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
41 static struct vfsmount *balloon_mnt;
42 #endif
43
44 enum 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
52 enum virtio_balloon_config_read {
53 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
54 };
55
56 struct 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
118 static struct virtio_device_id id_table[] = {
119 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
120 { 0 },
121 };
122
page_to_balloon_pfn(struct page * page)123 static 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
balloon_ack(struct virtqueue * vq)132 static void balloon_ack(struct virtqueue *vq)
133 {
134 struct virtio_balloon *vb = vq->vdev->priv;
135
136 wake_up(&vb->acked);
137 }
138
tell_host(struct virtio_balloon * vb,struct virtqueue * vq)139 static 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
set_page_pfns(struct virtio_balloon * vb,__virtio32 pfns[],struct page * page)155 static 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
fill_balloon(struct virtio_balloon * vb,size_t num)169 static 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
release_pages_balloon(struct virtio_balloon * vb,struct list_head * pages)219 static 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
leak_balloon(struct virtio_balloon * vb,size_t num)233 static 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
update_stat(struct virtio_balloon * vb,int idx,u16 tag,u64 val)269 static 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
update_balloon_stats(struct virtio_balloon * vb)279 static 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 */
stats_request(struct virtqueue * vq)328 static 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
stats_handle_request(struct virtio_balloon * vb)338 static 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
towards_target(struct virtio_balloon * vb)354 static 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. */
return_free_pages_to_mm(struct virtio_balloon * vb,unsigned long num_to_return)371 static 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
virtio_balloon_queue_free_page_work(struct virtio_balloon * vb)391 static 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
virtballoon_changed(struct virtio_device * vdev)404 static 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
update_balloon_size(struct virtio_balloon * vb)418 static 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
update_balloon_stats_func(struct work_struct * work)430 static 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
update_balloon_size_func(struct work_struct * work)439 static 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
init_vqs(struct virtio_balloon * vb)461 static 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
virtio_balloon_cmd_id_received(struct virtio_balloon * vb)525 static 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
send_cmd_id_start(struct virtio_balloon * vb)536 static 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
send_cmd_id_stop(struct virtio_balloon * vb)555 static 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
get_free_page_and_send(struct virtio_balloon * vb)572 static 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
send_free_pages(struct virtio_balloon * vb)619 static 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
virtio_balloon_report_free_page(struct virtio_balloon * vb)648 static 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
report_free_page_func(struct work_struct * work)668 static 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 */
virtballoon_migratepage(struct balloon_dev_info * vb_dev_info,struct page * newpage,struct page * page,enum migrate_mode mode)704 static 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 /*
725 * When we migrate a page to a different zone and adjusted the
726 * managed page count when inflating, we have to fixup the count of
727 * both involved zones.
728 */
729 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
730 page_zone(page) != page_zone(newpage)) {
731 adjust_managed_page_count(page, 1);
732 adjust_managed_page_count(newpage, -1);
733 }
734
735 /* balloon's page migration 1st step -- inflate "newpage" */
736 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
737 balloon_page_insert(vb_dev_info, newpage);
738 vb_dev_info->isolated_pages--;
739 __count_vm_event(BALLOON_MIGRATE);
740 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
741 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
742 set_page_pfns(vb, vb->pfns, newpage);
743 tell_host(vb, vb->inflate_vq);
744
745 /* balloon's page migration 2nd step -- deflate "page" */
746 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
747 balloon_page_delete(page);
748 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
749 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
750 set_page_pfns(vb, vb->pfns, page);
751 tell_host(vb, vb->deflate_vq);
752
753 mutex_unlock(&vb->balloon_lock);
754
755 put_page(page); /* balloon reference */
756
757 return MIGRATEPAGE_SUCCESS;
758 }
759
balloon_init_fs_context(struct fs_context * fc)760 static int balloon_init_fs_context(struct fs_context *fc)
761 {
762 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
763 }
764
765 static struct file_system_type balloon_fs = {
766 .name = "balloon-kvm",
767 .init_fs_context = balloon_init_fs_context,
768 .kill_sb = kill_anon_super,
769 };
770
771 #endif /* CONFIG_BALLOON_COMPACTION */
772
shrink_free_pages(struct virtio_balloon * vb,unsigned long pages_to_free)773 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
774 unsigned long pages_to_free)
775 {
776 unsigned long blocks_to_free, blocks_freed;
777
778 pages_to_free = round_up(pages_to_free,
779 1 << VIRTIO_BALLOON_FREE_PAGE_ORDER);
780 blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
781 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
782
783 return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
784 }
785
leak_balloon_pages(struct virtio_balloon * vb,unsigned long pages_to_free)786 static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
787 unsigned long pages_to_free)
788 {
789 return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
790 VIRTIO_BALLOON_PAGES_PER_PAGE;
791 }
792
shrink_balloon_pages(struct virtio_balloon * vb,unsigned long pages_to_free)793 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
794 unsigned long pages_to_free)
795 {
796 unsigned long pages_freed = 0;
797
798 /*
799 * One invocation of leak_balloon can deflate at most
800 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
801 * multiple times to deflate pages till reaching pages_to_free.
802 */
803 while (vb->num_pages && pages_freed < pages_to_free)
804 pages_freed += leak_balloon_pages(vb,
805 pages_to_free - pages_freed);
806
807 update_balloon_size(vb);
808
809 return pages_freed;
810 }
811
virtio_balloon_shrinker_scan(struct shrinker * shrinker,struct shrink_control * sc)812 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
813 struct shrink_control *sc)
814 {
815 unsigned long pages_to_free, pages_freed = 0;
816 struct virtio_balloon *vb = container_of(shrinker,
817 struct virtio_balloon, shrinker);
818
819 pages_to_free = sc->nr_to_scan;
820
821 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
822 pages_freed = shrink_free_pages(vb, pages_to_free);
823
824 if (pages_freed >= pages_to_free)
825 return pages_freed;
826
827 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
828
829 return pages_freed;
830 }
831
virtio_balloon_shrinker_count(struct shrinker * shrinker,struct shrink_control * sc)832 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
833 struct shrink_control *sc)
834 {
835 struct virtio_balloon *vb = container_of(shrinker,
836 struct virtio_balloon, shrinker);
837 unsigned long count;
838
839 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
840 count += vb->num_free_page_blocks << VIRTIO_BALLOON_FREE_PAGE_ORDER;
841
842 return count;
843 }
844
virtio_balloon_unregister_shrinker(struct virtio_balloon * vb)845 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
846 {
847 unregister_shrinker(&vb->shrinker);
848 }
849
virtio_balloon_register_shrinker(struct virtio_balloon * vb)850 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
851 {
852 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
853 vb->shrinker.count_objects = virtio_balloon_shrinker_count;
854 vb->shrinker.seeks = DEFAULT_SEEKS;
855
856 return register_shrinker(&vb->shrinker);
857 }
858
virtballoon_probe(struct virtio_device * vdev)859 static int virtballoon_probe(struct virtio_device *vdev)
860 {
861 struct virtio_balloon *vb;
862 __u32 poison_val;
863 int err;
864
865 if (!vdev->config->get) {
866 dev_err(&vdev->dev, "%s failure: config access disabled\n",
867 __func__);
868 return -EINVAL;
869 }
870
871 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
872 if (!vb) {
873 err = -ENOMEM;
874 goto out;
875 }
876
877 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
878 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
879 spin_lock_init(&vb->stop_update_lock);
880 mutex_init(&vb->balloon_lock);
881 init_waitqueue_head(&vb->acked);
882 vb->vdev = vdev;
883
884 balloon_devinfo_init(&vb->vb_dev_info);
885
886 err = init_vqs(vb);
887 if (err)
888 goto out_free_vb;
889
890 #ifdef CONFIG_BALLOON_COMPACTION
891 balloon_mnt = kern_mount(&balloon_fs);
892 if (IS_ERR(balloon_mnt)) {
893 err = PTR_ERR(balloon_mnt);
894 goto out_del_vqs;
895 }
896
897 vb->vb_dev_info.migratepage = virtballoon_migratepage;
898 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
899 if (IS_ERR(vb->vb_dev_info.inode)) {
900 err = PTR_ERR(vb->vb_dev_info.inode);
901 kern_unmount(balloon_mnt);
902 goto out_del_vqs;
903 }
904 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
905 #endif
906 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
907 /*
908 * There is always one entry reserved for cmd id, so the ring
909 * size needs to be at least two to report free page hints.
910 */
911 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
912 err = -ENOSPC;
913 goto out_del_vqs;
914 }
915 vb->balloon_wq = alloc_workqueue("balloon-wq",
916 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
917 if (!vb->balloon_wq) {
918 err = -ENOMEM;
919 goto out_del_vqs;
920 }
921 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
922 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
923 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
924 VIRTIO_BALLOON_CMD_ID_STOP);
925 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
926 VIRTIO_BALLOON_CMD_ID_STOP);
927 spin_lock_init(&vb->free_page_list_lock);
928 INIT_LIST_HEAD(&vb->free_page_list);
929 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
930 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
931 virtio_cwrite(vb->vdev, struct virtio_balloon_config,
932 poison_val, &poison_val);
933 }
934 }
935 /*
936 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
937 * shrinker needs to be registered to relieve memory pressure.
938 */
939 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
940 err = virtio_balloon_register_shrinker(vb);
941 if (err)
942 goto out_del_balloon_wq;
943 }
944 virtio_device_ready(vdev);
945
946 if (towards_target(vb))
947 virtballoon_changed(vdev);
948 return 0;
949
950 out_del_balloon_wq:
951 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
952 destroy_workqueue(vb->balloon_wq);
953 out_del_vqs:
954 vdev->config->del_vqs(vdev);
955 out_free_vb:
956 kfree(vb);
957 out:
958 return err;
959 }
960
remove_common(struct virtio_balloon * vb)961 static void remove_common(struct virtio_balloon *vb)
962 {
963 /* There might be pages left in the balloon: free them. */
964 while (vb->num_pages)
965 leak_balloon(vb, vb->num_pages);
966 update_balloon_size(vb);
967
968 /* Now we reset the device so we can clean up the queues. */
969 vb->vdev->config->reset(vb->vdev);
970
971 vb->vdev->config->del_vqs(vb->vdev);
972 }
973
virtballoon_remove(struct virtio_device * vdev)974 static void virtballoon_remove(struct virtio_device *vdev)
975 {
976 struct virtio_balloon *vb = vdev->priv;
977
978 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
979 virtio_balloon_unregister_shrinker(vb);
980 spin_lock_irq(&vb->stop_update_lock);
981 vb->stop_update = true;
982 spin_unlock_irq(&vb->stop_update_lock);
983 cancel_work_sync(&vb->update_balloon_size_work);
984 cancel_work_sync(&vb->update_balloon_stats_work);
985
986 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
987 cancel_work_sync(&vb->report_free_page_work);
988 destroy_workqueue(vb->balloon_wq);
989 }
990
991 remove_common(vb);
992 #ifdef CONFIG_BALLOON_COMPACTION
993 if (vb->vb_dev_info.inode)
994 iput(vb->vb_dev_info.inode);
995
996 kern_unmount(balloon_mnt);
997 #endif
998 kfree(vb);
999 }
1000
1001 #ifdef CONFIG_PM_SLEEP
virtballoon_freeze(struct virtio_device * vdev)1002 static int virtballoon_freeze(struct virtio_device *vdev)
1003 {
1004 struct virtio_balloon *vb = vdev->priv;
1005
1006 /*
1007 * The workqueue is already frozen by the PM core before this
1008 * function is called.
1009 */
1010 remove_common(vb);
1011 return 0;
1012 }
1013
virtballoon_restore(struct virtio_device * vdev)1014 static int virtballoon_restore(struct virtio_device *vdev)
1015 {
1016 struct virtio_balloon *vb = vdev->priv;
1017 int ret;
1018
1019 ret = init_vqs(vdev->priv);
1020 if (ret)
1021 return ret;
1022
1023 virtio_device_ready(vdev);
1024
1025 if (towards_target(vb))
1026 virtballoon_changed(vdev);
1027 update_balloon_size(vb);
1028 return 0;
1029 }
1030 #endif
1031
virtballoon_validate(struct virtio_device * vdev)1032 static int virtballoon_validate(struct virtio_device *vdev)
1033 {
1034 if (!page_poisoning_enabled())
1035 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1036
1037 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1038 return 0;
1039 }
1040
1041 static unsigned int features[] = {
1042 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1043 VIRTIO_BALLOON_F_STATS_VQ,
1044 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1045 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1046 VIRTIO_BALLOON_F_PAGE_POISON,
1047 };
1048
1049 static struct virtio_driver virtio_balloon_driver = {
1050 .feature_table = features,
1051 .feature_table_size = ARRAY_SIZE(features),
1052 .driver.name = KBUILD_MODNAME,
1053 .driver.owner = THIS_MODULE,
1054 .id_table = id_table,
1055 .validate = virtballoon_validate,
1056 .probe = virtballoon_probe,
1057 .remove = virtballoon_remove,
1058 .config_changed = virtballoon_changed,
1059 #ifdef CONFIG_PM_SLEEP
1060 .freeze = virtballoon_freeze,
1061 .restore = virtballoon_restore,
1062 #endif
1063 };
1064
1065 module_virtio_driver(virtio_balloon_driver);
1066 MODULE_DEVICE_TABLE(virtio, id_table);
1067 MODULE_DESCRIPTION("Virtio balloon driver");
1068 MODULE_LICENSE("GPL");
1069