloon: free them. */
1033 while (vb->num_pages)
1034 leak_balloon(vb, vb->num_pages);
1035 update_balloon_size(vb);
1036
1037 /* There might be free pages that are being reported: release them. */
1038 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1039 return_free_pages_to_mm(vb, ULONG_MAX);
1040
1041 /* Now we reset the device so we can clean up the queues. */
1042 vb->vdev->config->reset(vb->vdev);
1043
1044 vb->vdev->config->del_vqs(vb->vdev);
1045}
1046
1047static void virtballoon_remove(struct virtio_device *vdev)
1048{
1049 struct virtio_balloon *vb = vdev->priv;
1050
1051 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1052 page_reporting_unregister(&vb->pr_dev_info);
1053 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1054 unregister_oom_notifier(&vb->oom_nb);
1055 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1056 virtio_balloon_unregister_shrinker(vb);
1057 spin_lock_irq(&vb->stop_update_lock);
1058 vb->stop_update = true;
1059 spin_unlock_irq(&vb->stop_update_lock);
1060 cancel_work_sync(&vb->update_balloon_size_work);
1061 cancel_work_sync(&vb->update_balloon_stats_work);
1062
1063 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1064 cancel_work_sync(&vb->report_free_page_work);
1065 destroy_workqueue(vb->balloon_wq);
1066 }
1067
1068 remove_common(vb);
1069#ifdef CONFIG_BALLOON_COMPACTION
1070 if (vb->vb_dev_info.inode)
1071 iput(vb->vb_dev_info.inode);
1072
1073 kern_unmount(balloon_mnt);
1074#endif
1075 kfree(vb);
1076}
1077
1078#ifdef CONFIG_PM_SLEEP
1079static int virtballoon_freeze(struct virtio_device *vdev)
1080{
1081 struct virtio_balloon *vb = vdev->priv;
1082
1083 /*
1084 * The workqueue is already frozen by the PM core before this
1085 * function is called.
1086 */
1087 remove_common(vb);
1088 return 0;
1089}
1090
1091static int virtballoon_restore(struct virtio_device *vdev)
1092{
1093 struct virtio_balloon *vb = vdev->priv;
1094 int ret;
1095
1096 ret = init_vqs(vdev->priv);
1097 if (ret)
1098 return ret;
1099
1100 virtio_device_ready(vdev);
1101
1102 if (towards_target(vb))
1103 virtballoon_changed(vdev);
1104 update_balloon_size(vb);
1105 return 0;
1106}
1107#endif
1108
1109static int virtballoon_validate(struct virtio_device *vdev)
1110{
1111 /*
1112 * Inform the hypervisor that our pages are poisoned or
1113 * initialized. If we cannot do that then we should disable
1114 * page reporting as it could potentially change the contents
1115 * of our free pages.
1116 */
1117 if (!want_init_on_free() &&
1118 (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
1119 !page_poisoning_enabled()))
1120 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1121 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1122 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1123
1124 __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1125 return 0;
1126}
1127
1128static unsigned int features[] = {
1129 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1130 VIRTIO_BALLOON_F_STATS_VQ,
1131 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1132 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1133 VIRTIO_BALLOON_F_PAGE_POISON,
1134 VIRTIO_BALLOON_F_REPORTING,
1135};
1136
1137static struct virtio_driver virtio_balloon_driver = {
1138 .feature_table = features,
1139 .feature_table_size = ARRAY_SIZE(features),
1140 .driver.name = KBUILD_MODNAME,
1141 .driver.owner = THIS_MODULE,
1142 .id_table = id_table,
1143 .validate = virtballoon_validate,
1144 .probe = virtballoon_probe,
1145 .remove = virtballoon_remove,
1146 .config_changed = virtballoon_changed,
1147#ifdef CONFIG_PM_SLEEP
1148 .freeze = virtballoon_freeze,
1149 .restore = virtballoon_restore,
1150#endif
1151};
1152
1153module_virtio_driver(virtio_balloon_driver);
1154MODULE_DEVICE_TABLE(virtio, id_table);
1155MODULE_DESCRIPTION("Virtio balloon driver");
1156MODULE_LICENSE("GPL");