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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/wait.h>
18#include <linux/mm.h>
19#include <linux/mount.h>
20#include <linux/magic.h>
21#include <linux/pseudo_fs.h>
22
23/*
24 * Balloon device works in 4K page units. So each page is pointed to by
25 * multiple balloon pages. All memory counters in this driver are in balloon
26 * page units.
27 */
28#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
29#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
30#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
31
32#define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
33 __GFP_NOMEMALLOC)
34/* The order of free page blocks to report to host */
35#define VIRTIO_BALLOON_FREE_PAGE_ORDER (MAX_ORDER - 1)
36/* The size of a free page block in bytes */
37#define VIRTIO_BALLOON_FREE_PAGE_SIZE \
38 (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
39
40#ifdef CONFIG_BALLOON_COMPACTION
41static struct vfsmount *balloon_mnt;
42#endif
43
44enum virtio_balloon_vq {
45 VIRTIO_BALLOON_VQ_INFLATE,
46 VIRTIO_BALLOON_VQ_DEFLATE,
47 VIRTIO_BALLOON_VQ_STATS,
48 VIRTIO_BALLOON_VQ_FREE_PAGE,
49 VIRTIO_BALLOON_VQ_MAX
50};
51
52enum virtio_balloon_config_read {
53 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
54};
55
56struct virtio_balloon {
57 struct virtio_device *vdev;
58 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
59
60 /* Balloon's own wq for cpu-intensive work items */
61 struct workqueue_struct *balloon_wq;
62 /* The free page reporting work item submitted to the balloon wq */
63 struct work_struct report_free_page_work;
64
65 /* The balloon servicing is delegated to a freezable workqueue. */
66 struct work_struct update_balloon_stats_work;
67 struct work_struct update_balloon_size_work;
68
69 /* Prevent updating balloon when it is being canceled. */
70 spinlock_t stop_update_lock;
71 bool stop_update;
72 /* Bitmap to indicate if reading the related config fields are needed */
73 unsigned long config_read_bitmap;
74
75 /* The list of allocated free pages, waiting to be given back to mm */
76 struct list_head free_page_list;
77 spinlock_t free_page_list_lock;
78 /* The number of free page blocks on the above list */
79 unsigned long num_free_page_blocks;
80 /*
81 * The cmd id received from host.
82 * Read it via virtio_balloon_cmd_id_received to get the latest value
83 * sent from host.
84 */
85 u32 cmd_id_received_cache;
86 /* The cmd id that is actively in use */
87 __virtio32 cmd_id_active;
88 /* Buffer to store the stop sign */
89 __virtio32 cmd_id_stop;
90
91 /* Waiting for host to ack the pages we released. */
92 wait_queue_head_t acked;
93
94 /* Number of balloon pages we've told the Host we're not using. */
95 unsigned int num_pages;
96 /*
97 * The pages we've told the Host we're not using are enqueued
98 * at vb_dev_info->pages list.
99 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
100 * to num_pages above.
101 */
102 struct balloon_dev_info vb_dev_info;
103
104 /* Synchronize access/update to this struct virtio_balloon elements */
105 struct mutex balloon_lock;
106
107 /* The array of pfns we tell the Host about. */
108 unsigned int num_pfns;
109 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
110
111 /* Memory statistics */
112 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
113
114 /* To register a shrinker to shrink memory upon memory pressure */
115 struct shrinker shrinker;
116};
117
118static struct virtio_device_id id_table[] = {
119 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
120 { 0 },
121};
122
123static u32 page_to_balloon_pfn(struct page *page)
124{
125 unsigned long pfn = page_to_pfn(page);
126
127 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
128 /* Convert pfn from Linux page size to balloon page size. */
129 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
130}
131
132static void balloon_ack(struct virtqueue *vq)
133{
134 struct virtio_balloon *vb = vq->vdev->priv;
135
136 wake_up(&vb->acked);
137}
138
139static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
140{
141 struct scatterlist sg;
142 unsigned int len;
143
144 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
145
146 /* We should always be able to add one buffer to an empty queue. */
147 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
148 virtqueue_kick(vq);
149
150 /* When host has read buffer, this completes via balloon_ack */
151 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
152
153}
154
155static void set_page_pfns(struct virtio_balloon *vb,
156 __virtio32 pfns[], struct page *page)
157{
158 unsigned int i;
159
160 /*
161 * Set balloon pfns pointing at this page.
162 * Note that the first pfn points at start of the page.
163 */
164 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
165 pfns[i] = cpu_to_virtio32(vb->vdev,
166 page_to_balloon_pfn(page) + i);
167}
168
169static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
170{
171 unsigned num_allocated_pages;
172 unsigned num_pfns;
173 struct page *page;
174 LIST_HEAD(pages);
175
176 /* We can only do one array worth at a time. */
177 num = min(num, ARRAY_SIZE(vb->pfns));
178
179 for (num_pfns = 0; num_pfns < num;
180 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
181 struct page *page = balloon_page_alloc();
182
183 if (!page) {
184 dev_info_ratelimited(&vb->vdev->dev,
185 "Out of puff! Can't get %u pages\n",
186 VIRTIO_BALLOON_PAGES_PER_PAGE);
187 /* Sleep for at least 1/5 of a second before retry. */
188 msleep(200);
189 break;
190 }
191
192 balloon_page_push(&pages, page);
193 }
194
195 mutex_lock(&vb->balloon_lock);
196
197 vb->num_pfns = 0;
198
199 while ((page = balloon_page_pop(&pages))) {
200 balloon_page_enqueue(&vb->vb_dev_info, page);
201
202 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
203 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
204 if (!virtio_has_feature(vb->vdev,
205 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
206 adjust_managed_page_count(page, -1);
207 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
208 }
209
210 num_allocated_pages = vb->num_pfns;
211 /* Did we get any? */
212 if (vb->num_pfns != 0)
213 tell_host(vb, vb->inflate_vq);
214 mutex_unlock(&vb->balloon_lock);
215
216 return num_allocated_pages;
217}
218
219static void release_pages_balloon(struct virtio_balloon *vb,
220 struct list_head *pages)
221{
222 struct page *page, *next;
223
224 list_for_each_entry_safe(page, next, pages, lru) {
225 if (!virtio_has_feature(vb->vdev,
226 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
227 adjust_managed_page_count(page, 1);
228 list_del(&page->lru);
229 put_page(page); /* balloon reference */
230 }
231}
232
233static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
234{
235 unsigned num_freed_pages;
236 struct page *page;
237 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
238 LIST_HEAD(pages);
239
240 /* We can only do one array worth at a time. */
241 num = min(num, ARRAY_SIZE(vb->pfns));
242
243 mutex_lock(&vb->balloon_lock);
244 /* We can't release more pages than taken */
245 num = min(num, (size_t)vb->num_pages);
246 for (vb->num_pfns = 0; vb->num_pfns < num;
247 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
248 page = balloon_page_dequeue(vb_dev_info);
249 if (!page)
250 break;
251 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
252 list_add(&page->lru, &pages);
253 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
254 }
255
256 num_freed_pages = vb->num_pfns;
257 /*
258 * Note that if
259 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
260 * is true, we *have* to do it in this order
261 */
262 if (vb->num_pfns != 0)
263 tell_host(vb, vb->deflate_vq);
264 release_pages_balloon(vb, &pages);
265 mutex_unlock(&vb->balloon_lock);
266 return num_freed_pages;
267}
268
269static inline void update_stat(struct virtio_balloon *vb, int idx,
270 u16 tag, u64 val)
271{
272 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
273 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
274 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
275}
276
277#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
278
279static unsigned int update_balloon_stats(struct virtio_balloon *vb)
280{
281 unsigned long events[NR_VM_EVENT_ITEMS];
282 struct sysinfo i;
283 unsigned int idx = 0;
284 long available;
285 unsigned long caches;
286
287 all_vm_events(events);
288 si_meminfo(&i);
289
290 available = si_mem_available();
291 caches = global_node_page_state(NR_FILE_PAGES);
292
293#ifdef CONFIG_VM_EVENT_COUNTERS
294 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
295 pages_to_bytes(events[PSWPIN]));
296 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
297 pages_to_bytes(events[PSWPOUT]));
298 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
299 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
300#ifdef CONFIG_HUGETLB_PAGE
301 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
302 events[HTLB_BUDDY_PGALLOC]);
303 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
304 events[HTLB_BUDDY_PGALLOC_FAIL]);
305#endif
306#endif
307 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
308 pages_to_bytes(i.freeram));
309 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
310 pages_to_bytes(i.totalram));
311 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
312 pages_to_bytes(available));
313 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
314 pages_to_bytes(caches));
315
316 return idx;
317}
318
319/*
320 * While most virtqueues communicate guest-initiated requests to the hypervisor,
321 * the stats queue operates in reverse. The driver initializes the virtqueue
322 * with a single buffer. From that point forward, all conversations consist of
323 * a hypervisor request (a call to this function) which directs us to refill
324 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
325 * we delegate the job to a freezable workqueue that will do the actual work via
326 * stats_handle_request().
327 */
328static void stats_request(struct virtqueue *vq)
329{
330 struct virtio_balloon *vb = vq->vdev->priv;
331
332 spin_lock(&vb->stop_update_lock);
333 if (!vb->stop_update)
334 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
335 spin_unlock(&vb->stop_update_lock);
336}
337
338static void stats_handle_request(struct virtio_balloon *vb)
339{
340 struct virtqueue *vq;
341 struct scatterlist sg;
342 unsigned int len, num_stats;
343
344 num_stats = update_balloon_stats(vb);
345
346 vq = vb->stats_vq;
347 if (!virtqueue_get_buf(vq, &len))
348 return;
349 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
350 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
351 virtqueue_kick(vq);
352}
353
354static inline s64 towards_target(struct virtio_balloon *vb)
355{
356 s64 target;
357 u32 num_pages;
358
359 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
360 &num_pages);
361
362 /* Legacy balloon config space is LE, unlike all other devices. */
363 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
364 num_pages = le32_to_cpu((__force __le32)num_pages);
365
366 target = num_pages;
367 return target - vb->num_pages;
368}
369
370/* Gives back @num_to_return blocks of free pages to mm. */
371static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
372 unsigned long num_to_return)
373{
374 struct page *page;
375 unsigned long num_returned;
376
377 spin_lock_irq(&vb->free_page_list_lock);
378 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
379 page = balloon_page_pop(&vb->free_page_list);
380 if (!page)
381 break;
382 free_pages((unsigned long)page_address(page),
383 VIRTIO_BALLOON_FREE_PAGE_ORDER);
384 }
385 vb->num_free_page_blocks -= num_returned;
386 spin_unlock_irq(&vb->free_page_list_lock);
387
388 return num_returned;
389}
390
391static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
392{
393 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
394 return;
395
396 /* No need to queue the work if the bit was already set. */
397 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
398 &vb->config_read_bitmap))
399 return;
400
401 queue_work(vb->balloon_wq, &vb->report_free_page_work);
402}
403
404static void virtballoon_changed(struct virtio_device *vdev)
405{
406 struct virtio_balloon *vb = vdev->priv;
407 unsigned long flags;
408
409 spin_lock_irqsave(&vb->stop_update_lock, flags);
410 if (!vb->stop_update) {
411 queue_work(system_freezable_wq,
412 &vb->update_balloon_size_work);
413 virtio_balloon_queue_free_page_work(vb);
414 }
415 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
416}
417
418static void update_balloon_size(struct virtio_balloon *vb)
419{
420 u32 actual = vb->num_pages;
421
422 /* Legacy balloon config space is LE, unlike all other devices. */
423 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
424 actual = (__force u32)cpu_to_le32(actual);
425
426 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
427 &actual);
428}
429
430static void update_balloon_stats_func(struct work_struct *work)
431{
432 struct virtio_balloon *vb;
433
434 vb = container_of(work, struct virtio_balloon,
435 update_balloon_stats_work);
436 stats_handle_request(vb);
437}
438
439static void update_balloon_size_func(struct work_struct *work)
440{
441 struct virtio_balloon *vb;
442 s64 diff;
443
444 vb = container_of(work, struct virtio_balloon,
445 update_balloon_size_work);
446 diff = towards_target(vb);
447
448 if (!diff)
449 return;
450
451 if (diff > 0)
452 diff -= fill_balloon(vb, diff);
453 else
454 diff += leak_balloon(vb, -diff);
455 update_balloon_size(vb);
456
457 if (diff)
458 queue_work(system_freezable_wq, work);
459}
460
461static int init_vqs(struct virtio_balloon *vb)
462{
463 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
464 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
465 const char *names[VIRTIO_BALLOON_VQ_MAX];
466 int err;
467
468 /*
469 * Inflateq and deflateq are used unconditionally. The names[]
470 * will be NULL if the related feature is not enabled, which will
471 * cause no allocation for the corresponding virtqueue in find_vqs.
472 */
473 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
474 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
475 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
476 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
477 names[VIRTIO_BALLOON_VQ_STATS] = NULL;
478 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
479
480 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
481 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
482 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
483 }
484
485 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
486 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
487 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
488 }
489
490 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
491 vqs, callbacks, names, NULL, NULL);
492 if (err)
493 return err;
494
495 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
496 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
497 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
498 struct scatterlist sg;
499 unsigned int num_stats;
500 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
501
502 /*
503 * Prime this virtqueue with one buffer so the hypervisor can
504 * use it to signal us later (it can't be broken yet!).
505 */
506 num_stats = update_balloon_stats(vb);
507
508 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
509 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
510 GFP_KERNEL);
511 if (err) {
512 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
513 __func__);
514 return err;
515 }
516 virtqueue_kick(vb->stats_vq);
517 }
518
519 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
520 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
521
522 return 0;
523}
524
525static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
526{
527 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
528 &vb->config_read_bitmap))
529 virtio_cread(vb->vdev, struct virtio_balloon_config,
530 free_page_report_cmd_id,
531 &vb->cmd_id_received_cache);
532
533 return vb->cmd_id_received_cache;
534}
535
536static int send_cmd_id_start(struct virtio_balloon *vb)
537{
538 struct scatterlist sg;
539 struct virtqueue *vq = vb->free_page_vq;
540 int err, unused;
541
542 /* Detach all the used buffers from the vq */
543 while (virtqueue_get_buf(vq, &unused))
544 ;
545
546 vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
547 virtio_balloon_cmd_id_received(vb));
548 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
549 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
550 if (!err)
551 virtqueue_kick(vq);
552 return err;
553}
554
555static int send_cmd_id_stop(struct virtio_balloon *vb)
556{
557 struct scatterlist sg;
558 struct virtqueue *vq = vb->free_page_vq;
559 int err, unused;
560
561 /* Detach all the used buffers from the vq */
562 while (virtqueue_get_buf(vq, &unused))
563 ;
564
565 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
566 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
567 if (!err)
568 virtqueue_kick(vq);
569 return err;
570}
571
572static int get_free_page_and_send(struct virtio_balloon *vb)
573{
574 struct virtqueue *vq = vb->free_page_vq;
575 struct page *page;
576 struct scatterlist sg;
577 int err, unused;
578 void *p;
579
580 /* Detach all the used buffers from the vq */
581 while (virtqueue_get_buf(vq, &unused))
582 ;
583
584 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
585 VIRTIO_BALLOON_FREE_PAGE_ORDER);
586 /*
587 * When the allocation returns NULL, it indicates that we have got all
588 * the possible free pages, so return -EINTR to stop.
589 */
590 if (!page)
591 return -EINTR;
592
593 p = page_address(page);
594 sg_init_one(&sg, p, VIRTIO_BALLOON_FREE_PAGE_SIZE);
595 /* There is always 1 entry reserved for the cmd id to use. */
596 if (vq->num_free > 1) {
597 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
598 if (unlikely(err)) {
599 free_pages((unsigned long)p,
600 VIRTIO_BALLOON_FREE_PAGE_ORDER);
601 return err;
602 }
603 virtqueue_kick(vq);
604 spin_lock_irq(&vb->free_page_list_lock);
605 balloon_page_push(&vb->free_page_list, page);
606 vb->num_free_page_blocks++;
607 spin_unlock_irq(&vb->free_page_list_lock);
608 } else {
609 /*
610 * The vq has no available entry to add this page block, so
611 * just free it.
612 */
613 free_pages((unsigned long)p, VIRTIO_BALLOON_FREE_PAGE_ORDER);
614 }
615
616 return 0;
617}
618
619static int send_free_pages(struct virtio_balloon *vb)
620{
621 int err;
622 u32 cmd_id_active;
623
624 while (1) {
625 /*
626 * If a stop id or a new cmd id was just received from host,
627 * stop the reporting.
628 */
629 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
630 if (unlikely(cmd_id_active !=
631 virtio_balloon_cmd_id_received(vb)))
632 break;
633
634 /*
635 * The free page blocks are allocated and sent to host one by
636 * one.
637 */
638 err = get_free_page_and_send(vb);
639 if (err == -EINTR)
640 break;
641 else if (unlikely(err))
642 return err;
643 }
644
645 return 0;
646}
647
648static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
649{
650 int err;
651 struct device *dev = &vb->vdev->dev;
652
653 /* Start by sending the received cmd id to host with an outbuf. */
654 err = send_cmd_id_start(vb);
655 if (unlikely(err))
656 dev_err(dev, "Failed to send a start id, err = %d\n", err);
657
658 err = send_free_pages(vb);
659 if (unlikely(err))
660 dev_err(dev, "Failed to send a free page, err = %d\n", err);
661
662 /* End by sending a stop id to host with an outbuf. */
663 err = send_cmd_id_stop(vb);
664 if (unlikely(err))
665 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
666}
667
668static void report_free_page_func(struct work_struct *work)
669{
670 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
671 report_free_page_work);
672 u32 cmd_id_received;
673
674 cmd_id_received = virtio_balloon_cmd_id_received(vb);
675 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
676 /* Pass ULONG_MAX to give back all the free pages */
677 return_free_pages_to_mm(vb, ULONG_MAX);
678 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
679 cmd_id_received !=
680 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
681 virtio_balloon_report_free_page(vb);
682 }
683}
684
685#ifdef CONFIG_BALLOON_COMPACTION
686/*
687 * virtballoon_migratepage - perform the balloon page migration on behalf of
688 * a compation thread. (called under page lock)
689 * @vb_dev_info: the balloon device
690 * @newpage: page that will replace the isolated page after migration finishes.
691 * @page : the isolated (old) page that is about to be migrated to newpage.
692 * @mode : compaction mode -- not used for balloon page migration.
693 *
694 * After a ballooned page gets isolated by compaction procedures, this is the
695 * function that performs the page migration on behalf of a compaction thread
696 * The page migration for virtio balloon is done in a simple swap fashion which
697 * follows these two macro steps:
698 * 1) insert newpage into vb->pages list and update the host about it;
699 * 2) update the host about the old page removed from vb->pages list;
700 *
701 * This function preforms the balloon page migration task.
702 * Called through balloon_mapping->a_ops->migratepage
703 */
704static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
705 struct page *newpage, struct page *page, enum migrate_mode mode)
706{
707 struct virtio_balloon *vb = container_of(vb_dev_info,
708 struct virtio_balloon, vb_dev_info);
709 unsigned long flags;
710
711 /*
712 * In order to avoid lock contention while migrating pages concurrently
713 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
714 * this turn, as it is easier to retry the page migration later.
715 * This also prevents fill_balloon() getting stuck into a mutex
716 * recursion in the case it ends up triggering memory compaction
717 * while it is attempting to inflate the ballon.
718 */
719 if (!mutex_trylock(&vb->balloon_lock))
720 return -EAGAIN;
721
722 get_page(newpage); /* balloon reference */
723
724 /* balloon's page migration 1st step -- inflate "newpage" */
725 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
726 balloon_page_insert(vb_dev_info, newpage);
727 vb_dev_info->isolated_pages--;
728 __count_vm_event(BALLOON_MIGRATE);
729 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
730 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
731 set_page_pfns(vb, vb->pfns, newpage);
732 tell_host(vb, vb->inflate_vq);
733
734 /* balloon's page migration 2nd step -- deflate "page" */
735 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
736 balloon_page_delete(page);
737 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
738 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
739 set_page_pfns(vb, vb->pfns, page);
740 tell_host(vb, vb->deflate_vq);
741
742 mutex_unlock(&vb->balloon_lock);
743
744 put_page(page); /* balloon reference */
745
746 return MIGRATEPAGE_SUCCESS;
747}
748
749static int balloon_init_fs_context(struct fs_context *fc)
750{
751 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
752}
753
754static struct file_system_type balloon_fs = {
755 .name = "balloon-kvm",
756 .init_fs_context = balloon_init_fs_context,
757 .kill_sb = kill_anon_super,
758};
759
760#endif /* CONFIG_BALLOON_COMPACTION */
761
762static unsigned long shrink_free_pages(struct virtio_balloon *vb,
763 unsigned long pages_to_free)
764{
765 unsigned long blocks_to_free, blocks_freed;
766
767 pages_to_free = round_up(pages_to_free,
768 1 << VIRTIO_BALLOON_FREE_PAGE_ORDER);
769 blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
770 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
771
772 return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
773}
774
775static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
776 unsigned long pages_to_free)
777{
778 return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
779 VIRTIO_BALLOON_PAGES_PER_PAGE;
780}
781
782static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
783 unsigned long pages_to_free)
784{
785 unsigned long pages_freed = 0;
786
787 /*
788 * One invocation of leak_balloon can deflate at most
789 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
790 * multiple times to deflate pages till reaching pages_to_free.
791 */
792 while (vb->num_pages && pages_freed < pages_to_free)
793 pages_freed += leak_balloon_pages(vb,
794 pages_to_free - pages_freed);
795
796 update_balloon_size(vb);
797
798 return pages_freed;
799}
800
801static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
802 struct shrink_control *sc)
803{
804 unsigned long pages_to_free, pages_freed = 0;
805 struct virtio_balloon *vb = container_of(shrinker,
806 struct virtio_balloon, shrinker);
807
808 pages_to_free = sc->nr_to_scan;
809
810 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
811 pages_freed = shrink_free_pages(vb, pages_to_free);
812
813 if (pages_freed >= pages_to_free)
814 return pages_freed;
815
816 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
817
818 return pages_freed;
819}
820
821static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
822 struct shrink_control *sc)
823{
824 struct virtio_balloon *vb = container_of(shrinker,
825 struct virtio_balloon, shrinker);
826 unsigned long count;
827
828 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
829 count += vb->num_free_page_blocks << VIRTIO_BALLOON_FREE_PAGE_ORDER;
830
831 return count;
832}
833
834static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
835{
836 unregister_shrinker(&vb->shrinker);
837}
838
839static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
840{
841 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
842 vb->shrinker.count_objects = virtio_balloon_shrinker_count;
843 vb->shrinker.seeks = DEFAULT_SEEKS;
844
845 return register_shrinker(&vb->shrinker);
846}
847
848static int virtballoon_probe(struct virtio_device *vdev)
849{
850 struct virtio_balloon *vb;
851 __u32 poison_val;
852 int err;
853
854 if (!vdev->config->get) {
855 dev_err(&vdev->dev, "%s failure: config access disabled\n",
856 __func__);
857 return -EINVAL;
858 }
859
860 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
861 if (!vb) {
862 err = -ENOMEM;
863 goto out;
864 }
865
866 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
867 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
868 spin_lock_init(&vb->stop_update_lock);
869 mutex_init(&vb->balloon_lock);
870 init_waitqueue_head(&vb->acked);
871 vb->vdev = vdev;
872
873 balloon_devinfo_init(&vb->vb_dev_info);
874
875 err = init_vqs(vb);
876 if (err)
877 goto out_free_vb;
878
879#ifdef CONFIG_BALLOON_COMPACTION
880 balloon_mnt = kern_mount(&balloon_fs);
881 if (IS_ERR(balloon_mnt)) {
882 err = PTR_ERR(balloon_mnt);
883 goto out_del_vqs;
884 }
885
886 vb->vb_dev_info.migratepage = virtballoon_migratepage;
887 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
888 if (IS_ERR(vb->vb_dev_info.inode)) {
889 err = PTR_ERR(vb->vb_dev_info.inode);
890 kern_unmount(balloon_mnt);
891 goto out_del_vqs;
892 }
893 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
894#endif
895 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
896 /*
897 * There is always one entry reserved for cmd id, so the ring
898 * size needs to be at least two to report free page hints.
899 */
900 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
901 err = -ENOSPC;
902 goto out_del_vqs;
903 }
904 vb->balloon_wq = alloc_workqueue("balloon-wq",
905 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
906 if (!vb->balloon_wq) {
907 err = -ENOMEM;
908 goto out_del_vqs;
909 }
910 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
911 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
912 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
913 VIRTIO_BALLOON_CMD_ID_STOP);
914 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
915 VIRTIO_BALLOON_CMD_ID_STOP);
916 spin_lock_init(&vb->free_page_list_lock);
917 INIT_LIST_HEAD(&vb->free_page_list);
918 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
919 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
920 virtio_cwrite(vb->vdev, struct virtio_balloon_config,
921 poison_val, &poison_val);
922 }
923 }
924 /*
925 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
926 * shrinker needs to be registered to relieve memory pressure.
927 */
928 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
929 err = virtio_balloon_register_shrinker(vb);
930 if (err)
931 goto out_del_balloon_wq;
932 }
933 virtio_device_ready(vdev);
934
935 if (towards_target(vb))
936 virtballoon_changed(vdev);
937 return 0;
938
939out_del_balloon_wq:
940 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
941 destroy_workqueue(vb->balloon_wq);
942out_del_vqs:
943 vdev->config->del_vqs(vdev);
944out_free_vb:
945 kfree(vb);
946out:
947 return err;
948}
949
950static void remove_common(struct virtio_balloon *vb)
951{
952 /* There might be pages left in the balloon: free them. */
953 while (vb->num_pages)
954 leak_balloon(vb, vb->num_pages);
955 update_balloon_size(vb);
956
957 /* Now we reset the device so we can clean up the queues. */
958 vb->vdev->config->reset(vb->vdev);
959
960 vb->vdev->config->del_vqs(vb->vdev);
961}
962
963static void virtballoon_remove(struct virtio_device *vdev)
964{
965 struct virtio_balloon *vb = vdev->priv;
966
967 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
968 virtio_balloon_unregister_shrinker(vb);
969 spin_lock_irq(&vb->stop_update_lock);
970 vb->stop_update = true;
971 spin_unlock_irq(&vb->stop_update_lock);
972 cancel_work_sync(&vb->update_balloon_size_work);
973 cancel_work_sync(&vb->update_balloon_stats_work);
974
975 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
976 cancel_work_sync(&vb->report_free_page_work);
977 destroy_workqueue(vb->balloon_wq);
978 }
979
980 remove_common(vb);
981#ifdef CONFIG_BALLOON_COMPACTION
982 if (vb->vb_dev_info.inode)
983 iput(vb->vb_dev_info.inode);
984
985 kern_unmount(balloon_mnt);
986#endif
987 kfree(vb);
988}
989
990#ifdef CONFIG_PM_SLEEP
991static int virtballoon_freeze(struct virtio_device *vdev)
992{
993 struct virtio_balloon *vb = vdev->priv;
994
995 /*
996 * The workqueue is already frozen by the PM core before this
997 * function is called.
998 */
999 remove_common(vb);
1000 return 0;
1001}
1002
1003static int virtballoon_restore(struct virtio_device *vdev)
1004{
1005 struct virtio_balloon *vb = vdev->priv;
1006 int ret;
1007
1008 ret = init_vqs(vdev->priv);
1009 if (ret)
1010 return ret;
1011
1012 virtio_device_ready(vdev);
1013
1014 if (towards_target(vb))
1015 virtballoon_changed(vdev);
1016 update_balloon_size(vb);
1017 return 0;
1018}
1019#endif
1020
1021static int virtballoon_validate(struct virtio_device *vdev)
1022{
1023 if (!page_poisoning_enabled())
1024 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1025
1026 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1027 return 0;
1028}
1029
1030static unsigned int features[] = {
1031 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1032 VIRTIO_BALLOON_F_STATS_VQ,
1033 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1034 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1035 VIRTIO_BALLOON_F_PAGE_POISON,
1036};
1037
1038static struct virtio_driver virtio_balloon_driver = {
1039 .feature_table = features,
1040 .feature_table_size = ARRAY_SIZE(features),
1041 .driver.name = KBUILD_MODNAME,
1042 .driver.owner = THIS_MODULE,
1043 .id_table = id_table,
1044 .validate = virtballoon_validate,
1045 .probe = virtballoon_probe,
1046 .remove = virtballoon_remove,
1047 .config_changed = virtballoon_changed,
1048#ifdef CONFIG_PM_SLEEP
1049 .freeze = virtballoon_freeze,
1050 .restore = virtballoon_restore,
1051#endif
1052};
1053
1054module_virtio_driver(virtio_balloon_driver);
1055MODULE_DEVICE_TABLE(virtio, id_table);
1056MODULE_DESCRIPTION("Virtio balloon driver");
1057MODULE_LICENSE("GPL");
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/kthread.h>
26#include <linux/freezer.h>
27#include <linux/delay.h>
28#include <linux/slab.h>
29#include <linux/module.h>
30
31/*
32 * Balloon device works in 4K page units. So each page is pointed to by
33 * multiple balloon pages. All memory counters in this driver are in balloon
34 * page units.
35 */
36#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
37
38struct virtio_balloon
39{
40 struct virtio_device *vdev;
41 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
42
43 /* Where the ballooning thread waits for config to change. */
44 wait_queue_head_t config_change;
45
46 /* The thread servicing the balloon. */
47 struct task_struct *thread;
48
49 /* Waiting for host to ack the pages we released. */
50 wait_queue_head_t acked;
51
52 /* Number of balloon pages we've told the Host we're not using. */
53 unsigned int num_pages;
54 /*
55 * The pages we've told the Host we're not using.
56 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
57 * to num_pages above.
58 */
59 struct list_head pages;
60
61 /* The array of pfns we tell the Host about. */
62 unsigned int num_pfns;
63 u32 pfns[256];
64
65 /* Memory statistics */
66 int need_stats_update;
67 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
68};
69
70static struct virtio_device_id id_table[] = {
71 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
72 { 0 },
73};
74
75static u32 page_to_balloon_pfn(struct page *page)
76{
77 unsigned long pfn = page_to_pfn(page);
78
79 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
80 /* Convert pfn from Linux page size to balloon page size. */
81 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
82}
83
84static struct page *balloon_pfn_to_page(u32 pfn)
85{
86 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
87 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
88}
89
90static void balloon_ack(struct virtqueue *vq)
91{
92 struct virtio_balloon *vb = vq->vdev->priv;
93
94 wake_up(&vb->acked);
95}
96
97static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
98{
99 struct scatterlist sg;
100 unsigned int len;
101
102 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
103
104 /* We should always be able to add one buffer to an empty queue. */
105 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
106 BUG();
107 virtqueue_kick(vq);
108
109 /* When host has read buffer, this completes via balloon_ack */
110 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
111}
112
113static void set_page_pfns(u32 pfns[], struct page *page)
114{
115 unsigned int i;
116
117 /* Set balloon pfns pointing at this page.
118 * Note that the first pfn points at start of the page. */
119 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
120 pfns[i] = page_to_balloon_pfn(page) + i;
121}
122
123static void fill_balloon(struct virtio_balloon *vb, size_t num)
124{
125 /* We can only do one array worth at a time. */
126 num = min(num, ARRAY_SIZE(vb->pfns));
127
128 for (vb->num_pfns = 0; vb->num_pfns < num;
129 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
130 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
131 __GFP_NOMEMALLOC | __GFP_NOWARN);
132 if (!page) {
133 if (printk_ratelimit())
134 dev_printk(KERN_INFO, &vb->vdev->dev,
135 "Out of puff! Can't get %zu pages\n",
136 num);
137 /* Sleep for at least 1/5 of a second before retry. */
138 msleep(200);
139 break;
140 }
141 set_page_pfns(vb->pfns + vb->num_pfns, page);
142 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
143 totalram_pages--;
144 list_add(&page->lru, &vb->pages);
145 }
146
147 /* Didn't get any? Oh well. */
148 if (vb->num_pfns == 0)
149 return;
150
151 tell_host(vb, vb->inflate_vq);
152}
153
154static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
155{
156 unsigned int i;
157
158 /* Find pfns pointing at start of each page, get pages and free them. */
159 for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
160 __free_page(balloon_pfn_to_page(pfns[i]));
161 totalram_pages++;
162 }
163}
164
165static void leak_balloon(struct virtio_balloon *vb, size_t num)
166{
167 struct page *page;
168
169 /* We can only do one array worth at a time. */
170 num = min(num, ARRAY_SIZE(vb->pfns));
171
172 for (vb->num_pfns = 0; vb->num_pfns < num;
173 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
174 page = list_first_entry(&vb->pages, struct page, lru);
175 list_del(&page->lru);
176 set_page_pfns(vb->pfns + vb->num_pfns, page);
177 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
178 }
179
180 /*
181 * Note that if
182 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
183 * is true, we *have* to do it in this order
184 */
185 tell_host(vb, vb->deflate_vq);
186 release_pages_by_pfn(vb->pfns, vb->num_pfns);
187}
188
189static inline void update_stat(struct virtio_balloon *vb, int idx,
190 u16 tag, u64 val)
191{
192 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
193 vb->stats[idx].tag = tag;
194 vb->stats[idx].val = val;
195}
196
197#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
198
199static void update_balloon_stats(struct virtio_balloon *vb)
200{
201 unsigned long events[NR_VM_EVENT_ITEMS];
202 struct sysinfo i;
203 int idx = 0;
204
205 all_vm_events(events);
206 si_meminfo(&i);
207
208 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
209 pages_to_bytes(events[PSWPIN]));
210 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
211 pages_to_bytes(events[PSWPOUT]));
212 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
213 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
214 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
215 pages_to_bytes(i.freeram));
216 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
217 pages_to_bytes(i.totalram));
218}
219
220/*
221 * While most virtqueues communicate guest-initiated requests to the hypervisor,
222 * the stats queue operates in reverse. The driver initializes the virtqueue
223 * with a single buffer. From that point forward, all conversations consist of
224 * a hypervisor request (a call to this function) which directs us to refill
225 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
226 * we notify our kthread which does the actual work via stats_handle_request().
227 */
228static void stats_request(struct virtqueue *vq)
229{
230 struct virtio_balloon *vb = vq->vdev->priv;
231
232 vb->need_stats_update = 1;
233 wake_up(&vb->config_change);
234}
235
236static void stats_handle_request(struct virtio_balloon *vb)
237{
238 struct virtqueue *vq;
239 struct scatterlist sg;
240 unsigned int len;
241
242 vb->need_stats_update = 0;
243 update_balloon_stats(vb);
244
245 vq = vb->stats_vq;
246 if (!virtqueue_get_buf(vq, &len))
247 return;
248 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
249 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
250 BUG();
251 virtqueue_kick(vq);
252}
253
254static void virtballoon_changed(struct virtio_device *vdev)
255{
256 struct virtio_balloon *vb = vdev->priv;
257
258 wake_up(&vb->config_change);
259}
260
261static inline s64 towards_target(struct virtio_balloon *vb)
262{
263 __le32 v;
264 s64 target;
265
266 vb->vdev->config->get(vb->vdev,
267 offsetof(struct virtio_balloon_config, num_pages),
268 &v, sizeof(v));
269 target = le32_to_cpu(v);
270 return target - vb->num_pages;
271}
272
273static void update_balloon_size(struct virtio_balloon *vb)
274{
275 __le32 actual = cpu_to_le32(vb->num_pages);
276
277 vb->vdev->config->set(vb->vdev,
278 offsetof(struct virtio_balloon_config, actual),
279 &actual, sizeof(actual));
280}
281
282static int balloon(void *_vballoon)
283{
284 struct virtio_balloon *vb = _vballoon;
285
286 set_freezable();
287 while (!kthread_should_stop()) {
288 s64 diff;
289
290 try_to_freeze();
291 wait_event_interruptible(vb->config_change,
292 (diff = towards_target(vb)) != 0
293 || vb->need_stats_update
294 || kthread_should_stop()
295 || freezing(current));
296 if (vb->need_stats_update)
297 stats_handle_request(vb);
298 if (diff > 0)
299 fill_balloon(vb, diff);
300 else if (diff < 0)
301 leak_balloon(vb, -diff);
302 update_balloon_size(vb);
303 }
304 return 0;
305}
306
307static int init_vqs(struct virtio_balloon *vb)
308{
309 struct virtqueue *vqs[3];
310 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
311 const char *names[] = { "inflate", "deflate", "stats" };
312 int err, nvqs;
313
314 /*
315 * We expect two virtqueues: inflate and deflate, and
316 * optionally stat.
317 */
318 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
319 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
320 if (err)
321 return err;
322
323 vb->inflate_vq = vqs[0];
324 vb->deflate_vq = vqs[1];
325 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
326 struct scatterlist sg;
327 vb->stats_vq = vqs[2];
328
329 /*
330 * Prime this virtqueue with one buffer so the hypervisor can
331 * use it to signal us later.
332 */
333 sg_init_one(&sg, vb->stats, sizeof vb->stats);
334 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
335 < 0)
336 BUG();
337 virtqueue_kick(vb->stats_vq);
338 }
339 return 0;
340}
341
342static int virtballoon_probe(struct virtio_device *vdev)
343{
344 struct virtio_balloon *vb;
345 int err;
346
347 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
348 if (!vb) {
349 err = -ENOMEM;
350 goto out;
351 }
352
353 INIT_LIST_HEAD(&vb->pages);
354 vb->num_pages = 0;
355 init_waitqueue_head(&vb->config_change);
356 init_waitqueue_head(&vb->acked);
357 vb->vdev = vdev;
358 vb->need_stats_update = 0;
359
360 err = init_vqs(vb);
361 if (err)
362 goto out_free_vb;
363
364 vb->thread = kthread_run(balloon, vb, "vballoon");
365 if (IS_ERR(vb->thread)) {
366 err = PTR_ERR(vb->thread);
367 goto out_del_vqs;
368 }
369
370 return 0;
371
372out_del_vqs:
373 vdev->config->del_vqs(vdev);
374out_free_vb:
375 kfree(vb);
376out:
377 return err;
378}
379
380static void remove_common(struct virtio_balloon *vb)
381{
382 /* There might be pages left in the balloon: free them. */
383 while (vb->num_pages)
384 leak_balloon(vb, vb->num_pages);
385 update_balloon_size(vb);
386
387 /* Now we reset the device so we can clean up the queues. */
388 vb->vdev->config->reset(vb->vdev);
389
390 vb->vdev->config->del_vqs(vb->vdev);
391}
392
393static void __devexit virtballoon_remove(struct virtio_device *vdev)
394{
395 struct virtio_balloon *vb = vdev->priv;
396
397 kthread_stop(vb->thread);
398 remove_common(vb);
399 kfree(vb);
400}
401
402#ifdef CONFIG_PM
403static int virtballoon_freeze(struct virtio_device *vdev)
404{
405 struct virtio_balloon *vb = vdev->priv;
406
407 /*
408 * The kthread is already frozen by the PM core before this
409 * function is called.
410 */
411
412 remove_common(vb);
413 return 0;
414}
415
416static int virtballoon_restore(struct virtio_device *vdev)
417{
418 struct virtio_balloon *vb = vdev->priv;
419 int ret;
420
421 ret = init_vqs(vdev->priv);
422 if (ret)
423 return ret;
424
425 fill_balloon(vb, towards_target(vb));
426 update_balloon_size(vb);
427 return 0;
428}
429#endif
430
431static unsigned int features[] = {
432 VIRTIO_BALLOON_F_MUST_TELL_HOST,
433 VIRTIO_BALLOON_F_STATS_VQ,
434};
435
436static struct virtio_driver virtio_balloon_driver = {
437 .feature_table = features,
438 .feature_table_size = ARRAY_SIZE(features),
439 .driver.name = KBUILD_MODNAME,
440 .driver.owner = THIS_MODULE,
441 .id_table = id_table,
442 .probe = virtballoon_probe,
443 .remove = __devexit_p(virtballoon_remove),
444 .config_changed = virtballoon_changed,
445#ifdef CONFIG_PM
446 .freeze = virtballoon_freeze,
447 .restore = virtballoon_restore,
448#endif
449};
450
451static int __init init(void)
452{
453 return register_virtio_driver(&virtio_balloon_driver);
454}
455
456static void __exit fini(void)
457{
458 unregister_virtio_driver(&virtio_balloon_driver);
459}
460module_init(init);
461module_exit(fini);
462
463MODULE_DEVICE_TABLE(virtio, id_table);
464MODULE_DESCRIPTION("Virtio balloon driver");
465MODULE_LICENSE("GPL");