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 wakeup_lock;
125 bool processing_wakeup_event;
126 u32 wakeup_signal_mask;
129 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST (1 << 0)
130 #define VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS (1 << 1)
132 static const struct virtio_device_id id_table[] = {
133 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
137 static u32 page_to_balloon_pfn(struct page *page)
139 unsigned long pfn = page_to_pfn(page);
141 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
142 /* Convert pfn from Linux page size to balloon page size. */
143 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
146 static void start_wakeup_event(struct virtio_balloon *vb, u32 mask)
150 spin_lock_irqsave(&vb->wakeup_lock, flags);
151 vb->wakeup_signal_mask |= mask;
152 if (!vb->processing_wakeup_event) {
153 vb->processing_wakeup_event = true;
154 pm_stay_awake(&vb->vdev->dev);
156 spin_unlock_irqrestore(&vb->wakeup_lock, flags);
159 static void process_wakeup_event(struct virtio_balloon *vb, u32 mask)
161 spin_lock_irq(&vb->wakeup_lock);
162 vb->wakeup_signal_mask &= ~mask;
163 spin_unlock_irq(&vb->wakeup_lock);
166 static void finish_wakeup_event(struct virtio_balloon *vb)
168 spin_lock_irq(&vb->wakeup_lock);
169 if (!vb->wakeup_signal_mask && vb->processing_wakeup_event) {
170 vb->processing_wakeup_event = false;
171 pm_relax(&vb->vdev->dev);
173 spin_unlock_irq(&vb->wakeup_lock);
176 static void balloon_ack(struct virtqueue *vq)
178 struct virtio_balloon *vb = vq->vdev->priv;
183 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
185 struct scatterlist sg;
188 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
190 /* We should always be able to add one buffer to an empty queue. */
191 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
194 /* When host has read buffer, this completes via balloon_ack */
195 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
199 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
200 struct scatterlist *sg, unsigned int nents)
202 struct virtio_balloon *vb =
203 container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
204 struct virtqueue *vq = vb->reporting_vq;
205 unsigned int unused, err;
207 /* We should always be able to add these buffers to an empty queue. */
208 err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
211 * In the extremely unlikely case that something has occurred and we
212 * are able to trigger an error we will simply display a warning
213 * and exit without actually processing the pages.
215 if (WARN_ON_ONCE(err))
220 /* When host has read buffer, this completes via balloon_ack */
221 wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
226 static void set_page_pfns(struct virtio_balloon *vb,
227 __virtio32 pfns[], struct page *page)
231 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
234 * Set balloon pfns pointing at this page.
235 * Note that the first pfn points at start of the page.
237 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
238 pfns[i] = cpu_to_virtio32(vb->vdev,
239 page_to_balloon_pfn(page) + i);
242 static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
244 unsigned int num_allocated_pages;
245 unsigned int num_pfns;
249 /* We can only do one array worth at a time. */
250 num = min(num, ARRAY_SIZE(vb->pfns));
252 for (num_pfns = 0; num_pfns < num;
253 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
254 struct page *page = balloon_page_alloc();
257 dev_info_ratelimited(&vb->vdev->dev,
258 "Out of puff! Can't get %u pages\n",
259 VIRTIO_BALLOON_PAGES_PER_PAGE);
260 /* Sleep for at least 1/5 of a second before retry. */
265 balloon_page_push(&pages, page);
268 mutex_lock(&vb->balloon_lock);
272 while ((page = balloon_page_pop(&pages))) {
273 balloon_page_enqueue(&vb->vb_dev_info, page);
275 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
276 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
277 if (!virtio_has_feature(vb->vdev,
278 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
279 adjust_managed_page_count(page, -1);
280 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
283 num_allocated_pages = vb->num_pfns;
284 /* Did we get any? */
285 if (vb->num_pfns != 0)
286 tell_host(vb, vb->inflate_vq);
287 mutex_unlock(&vb->balloon_lock);
289 return num_allocated_pages;
292 static void release_pages_balloon(struct virtio_balloon *vb,
293 struct list_head *pages)
295 struct page *page, *next;
297 list_for_each_entry_safe(page, next, pages, lru) {
298 if (!virtio_has_feature(vb->vdev,
299 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
300 adjust_managed_page_count(page, 1);
301 list_del(&page->lru);
302 put_page(page); /* balloon reference */
306 static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num)
308 unsigned int num_freed_pages;
310 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
313 /* We can only do one array worth at a time. */
314 num = min(num, ARRAY_SIZE(vb->pfns));
316 mutex_lock(&vb->balloon_lock);
317 /* We can't release more pages than taken */
318 num = min(num, (size_t)vb->num_pages);
319 for (vb->num_pfns = 0; vb->num_pfns < num;
320 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
321 page = balloon_page_dequeue(vb_dev_info);
324 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
325 list_add(&page->lru, &pages);
326 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
329 num_freed_pages = vb->num_pfns;
332 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
333 * is true, we *have* to do it in this order
335 if (vb->num_pfns != 0)
336 tell_host(vb, vb->deflate_vq);
337 release_pages_balloon(vb, &pages);
338 mutex_unlock(&vb->balloon_lock);
339 return num_freed_pages;
342 static inline void update_stat(struct virtio_balloon *vb, int idx,
345 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
346 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
347 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
350 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
352 #ifdef CONFIG_VM_EVENT_COUNTERS
353 /* Return the number of entries filled by vm events */
354 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
356 unsigned long events[NR_VM_EVENT_ITEMS];
357 unsigned int idx = 0;
359 all_vm_events(events);
360 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
361 pages_to_bytes(events[PSWPIN]));
362 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
363 pages_to_bytes(events[PSWPOUT]));
364 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
365 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
367 #ifdef CONFIG_HUGETLB_PAGE
368 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
369 events[HTLB_BUDDY_PGALLOC]);
370 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
371 events[HTLB_BUDDY_PGALLOC_FAIL]);
372 #endif /* CONFIG_HUGETLB_PAGE */
376 #else /* CONFIG_VM_EVENT_COUNTERS */
377 static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
381 #endif /* CONFIG_VM_EVENT_COUNTERS */
383 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
388 unsigned long caches;
390 idx = update_balloon_vm_stats(vb);
393 available = si_mem_available();
394 caches = global_node_page_state(NR_FILE_PAGES);
395 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
396 pages_to_bytes(i.freeram));
397 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
398 pages_to_bytes(i.totalram));
399 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
400 pages_to_bytes(available));
401 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
402 pages_to_bytes(caches));
408 * While most virtqueues communicate guest-initiated requests to the hypervisor,
409 * the stats queue operates in reverse. The driver initializes the virtqueue
410 * with a single buffer. From that point forward, all conversations consist of
411 * a hypervisor request (a call to this function) which directs us to refill
412 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
413 * we delegate the job to a freezable workqueue that will do the actual work via
414 * stats_handle_request().
416 static void stats_request(struct virtqueue *vq)
418 struct virtio_balloon *vb = vq->vdev->priv;
420 spin_lock(&vb->stop_update_lock);
421 if (!vb->stop_update) {
422 start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
423 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
425 spin_unlock(&vb->stop_update_lock);
428 static void stats_handle_request(struct virtio_balloon *vb)
430 struct virtqueue *vq;
431 struct scatterlist sg;
432 unsigned int len, num_stats;
434 num_stats = update_balloon_stats(vb);
437 if (!virtqueue_get_buf(vq, &len))
439 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
440 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
444 static inline s64 towards_target(struct virtio_balloon *vb)
449 /* Legacy balloon config space is LE, unlike all other devices. */
450 virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
454 * Aligned up to guest page size to avoid inflating and deflating
457 target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
458 return target - vb->num_pages;
461 /* Gives back @num_to_return blocks of free pages to mm. */
462 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
463 unsigned long num_to_return)
466 unsigned long num_returned;
468 spin_lock_irq(&vb->free_page_list_lock);
469 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
470 page = balloon_page_pop(&vb->free_page_list);
473 free_pages((unsigned long)page_address(page),
474 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
476 vb->num_free_page_blocks -= num_returned;
477 spin_unlock_irq(&vb->free_page_list_lock);
482 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
484 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
487 /* No need to queue the work if the bit was already set. */
488 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
489 &vb->config_read_bitmap))
492 queue_work(vb->balloon_wq, &vb->report_free_page_work);
495 static void start_update_balloon_size(struct virtio_balloon *vb)
497 start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
498 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
501 static void virtballoon_changed(struct virtio_device *vdev)
503 struct virtio_balloon *vb = vdev->priv;
506 spin_lock_irqsave(&vb->stop_update_lock, flags);
507 if (!vb->stop_update) {
508 start_update_balloon_size(vb);
509 virtio_balloon_queue_free_page_work(vb);
511 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
514 static void update_balloon_size(struct virtio_balloon *vb)
516 u32 actual = vb->num_pages;
518 /* Legacy balloon config space is LE, unlike all other devices. */
519 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
523 static void update_balloon_stats_func(struct work_struct *work)
525 struct virtio_balloon *vb;
527 vb = container_of(work, struct virtio_balloon,
528 update_balloon_stats_work);
530 process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
531 stats_handle_request(vb);
532 finish_wakeup_event(vb);
535 static void update_balloon_size_func(struct work_struct *work)
537 struct virtio_balloon *vb;
540 vb = container_of(work, struct virtio_balloon,
541 update_balloon_size_work);
543 process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
545 diff = towards_target(vb);
549 diff -= fill_balloon(vb, diff);
551 diff += leak_balloon(vb, -diff);
552 update_balloon_size(vb);
556 queue_work(system_freezable_wq, work);
558 finish_wakeup_event(vb);
561 static int init_vqs(struct virtio_balloon *vb)
563 struct virtqueue_info vqs_info[VIRTIO_BALLOON_VQ_MAX] = {};
564 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
568 * Inflateq and deflateq are used unconditionally. The names[]
569 * will be NULL if the related feature is not enabled, which will
570 * cause no allocation for the corresponding virtqueue in find_vqs.
572 vqs_info[VIRTIO_BALLOON_VQ_INFLATE].callback = balloon_ack;
573 vqs_info[VIRTIO_BALLOON_VQ_INFLATE].name = "inflate";
574 vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].callback = balloon_ack;
575 vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].name = "deflate";
577 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
578 vqs_info[VIRTIO_BALLOON_VQ_STATS].name = "stats";
579 vqs_info[VIRTIO_BALLOON_VQ_STATS].callback = stats_request;
582 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
583 vqs_info[VIRTIO_BALLOON_VQ_FREE_PAGE].name = "free_page_vq";
585 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
586 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].name = "reporting_vq";
587 vqs_info[VIRTIO_BALLOON_VQ_REPORTING].callback = balloon_ack;
590 err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
595 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
596 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
597 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
598 struct scatterlist sg;
599 unsigned int num_stats;
600 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
603 * Prime this virtqueue with one buffer so the hypervisor can
604 * use it to signal us later (it can't be broken yet!).
606 num_stats = update_balloon_stats(vb);
608 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
609 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
612 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
616 virtqueue_kick(vb->stats_vq);
619 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
620 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
622 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
623 vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
628 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
630 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
631 &vb->config_read_bitmap)) {
632 /* Legacy balloon config space is LE, unlike all other devices. */
633 virtio_cread_le(vb->vdev, struct virtio_balloon_config,
634 free_page_hint_cmd_id,
635 &vb->cmd_id_received_cache);
638 return vb->cmd_id_received_cache;
641 static int send_cmd_id_start(struct virtio_balloon *vb)
643 struct scatterlist sg;
644 struct virtqueue *vq = vb->free_page_vq;
647 /* Detach all the used buffers from the vq */
648 while (virtqueue_get_buf(vq, &unused))
651 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
652 virtio_balloon_cmd_id_received(vb));
653 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
654 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
660 static int send_cmd_id_stop(struct virtio_balloon *vb)
662 struct scatterlist sg;
663 struct virtqueue *vq = vb->free_page_vq;
666 /* Detach all the used buffers from the vq */
667 while (virtqueue_get_buf(vq, &unused))
670 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
671 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
677 static int get_free_page_and_send(struct virtio_balloon *vb)
679 struct virtqueue *vq = vb->free_page_vq;
681 struct scatterlist sg;
685 /* Detach all the used buffers from the vq */
686 while (virtqueue_get_buf(vq, &unused))
689 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
690 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
692 * When the allocation returns NULL, it indicates that we have got all
693 * the possible free pages, so return -EINTR to stop.
698 p = page_address(page);
699 sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
700 /* There is always 1 entry reserved for the cmd id to use. */
701 if (vq->num_free > 1) {
702 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
704 free_pages((unsigned long)p,
705 VIRTIO_BALLOON_HINT_BLOCK_ORDER);
709 spin_lock_irq(&vb->free_page_list_lock);
710 balloon_page_push(&vb->free_page_list, page);
711 vb->num_free_page_blocks++;
712 spin_unlock_irq(&vb->free_page_list_lock);
715 * The vq has no available entry to add this page block, so
718 free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
724 static int send_free_pages(struct virtio_balloon *vb)
731 * If a stop id or a new cmd id was just received from host,
732 * stop the reporting.
734 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
735 if (unlikely(cmd_id_active !=
736 virtio_balloon_cmd_id_received(vb)))
740 * The free page blocks are allocated and sent to host one by
743 err = get_free_page_and_send(vb);
746 else if (unlikely(err))
753 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
756 struct device *dev = &vb->vdev->dev;
758 /* Start by sending the received cmd id to host with an outbuf. */
759 err = send_cmd_id_start(vb);
761 dev_err(dev, "Failed to send a start id, err = %d\n", err);
763 err = send_free_pages(vb);
765 dev_err(dev, "Failed to send a free page, err = %d\n", err);
767 /* End by sending a stop id to host with an outbuf. */
768 err = send_cmd_id_stop(vb);
770 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
773 static void report_free_page_func(struct work_struct *work)
775 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
776 report_free_page_work);
779 cmd_id_received = virtio_balloon_cmd_id_received(vb);
780 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
781 /* Pass ULONG_MAX to give back all the free pages */
782 return_free_pages_to_mm(vb, ULONG_MAX);
783 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
785 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
786 virtio_balloon_report_free_page(vb);
790 #ifdef CONFIG_BALLOON_COMPACTION
792 * virtballoon_migratepage - perform the balloon page migration on behalf of
793 * a compaction thread. (called under page lock)
794 * @vb_dev_info: the balloon device
795 * @newpage: page that will replace the isolated page after migration finishes.
796 * @page : the isolated (old) page that is about to be migrated to newpage.
797 * @mode : compaction mode -- not used for balloon page migration.
799 * After a ballooned page gets isolated by compaction procedures, this is the
800 * function that performs the page migration on behalf of a compaction thread
801 * The page migration for virtio balloon is done in a simple swap fashion which
802 * follows these two macro steps:
803 * 1) insert newpage into vb->pages list and update the host about it;
804 * 2) update the host about the old page removed from vb->pages list;
806 * This function preforms the balloon page migration task.
807 * Called through movable_operations->migrate_page
809 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
810 struct page *newpage, struct page *page, enum migrate_mode mode)
812 struct virtio_balloon *vb = container_of(vb_dev_info,
813 struct virtio_balloon, vb_dev_info);
817 * In order to avoid lock contention while migrating pages concurrently
818 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
819 * this turn, as it is easier to retry the page migration later.
820 * This also prevents fill_balloon() getting stuck into a mutex
821 * recursion in the case it ends up triggering memory compaction
822 * while it is attempting to inflate the ballon.
824 if (!mutex_trylock(&vb->balloon_lock))
827 get_page(newpage); /* balloon reference */
830 * When we migrate a page to a different zone and adjusted the
831 * managed page count when inflating, we have to fixup the count of
832 * both involved zones.
834 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
835 page_zone(page) != page_zone(newpage)) {
836 adjust_managed_page_count(page, 1);
837 adjust_managed_page_count(newpage, -1);
840 /* balloon's page migration 1st step -- inflate "newpage" */
841 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
842 balloon_page_insert(vb_dev_info, newpage);
843 vb_dev_info->isolated_pages--;
844 __count_vm_event(BALLOON_MIGRATE);
845 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
846 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
847 set_page_pfns(vb, vb->pfns, newpage);
848 tell_host(vb, vb->inflate_vq);
850 /* balloon's page migration 2nd step -- deflate "page" */
851 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
852 balloon_page_delete(page);
853 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
854 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
855 set_page_pfns(vb, vb->pfns, page);
856 tell_host(vb, vb->deflate_vq);
858 mutex_unlock(&vb->balloon_lock);
860 put_page(page); /* balloon reference */
862 return MIGRATEPAGE_SUCCESS;
864 #endif /* CONFIG_BALLOON_COMPACTION */
866 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
867 unsigned long pages_to_free)
869 unsigned long blocks_to_free, blocks_freed;
871 pages_to_free = round_up(pages_to_free,
872 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
873 blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
874 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
876 return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
879 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
880 struct shrink_control *sc)
882 struct virtio_balloon *vb = shrinker->private_data;
884 return shrink_free_pages(vb, sc->nr_to_scan);
887 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
888 struct shrink_control *sc)
890 struct virtio_balloon *vb = shrinker->private_data;
892 return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
895 static int virtio_balloon_oom_notify(struct notifier_block *nb,
896 unsigned long dummy, void *parm)
898 struct virtio_balloon *vb = container_of(nb,
899 struct virtio_balloon, oom_nb);
900 unsigned long *freed = parm;
902 *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
903 VIRTIO_BALLOON_PAGES_PER_PAGE;
904 update_balloon_size(vb);
909 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
911 shrinker_free(vb->shrinker);
914 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
916 vb->shrinker = shrinker_alloc(0, "virtio-balloon");
920 vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
921 vb->shrinker->count_objects = virtio_balloon_shrinker_count;
922 vb->shrinker->private_data = vb;
924 shrinker_register(vb->shrinker);
929 static int virtballoon_probe(struct virtio_device *vdev)
931 struct virtio_balloon *vb;
934 if (!vdev->config->get) {
935 dev_err(&vdev->dev, "%s failure: config access disabled\n",
940 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
946 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
947 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
948 spin_lock_init(&vb->stop_update_lock);
949 mutex_init(&vb->balloon_lock);
950 init_waitqueue_head(&vb->acked);
953 balloon_devinfo_init(&vb->vb_dev_info);
959 #ifdef CONFIG_BALLOON_COMPACTION
960 vb->vb_dev_info.migratepage = virtballoon_migratepage;
962 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
964 * There is always one entry reserved for cmd id, so the ring
965 * size needs to be at least two to report free page hints.
967 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
971 vb->balloon_wq = alloc_workqueue("balloon-wq",
972 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
973 if (!vb->balloon_wq) {
977 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
978 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
979 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
980 VIRTIO_BALLOON_CMD_ID_STOP);
981 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
982 VIRTIO_BALLOON_CMD_ID_STOP);
983 spin_lock_init(&vb->free_page_list_lock);
984 INIT_LIST_HEAD(&vb->free_page_list);
986 * We're allowed to reuse any free pages, even if they are
987 * still to be processed by the host.
989 err = virtio_balloon_register_shrinker(vb);
991 goto out_del_balloon_wq;
994 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
995 vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
996 vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
997 err = register_oom_notifier(&vb->oom_nb);
999 goto out_unregister_shrinker;
1002 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
1003 /* Start with poison val of 0 representing general init */
1004 __u32 poison_val = 0;
1007 * Let the hypervisor know that we are expecting a
1008 * specific value to be written back in balloon pages.
1010 * If the PAGE_POISON value was larger than a byte we would
1011 * need to byte swap poison_val here to guarantee it is
1012 * little-endian. However for now it is a single byte so we
1013 * can pass it as-is.
1015 if (!want_init_on_free())
1016 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
1018 virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
1019 poison_val, &poison_val);
1022 vb->pr_dev_info.report = virtballoon_free_page_report;
1023 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
1024 unsigned int capacity;
1026 capacity = virtqueue_get_vring_size(vb->reporting_vq);
1027 if (capacity < PAGE_REPORTING_CAPACITY) {
1029 goto out_unregister_oom;
1033 * The default page reporting order is @pageblock_order, which
1034 * corresponds to 512MB in size on ARM64 when 64KB base page
1035 * size is used. The page reporting won't be triggered if the
1036 * freeing page can't come up with a free area like that huge.
1037 * So we specify the page reporting order to 5, corresponding
1038 * to 2MB. It helps to avoid THP splitting if 4KB base page
1039 * size is used by host.
1041 * Ideally, the page reporting order is selected based on the
1042 * host's base page size. However, it needs more work to report
1043 * that value. The hard-coded order would be fine currently.
1045 #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
1046 vb->pr_dev_info.order = 5;
1049 err = page_reporting_register(&vb->pr_dev_info);
1051 goto out_unregister_oom;
1054 spin_lock_init(&vb->wakeup_lock);
1057 * The virtio balloon itself can't wake up the device, but it is
1058 * responsible for processing wakeup events passed up from the transport
1059 * layer. Wakeup sources don't support nesting/chaining calls, so we use
1060 * our own wakeup source to ensure wakeup events are properly handled
1061 * without trampling on the transport layer's wakeup source.
1063 device_set_wakeup_capable(&vb->vdev->dev, true);
1065 virtio_device_ready(vdev);
1067 if (towards_target(vb))
1068 virtballoon_changed(vdev);
1072 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1073 unregister_oom_notifier(&vb->oom_nb);
1074 out_unregister_shrinker:
1075 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1076 virtio_balloon_unregister_shrinker(vb);
1078 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1079 destroy_workqueue(vb->balloon_wq);
1081 vdev->config->del_vqs(vdev);
1088 static void remove_common(struct virtio_balloon *vb)
1090 /* There might be pages left in the balloon: free them. */
1091 while (vb->num_pages)
1092 leak_balloon(vb, vb->num_pages);
1093 update_balloon_size(vb);
1095 /* There might be free pages that are being reported: release them. */
1096 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1097 return_free_pages_to_mm(vb, ULONG_MAX);
1099 /* Now we reset the device so we can clean up the queues. */
1100 virtio_reset_device(vb->vdev);
1102 vb->vdev->config->del_vqs(vb->vdev);
1105 static void virtballoon_remove(struct virtio_device *vdev)
1107 struct virtio_balloon *vb = vdev->priv;
1109 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
1110 page_reporting_unregister(&vb->pr_dev_info);
1111 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
1112 unregister_oom_notifier(&vb->oom_nb);
1113 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
1114 virtio_balloon_unregister_shrinker(vb);
1115 spin_lock_irq(&vb->stop_update_lock);
1116 vb->stop_update = true;
1117 spin_unlock_irq(&vb->stop_update_lock);
1118 cancel_work_sync(&vb->update_balloon_size_work);
1119 cancel_work_sync(&vb->update_balloon_stats_work);
1121 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
1122 cancel_work_sync(&vb->report_free_page_work);
1123 destroy_workqueue(vb->balloon_wq);
1130 #ifdef CONFIG_PM_SLEEP
1131 static int virtballoon_freeze(struct virtio_device *vdev)
1133 struct virtio_balloon *vb = vdev->priv;
1136 * The workqueue is already frozen by the PM core before this
1137 * function is called.
1143 static int virtballoon_restore(struct virtio_device *vdev)
1145 struct virtio_balloon *vb = vdev->priv;
1148 ret = init_vqs(vdev->priv);
1152 virtio_device_ready(vdev);
1154 if (towards_target(vb))
1155 virtballoon_changed(vdev);
1156 update_balloon_size(vb);
1161 static int virtballoon_validate(struct virtio_device *vdev)
1164 * Inform the hypervisor that our pages are poisoned or
1165 * initialized. If we cannot do that then we should disable
1166 * page reporting as it could potentially change the contents
1167 * of our free pages.
1169 if (!want_init_on_free() && !page_poisoning_enabled_static())
1170 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1171 else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
1172 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
1174 __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
1178 static unsigned int features[] = {
1179 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1180 VIRTIO_BALLOON_F_STATS_VQ,
1181 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1182 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1183 VIRTIO_BALLOON_F_PAGE_POISON,
1184 VIRTIO_BALLOON_F_REPORTING,
1187 static struct virtio_driver virtio_balloon_driver = {
1188 .feature_table = features,
1189 .feature_table_size = ARRAY_SIZE(features),
1190 .driver.name = KBUILD_MODNAME,
1191 .id_table = id_table,
1192 .validate = virtballoon_validate,
1193 .probe = virtballoon_probe,
1194 .remove = virtballoon_remove,
1195 .config_changed = virtballoon_changed,
1196 #ifdef CONFIG_PM_SLEEP
1197 .freeze = virtballoon_freeze,
1198 .restore = virtballoon_restore,
1202 module_virtio_driver(virtio_balloon_driver);
1203 MODULE_DEVICE_TABLE(virtio, id_table);
1204 MODULE_DESCRIPTION("Virtio balloon driver");
1205 MODULE_LICENSE("GPL");