1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
4 * Tosatti's implementations.
6 * Copyright 2008 Rusty Russell IBM Corporation
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>
19 #include <linux/mount.h>
20 #include <linux/magic.h>
21 #include <linux/pseudo_fs.h>
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
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
32 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
34 /* The order of free page blocks to report to host */
35 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
36 /* The size of a free page block in bytes */
37 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
38 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
39 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
41 #ifdef CONFIG_BALLOON_COMPACTION
42 static struct vfsmount *balloon_mnt;
45 enum virtio_balloon_vq {
46 VIRTIO_BALLOON_VQ_INFLATE,
47 VIRTIO_BALLOON_VQ_DEFLATE,
48 VIRTIO_BALLOON_VQ_STATS,
49 VIRTIO_BALLOON_VQ_FREE_PAGE,
53 enum virtio_balloon_config_read {
54 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
57 struct virtio_balloon {
58 struct virtio_device *vdev;
59 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
61 /* Balloon's own wq for cpu-intensive work items */
62 struct workqueue_struct *balloon_wq;
63 /* The free page reporting work item submitted to the balloon wq */
64 struct work_struct report_free_page_work;
66 /* The balloon servicing is delegated to a freezable workqueue. */
67 struct work_struct update_balloon_stats_work;
68 struct work_struct update_balloon_size_work;
70 /* Prevent updating balloon when it is being canceled. */
71 spinlock_t stop_update_lock;
73 /* Bitmap to indicate if reading the related config fields are needed */
74 unsigned long config_read_bitmap;
76 /* The list of allocated free pages, waiting to be given back to mm */
77 struct list_head free_page_list;
78 spinlock_t free_page_list_lock;
79 /* The number of free page blocks on the above list */
80 unsigned long num_free_page_blocks;
82 * The cmd id received from host.
83 * Read it via virtio_balloon_cmd_id_received to get the latest value
86 u32 cmd_id_received_cache;
87 /* The cmd id that is actively in use */
88 __virtio32 cmd_id_active;
89 /* Buffer to store the stop sign */
90 __virtio32 cmd_id_stop;
92 /* Waiting for host to ack the pages we released. */
93 wait_queue_head_t acked;
95 /* Number of balloon pages we've told the Host we're not using. */
96 unsigned int num_pages;
98 * The pages we've told the Host we're not using are enqueued
99 * at vb_dev_info->pages list.
100 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
101 * to num_pages above.
103 struct balloon_dev_info vb_dev_info;
105 /* Synchronize access/update to this struct virtio_balloon elements */
106 struct mutex balloon_lock;
108 /* The array of pfns we tell the Host about. */
109 unsigned int num_pfns;
110 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
112 /* Memory statistics */
113 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
115 /* To register a shrinker to shrink memory upon memory pressure */
116 struct shrinker shrinker;
119 static struct virtio_device_id id_table[] = {
120 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
124 static u32 page_to_balloon_pfn(struct page *page)
126 unsigned long pfn = page_to_pfn(page);
128 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
129 /* Convert pfn from Linux page size to balloon page size. */
130 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
133 static void balloon_ack(struct virtqueue *vq)
135 struct virtio_balloon *vb = vq->vdev->priv;
140 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
142 struct scatterlist sg;
145 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
147 /* We should always be able to add one buffer to an empty queue. */
148 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
151 /* When host has read buffer, this completes via balloon_ack */
152 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
156 static void set_page_pfns(struct virtio_balloon *vb,
157 __virtio32 pfns[], struct page *page)
161 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
164 * Set balloon pfns pointing at this page.
165 * Note that the first pfn points at start of the page.
167 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
168 pfns[i] = cpu_to_virtio32(vb->vdev,
169 page_to_balloon_pfn(page) + i);
172 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
174 unsigned num_allocated_pages;
179 /* We can only do one array worth at a time. */
180 num = min(num, ARRAY_SIZE(vb->pfns));
182 for (num_pfns = 0; num_pfns < num;
183 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
184 struct page *page = balloon_page_alloc();
187 dev_info_ratelimited(&vb->vdev->dev,
188 "Out of puff! Can't get %u pages\n",
189 VIRTIO_BALLOON_PAGES_PER_PAGE);
190 /* Sleep for at least 1/5 of a second before retry. */
195 balloon_page_push(&pages, page);
198 mutex_lock(&vb->balloon_lock);
202 while ((page = balloon_page_pop(&pages))) {
203 balloon_page_enqueue(&vb->vb_dev_info, page);
205 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
206 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
207 if (!virtio_has_feature(vb->vdev,
208 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
209 adjust_managed_page_count(page, -1);
210 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
213 num_allocated_pages = vb->num_pfns;
214 /* Did we get any? */
215 if (vb->num_pfns != 0)
216 tell_host(vb, vb->inflate_vq);
217 mutex_unlock(&vb->balloon_lock);
219 return num_allocated_pages;
222 static void release_pages_balloon(struct virtio_balloon *vb,
223 struct list_head *pages)
225 struct page *page, *next;
227 list_for_each_entry_safe(page, next, pages, lru) {
228 if (!virtio_has_feature(vb->vdev,
229 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
230 adjust_managed_page_count(page, 1);
231 list_del(&page->lru);
232 put_page(page); /* balloon reference */
236 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
238 unsigned num_freed_pages;
240 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
243 /* We can only do one array worth at a time. */
244 num = min(num, ARRAY_SIZE(vb->pfns));
246 mutex_lock(&vb->balloon_lock);
247 /* We can't release more pages than taken */
248 num = min(num, (size_t)vb->num_pages);
249 for (vb->num_pfns = 0; vb->num_pfns < num;
250 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
251 page = balloon_page_dequeue(vb_dev_info);
254 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
255 list_add(&page->lru, &pages);
256 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
259 num_freed_pages = vb->num_pfns;
262 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
263 * is true, we *have* to do it in this order
265 if (vb->num_pfns != 0)
266 tell_host(vb, vb->deflate_vq);
267 release_pages_balloon(vb, &pages);
268 mutex_unlock(&vb->balloon_lock);
269 return num_freed_pages;
272 static inline void update_stat(struct virtio_balloon *vb, int idx,
275 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
276 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
277 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
280 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
282 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
284 unsigned long events[NR_VM_EVENT_ITEMS];
286 unsigned int idx = 0;
288 unsigned long caches;
290 all_vm_events(events);
293 available = si_mem_available();
294 caches = global_node_page_state(NR_FILE_PAGES);
296 #ifdef CONFIG_VM_EVENT_COUNTERS
297 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
298 pages_to_bytes(events[PSWPIN]));
299 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
300 pages_to_bytes(events[PSWPOUT]));
301 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
302 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
303 #ifdef CONFIG_HUGETLB_PAGE
304 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
305 events[HTLB_BUDDY_PGALLOC]);
306 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
307 events[HTLB_BUDDY_PGALLOC_FAIL]);
310 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
311 pages_to_bytes(i.freeram));
312 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
313 pages_to_bytes(i.totalram));
314 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
315 pages_to_bytes(available));
316 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
317 pages_to_bytes(caches));
323 * While most virtqueues communicate guest-initiated requests to the hypervisor,
324 * the stats queue operates in reverse. The driver initializes the virtqueue
325 * with a single buffer. From that point forward, all conversations consist of
326 * a hypervisor request (a call to this function) which directs us to refill
327 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
328 * we delegate the job to a freezable workqueue that will do the actual work via
329 * stats_handle_request().
331 static void stats_request(struct virtqueue *vq)
333 struct virtio_balloon *vb = vq->vdev->priv;
335 spin_lock(&vb->stop_update_lock);
336 if (!vb->stop_update)
337 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
338 spin_unlock(&vb->stop_update_lock);
341 static void stats_handle_request(struct virtio_balloon *vb)
343 struct virtqueue *vq;
344 struct scatterlist sg;
345 unsigned int len, num_stats;
347 num_stats = update_balloon_stats(vb);
350 if (!virtqueue_get_buf(vq, &len))
352 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
353 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
357 static inline s64 towards_target(struct virtio_balloon *vb)
362 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
365 /* Legacy balloon config space is LE, unlike all other devices. */
366 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
367 num_pages = le32_to_cpu((__force __le32)num_pages);
370 return target - vb->num_pages;
373 /* Gives back @num_to_return blocks of free pages to mm. */
374 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
375 unsigned long num_to_return)
378 unsigned long num_returned;
380 spin_lock_irq(&vb->free_page_list_lock);
381 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
382 page = balloon_page_pop(&vb->free_page_list);
385 free_pages((unsigned long)page_address(page),
386 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
388 vb->num_free_page_blocks -= num_returned;
389 spin_unlock_irq(&vb->free_page_list_lock);
394 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
396 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
399 /* No need to queue the work if the bit was already set. */
400 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
401 &vb->config_read_bitmap))
404 queue_work(vb->balloon_wq, &vb->report_free_page_work);
407 static void virtballoon_changed(struct virtio_device *vdev)
409 struct virtio_balloon *vb = vdev->priv;
412 spin_lock_irqsave(&vb->stop_update_lock, flags);
413 if (!vb->stop_update) {
414 queue_work(system_freezable_wq,
415 &vb->update_balloon_size_work);
416 virtio_balloon_queue_free_page_work(vb);
418 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
421 static void update_balloon_size(struct virtio_balloon *vb)
423 u32 actual = vb->num_pages;
425 /* Legacy balloon config space is LE, unlike all other devices. */
426 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
427 actual = (__force u32)cpu_to_le32(actual);
429 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
433 static void update_balloon_stats_func(struct work_struct *work)
435 struct virtio_balloon *vb;
437 vb = container_of(work, struct virtio_balloon,
438 update_balloon_stats_work);
439 stats_handle_request(vb);
442 static void update_balloon_size_func(struct work_struct *work)
444 struct virtio_balloon *vb;
447 vb = container_of(work, struct virtio_balloon,
448 update_balloon_size_work);
449 diff = towards_target(vb);
455 diff -= fill_balloon(vb, diff);
457 diff += leak_balloon(vb, -diff);
458 update_balloon_size(vb);
461 queue_work(system_freezable_wq, work);
464 static int init_vqs(struct virtio_balloon *vb)
466 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
467 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
468 const char *names[VIRTIO_BALLOON_VQ_MAX];
472 * Inflateq and deflateq are used unconditionally. The names[]
473 * will be NULL if the related feature is not enabled, which will
474 * cause no allocation for the corresponding virtqueue in find_vqs.
476 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
477 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
478 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
479 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
480 callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
481 names[VIRTIO_BALLOON_VQ_STATS] = NULL;
482 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
483 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
485 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
486 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
487 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
490 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
491 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
492 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
495 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
496 vqs, callbacks, names, NULL, NULL);
500 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
501 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
502 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
503 struct scatterlist sg;
504 unsigned int num_stats;
505 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
508 * Prime this virtqueue with one buffer so the hypervisor can
509 * use it to signal us later (it can't be broken yet!).
511 num_stats = update_balloon_stats(vb);
513 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
514 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
517 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
521 virtqueue_kick(vb->stats_vq);
524 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
525 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
530 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
532 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
533 &vb->config_read_bitmap))
534 virtio_cread(vb->vdev, struct virtio_balloon_config,
535 free_page_report_cmd_id,
536 &vb->cmd_id_received_cache);
538 return vb->cmd_id_received_cache;
541 static int send_cmd_id_start(struct virtio_balloon *vb)
543 struct scatterlist sg;
544 struct virtqueue *vq = vb->free_page_vq;
547 /* Detach all the used buffers from the vq */
548 while (virtqueue_get_buf(vq, &unused))
551 vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
552 virtio_balloon_cmd_id_received(vb));
553 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
554 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
560 static int send_cmd_id_stop(struct virtio_balloon *vb)
562 struct scatterlist sg;
563 struct virtqueue *vq = vb->free_page_vq;
566 /* Detach all the used buffers from the vq */
567 while (virtqueue_get_buf(vq, &unused))
570 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
571 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
577 static int get_free_page_and_send(struct virtio_balloon *vb)
579 struct virtqueue *vq = vb->free_page_vq;
581 struct scatterlist sg;
585 /* Detach all the used buffers from the vq */
586 while (virtqueue_get_buf(vq, &unused))
589 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
590 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
592 * When the allocation returns NULL, it indicates that we have got all
593 * the possible free pages, so return -EINTR to stop.
598 p = page_address(page);
599 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
600 /* There is always 1 entry reserved for the cmd id to use. */
601 if (vq->num_free > 1) {
602 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
604 free_pages((unsigned long)p,
605 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
609 spin_lock_irq(&vb->free_page_list_lock);
610 balloon_page_push(&vb->free_page_list, page);
611 vb->num_free_page_blocks++;
612 spin_unlock_irq(&vb->free_page_list_lock);
615 * The vq has no available entry to add this page block, so
618 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
624 static int send_free_pages(struct virtio_balloon *vb)
631 * If a stop id or a new cmd id was just received from host,
632 * stop the reporting.
634 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
635 if (unlikely(cmd_id_active !=
636 virtio_balloon_cmd_id_received(vb)))
640 * The free page blocks are allocated and sent to host one by
643 err = get_free_page_and_send(vb);
646 else if (unlikely(err))
653 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
656 struct device *dev = &vb->vdev->dev;
658 /* Start by sending the received cmd id to host with an outbuf. */
659 err = send_cmd_id_start(vb);
661 dev_err(dev, "Failed to send a start id, err = %d\n", err);
663 err = send_free_pages(vb);
665 dev_err(dev, "Failed to send a free page, err = %d\n", err);
667 /* End by sending a stop id to host with an outbuf. */
668 err = send_cmd_id_stop(vb);
670 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
673 static void report_free_page_func(struct work_struct *work)
675 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
676 report_free_page_work);
679 cmd_id_received = virtio_balloon_cmd_id_received(vb);
680 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
681 /* Pass ULONG_MAX to give back all the free pages */
682 return_free_pages_to_mm(vb, ULONG_MAX);
683 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
685 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
686 virtio_balloon_report_free_page(vb);
690 #ifdef CONFIG_BALLOON_COMPACTION
692 * virtballoon_migratepage - perform the balloon page migration on behalf of
693 * a compation thread. (called under page lock)
694 * @vb_dev_info: the balloon device
695 * @newpage: page that will replace the isolated page after migration finishes.
696 * @page : the isolated (old) page that is about to be migrated to newpage.
697 * @mode : compaction mode -- not used for balloon page migration.
699 * After a ballooned page gets isolated by compaction procedures, this is the
700 * function that performs the page migration on behalf of a compaction thread
701 * The page migration for virtio balloon is done in a simple swap fashion which
702 * follows these two macro steps:
703 * 1) insert newpage into vb->pages list and update the host about it;
704 * 2) update the host about the old page removed from vb->pages list;
706 * This function preforms the balloon page migration task.
707 * Called through balloon_mapping->a_ops->migratepage
709 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
710 struct page *newpage, struct page *page, enum migrate_mode mode)
712 struct virtio_balloon *vb = container_of(vb_dev_info,
713 struct virtio_balloon, vb_dev_info);
717 * In order to avoid lock contention while migrating pages concurrently
718 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
719 * this turn, as it is easier to retry the page migration later.
720 * This also prevents fill_balloon() getting stuck into a mutex
721 * recursion in the case it ends up triggering memory compaction
722 * while it is attempting to inflate the ballon.
724 if (!mutex_trylock(&vb->balloon_lock))
727 get_page(newpage); /* balloon reference */
730 * When we migrate a page to a different zone and adjusted the
731 * managed page count when inflating, we have to fixup the count of
732 * both involved zones.
734 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
735 page_zone(page) != page_zone(newpage)) {
736 adjust_managed_page_count(page, 1);
737 adjust_managed_page_count(newpage, -1);
740 /* balloon's page migration 1st step -- inflate "newpage" */
741 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
742 balloon_page_insert(vb_dev_info, newpage);
743 vb_dev_info->isolated_pages--;
744 __count_vm_event(BALLOON_MIGRATE);
745 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
746 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
747 set_page_pfns(vb, vb->pfns, newpage);
748 tell_host(vb, vb->inflate_vq);
750 /* balloon's page migration 2nd step -- deflate "page" */
751 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
752 balloon_page_delete(page);
753 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
754 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
755 set_page_pfns(vb, vb->pfns, page);
756 tell_host(vb, vb->deflate_vq);
758 mutex_unlock(&vb->balloon_lock);
760 put_page(page); /* balloon reference */
762 return MIGRATEPAGE_SUCCESS;
765 static int balloon_init_fs_context(struct fs_context *fc)
767 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
770 static struct file_system_type balloon_fs = {
771 .name = "balloon-kvm",
772 .init_fs_context = balloon_init_fs_context,
773 .kill_sb = kill_anon_super,
776 #endif /* CONFIG_BALLOON_COMPACTION */
778 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
779 unsigned long pages_to_free)
781 unsigned long blocks_to_free, blocks_freed;
783 pages_to_free = round_up(pages_to_free,
784 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
785 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
786 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
788 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
791 static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
792 unsigned long pages_to_free)
794 return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
795 VIRTIO_BALLOON_PAGES_PER_PAGE;
798 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
799 unsigned long pages_to_free)
801 unsigned long pages_freed = 0;
804 * One invocation of leak_balloon can deflate at most
805 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
806 * multiple times to deflate pages till reaching pages_to_free.
808 while (vb->num_pages && pages_freed < pages_to_free)
809 pages_freed += leak_balloon_pages(vb,
810 pages_to_free - pages_freed);
812 update_balloon_size(vb);
817 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
818 struct shrink_control *sc)
820 unsigned long pages_to_free, pages_freed = 0;
821 struct virtio_balloon *vb = container_of(shrinker,
822 struct virtio_balloon, shrinker);
824 pages_to_free = sc->nr_to_scan;
826 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
827 pages_freed = shrink_free_pages(vb, pages_to_free);
829 if (pages_freed >= pages_to_free)
832 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
837 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
838 struct shrink_control *sc)
840 struct virtio_balloon *vb = container_of(shrinker,
841 struct virtio_balloon, shrinker);
844 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
845 count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
850 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
852 unregister_shrinker(&vb->shrinker);
855 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
857 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
858 vb->shrinker.count_objects = virtio_balloon_shrinker_count;
859 vb->shrinker.seeks = DEFAULT_SEEKS;
861 return register_shrinker(&vb->shrinker);
864 static int virtballoon_probe(struct virtio_device *vdev)
866 struct virtio_balloon *vb;
870 if (!vdev->config->get) {
871 dev_err(&vdev->dev, "%s failure: config access disabled\n",
876 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
882 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
883 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
884 spin_lock_init(&vb->stop_update_lock);
885 mutex_init(&vb->balloon_lock);
886 init_waitqueue_head(&vb->acked);
889 balloon_devinfo_init(&vb->vb_dev_info);
895 #ifdef CONFIG_BALLOON_COMPACTION
896 balloon_mnt = kern_mount(&balloon_fs);
897 if (IS_ERR(balloon_mnt)) {
898 err = PTR_ERR(balloon_mnt);
902 vb->vb_dev_info.migratepage = virtballoon_migratepage;
903 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
904 if (IS_ERR(vb->vb_dev_info.inode)) {
905 err = PTR_ERR(vb->vb_dev_info.inode);
906 goto out_kern_unmount;
908 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
910 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
912 * There is always one entry reserved for cmd id, so the ring
913 * size needs to be at least two to report free page hints.
915 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
919 vb->balloon_wq = alloc_workqueue("balloon-wq",
920 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
921 if (!vb->balloon_wq) {
925 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
926 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
927 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
928 VIRTIO_BALLOON_CMD_ID_STOP);
929 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
930 VIRTIO_BALLOON_CMD_ID_STOP);
931 spin_lock_init(&vb->free_page_list_lock);
932 INIT_LIST_HEAD(&vb->free_page_list);
933 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
934 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
935 virtio_cwrite(vb->vdev, struct virtio_balloon_config,
936 poison_val, &poison_val);
940 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
941 * shrinker needs to be registered to relieve memory pressure.
943 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
944 err = virtio_balloon_register_shrinker(vb);
946 goto out_del_balloon_wq;
948 virtio_device_ready(vdev);
950 if (towards_target(vb))
951 virtballoon_changed(vdev);
955 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
956 destroy_workqueue(vb->balloon_wq);
958 #ifdef CONFIG_BALLOON_COMPACTION
959 iput(vb->vb_dev_info.inode);
961 kern_unmount(balloon_mnt);
964 vdev->config->del_vqs(vdev);
971 static void remove_common(struct virtio_balloon *vb)
973 /* There might be pages left in the balloon: free them. */
974 while (vb->num_pages)
975 leak_balloon(vb, vb->num_pages);
976 update_balloon_size(vb);
978 /* There might be free pages that are being reported: release them. */
979 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
980 return_free_pages_to_mm(vb, ULONG_MAX);
982 /* Now we reset the device so we can clean up the queues. */
983 vb->vdev->config->reset(vb->vdev);
985 vb->vdev->config->del_vqs(vb->vdev);
988 static void virtballoon_remove(struct virtio_device *vdev)
990 struct virtio_balloon *vb = vdev->priv;
992 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
993 virtio_balloon_unregister_shrinker(vb);
994 spin_lock_irq(&vb->stop_update_lock);
995 vb->stop_update = true;
996 spin_unlock_irq(&vb->stop_update_lock);
997 cancel_work_sync(&vb->update_balloon_size_work);
998 cancel_work_sync(&vb->update_balloon_stats_work);
1000 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1001 cancel_work_sync(&vb->report_free_page_work);
1002 destroy_workqueue(vb->balloon_wq);
1006 #ifdef CONFIG_BALLOON_COMPACTION
1007 if (vb->vb_dev_info.inode)
1008 iput(vb->vb_dev_info.inode);
1010 kern_unmount(balloon_mnt);
1015 #ifdef CONFIG_PM_SLEEP
1016 static int virtballoon_freeze(struct virtio_device *vdev)
1018 struct virtio_balloon *vb = vdev->priv;
1021 * The workqueue is already frozen by the PM core before this
1022 * function is called.
1028 static int virtballoon_restore(struct virtio_device *vdev)
1030 struct virtio_balloon *vb = vdev->priv;
1033 ret = init_vqs(vdev->priv);
1037 virtio_device_ready(vdev);
1039 if (towards_target(vb))
1040 virtballoon_changed(vdev);
1041 update_balloon_size(vb);
1046 static int virtballoon_validate(struct virtio_device *vdev)
1048 if (!page_poisoning_enabled())
1049 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1051 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1055 static unsigned int features[] = {
1056 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1057 VIRTIO_BALLOON_F_STATS_VQ,
1058 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1059 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1060 VIRTIO_BALLOON_F_PAGE_POISON,
1063 static struct virtio_driver virtio_balloon_driver = {
1064 .feature_table = features,
1065 .feature_table_size = ARRAY_SIZE(features),
1066 .driver.name = KBUILD_MODNAME,
1067 .driver.owner = THIS_MODULE,
1068 .id_table = id_table,
1069 .validate = virtballoon_validate,
1070 .probe = virtballoon_probe,
1071 .remove = virtballoon_remove,
1072 .config_changed = virtballoon_changed,
1073 #ifdef CONFIG_PM_SLEEP
1074 .freeze = virtballoon_freeze,
1075 .restore = virtballoon_restore,
1079 module_virtio_driver(virtio_balloon_driver);
1080 MODULE_DEVICE_TABLE(virtio, id_table);
1081 MODULE_DESCRIPTION("Virtio balloon driver");
1082 MODULE_LICENSE("GPL");