2 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
3 * Tosatti's implementations.
5 * Copyright 2008 Rusty Russell IBM Corporation
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 #include <linux/virtio.h>
23 #include <linux/virtio_balloon.h>
24 #include <linux/swap.h>
25 #include <linux/workqueue.h>
26 #include <linux/delay.h>
27 #include <linux/slab.h>
28 #include <linux/module.h>
29 #include <linux/balloon_compaction.h>
30 #include <linux/wait.h>
32 #include <linux/mount.h>
33 #include <linux/magic.h>
36 * Balloon device works in 4K page units. So each page is pointed to by
37 * multiple balloon pages. All memory counters in this driver are in balloon
40 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
41 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
44 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
46 /* The order of free page blocks to report to host */
47 #define VIRTIO_BALLOON_FREE_PAGE_ORDER (MAX_ORDER - 1)
48 /* The size of a free page block in bytes */
49 #define VIRTIO_BALLOON_FREE_PAGE_SIZE \
50 (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
52 #ifdef CONFIG_BALLOON_COMPACTION
53 static struct vfsmount *balloon_mnt;
56 enum virtio_balloon_vq {
57 VIRTIO_BALLOON_VQ_INFLATE,
58 VIRTIO_BALLOON_VQ_DEFLATE,
59 VIRTIO_BALLOON_VQ_STATS,
60 VIRTIO_BALLOON_VQ_FREE_PAGE,
64 enum virtio_balloon_config_read {
65 VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
68 struct virtio_balloon {
69 struct virtio_device *vdev;
70 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
72 /* Balloon's own wq for cpu-intensive work items */
73 struct workqueue_struct *balloon_wq;
74 /* The free page reporting work item submitted to the balloon wq */
75 struct work_struct report_free_page_work;
77 /* The balloon servicing is delegated to a freezable workqueue. */
78 struct work_struct update_balloon_stats_work;
79 struct work_struct update_balloon_size_work;
81 /* Prevent updating balloon when it is being canceled. */
82 spinlock_t stop_update_lock;
84 /* Bitmap to indicate if reading the related config fields are needed */
85 unsigned long config_read_bitmap;
87 /* The list of allocated free pages, waiting to be given back to mm */
88 struct list_head free_page_list;
89 spinlock_t free_page_list_lock;
90 /* The number of free page blocks on the above list */
91 unsigned long num_free_page_blocks;
93 * The cmd id received from host.
94 * Read it via virtio_balloon_cmd_id_received to get the latest value
97 u32 cmd_id_received_cache;
98 /* The cmd id that is actively in use */
99 __virtio32 cmd_id_active;
100 /* Buffer to store the stop sign */
101 __virtio32 cmd_id_stop;
103 /* Waiting for host to ack the pages we released. */
104 wait_queue_head_t acked;
106 /* Number of balloon pages we've told the Host we're not using. */
107 unsigned int num_pages;
109 * The pages we've told the Host we're not using are enqueued
110 * at vb_dev_info->pages list.
111 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
112 * to num_pages above.
114 struct balloon_dev_info vb_dev_info;
116 /* Synchronize access/update to this struct virtio_balloon elements */
117 struct mutex balloon_lock;
119 /* The array of pfns we tell the Host about. */
120 unsigned int num_pfns;
121 __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
123 /* Memory statistics */
124 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
126 /* To register a shrinker to shrink memory upon memory pressure */
127 struct shrinker shrinker;
130 static struct virtio_device_id id_table[] = {
131 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
135 static u32 page_to_balloon_pfn(struct page *page)
137 unsigned long pfn = page_to_pfn(page);
139 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
140 /* Convert pfn from Linux page size to balloon page size. */
141 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
144 static void balloon_ack(struct virtqueue *vq)
146 struct virtio_balloon *vb = vq->vdev->priv;
151 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
153 struct scatterlist sg;
156 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
158 /* We should always be able to add one buffer to an empty queue. */
159 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
162 /* When host has read buffer, this completes via balloon_ack */
163 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
167 static void set_page_pfns(struct virtio_balloon *vb,
168 __virtio32 pfns[], struct page *page)
173 * Set balloon pfns pointing at this page.
174 * Note that the first pfn points at start of the page.
176 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
177 pfns[i] = cpu_to_virtio32(vb->vdev,
178 page_to_balloon_pfn(page) + i);
181 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
183 unsigned num_allocated_pages;
188 /* We can only do one array worth at a time. */
189 num = min(num, ARRAY_SIZE(vb->pfns));
191 for (num_pfns = 0; num_pfns < num;
192 num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
193 struct page *page = balloon_page_alloc();
196 dev_info_ratelimited(&vb->vdev->dev,
197 "Out of puff! Can't get %u pages\n",
198 VIRTIO_BALLOON_PAGES_PER_PAGE);
199 /* Sleep for at least 1/5 of a second before retry. */
204 balloon_page_push(&pages, page);
207 mutex_lock(&vb->balloon_lock);
211 while ((page = balloon_page_pop(&pages))) {
212 balloon_page_enqueue(&vb->vb_dev_info, page);
214 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
215 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
216 if (!virtio_has_feature(vb->vdev,
217 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
218 adjust_managed_page_count(page, -1);
219 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
222 num_allocated_pages = vb->num_pfns;
223 /* Did we get any? */
224 if (vb->num_pfns != 0)
225 tell_host(vb, vb->inflate_vq);
226 mutex_unlock(&vb->balloon_lock);
228 return num_allocated_pages;
231 static void release_pages_balloon(struct virtio_balloon *vb,
232 struct list_head *pages)
234 struct page *page, *next;
236 list_for_each_entry_safe(page, next, pages, lru) {
237 if (!virtio_has_feature(vb->vdev,
238 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
239 adjust_managed_page_count(page, 1);
240 list_del(&page->lru);
241 put_page(page); /* balloon reference */
245 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
247 unsigned num_freed_pages;
249 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
252 /* We can only do one array worth at a time. */
253 num = min(num, ARRAY_SIZE(vb->pfns));
255 mutex_lock(&vb->balloon_lock);
256 /* We can't release more pages than taken */
257 num = min(num, (size_t)vb->num_pages);
258 for (vb->num_pfns = 0; vb->num_pfns < num;
259 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
260 page = balloon_page_dequeue(vb_dev_info);
263 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
264 list_add(&page->lru, &pages);
265 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
268 num_freed_pages = vb->num_pfns;
271 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
272 * is true, we *have* to do it in this order
274 if (vb->num_pfns != 0)
275 tell_host(vb, vb->deflate_vq);
276 release_pages_balloon(vb, &pages);
277 mutex_unlock(&vb->balloon_lock);
278 return num_freed_pages;
281 static inline void update_stat(struct virtio_balloon *vb, int idx,
284 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
285 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
286 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
289 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
291 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
293 unsigned long events[NR_VM_EVENT_ITEMS];
295 unsigned int idx = 0;
297 unsigned long caches;
299 all_vm_events(events);
302 available = si_mem_available();
303 caches = global_node_page_state(NR_FILE_PAGES);
305 #ifdef CONFIG_VM_EVENT_COUNTERS
306 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
307 pages_to_bytes(events[PSWPIN]));
308 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
309 pages_to_bytes(events[PSWPOUT]));
310 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
311 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
312 #ifdef CONFIG_HUGETLB_PAGE
313 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
314 events[HTLB_BUDDY_PGALLOC]);
315 update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
316 events[HTLB_BUDDY_PGALLOC_FAIL]);
319 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
320 pages_to_bytes(i.freeram));
321 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
322 pages_to_bytes(i.totalram));
323 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
324 pages_to_bytes(available));
325 update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
326 pages_to_bytes(caches));
332 * While most virtqueues communicate guest-initiated requests to the hypervisor,
333 * the stats queue operates in reverse. The driver initializes the virtqueue
334 * with a single buffer. From that point forward, all conversations consist of
335 * a hypervisor request (a call to this function) which directs us to refill
336 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
337 * we delegate the job to a freezable workqueue that will do the actual work via
338 * stats_handle_request().
340 static void stats_request(struct virtqueue *vq)
342 struct virtio_balloon *vb = vq->vdev->priv;
344 spin_lock(&vb->stop_update_lock);
345 if (!vb->stop_update)
346 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
347 spin_unlock(&vb->stop_update_lock);
350 static void stats_handle_request(struct virtio_balloon *vb)
352 struct virtqueue *vq;
353 struct scatterlist sg;
354 unsigned int len, num_stats;
356 num_stats = update_balloon_stats(vb);
359 if (!virtqueue_get_buf(vq, &len))
361 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
362 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
366 static inline s64 towards_target(struct virtio_balloon *vb)
371 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
374 /* Legacy balloon config space is LE, unlike all other devices. */
375 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
376 num_pages = le32_to_cpu((__force __le32)num_pages);
379 return target - vb->num_pages;
382 /* Gives back @num_to_return blocks of free pages to mm. */
383 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
384 unsigned long num_to_return)
387 unsigned long num_returned;
389 spin_lock_irq(&vb->free_page_list_lock);
390 for (num_returned = 0; num_returned < num_to_return; num_returned++) {
391 page = balloon_page_pop(&vb->free_page_list);
394 free_pages((unsigned long)page_address(page),
395 VIRTIO_BALLOON_FREE_PAGE_ORDER);
397 vb->num_free_page_blocks -= num_returned;
398 spin_unlock_irq(&vb->free_page_list_lock);
403 static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
405 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
408 /* No need to queue the work if the bit was already set. */
409 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
410 &vb->config_read_bitmap))
413 queue_work(vb->balloon_wq, &vb->report_free_page_work);
416 static void virtballoon_changed(struct virtio_device *vdev)
418 struct virtio_balloon *vb = vdev->priv;
421 spin_lock_irqsave(&vb->stop_update_lock, flags);
422 if (!vb->stop_update) {
423 queue_work(system_freezable_wq,
424 &vb->update_balloon_size_work);
425 virtio_balloon_queue_free_page_work(vb);
427 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
430 static void update_balloon_size(struct virtio_balloon *vb)
432 u32 actual = vb->num_pages;
434 /* Legacy balloon config space is LE, unlike all other devices. */
435 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
436 actual = (__force u32)cpu_to_le32(actual);
438 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
442 static void update_balloon_stats_func(struct work_struct *work)
444 struct virtio_balloon *vb;
446 vb = container_of(work, struct virtio_balloon,
447 update_balloon_stats_work);
448 stats_handle_request(vb);
451 static void update_balloon_size_func(struct work_struct *work)
453 struct virtio_balloon *vb;
456 vb = container_of(work, struct virtio_balloon,
457 update_balloon_size_work);
458 diff = towards_target(vb);
464 diff -= fill_balloon(vb, diff);
466 diff += leak_balloon(vb, -diff);
467 update_balloon_size(vb);
470 queue_work(system_freezable_wq, work);
473 static int init_vqs(struct virtio_balloon *vb)
475 struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
476 vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
477 const char *names[VIRTIO_BALLOON_VQ_MAX];
481 * Inflateq and deflateq are used unconditionally. The names[]
482 * will be NULL if the related feature is not enabled, which will
483 * cause no allocation for the corresponding virtqueue in find_vqs.
485 callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
486 names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
487 callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
488 names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
489 names[VIRTIO_BALLOON_VQ_STATS] = NULL;
490 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
492 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
493 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
494 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
497 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
498 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
499 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
502 err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
503 vqs, callbacks, names, NULL, NULL);
507 vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
508 vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
509 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
510 struct scatterlist sg;
511 unsigned int num_stats;
512 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
515 * Prime this virtqueue with one buffer so the hypervisor can
516 * use it to signal us later (it can't be broken yet!).
518 num_stats = update_balloon_stats(vb);
520 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
521 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
524 dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
528 virtqueue_kick(vb->stats_vq);
531 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
532 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
537 static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
539 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
540 &vb->config_read_bitmap))
541 virtio_cread(vb->vdev, struct virtio_balloon_config,
542 free_page_report_cmd_id,
543 &vb->cmd_id_received_cache);
545 return vb->cmd_id_received_cache;
548 static int send_cmd_id_start(struct virtio_balloon *vb)
550 struct scatterlist sg;
551 struct virtqueue *vq = vb->free_page_vq;
554 /* Detach all the used buffers from the vq */
555 while (virtqueue_get_buf(vq, &unused))
558 vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
559 virtio_balloon_cmd_id_received(vb));
560 sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
561 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
567 static int send_cmd_id_stop(struct virtio_balloon *vb)
569 struct scatterlist sg;
570 struct virtqueue *vq = vb->free_page_vq;
573 /* Detach all the used buffers from the vq */
574 while (virtqueue_get_buf(vq, &unused))
577 sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
578 err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
584 static int get_free_page_and_send(struct virtio_balloon *vb)
586 struct virtqueue *vq = vb->free_page_vq;
588 struct scatterlist sg;
592 /* Detach all the used buffers from the vq */
593 while (virtqueue_get_buf(vq, &unused))
596 page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
597 VIRTIO_BALLOON_FREE_PAGE_ORDER);
599 * When the allocation returns NULL, it indicates that we have got all
600 * the possible free pages, so return -EINTR to stop.
605 p = page_address(page);
606 sg_init_one(&sg, p, VIRTIO_BALLOON_FREE_PAGE_SIZE);
607 /* There is always 1 entry reserved for the cmd id to use. */
608 if (vq->num_free > 1) {
609 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
611 free_pages((unsigned long)p,
612 VIRTIO_BALLOON_FREE_PAGE_ORDER);
616 spin_lock_irq(&vb->free_page_list_lock);
617 balloon_page_push(&vb->free_page_list, page);
618 vb->num_free_page_blocks++;
619 spin_unlock_irq(&vb->free_page_list_lock);
622 * The vq has no available entry to add this page block, so
625 free_pages((unsigned long)p, VIRTIO_BALLOON_FREE_PAGE_ORDER);
631 static int send_free_pages(struct virtio_balloon *vb)
638 * If a stop id or a new cmd id was just received from host,
639 * stop the reporting.
641 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
642 if (unlikely(cmd_id_active !=
643 virtio_balloon_cmd_id_received(vb)))
647 * The free page blocks are allocated and sent to host one by
650 err = get_free_page_and_send(vb);
653 else if (unlikely(err))
660 static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
663 struct device *dev = &vb->vdev->dev;
665 /* Start by sending the received cmd id to host with an outbuf. */
666 err = send_cmd_id_start(vb);
668 dev_err(dev, "Failed to send a start id, err = %d\n", err);
670 err = send_free_pages(vb);
672 dev_err(dev, "Failed to send a free page, err = %d\n", err);
674 /* End by sending a stop id to host with an outbuf. */
675 err = send_cmd_id_stop(vb);
677 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
680 static void report_free_page_func(struct work_struct *work)
682 struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
683 report_free_page_work);
686 cmd_id_received = virtio_balloon_cmd_id_received(vb);
687 if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
688 /* Pass ULONG_MAX to give back all the free pages */
689 return_free_pages_to_mm(vb, ULONG_MAX);
690 } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
692 virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
693 virtio_balloon_report_free_page(vb);
697 #ifdef CONFIG_BALLOON_COMPACTION
699 * virtballoon_migratepage - perform the balloon page migration on behalf of
700 * a compation thread. (called under page lock)
701 * @vb_dev_info: the balloon device
702 * @newpage: page that will replace the isolated page after migration finishes.
703 * @page : the isolated (old) page that is about to be migrated to newpage.
704 * @mode : compaction mode -- not used for balloon page migration.
706 * After a ballooned page gets isolated by compaction procedures, this is the
707 * function that performs the page migration on behalf of a compaction thread
708 * The page migration for virtio balloon is done in a simple swap fashion which
709 * follows these two macro steps:
710 * 1) insert newpage into vb->pages list and update the host about it;
711 * 2) update the host about the old page removed from vb->pages list;
713 * This function preforms the balloon page migration task.
714 * Called through balloon_mapping->a_ops->migratepage
716 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
717 struct page *newpage, struct page *page, enum migrate_mode mode)
719 struct virtio_balloon *vb = container_of(vb_dev_info,
720 struct virtio_balloon, vb_dev_info);
724 * In order to avoid lock contention while migrating pages concurrently
725 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
726 * this turn, as it is easier to retry the page migration later.
727 * This also prevents fill_balloon() getting stuck into a mutex
728 * recursion in the case it ends up triggering memory compaction
729 * while it is attempting to inflate the ballon.
731 if (!mutex_trylock(&vb->balloon_lock))
734 get_page(newpage); /* balloon reference */
736 /* balloon's page migration 1st step -- inflate "newpage" */
737 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
738 balloon_page_insert(vb_dev_info, newpage);
739 vb_dev_info->isolated_pages--;
740 __count_vm_event(BALLOON_MIGRATE);
741 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
742 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
743 set_page_pfns(vb, vb->pfns, newpage);
744 tell_host(vb, vb->inflate_vq);
746 /* balloon's page migration 2nd step -- deflate "page" */
747 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
748 balloon_page_delete(page);
749 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
750 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
751 set_page_pfns(vb, vb->pfns, page);
752 tell_host(vb, vb->deflate_vq);
754 mutex_unlock(&vb->balloon_lock);
756 put_page(page); /* balloon reference */
758 return MIGRATEPAGE_SUCCESS;
761 static struct dentry *balloon_mount(struct file_system_type *fs_type,
762 int flags, const char *dev_name, void *data)
764 static const struct dentry_operations ops = {
765 .d_dname = simple_dname,
768 return mount_pseudo(fs_type, "balloon-kvm:", NULL, &ops,
772 static struct file_system_type balloon_fs = {
773 .name = "balloon-kvm",
774 .mount = balloon_mount,
775 .kill_sb = kill_anon_super,
778 #endif /* CONFIG_BALLOON_COMPACTION */
780 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
781 unsigned long pages_to_free)
783 unsigned long blocks_to_free, blocks_freed;
785 pages_to_free = round_up(pages_to_free,
786 1 << VIRTIO_BALLOON_FREE_PAGE_ORDER);
787 blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
788 blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
790 return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
793 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
794 unsigned long pages_to_free)
796 unsigned long pages_freed = 0;
799 * One invocation of leak_balloon can deflate at most
800 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
801 * multiple times to deflate pages till reaching pages_to_free.
803 while (vb->num_pages && pages_to_free) {
804 pages_freed += leak_balloon(vb, pages_to_free) /
805 VIRTIO_BALLOON_PAGES_PER_PAGE;
806 pages_to_free -= pages_freed;
808 update_balloon_size(vb);
813 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
814 struct shrink_control *sc)
816 unsigned long pages_to_free, pages_freed = 0;
817 struct virtio_balloon *vb = container_of(shrinker,
818 struct virtio_balloon, shrinker);
820 pages_to_free = sc->nr_to_scan * VIRTIO_BALLOON_PAGES_PER_PAGE;
822 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
823 pages_freed = shrink_free_pages(vb, pages_to_free);
825 if (pages_freed >= pages_to_free)
828 pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
833 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
834 struct shrink_control *sc)
836 struct virtio_balloon *vb = container_of(shrinker,
837 struct virtio_balloon, shrinker);
840 count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
841 count += vb->num_free_page_blocks >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
846 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
848 unregister_shrinker(&vb->shrinker);
851 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
853 vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
854 vb->shrinker.count_objects = virtio_balloon_shrinker_count;
855 vb->shrinker.seeks = DEFAULT_SEEKS;
857 return register_shrinker(&vb->shrinker);
860 static int virtballoon_probe(struct virtio_device *vdev)
862 struct virtio_balloon *vb;
866 if (!vdev->config->get) {
867 dev_err(&vdev->dev, "%s failure: config access disabled\n",
872 vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
878 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
879 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
880 spin_lock_init(&vb->stop_update_lock);
881 mutex_init(&vb->balloon_lock);
882 init_waitqueue_head(&vb->acked);
885 balloon_devinfo_init(&vb->vb_dev_info);
891 #ifdef CONFIG_BALLOON_COMPACTION
892 balloon_mnt = kern_mount(&balloon_fs);
893 if (IS_ERR(balloon_mnt)) {
894 err = PTR_ERR(balloon_mnt);
898 vb->vb_dev_info.migratepage = virtballoon_migratepage;
899 vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
900 if (IS_ERR(vb->vb_dev_info.inode)) {
901 err = PTR_ERR(vb->vb_dev_info.inode);
902 kern_unmount(balloon_mnt);
905 vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
907 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
909 * There is always one entry reserved for cmd id, so the ring
910 * size needs to be at least two to report free page hints.
912 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
916 vb->balloon_wq = alloc_workqueue("balloon-wq",
917 WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
918 if (!vb->balloon_wq) {
922 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
923 vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
924 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
925 VIRTIO_BALLOON_CMD_ID_STOP);
926 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
927 VIRTIO_BALLOON_CMD_ID_STOP);
928 spin_lock_init(&vb->free_page_list_lock);
929 INIT_LIST_HEAD(&vb->free_page_list);
930 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
931 memset(&poison_val, PAGE_POISON, sizeof(poison_val));
932 virtio_cwrite(vb->vdev, struct virtio_balloon_config,
933 poison_val, &poison_val);
937 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
938 * shrinker needs to be registered to relieve memory pressure.
940 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
941 err = virtio_balloon_register_shrinker(vb);
943 goto out_del_balloon_wq;
945 virtio_device_ready(vdev);
947 if (towards_target(vb))
948 virtballoon_changed(vdev);
952 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
953 destroy_workqueue(vb->balloon_wq);
955 vdev->config->del_vqs(vdev);
962 static void remove_common(struct virtio_balloon *vb)
964 /* There might be pages left in the balloon: free them. */
965 while (vb->num_pages)
966 leak_balloon(vb, vb->num_pages);
967 update_balloon_size(vb);
969 /* Now we reset the device so we can clean up the queues. */
970 vb->vdev->config->reset(vb->vdev);
972 vb->vdev->config->del_vqs(vb->vdev);
975 static void virtballoon_remove(struct virtio_device *vdev)
977 struct virtio_balloon *vb = vdev->priv;
979 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
980 virtio_balloon_unregister_shrinker(vb);
981 spin_lock_irq(&vb->stop_update_lock);
982 vb->stop_update = true;
983 spin_unlock_irq(&vb->stop_update_lock);
984 cancel_work_sync(&vb->update_balloon_size_work);
985 cancel_work_sync(&vb->update_balloon_stats_work);
987 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
988 cancel_work_sync(&vb->report_free_page_work);
989 destroy_workqueue(vb->balloon_wq);
993 #ifdef CONFIG_BALLOON_COMPACTION
994 if (vb->vb_dev_info.inode)
995 iput(vb->vb_dev_info.inode);
997 kern_unmount(balloon_mnt);
1002 #ifdef CONFIG_PM_SLEEP
1003 static int virtballoon_freeze(struct virtio_device *vdev)
1005 struct virtio_balloon *vb = vdev->priv;
1008 * The workqueue is already frozen by the PM core before this
1009 * function is called.
1015 static int virtballoon_restore(struct virtio_device *vdev)
1017 struct virtio_balloon *vb = vdev->priv;
1020 ret = init_vqs(vdev->priv);
1024 virtio_device_ready(vdev);
1026 if (towards_target(vb))
1027 virtballoon_changed(vdev);
1028 update_balloon_size(vb);
1033 static int virtballoon_validate(struct virtio_device *vdev)
1035 if (!page_poisoning_enabled())
1036 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1038 __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1042 static unsigned int features[] = {
1043 VIRTIO_BALLOON_F_MUST_TELL_HOST,
1044 VIRTIO_BALLOON_F_STATS_VQ,
1045 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1046 VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1047 VIRTIO_BALLOON_F_PAGE_POISON,
1050 static struct virtio_driver virtio_balloon_driver = {
1051 .feature_table = features,
1052 .feature_table_size = ARRAY_SIZE(features),
1053 .driver.name = KBUILD_MODNAME,
1054 .driver.owner = THIS_MODULE,
1055 .id_table = id_table,
1056 .validate = virtballoon_validate,
1057 .probe = virtballoon_probe,
1058 .remove = virtballoon_remove,
1059 .config_changed = virtballoon_changed,
1060 #ifdef CONFIG_PM_SLEEP
1061 .freeze = virtballoon_freeze,
1062 .restore = virtballoon_restore,
1066 module_virtio_driver(virtio_balloon_driver);
1067 MODULE_DEVICE_TABLE(virtio, id_table);
1068 MODULE_DESCRIPTION("Virtio balloon driver");
1069 MODULE_LICENSE("GPL");