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/oom.h>
18 #include <linux/wait.h>
20 #include <linux/mount.h>
21 #include <linux/magic.h>
22 #include <linux/pseudo_fs.h>
23 #include <linux/page_reporting.h>
26 * Balloon device works in 4K page units. So each page is pointed to by
27 * multiple balloon pages. All memory counters in this driver are in balloon
30 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
31 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
32 /* Maximum number of (4k) pages to deflate on OOM notifications. */
33 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
34 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
36 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
38 /* The order of free page blocks to report to host */
39 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
40 /* The size of a free page block in bytes */
41 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
42 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
43 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
45 #ifdef CONFIG_BALLOON_COMPACTION
46 static struct vfsmount *balloon_mnt;
49 enum virtio_balloon_vq {
50 VIRTIO_BALLOON_VQ_INFLATE,
51 VIRTIO_BALLOON_VQ_DEFLATE,
52 VIRTIO_BALLOON_VQ_STATS,
53 VIRTIO_BALLOON_VQ_FREE_PAGE,
54 VIRTIO_BALLOON_VQ_REPORTING,
58 enum virtio_balloon_config_read {
59 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
62 struct virtio_balloon {
63 struct virtio_device *vdev;
64 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
66 /* Balloon's own wq for cpu-intensive work items */
67 struct workqueue_struct *balloon_wq;
68 /* The free page reporting work item submitted to the balloon wq */
69 struct work_struct report_free_page_work;
71 /* The balloon servicing is delegated to a freezable workqueue. */
72 struct work_struct update_balloon_stats_work;
73 struct work_struct update_balloon_size_work;
75 /* Prevent updating balloon when it is being canceled. */
76 spinlock_t stop_update_lock;
78 /* Bitmap to indicate if reading the related config fields are needed */
79 unsigned long config_read_bitmap;
81 /* The list of allocated free pages, waiting to be given back to mm */
82 struct list_head free_page_list;
83 spinlock_t free_page_list_lock;
84 /* The number of free page blocks on the above list */
85 unsigned long num_free_page_blocks;
87 * The cmd id received from host.
88 * Read it via virtio_balloon_cmd_id_received to get the latest value
91 u32 cmd_id_received_cache;
92 /* The cmd id that is actively in use */
93 __virtio32 cmd_id_active;
94 /* Buffer to store the stop sign */
95 __virtio32 cmd_id_stop;
97 /* Waiting for host to ack the pages we released. */
98 wait_queue_head_t acked;
100 /* Number of balloon pages we've told the Host we're not using. */
101 unsigned int num_pages;
103 * The pages we've told the Host we're not using are enqueued
104 * at vb_dev_info->pages list.
105 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
106 * to num_pages above.
108 struct balloon_dev_info vb_dev_info;
110 /* Synchronize access/update to this struct virtio_balloon elements */
111 struct mutex balloon_lock;
113 /* The array of pfns we tell the Host about. */
114 unsigned int num_pfns;
115 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
117 /* Memory statistics */
118 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
120 /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
121 struct shrinker shrinker;
123 /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
124 struct notifier_block oom_nb;
126 /* Free page reporting device */
127 struct virtqueue *reporting_vq;
128 struct page_reporting_dev_info pr_dev_info;
131 static const struct virtio_device_id id_table[] = {
132 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
136 static u32 page_to_balloon_pfn(struct page *page)
138 unsigned long pfn = page_to_pfn(page);
140 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
141 /* Convert pfn from Linux page size to balloon page size. */
142 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
145 static void balloon_ack(struct virtqueue *vq)
147 struct virtio_balloon *vb = vq->vdev->priv;
152 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
154 struct scatterlist sg;
157 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
159 /* We should always be able to add one buffer to an empty queue. */
160 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
163 /* When host has read buffer, this completes via balloon_ack */
164 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
168 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
169 struct scatterlist *sg, unsigned int nents)
171 struct virtio_balloon *vb =
172 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
173 struct virtqueue *vq = vb->reporting_vq;
174 unsigned int unused, err;
176 /* We should always be able to add these buffers to an empty queue. */
177 err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
180 * In the extremely unlikely case that something has occurred and we
181 * are able to trigger an error we will simply display a warning
182 * and exit without actually processing the pages.
184 if (WARN_ON_ONCE(err))
189 /* When host has read buffer, this completes via balloon_ack */
190 wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
195 static void set_page_pfns(struct virtio_balloon *vb,
196 __virtio32 pfns[], struct page *page)
200 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
203 * Set balloon pfns pointing at this page.
204 * Note that the first pfn points at start of the page.
206 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
207 pfns[i] = cpu_to_virtio32(vb->vdev,
208 page_to_balloon_pfn(page) + i);
211 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
213 unsigned num_allocated_pages;
218 /* We can only do one array worth at a time. */
219 num = min(num, ARRAY_SIZE(vb->pfns));
221 for (num_pfns = 0; num_pfns < num;
222 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
223 struct page *page = balloon_page_alloc();
226 dev_info_ratelimited(&vb->vdev->dev,
227 "Out of puff! Can't get %u pages\n",
228 VIRTIO_BALLOON_PAGES_PER_PAGE);
229 /* Sleep for at least 1/5 of a second before retry. */
234 balloon_page_push(&pages, page);
237 mutex_lock(&vb->balloon_lock);
241 while ((page = balloon_page_pop(&pages))) {
242 balloon_page_enqueue(&vb->vb_dev_info, page);
244 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
245 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
246 if (!virtio_has_feature(vb->vdev,
247 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
248 adjust_managed_page_count(page, -1);
249 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
252 num_allocated_pages = vb->num_pfns;
253 /* Did we get any? */
254 if (vb->num_pfns != 0)
255 tell_host(vb, vb->inflate_vq);
256 mutex_unlock(&vb->balloon_lock);
258 return num_allocated_pages;
261 static void release_pages_balloon(struct virtio_balloon *vb,
262 struct list_head *pages)
264 struct page *page, *next;
266 list_for_each_entry_safe(page, next, pages, lru) {
267 if (!virtio_has_feature(vb->vdev,
268 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
269 adjust_managed_page_count(page, 1);
270 list_del(&page->lru);
271 put_page(page); /* balloon reference */
275 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
277 unsigned num_freed_pages;
279 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
282 /* We can only do one array worth at a time. */
283 num = min(num, ARRAY_SIZE(vb->pfns));
285 mutex_lock(&vb->balloon_lock);
286 /* We can't release more pages than taken */
287 num = min(num, (size_t)vb->num_pages);
288 for (vb->num_pfns = 0; vb->num_pfns < num;
289 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
290 page = balloon_page_dequeue(vb_dev_info);
293 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
294 list_add(&page->lru, &pages);
295 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
298 num_freed_pages = vb->num_pfns;
301 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
302 * is true, we *have* to do it in this order
304 if (vb->num_pfns != 0)
305 tell_host(vb, vb->deflate_vq);
306 release_pages_balloon(vb, &pages);
307 mutex_unlock(&vb->balloon_lock);
308 return num_freed_pages;
311 static inline void update_stat(struct virtio_balloon *vb, int idx,
314 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
315 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
316 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
319 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
321 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
323 unsigned long events[NR_VM_EVENT_ITEMS];
325 unsigned int idx = 0;
327 unsigned long caches;
329 all_vm_events(events);
332 available = si_mem_available();
333 caches = global_node_page_state(NR_FILE_PAGES);
335 #ifdef CONFIG_VM_EVENT_COUNTERS
336 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
337 pages_to_bytes(events[PSWPIN]));
338 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
339 pages_to_bytes(events[PSWPOUT]));
340 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
341 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
342 #ifdef CONFIG_HUGETLB_PAGE
343 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
344 events[HTLB_BUDDY_PGALLOC]);
345 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
346 events[HTLB_BUDDY_PGALLOC_FAIL]);
349 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
350 pages_to_bytes(i.freeram));
351 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
352 pages_to_bytes(i.totalram));
353 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
354 pages_to_bytes(available));
355 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
356 pages_to_bytes(caches));
362 * While most virtqueues communicate guest-initiated requests to the hypervisor,
363 * the stats queue operates in reverse. The driver initializes the virtqueue
364 * with a single buffer. From that point forward, all conversations consist of
365 * a hypervisor request (a call to this function) which directs us to refill
366 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
367 * we delegate the job to a freezable workqueue that will do the actual work via
368 * stats_handle_request().
370 static void stats_request(struct virtqueue *vq)
372 struct virtio_balloon *vb = vq->vdev->priv;
374 spin_lock(&vb->stop_update_lock);
375 if (!vb->stop_update)
376 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
377 spin_unlock(&vb->stop_update_lock);
380 static void stats_handle_request(struct virtio_balloon *vb)
382 struct virtqueue *vq;
383 struct scatterlist sg;
384 unsigned int len, num_stats;
386 num_stats = update_balloon_stats(vb);
389 if (!virtqueue_get_buf(vq, &len))
391 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
392 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
396 static inline s64 towards_target(struct virtio_balloon *vb)
401 /* Legacy balloon config space is LE, unlike all other devices. */
402 virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
406 * Aligned up to guest page size to avoid inflating and deflating
409 target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
410 return target - vb->num_pages;
413 /* Gives back @num_to_return blocks of free pages to mm. */
414 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
415 unsigned long num_to_return)
418 unsigned long num_returned;
420 spin_lock_irq(&vb->free_page_list_lock);
421 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
422 page = balloon_page_pop(&vb->free_page_list);
425 free_pages((unsigned long)page_address(page),
426 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
428 vb->num_free_page_blocks -= num_returned;
429 spin_unlock_irq(&vb->free_page_list_lock);
434 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
436 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
439 /* No need to queue the work if the bit was already set. */
440 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
441 &vb->config_read_bitmap))
444 queue_work(vb->balloon_wq, &vb->report_free_page_work);
447 static void virtballoon_changed(struct virtio_device *vdev)
449 struct virtio_balloon *vb = vdev->priv;
452 spin_lock_irqsave(&vb->stop_update_lock, flags);
453 if (!vb->stop_update) {
454 queue_work(system_freezable_wq,
455 &vb->update_balloon_size_work);
456 virtio_balloon_queue_free_page_work(vb);
458 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
461 static void update_balloon_size(struct virtio_balloon *vb)
463 u32 actual = vb->num_pages;
465 /* Legacy balloon config space is LE, unlike all other devices. */
466 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
470 static void update_balloon_stats_func(struct work_struct *work)
472 struct virtio_balloon *vb;
474 vb = container_of(work, struct virtio_balloon,
475 update_balloon_stats_work);
476 stats_handle_request(vb);
479 static void update_balloon_size_func(struct work_struct *work)
481 struct virtio_balloon *vb;
484 vb = container_of(work, struct virtio_balloon,
485 update_balloon_size_work);
486 diff = towards_target(vb);
492 diff -= fill_balloon(vb, diff);
494 diff += leak_balloon(vb, -diff);
495 update_balloon_size(vb);
498 queue_work(system_freezable_wq, work);
501 static int init_vqs(struct virtio_balloon *vb)
503 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
504 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
505 const char *names[VIRTIO_BALLOON_VQ_MAX];
509 * Inflateq and deflateq are used unconditionally. The names[]
510 * will be NULL if the related feature is not enabled, which will
511 * cause no allocation for the corresponding virtqueue in find_vqs.
513 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
514 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
515 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
516 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
517 callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
518 names[VIRTIO_BALLOON_VQ_STATS] = NULL;
519 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
520 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
521 names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
523 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
524 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
525 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
528 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
529 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
530 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
533 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
534 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
535 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
538 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
539 vqs, callbacks, names, NULL, NULL);
543 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
544 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
545 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
546 struct scatterlist sg;
547 unsigned int num_stats;
548 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
551 * Prime this virtqueue with one buffer so the hypervisor can
552 * use it to signal us later (it can't be broken yet!).
554 num_stats = update_balloon_stats(vb);
556 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
557 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
560 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
564 virtqueue_kick(vb->stats_vq);
567 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
568 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
570 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
571 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
576 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
578 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
579 &vb->config_read_bitmap)) {
580 /* Legacy balloon config space is LE, unlike all other devices. */
581 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
582 free_page_hint_cmd_id,
583 &vb->cmd_id_received_cache);
586 return vb->cmd_id_received_cache;
589 static int send_cmd_id_start(struct virtio_balloon *vb)
591 struct scatterlist sg;
592 struct virtqueue *vq = vb->free_page_vq;
595 /* Detach all the used buffers from the vq */
596 while (virtqueue_get_buf(vq, &unused))
599 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
600 virtio_balloon_cmd_id_received(vb));
601 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
602 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
608 static int send_cmd_id_stop(struct virtio_balloon *vb)
610 struct scatterlist sg;
611 struct virtqueue *vq = vb->free_page_vq;
614 /* Detach all the used buffers from the vq */
615 while (virtqueue_get_buf(vq, &unused))
618 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
619 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
625 static int get_free_page_and_send(struct virtio_balloon *vb)
627 struct virtqueue *vq = vb->free_page_vq;
629 struct scatterlist sg;
633 /* Detach all the used buffers from the vq */
634 while (virtqueue_get_buf(vq, &unused))
637 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
638 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
640 * When the allocation returns NULL, it indicates that we have got all
641 * the possible free pages, so return -EINTR to stop.
646 p = page_address(page);
647 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
648 /* There is always 1 entry reserved for the cmd id to use. */
649 if (vq->num_free > 1) {
650 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
652 free_pages((unsigned long)p,
653 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
657 spin_lock_irq(&vb->free_page_list_lock);
658 balloon_page_push(&vb->free_page_list, page);
659 vb->num_free_page_blocks++;
660 spin_unlock_irq(&vb->free_page_list_lock);
663 * The vq has no available entry to add this page block, so
666 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
672 static int send_free_pages(struct virtio_balloon *vb)
679 * If a stop id or a new cmd id was just received from host,
680 * stop the reporting.
682 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
683 if (unlikely(cmd_id_active !=
684 virtio_balloon_cmd_id_received(vb)))
688 * The free page blocks are allocated and sent to host one by
691 err = get_free_page_and_send(vb);
694 else if (unlikely(err))
701 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
704 struct device *dev = &vb->vdev->dev;
706 /* Start by sending the received cmd id to host with an outbuf. */
707 err = send_cmd_id_start(vb);
709 dev_err(dev, "Failed to send a start id, err = %d\n", err);
711 err = send_free_pages(vb);
713 dev_err(dev, "Failed to send a free page, err = %d\n", err);
715 /* End by sending a stop id to host with an outbuf. */
716 err = send_cmd_id_stop(vb);
718 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
721 static void report_free_page_func(struct work_struct *work)
723 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
724 report_free_page_work);
727 cmd_id_received = virtio_balloon_cmd_id_received(vb);
728 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
729 /* Pass ULONG_MAX to give back all the free pages */
730 return_free_pages_to_mm(vb, ULONG_MAX);
731 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
733 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
734 virtio_balloon_report_free_page(vb);
738 #ifdef CONFIG_BALLOON_COMPACTION
740 * virtballoon_migratepage - perform the balloon page migration on behalf of
741 * a compation thread. (called under page lock)
742 * @vb_dev_info: the balloon device
743 * @newpage: page that will replace the isolated page after migration finishes.
744 * @page : the isolated (old) page that is about to be migrated to newpage.
745 * @mode : compaction mode -- not used for balloon page migration.
747 * After a ballooned page gets isolated by compaction procedures, this is the
748 * function that performs the page migration on behalf of a compaction thread
749 * The page migration for virtio balloon is done in a simple swap fashion which
750 * follows these two macro steps:
751 * 1) insert newpage into vb->pages list and update the host about it;
752 * 2) update the host about the old page removed from vb->pages list;
754 * This function preforms the balloon page migration task.
755 * Called through balloon_mapping->a_ops->migratepage
757 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
758 struct page *newpage, struct page *page, enum migrate_mode mode)
760 struct virtio_balloon *vb = container_of(vb_dev_info,
761 struct virtio_balloon, vb_dev_info);
765 * In order to avoid lock contention while migrating pages concurrently
766 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
767 * this turn, as it is easier to retry the page migration later.
768 * This also prevents fill_balloon() getting stuck into a mutex
769 * recursion in the case it ends up triggering memory compaction
770 * while it is attempting to inflate the ballon.
772 if (!mutex_trylock(&vb->balloon_lock))
775 get_page(newpage); /* balloon reference */
778 * When we migrate a page to a different zone and adjusted the
779 * managed page count when inflating, we have to fixup the count of
780 * both involved zones.
782 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
783 page_zone(page) != page_zone(newpage)) {
784 adjust_managed_page_count(page, 1);
785 adjust_managed_page_count(newpage, -1);
788 /* balloon's page migration 1st step -- inflate "newpage" */
789 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
790 balloon_page_insert(vb_dev_info, newpage);
791 vb_dev_info->isolated_pages--;
792 __count_vm_event(BALLOON_MIGRATE);
793 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
794 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
795 set_page_pfns(vb, vb->pfns, newpage);
796 tell_host(vb, vb->inflate_vq);
798 /* balloon's page migration 2nd step -- deflate "page" */
799 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
800 balloon_page_delete(page);
801 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
802 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
803 set_page_pfns(vb, vb->pfns, page);
804 tell_host(vb, vb->deflate_vq);
806 mutex_unlock(&vb->balloon_lock);
808 put_page(page); /* balloon reference */
810 return MIGRATEPAGE_SUCCESS;
813 static int balloon_init_fs_context(struct fs_context *fc)
815 return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
818 static struct file_system_type balloon_fs = {
819 .name = "balloon-kvm",
820 .init_fs_context = balloon_init_fs_context,
821 .kill_sb = kill_anon_super,
824 #endif /* CONFIG_BALLOON_COMPACTION */
826 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
827 unsigned long pages_to_free)
829 unsigned long blocks_to_free, blocks_freed;
831 pages_to_free = round_up(pages_to_free,
832 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
833 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
834 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
836 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
839 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
840 struct shrink_control *sc)
842 struct virtio_balloon *vb = container_of(shrinker,
843 struct virtio_balloon, shrinker);
845 return shrink_free_pages(vb, sc->nr_to_scan);
848 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
849 struct shrink_control *sc)
851 struct virtio_balloon *vb = container_of(shrinker,
852 struct virtio_balloon, shrinker);
854 return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
857 static int virtio_balloon_oom_notify(struct notifier_block *nb,
858 unsigned long dummy, void *parm)
860 struct virtio_balloon *vb = container_of(nb,
861 struct virtio_balloon, oom_nb);
862 unsigned long *freed = parm;
864 *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
865 VIRTIO_BALLOON_PAGES_PER_PAGE;
866 update_balloon_size(vb);
871 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
873 unregister_shrinker(&vb->shrinker);
876 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
878 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
879 vb->shrinker.count_objects = virtio_balloon_shrinker_count;
880 vb->shrinker.seeks = DEFAULT_SEEKS;
882 return register_shrinker(&vb->shrinker);
885 static int virtballoon_probe(struct virtio_device *vdev)
887 struct virtio_balloon *vb;
890 if (!vdev->config->get) {
891 dev_err(&vdev->dev, "%s failure: config access disabled\n",
896 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
902 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
903 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
904 spin_lock_init(&vb->stop_update_lock);
905 mutex_init(&vb->balloon_lock);
906 init_waitqueue_head(&vb->acked);
909 balloon_devinfo_init(&vb->vb_dev_info);
915 #ifdef CONFIG_BALLOON_COMPACTION
916 balloon_mnt = kern_mount(&balloon_fs);
917 if (IS_ERR(balloon_mnt)) {
918 err = PTR_ERR(balloon_mnt);
922 vb->vb_dev_info.migratepage = virtballoon_migratepage;
923 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
924 if (IS_ERR(vb->vb_dev_info.inode)) {
925 err = PTR_ERR(vb->vb_dev_info.inode);
926 goto out_kern_unmount;
928 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
930 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
932 * There is always one entry reserved for cmd id, so the ring
933 * size needs to be at least two to report free page hints.
935 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
939 vb->balloon_wq = alloc_workqueue("balloon-wq",
940 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
941 if (!vb->balloon_wq) {
945 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
946 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
947 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
948 VIRTIO_BALLOON_CMD_ID_STOP);
949 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
950 VIRTIO_BALLOON_CMD_ID_STOP);
951 spin_lock_init(&vb->free_page_list_lock);
952 INIT_LIST_HEAD(&vb->free_page_list);
954 * We're allowed to reuse any free pages, even if they are
955 * still to be processed by the host.
957 err = virtio_balloon_register_shrinker(vb);
959 goto out_del_balloon_wq;
962 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
963 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
964 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
965 err = register_oom_notifier(&vb->oom_nb);
967 goto out_unregister_shrinker;
970 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
971 /* Start with poison val of 0 representing general init */
972 __u32 poison_val = 0;
975 * Let the hypervisor know that we are expecting a
976 * specific value to be written back in balloon pages.
978 * If the PAGE_POISON value was larger than a byte we would
979 * need to byte swap poison_val here to guarantee it is
980 * little-endian. However for now it is a single byte so we
983 if (!want_init_on_free())
984 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
986 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
987 poison_val, &poison_val);
990 vb->pr_dev_info.report = virtballoon_free_page_report;
991 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
992 unsigned int capacity;
994 capacity = virtqueue_get_vring_size(vb->reporting_vq);
995 if (capacity < PAGE_REPORTING_CAPACITY) {
997 goto out_unregister_oom;
1000 err = page_reporting_register(&vb->pr_dev_info);
1002 goto out_unregister_oom;
1005 virtio_device_ready(vdev);
1007 if (towards_target(vb))
1008 virtballoon_changed(vdev);
1012 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1013 unregister_oom_notifier(&vb->oom_nb);
1014 out_unregister_shrinker:
1015 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1016 virtio_balloon_unregister_shrinker(vb);
1018 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1019 destroy_workqueue(vb->balloon_wq);
1021 #ifdef CONFIG_BALLOON_COMPACTION
1022 iput(vb->vb_dev_info.inode);
1024 kern_unmount(balloon_mnt);
1027 vdev->config->del_vqs(vdev);
1034 static void remove_common(struct virtio_balloon *vb)
1036 /* There might be pages left in the balloon: free them. */
1037 while (vb->num_pages)
1038 leak_balloon(vb, vb->num_pages);
1039 update_balloon_size(vb);
1041 /* There might be free pages that are being reported: release them. */
1042 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1043 return_free_pages_to_mm(vb, ULONG_MAX);
1045 /* Now we reset the device so we can clean up the queues. */
1046 vb->vdev->config->reset(vb->vdev);
1048 vb->vdev->config->del_vqs(vb->vdev);
1051 static void virtballoon_remove(struct virtio_device *vdev)
1053 struct virtio_balloon *vb = vdev->priv;
1055 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1056 page_reporting_unregister(&vb->pr_dev_info);
1057 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1058 unregister_oom_notifier(&vb->oom_nb);
1059 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1060 virtio_balloon_unregister_shrinker(vb);
1061 spin_lock_irq(&vb->stop_update_lock);
1062 vb->stop_update = true;
1063 spin_unlock_irq(&vb->stop_update_lock);
1064 cancel_work_sync(&vb->update_balloon_size_work);
1065 cancel_work_sync(&vb->update_balloon_stats_work);
1067 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1068 cancel_work_sync(&vb->report_free_page_work);
1069 destroy_workqueue(vb->balloon_wq);
1073 #ifdef CONFIG_BALLOON_COMPACTION
1074 if (vb->vb_dev_info.inode)
1075 iput(vb->vb_dev_info.inode);
1077 kern_unmount(balloon_mnt);
1082 #ifdef CONFIG_PM_SLEEP
1083 static int virtballoon_freeze(struct virtio_device *vdev)
1085 struct virtio_balloon *vb = vdev->priv;
1088 * The workqueue is already frozen by the PM core before this
1089 * function is called.
1095 static int virtballoon_restore(struct virtio_device *vdev)
1097 struct virtio_balloon *vb = vdev->priv;
1100 ret = init_vqs(vdev->priv);
1104 virtio_device_ready(vdev);
1106 if (towards_target(vb))
1107 virtballoon_changed(vdev);
1108 update_balloon_size(vb);
1113 static int virtballoon_validate(struct virtio_device *vdev)
1116 * Inform the hypervisor that our pages are poisoned or
1117 * initialized. If we cannot do that then we should disable
1118 * page reporting as it could potentially change the contents
1119 * of our free pages.
1121 if (!want_init_on_free() &&
1122 (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
1123 !page_poisoning_enabled()))
1124 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1125 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1126 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1128 __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1132 static unsigned int features[] = {
1133 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1134 VIRTIO_BALLOON_F_STATS_VQ,
1135 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1136 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1137 VIRTIO_BALLOON_F_PAGE_POISON,
1138 VIRTIO_BALLOON_F_REPORTING,
1141 static struct virtio_driver virtio_balloon_driver = {
1142 .feature_table = features,
1143 .feature_table_size = ARRAY_SIZE(features),
1144 .driver.name = KBUILD_MODNAME,
1145 .driver.owner = THIS_MODULE,
1146 .id_table = id_table,
1147 .validate = virtballoon_validate,
1148 .probe = virtballoon_probe,
1149 .remove = virtballoon_remove,
1150 .config_changed = virtballoon_changed,
1151 #ifdef CONFIG_PM_SLEEP
1152 .freeze = virtballoon_freeze,
1153 .restore = virtballoon_restore,
1157 module_virtio_driver(virtio_balloon_driver);
1158 MODULE_DEVICE_TABLE(virtio, id_table);
1159 MODULE_DESCRIPTION("Virtio balloon driver");
1160 MODULE_LICENSE("GPL");