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

source code of linux/drivers/virtio/virtio_balloon.c