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/page_reporting.h>
23 * Balloon device works in 4K page units. So each page is pointed to by
24 * multiple balloon pages. All memory counters in this driver are in balloon
27 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
28 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
29 /* Maximum number of (4k) pages to deflate on OOM notifications. */
30 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
31 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
33 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
35 /* The order of free page blocks to report to host */
36 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER MAX_PAGE_ORDER
37 /* The size of a free page block in bytes */
38 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
39 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
40 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
42 enum virtio_balloon_vq {
43 VIRTIO_BALLOON_VQ_INFLATE,
44 VIRTIO_BALLOON_VQ_DEFLATE,
45 VIRTIO_BALLOON_VQ_STATS,
46 VIRTIO_BALLOON_VQ_FREE_PAGE,
47 VIRTIO_BALLOON_VQ_REPORTING,
51 enum virtio_balloon_config_read {
52 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
55 struct virtio_balloon {
56 struct virtio_device *vdev;
57 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
59 /* Balloon's own wq for cpu-intensive work items */
60 struct workqueue_struct *balloon_wq;
61 /* The free page reporting work item submitted to the balloon wq */
62 struct work_struct report_free_page_work;
64 /* The balloon servicing is delegated to a freezable workqueue. */
65 struct work_struct update_balloon_stats_work;
66 struct work_struct update_balloon_size_work;
68 /* Prevent updating balloon when it is being canceled. */
69 spinlock_t stop_update_lock;
71 /* Bitmap to indicate if reading the related config fields are needed */
72 unsigned long config_read_bitmap;
74 /* The list of allocated free pages, waiting to be given back to mm */
75 struct list_head free_page_list;
76 spinlock_t free_page_list_lock;
77 /* The number of free page blocks on the above list */
78 unsigned long num_free_page_blocks;
80 * The cmd id received from host.
81 * Read it via virtio_balloon_cmd_id_received to get the latest value
84 u32 cmd_id_received_cache;
85 /* The cmd id that is actively in use */
86 __virtio32 cmd_id_active;
87 /* Buffer to store the stop sign */
88 __virtio32 cmd_id_stop;
90 /* Waiting for host to ack the pages we released. */
91 wait_queue_head_t acked;
93 /* Number of balloon pages we've told the Host we're not using. */
94 unsigned int num_pages;
96 * The pages we've told the Host we're not using are enqueued
97 * at vb_dev_info->pages list.
98 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
101 struct balloon_dev_info vb_dev_info;
103 /* Synchronize access/update to this struct virtio_balloon elements */
104 struct mutex balloon_lock;
106 /* The array of pfns we tell the Host about. */
107 unsigned int num_pfns;
108 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
110 /* Memory statistics */
111 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
113 /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
114 struct shrinker *shrinker;
116 /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
117 struct notifier_block oom_nb;
119 /* Free page reporting device */
120 struct virtqueue *reporting_vq;
121 struct page_reporting_dev_info pr_dev_info;
123 /* State for keeping the wakeup_source active while adjusting the balloon */
124 spinlock_t adjustment_lock;
125 bool adjustment_signal_pending;
126 bool adjustment_in_progress;
129 static const struct virtio_device_id id_table[] = {
130 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
134 static u32 page_to_balloon_pfn(struct page *page)
136 unsigned long pfn = page_to_pfn(page);
138 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
139 /* Convert pfn from Linux page size to balloon page size. */
140 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
143 static void balloon_ack(struct virtqueue *vq)
145 struct virtio_balloon *vb = vq->vdev->priv;
150 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
152 struct scatterlist sg;
155 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
157 /* We should always be able to add one buffer to an empty queue. */
158 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
161 /* When host has read buffer, this completes via balloon_ack */
162 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
166 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
167 struct scatterlist *sg, unsigned int nents)
169 struct virtio_balloon *vb =
170 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
171 struct virtqueue *vq = vb->reporting_vq;
172 unsigned int unused, err;
174 /* We should always be able to add these buffers to an empty queue. */
175 err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
178 * In the extremely unlikely case that something has occurred and we
179 * are able to trigger an error we will simply display a warning
180 * and exit without actually processing the pages.
182 if (WARN_ON_ONCE(err))
187 /* When host has read buffer, this completes via balloon_ack */
188 wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
193 static void set_page_pfns(struct virtio_balloon *vb,
194 __virtio32 pfns[], struct page *page)
198 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
201 * Set balloon pfns pointing at this page.
202 * Note that the first pfn points at start of the page.
204 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
205 pfns[i] = cpu_to_virtio32(vb->vdev,
206 page_to_balloon_pfn(page) + i);
209 static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
211 unsigned int num_allocated_pages;
212 unsigned int num_pfns;
216 /* We can only do one array worth at a time. */
217 num = min(num, ARRAY_SIZE(vb->pfns));
219 for (num_pfns = 0; num_pfns < num;
220 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
221 struct page *page = balloon_page_alloc();
224 dev_info_ratelimited(&vb->vdev->dev,
225 "Out of puff! Can't get %u pages\n",
226 VIRTIO_BALLOON_PAGES_PER_PAGE);
227 /* Sleep for at least 1/5 of a second before retry. */
232 balloon_page_push(&pages, page);
235 mutex_lock(&vb->balloon_lock);
239 while ((page = balloon_page_pop(&pages))) {
240 balloon_page_enqueue(&vb->vb_dev_info, page);
242 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
243 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
244 if (!virtio_has_feature(vb->vdev,
245 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
246 adjust_managed_page_count(page, -1);
247 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
250 num_allocated_pages = vb->num_pfns;
251 /* Did we get any? */
252 if (vb->num_pfns != 0)
253 tell_host(vb, vb->inflate_vq);
254 mutex_unlock(&vb->balloon_lock);
256 return num_allocated_pages;
259 static void release_pages_balloon(struct virtio_balloon *vb,
260 struct list_head *pages)
262 struct page *page, *next;
264 list_for_each_entry_safe(page, next, pages, lru) {
265 if (!virtio_has_feature(vb->vdev,
266 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
267 adjust_managed_page_count(page, 1);
268 list_del(&page->lru);
269 put_page(page); /* balloon reference */
273 static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num)
275 unsigned int num_freed_pages;
277 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
280 /* We can only do one array worth at a time. */
281 num = min(num, ARRAY_SIZE(vb->pfns));
283 mutex_lock(&vb->balloon_lock);
284 /* We can't release more pages than taken */
285 num = min(num, (size_t)vb->num_pages);
286 for (vb->num_pfns = 0; vb->num_pfns < num;
287 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
288 page = balloon_page_dequeue(vb_dev_info);
291 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
292 list_add(&page->lru, &pages);
293 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
296 num_freed_pages = vb->num_pfns;
299 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
300 * is true, we *have* to do it in this order
302 if (vb->num_pfns != 0)
303 tell_host(vb, vb->deflate_vq);
304 release_pages_balloon(vb, &pages);
305 mutex_unlock(&vb->balloon_lock);
306 return num_freed_pages;
309 static inline void update_stat(struct virtio_balloon *vb, int idx,
312 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
313 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
314 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
317 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
319 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
321 unsigned long events[NR_VM_EVENT_ITEMS];
323 unsigned int idx = 0;
325 unsigned long caches;
327 all_vm_events(events);
330 available = si_mem_available();
331 caches = global_node_page_state(NR_FILE_PAGES);
333 #ifdef CONFIG_VM_EVENT_COUNTERS
334 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
335 pages_to_bytes(events[PSWPIN]));
336 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
337 pages_to_bytes(events[PSWPOUT]));
338 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
339 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
340 #ifdef CONFIG_HUGETLB_PAGE
341 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
342 events[HTLB_BUDDY_PGALLOC]);
343 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
344 events[HTLB_BUDDY_PGALLOC_FAIL]);
347 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
348 pages_to_bytes(i.freeram));
349 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
350 pages_to_bytes(i.totalram));
351 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
352 pages_to_bytes(available));
353 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
354 pages_to_bytes(caches));
360 * While most virtqueues communicate guest-initiated requests to the hypervisor,
361 * the stats queue operates in reverse. The driver initializes the virtqueue
362 * with a single buffer. From that point forward, all conversations consist of
363 * a hypervisor request (a call to this function) which directs us to refill
364 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
365 * we delegate the job to a freezable workqueue that will do the actual work via
366 * stats_handle_request().
368 static void stats_request(struct virtqueue *vq)
370 struct virtio_balloon *vb = vq->vdev->priv;
372 spin_lock(&vb->stop_update_lock);
373 if (!vb->stop_update)
374 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
375 spin_unlock(&vb->stop_update_lock);
378 static void stats_handle_request(struct virtio_balloon *vb)
380 struct virtqueue *vq;
381 struct scatterlist sg;
382 unsigned int len, num_stats;
384 num_stats = update_balloon_stats(vb);
387 if (!virtqueue_get_buf(vq, &len))
389 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
390 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
394 static inline s64 towards_target(struct virtio_balloon *vb)
399 /* Legacy balloon config space is LE, unlike all other devices. */
400 virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
404 * Aligned up to guest page size to avoid inflating and deflating
407 target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
408 return target - vb->num_pages;
411 /* Gives back @num_to_return blocks of free pages to mm. */
412 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
413 unsigned long num_to_return)
416 unsigned long num_returned;
418 spin_lock_irq(&vb->free_page_list_lock);
419 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
420 page = balloon_page_pop(&vb->free_page_list);
423 free_pages((unsigned long)page_address(page),
424 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
426 vb->num_free_page_blocks -= num_returned;
427 spin_unlock_irq(&vb->free_page_list_lock);
432 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
434 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
437 /* No need to queue the work if the bit was already set. */
438 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
439 &vb->config_read_bitmap))
442 queue_work(vb->balloon_wq, &vb->report_free_page_work);
445 static void start_update_balloon_size(struct virtio_balloon *vb)
449 spin_lock_irqsave(&vb->adjustment_lock, flags);
450 vb->adjustment_signal_pending = true;
451 if (!vb->adjustment_in_progress) {
452 vb->adjustment_in_progress = true;
453 pm_stay_awake(vb->vdev->dev.parent);
455 spin_unlock_irqrestore(&vb->adjustment_lock, flags);
457 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
460 static void end_update_balloon_size(struct virtio_balloon *vb)
462 spin_lock_irq(&vb->adjustment_lock);
463 if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) {
464 vb->adjustment_in_progress = false;
465 pm_relax(vb->vdev->dev.parent);
467 spin_unlock_irq(&vb->adjustment_lock);
470 static void virtballoon_changed(struct virtio_device *vdev)
472 struct virtio_balloon *vb = vdev->priv;
475 spin_lock_irqsave(&vb->stop_update_lock, flags);
476 if (!vb->stop_update) {
477 start_update_balloon_size(vb);
478 virtio_balloon_queue_free_page_work(vb);
480 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
483 static void update_balloon_size(struct virtio_balloon *vb)
485 u32 actual = vb->num_pages;
487 /* Legacy balloon config space is LE, unlike all other devices. */
488 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
492 static void update_balloon_stats_func(struct work_struct *work)
494 struct virtio_balloon *vb;
496 vb = container_of(work, struct virtio_balloon,
497 update_balloon_stats_work);
498 stats_handle_request(vb);
501 static void update_balloon_size_func(struct work_struct *work)
503 struct virtio_balloon *vb;
506 vb = container_of(work, struct virtio_balloon,
507 update_balloon_size_work);
509 spin_lock_irq(&vb->adjustment_lock);
510 vb->adjustment_signal_pending = false;
511 spin_unlock_irq(&vb->adjustment_lock);
513 diff = towards_target(vb);
517 diff -= fill_balloon(vb, diff);
519 diff += leak_balloon(vb, -diff);
520 update_balloon_size(vb);
524 queue_work(system_freezable_wq, work);
526 end_update_balloon_size(vb);
529 static int init_vqs(struct virtio_balloon *vb)
531 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
532 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
533 const char *names[VIRTIO_BALLOON_VQ_MAX];
537 * Inflateq and deflateq are used unconditionally. The names[]
538 * will be NULL if the related feature is not enabled, which will
539 * cause no allocation for the corresponding virtqueue in find_vqs.
541 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
542 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
543 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
544 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
545 callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
546 names[VIRTIO_BALLOON_VQ_STATS] = NULL;
547 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
548 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
549 names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
551 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
552 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
553 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
556 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
557 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
558 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
561 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
562 names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
563 callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
566 err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
567 callbacks, names, NULL);
571 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
572 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
573 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
574 struct scatterlist sg;
575 unsigned int num_stats;
576 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
579 * Prime this virtqueue with one buffer so the hypervisor can
580 * use it to signal us later (it can't be broken yet!).
582 num_stats = update_balloon_stats(vb);
584 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
585 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
588 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
592 virtqueue_kick(vb->stats_vq);
595 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
596 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
598 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
599 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
604 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
606 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
607 &vb->config_read_bitmap)) {
608 /* Legacy balloon config space is LE, unlike all other devices. */
609 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
610 free_page_hint_cmd_id,
611 &vb->cmd_id_received_cache);
614 return vb->cmd_id_received_cache;
617 static int send_cmd_id_start(struct virtio_balloon *vb)
619 struct scatterlist sg;
620 struct virtqueue *vq = vb->free_page_vq;
623 /* Detach all the used buffers from the vq */
624 while (virtqueue_get_buf(vq, &unused))
627 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
628 virtio_balloon_cmd_id_received(vb));
629 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
630 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
636 static int send_cmd_id_stop(struct virtio_balloon *vb)
638 struct scatterlist sg;
639 struct virtqueue *vq = vb->free_page_vq;
642 /* Detach all the used buffers from the vq */
643 while (virtqueue_get_buf(vq, &unused))
646 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
647 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
653 static int get_free_page_and_send(struct virtio_balloon *vb)
655 struct virtqueue *vq = vb->free_page_vq;
657 struct scatterlist sg;
661 /* Detach all the used buffers from the vq */
662 while (virtqueue_get_buf(vq, &unused))
665 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
666 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
668 * When the allocation returns NULL, it indicates that we have got all
669 * the possible free pages, so return -EINTR to stop.
674 p = page_address(page);
675 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
676 /* There is always 1 entry reserved for the cmd id to use. */
677 if (vq->num_free > 1) {
678 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
680 free_pages((unsigned long)p,
681 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
685 spin_lock_irq(&vb->free_page_list_lock);
686 balloon_page_push(&vb->free_page_list, page);
687 vb->num_free_page_blocks++;
688 spin_unlock_irq(&vb->free_page_list_lock);
691 * The vq has no available entry to add this page block, so
694 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
700 static int send_free_pages(struct virtio_balloon *vb)
707 * If a stop id or a new cmd id was just received from host,
708 * stop the reporting.
710 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
711 if (unlikely(cmd_id_active !=
712 virtio_balloon_cmd_id_received(vb)))
716 * The free page blocks are allocated and sent to host one by
719 err = get_free_page_and_send(vb);
722 else if (unlikely(err))
729 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
732 struct device *dev = &vb->vdev->dev;
734 /* Start by sending the received cmd id to host with an outbuf. */
735 err = send_cmd_id_start(vb);
737 dev_err(dev, "Failed to send a start id, err = %d\n", err);
739 err = send_free_pages(vb);
741 dev_err(dev, "Failed to send a free page, err = %d\n", err);
743 /* End by sending a stop id to host with an outbuf. */
744 err = send_cmd_id_stop(vb);
746 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
749 static void report_free_page_func(struct work_struct *work)
751 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
752 report_free_page_work);
755 cmd_id_received = virtio_balloon_cmd_id_received(vb);
756 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
757 /* Pass ULONG_MAX to give back all the free pages */
758 return_free_pages_to_mm(vb, ULONG_MAX);
759 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
761 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
762 virtio_balloon_report_free_page(vb);
766 #ifdef CONFIG_BALLOON_COMPACTION
768 * virtballoon_migratepage - perform the balloon page migration on behalf of
769 * a compaction thread. (called under page lock)
770 * @vb_dev_info: the balloon device
771 * @newpage: page that will replace the isolated page after migration finishes.
772 * @page : the isolated (old) page that is about to be migrated to newpage.
773 * @mode : compaction mode -- not used for balloon page migration.
775 * After a ballooned page gets isolated by compaction procedures, this is the
776 * function that performs the page migration on behalf of a compaction thread
777 * The page migration for virtio balloon is done in a simple swap fashion which
778 * follows these two macro steps:
779 * 1) insert newpage into vb->pages list and update the host about it;
780 * 2) update the host about the old page removed from vb->pages list;
782 * This function preforms the balloon page migration task.
783 * Called through movable_operations->migrate_page
785 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
786 struct page *newpage, struct page *page, enum migrate_mode mode)
788 struct virtio_balloon *vb = container_of(vb_dev_info,
789 struct virtio_balloon, vb_dev_info);
793 * In order to avoid lock contention while migrating pages concurrently
794 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
795 * this turn, as it is easier to retry the page migration later.
796 * This also prevents fill_balloon() getting stuck into a mutex
797 * recursion in the case it ends up triggering memory compaction
798 * while it is attempting to inflate the ballon.
800 if (!mutex_trylock(&vb->balloon_lock))
803 get_page(newpage); /* balloon reference */
806 * When we migrate a page to a different zone and adjusted the
807 * managed page count when inflating, we have to fixup the count of
808 * both involved zones.
810 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
811 page_zone(page) != page_zone(newpage)) {
812 adjust_managed_page_count(page, 1);
813 adjust_managed_page_count(newpage, -1);
816 /* balloon's page migration 1st step -- inflate "newpage" */
817 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
818 balloon_page_insert(vb_dev_info, newpage);
819 vb_dev_info->isolated_pages--;
820 __count_vm_event(BALLOON_MIGRATE);
821 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
822 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
823 set_page_pfns(vb, vb->pfns, newpage);
824 tell_host(vb, vb->inflate_vq);
826 /* balloon's page migration 2nd step -- deflate "page" */
827 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
828 balloon_page_delete(page);
829 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
830 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
831 set_page_pfns(vb, vb->pfns, page);
832 tell_host(vb, vb->deflate_vq);
834 mutex_unlock(&vb->balloon_lock);
836 put_page(page); /* balloon reference */
838 return MIGRATEPAGE_SUCCESS;
840 #endif /* CONFIG_BALLOON_COMPACTION */
842 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
843 unsigned long pages_to_free)
845 unsigned long blocks_to_free, blocks_freed;
847 pages_to_free = round_up(pages_to_free,
848 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
849 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
850 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
852 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
855 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
856 struct shrink_control *sc)
858 struct virtio_balloon *vb = shrinker->private_data;
860 return shrink_free_pages(vb, sc->nr_to_scan);
863 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
864 struct shrink_control *sc)
866 struct virtio_balloon *vb = shrinker->private_data;
868 return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
871 static int virtio_balloon_oom_notify(struct notifier_block *nb,
872 unsigned long dummy, void *parm)
874 struct virtio_balloon *vb = container_of(nb,
875 struct virtio_balloon, oom_nb);
876 unsigned long *freed = parm;
878 *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
879 VIRTIO_BALLOON_PAGES_PER_PAGE;
880 update_balloon_size(vb);
885 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
887 shrinker_free(vb->shrinker);
890 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
892 vb->shrinker = shrinker_alloc(0, "virtio-balloon");
896 vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
897 vb->shrinker->count_objects = virtio_balloon_shrinker_count;
898 vb->shrinker->private_data = vb;
900 shrinker_register(vb->shrinker);
905 static int virtballoon_probe(struct virtio_device *vdev)
907 struct virtio_balloon *vb;
910 if (!vdev->config->get) {
911 dev_err(&vdev->dev, "%s failure: config access disabled\n",
916 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
922 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
923 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
924 spin_lock_init(&vb->stop_update_lock);
925 mutex_init(&vb->balloon_lock);
926 init_waitqueue_head(&vb->acked);
929 balloon_devinfo_init(&vb->vb_dev_info);
935 #ifdef CONFIG_BALLOON_COMPACTION
936 vb->vb_dev_info.migratepage = virtballoon_migratepage;
938 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
940 * There is always one entry reserved for cmd id, so the ring
941 * size needs to be at least two to report free page hints.
943 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
947 vb->balloon_wq = alloc_workqueue("balloon-wq",
948 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
949 if (!vb->balloon_wq) {
953 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
954 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
955 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
956 VIRTIO_BALLOON_CMD_ID_STOP);
957 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
958 VIRTIO_BALLOON_CMD_ID_STOP);
959 spin_lock_init(&vb->free_page_list_lock);
960 INIT_LIST_HEAD(&vb->free_page_list);
962 * We're allowed to reuse any free pages, even if they are
963 * still to be processed by the host.
965 err = virtio_balloon_register_shrinker(vb);
967 goto out_del_balloon_wq;
970 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
971 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
972 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
973 err = register_oom_notifier(&vb->oom_nb);
975 goto out_unregister_shrinker;
978 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
979 /* Start with poison val of 0 representing general init */
980 __u32 poison_val = 0;
983 * Let the hypervisor know that we are expecting a
984 * specific value to be written back in balloon pages.
986 * If the PAGE_POISON value was larger than a byte we would
987 * need to byte swap poison_val here to guarantee it is
988 * little-endian. However for now it is a single byte so we
991 if (!want_init_on_free())
992 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
994 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
995 poison_val, &poison_val);
998 vb->pr_dev_info.report = virtballoon_free_page_report;
999 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
1000 unsigned int capacity;
1002 capacity = virtqueue_get_vring_size(vb->reporting_vq);
1003 if (capacity < PAGE_REPORTING_CAPACITY) {
1005 goto out_unregister_oom;
1009 * The default page reporting order is @pageblock_order, which
1010 * corresponds to 512MB in size on ARM64 when 64KB base page
1011 * size is used. The page reporting won't be triggered if the
1012 * freeing page can't come up with a free area like that huge.
1013 * So we specify the page reporting order to 5, corresponding
1014 * to 2MB. It helps to avoid THP splitting if 4KB base page
1015 * size is used by host.
1017 * Ideally, the page reporting order is selected based on the
1018 * host's base page size. However, it needs more work to report
1019 * that value. The hard-coded order would be fine currently.
1021 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
1022 vb->pr_dev_info.order = 5;
1025 err = page_reporting_register(&vb->pr_dev_info);
1027 goto out_unregister_oom;
1030 spin_lock_init(&vb->adjustment_lock);
1032 virtio_device_ready(vdev);
1034 if (towards_target(vb))
1035 virtballoon_changed(vdev);
1039 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1040 unregister_oom_notifier(&vb->oom_nb);
1041 out_unregister_shrinker:
1042 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1043 virtio_balloon_unregister_shrinker(vb);
1045 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1046 destroy_workqueue(vb->balloon_wq);
1048 vdev->config->del_vqs(vdev);
1055 static void remove_common(struct virtio_balloon *vb)
1057 /* There might be pages left in the balloon: free them. */
1058 while (vb->num_pages)
1059 leak_balloon(vb, vb->num_pages);
1060 update_balloon_size(vb);
1062 /* There might be free pages that are being reported: release them. */
1063 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1064 return_free_pages_to_mm(vb, ULONG_MAX);
1066 /* Now we reset the device so we can clean up the queues. */
1067 virtio_reset_device(vb->vdev);
1069 vb->vdev->config->del_vqs(vb->vdev);
1072 static void virtballoon_remove(struct virtio_device *vdev)
1074 struct virtio_balloon *vb = vdev->priv;
1076 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1077 page_reporting_unregister(&vb->pr_dev_info);
1078 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1079 unregister_oom_notifier(&vb->oom_nb);
1080 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1081 virtio_balloon_unregister_shrinker(vb);
1082 spin_lock_irq(&vb->stop_update_lock);
1083 vb->stop_update = true;
1084 spin_unlock_irq(&vb->stop_update_lock);
1085 cancel_work_sync(&vb->update_balloon_size_work);
1086 cancel_work_sync(&vb->update_balloon_stats_work);
1088 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1089 cancel_work_sync(&vb->report_free_page_work);
1090 destroy_workqueue(vb->balloon_wq);
1097 #ifdef CONFIG_PM_SLEEP
1098 static int virtballoon_freeze(struct virtio_device *vdev)
1100 struct virtio_balloon *vb = vdev->priv;
1103 * The workqueue is already frozen by the PM core before this
1104 * function is called.
1110 static int virtballoon_restore(struct virtio_device *vdev)
1112 struct virtio_balloon *vb = vdev->priv;
1115 ret = init_vqs(vdev->priv);
1119 virtio_device_ready(vdev);
1121 if (towards_target(vb))
1122 virtballoon_changed(vdev);
1123 update_balloon_size(vb);
1128 static int virtballoon_validate(struct virtio_device *vdev)
1131 * Inform the hypervisor that our pages are poisoned or
1132 * initialized. If we cannot do that then we should disable
1133 * page reporting as it could potentially change the contents
1134 * of our free pages.
1136 if (!want_init_on_free() && !page_poisoning_enabled_static())
1137 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1138 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1139 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1141 __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1145 static unsigned int features[] = {
1146 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1147 VIRTIO_BALLOON_F_STATS_VQ,
1148 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1149 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1150 VIRTIO_BALLOON_F_PAGE_POISON,
1151 VIRTIO_BALLOON_F_REPORTING,
1154 static struct virtio_driver virtio_balloon_driver = {
1155 .feature_table = features,
1156 .feature_table_size = ARRAY_SIZE(features),
1157 .driver.name = KBUILD_MODNAME,
1158 .driver.owner = THIS_MODULE,
1159 .id_table = id_table,
1160 .validate = virtballoon_validate,
1161 .probe = virtballoon_probe,
1162 .remove = virtballoon_remove,
1163 .config_changed = virtballoon_changed,
1164 #ifdef CONFIG_PM_SLEEP
1165 .freeze = virtballoon_freeze,
1166 .restore = virtballoon_restore,
1170 module_virtio_driver(virtio_balloon_driver);
1171 MODULE_DEVICE_TABLE(virtio, id_table);
1172 MODULE_DESCRIPTION("Virtio balloon driver");
1173 MODULE_LICENSE("GPL");