| /* |
| * Virtio balloon implementation, inspired by Dor Laor and Marcelo |
| * Tosatti's implementations. |
| * |
| * Copyright 2008 Rusty Russell IBM Corporation |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include <linux/virtio.h> |
| #include <linux/virtio_balloon.h> |
| #include <linux/swap.h> |
| #include <linux/kthread.h> |
| #include <linux/freezer.h> |
| #include <linux/delay.h> |
| #include <linux/slab.h> |
| #include <linux/module.h> |
| #include <linux/balloon_compaction.h> |
| |
| /* |
| * Balloon device works in 4K page units. So each page is pointed to by |
| * multiple balloon pages. All memory counters in this driver are in balloon |
| * page units. |
| */ |
| #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) |
| #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 |
| |
| struct virtio_balloon |
| { |
| struct virtio_device *vdev; |
| struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; |
| |
| /* Where the ballooning thread waits for config to change. */ |
| wait_queue_head_t config_change; |
| |
| /* The thread servicing the balloon. */ |
| struct task_struct *thread; |
| |
| /* Waiting for host to ack the pages we released. */ |
| wait_queue_head_t acked; |
| |
| /* Number of balloon pages we've told the Host we're not using. */ |
| unsigned int num_pages; |
| /* |
| * The pages we've told the Host we're not using are enqueued |
| * at vb_dev_info->pages list. |
| * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE |
| * to num_pages above. |
| */ |
| struct balloon_dev_info *vb_dev_info; |
| |
| /* Synchronize access/update to this struct virtio_balloon elements */ |
| struct mutex balloon_lock; |
| |
| /* The array of pfns we tell the Host about. */ |
| unsigned int num_pfns; |
| u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; |
| |
| /* Memory statistics */ |
| int need_stats_update; |
| struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; |
| }; |
| |
| static struct virtio_device_id id_table[] = { |
| { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, |
| { 0 }, |
| }; |
| |
| static u32 page_to_balloon_pfn(struct page *page) |
| { |
| unsigned long pfn = page_to_pfn(page); |
| |
| BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); |
| /* Convert pfn from Linux page size to balloon page size. */ |
| return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE; |
| } |
| |
| static struct page *balloon_pfn_to_page(u32 pfn) |
| { |
| BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE); |
| return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE); |
| } |
| |
| static void balloon_ack(struct virtqueue *vq) |
| { |
| struct virtio_balloon *vb = vq->vdev->priv; |
| |
| wake_up(&vb->acked); |
| } |
| |
| static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) |
| { |
| struct scatterlist sg; |
| unsigned int len; |
| |
| sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); |
| |
| /* We should always be able to add one buffer to an empty queue. */ |
| if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0) |
| BUG(); |
| virtqueue_kick(vq); |
| |
| /* When host has read buffer, this completes via balloon_ack */ |
| wait_event(vb->acked, virtqueue_get_buf(vq, &len)); |
| } |
| |
| static void set_page_pfns(u32 pfns[], struct page *page) |
| { |
| unsigned int i; |
| |
| /* Set balloon pfns pointing at this page. |
| * Note that the first pfn points at start of the page. */ |
| for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) |
| pfns[i] = page_to_balloon_pfn(page) + i; |
| } |
| |
| static void fill_balloon(struct virtio_balloon *vb, size_t num) |
| { |
| struct balloon_dev_info *vb_dev_info = vb->vb_dev_info; |
| |
| /* We can only do one array worth at a time. */ |
| num = min(num, ARRAY_SIZE(vb->pfns)); |
| |
| mutex_lock(&vb->balloon_lock); |
| for (vb->num_pfns = 0; vb->num_pfns < num; |
| vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { |
| struct page *page = balloon_page_enqueue(vb_dev_info); |
| |
| if (!page) { |
| dev_info_ratelimited(&vb->vdev->dev, |
| "Out of puff! Can't get %u pages\n", |
| VIRTIO_BALLOON_PAGES_PER_PAGE); |
| /* Sleep for at least 1/5 of a second before retry. */ |
| msleep(200); |
| break; |
| } |
| set_page_pfns(vb->pfns + vb->num_pfns, page); |
| vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; |
| totalram_pages--; |
| } |
| |
| /* Did we get any? */ |
| if (vb->num_pfns != 0) |
| tell_host(vb, vb->inflate_vq); |
| mutex_unlock(&vb->balloon_lock); |
| } |
| |
| static void release_pages_by_pfn(const u32 pfns[], unsigned int num) |
| { |
| unsigned int i; |
| |
| /* Find pfns pointing at start of each page, get pages and free them. */ |
| for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) { |
| balloon_page_free(balloon_pfn_to_page(pfns[i])); |
| totalram_pages++; |
| } |
| } |
| |
| static void leak_balloon(struct virtio_balloon *vb, size_t num) |
| { |
| struct page *page; |
| struct balloon_dev_info *vb_dev_info = vb->vb_dev_info; |
| |
| /* We can only do one array worth at a time. */ |
| num = min(num, ARRAY_SIZE(vb->pfns)); |
| |
| mutex_lock(&vb->balloon_lock); |
| for (vb->num_pfns = 0; vb->num_pfns < num; |
| vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { |
| page = balloon_page_dequeue(vb_dev_info); |
| if (!page) |
| break; |
| set_page_pfns(vb->pfns + vb->num_pfns, page); |
| vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; |
| } |
| |
| /* |
| * Note that if |
| * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); |
| * is true, we *have* to do it in this order |
| */ |
| if (vb->num_pfns != 0) |
| tell_host(vb, vb->deflate_vq); |
| mutex_unlock(&vb->balloon_lock); |
| release_pages_by_pfn(vb->pfns, vb->num_pfns); |
| } |
| |
| static inline void update_stat(struct virtio_balloon *vb, int idx, |
| u16 tag, u64 val) |
| { |
| BUG_ON(idx >= VIRTIO_BALLOON_S_NR); |
| vb->stats[idx].tag = tag; |
| vb->stats[idx].val = val; |
| } |
| |
| #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) |
| |
| static void update_balloon_stats(struct virtio_balloon *vb) |
| { |
| unsigned long events[NR_VM_EVENT_ITEMS]; |
| struct sysinfo i; |
| int idx = 0; |
| |
| all_vm_events(events); |
| si_meminfo(&i); |
| |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, |
| pages_to_bytes(events[PSWPIN])); |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, |
| pages_to_bytes(events[PSWPOUT])); |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, |
| pages_to_bytes(i.freeram)); |
| update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, |
| pages_to_bytes(i.totalram)); |
| } |
| |
| /* |
| * While most virtqueues communicate guest-initiated requests to the hypervisor, |
| * the stats queue operates in reverse. The driver initializes the virtqueue |
| * with a single buffer. From that point forward, all conversations consist of |
| * a hypervisor request (a call to this function) which directs us to refill |
| * the virtqueue with a fresh stats buffer. Since stats collection can sleep, |
| * we notify our kthread which does the actual work via stats_handle_request(). |
| */ |
| static void stats_request(struct virtqueue *vq) |
| { |
| struct virtio_balloon *vb = vq->vdev->priv; |
| |
| vb->need_stats_update = 1; |
| wake_up(&vb->config_change); |
| } |
| |
| static void stats_handle_request(struct virtio_balloon *vb) |
| { |
| struct virtqueue *vq; |
| struct scatterlist sg; |
| unsigned int len; |
| |
| vb->need_stats_update = 0; |
| update_balloon_stats(vb); |
| |
| vq = vb->stats_vq; |
| if (!virtqueue_get_buf(vq, &len)) |
| return; |
| sg_init_one(&sg, vb->stats, sizeof(vb->stats)); |
| if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0) |
| BUG(); |
| virtqueue_kick(vq); |
| } |
| |
| static void virtballoon_changed(struct virtio_device *vdev) |
| { |
| struct virtio_balloon *vb = vdev->priv; |
| |
| wake_up(&vb->config_change); |
| } |
| |
| static inline s64 towards_target(struct virtio_balloon *vb) |
| { |
| __le32 v; |
| s64 target; |
| |
| vb->vdev->config->get(vb->vdev, |
| offsetof(struct virtio_balloon_config, num_pages), |
| &v, sizeof(v)); |
| target = le32_to_cpu(v); |
| return target - vb->num_pages; |
| } |
| |
| static void update_balloon_size(struct virtio_balloon *vb) |
| { |
| __le32 actual = cpu_to_le32(vb->num_pages); |
| |
| vb->vdev->config->set(vb->vdev, |
| offsetof(struct virtio_balloon_config, actual), |
| &actual, sizeof(actual)); |
| } |
| |
| static int balloon(void *_vballoon) |
| { |
| struct virtio_balloon *vb = _vballoon; |
| |
| set_freezable(); |
| while (!kthread_should_stop()) { |
| s64 diff; |
| |
| try_to_freeze(); |
| wait_event_interruptible(vb->config_change, |
| (diff = towards_target(vb)) != 0 |
| || vb->need_stats_update |
| || kthread_should_stop() |
| || freezing(current)); |
| if (vb->need_stats_update) |
| stats_handle_request(vb); |
| if (diff > 0) |
| fill_balloon(vb, diff); |
| else if (diff < 0) |
| leak_balloon(vb, -diff); |
| update_balloon_size(vb); |
| |
| /* |
| * For large balloon changes, we could spend a lot of time |
| * and always have work to do. Be nice if preempt disabled. |
| */ |
| cond_resched(); |
| } |
| return 0; |
| } |
| |
| static int init_vqs(struct virtio_balloon *vb) |
| { |
| struct virtqueue *vqs[3]; |
| vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; |
| const char *names[] = { "inflate", "deflate", "stats" }; |
| int err, nvqs; |
| |
| /* |
| * We expect two virtqueues: inflate and deflate, and |
| * optionally stat. |
| */ |
| nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; |
| err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names); |
| if (err) |
| return err; |
| |
| vb->inflate_vq = vqs[0]; |
| vb->deflate_vq = vqs[1]; |
| if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { |
| struct scatterlist sg; |
| vb->stats_vq = vqs[2]; |
| |
| /* |
| * Prime this virtqueue with one buffer so the hypervisor can |
| * use it to signal us later. |
| */ |
| sg_init_one(&sg, vb->stats, sizeof vb->stats); |
| if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) |
| < 0) |
| BUG(); |
| virtqueue_kick(vb->stats_vq); |
| } |
| return 0; |
| } |
| |
| static const struct address_space_operations virtio_balloon_aops; |
| #ifdef CONFIG_BALLOON_COMPACTION |
| /* |
| * virtballoon_migratepage - perform the balloon page migration on behalf of |
| * a compation thread. (called under page lock) |
| * @mapping: the page->mapping which will be assigned to the new migrated page. |
| * @newpage: page that will replace the isolated page after migration finishes. |
| * @page : the isolated (old) page that is about to be migrated to newpage. |
| * @mode : compaction mode -- not used for balloon page migration. |
| * |
| * After a ballooned page gets isolated by compaction procedures, this is the |
| * function that performs the page migration on behalf of a compaction thread |
| * The page migration for virtio balloon is done in a simple swap fashion which |
| * follows these two macro steps: |
| * 1) insert newpage into vb->pages list and update the host about it; |
| * 2) update the host about the old page removed from vb->pages list; |
| * |
| * This function preforms the balloon page migration task. |
| * Called through balloon_mapping->a_ops->migratepage |
| */ |
| int virtballoon_migratepage(struct address_space *mapping, |
| struct page *newpage, struct page *page, enum migrate_mode mode) |
| { |
| struct balloon_dev_info *vb_dev_info = balloon_page_device(page); |
| struct virtio_balloon *vb; |
| unsigned long flags; |
| |
| BUG_ON(!vb_dev_info); |
| |
| vb = vb_dev_info->balloon_device; |
| |
| /* |
| * In order to avoid lock contention while migrating pages concurrently |
| * to leak_balloon() or fill_balloon() we just give up the balloon_lock |
| * this turn, as it is easier to retry the page migration later. |
| * This also prevents fill_balloon() getting stuck into a mutex |
| * recursion in the case it ends up triggering memory compaction |
| * while it is attempting to inflate the ballon. |
| */ |
| if (!mutex_trylock(&vb->balloon_lock)) |
| return -EAGAIN; |
| |
| /* balloon's page migration 1st step -- inflate "newpage" */ |
| spin_lock_irqsave(&vb_dev_info->pages_lock, flags); |
| balloon_page_insert(newpage, mapping, &vb_dev_info->pages); |
| vb_dev_info->isolated_pages--; |
| spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); |
| vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; |
| set_page_pfns(vb->pfns, newpage); |
| tell_host(vb, vb->inflate_vq); |
| |
| /* |
| * balloon's page migration 2nd step -- deflate "page" |
| * |
| * It's safe to delete page->lru here because this page is at |
| * an isolated migration list, and this step is expected to happen here |
| */ |
| balloon_page_delete(page); |
| vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; |
| set_page_pfns(vb->pfns, page); |
| tell_host(vb, vb->deflate_vq); |
| |
| mutex_unlock(&vb->balloon_lock); |
| |
| return MIGRATEPAGE_BALLOON_SUCCESS; |
| } |
| |
| /* define the balloon_mapping->a_ops callback to allow balloon page migration */ |
| static const struct address_space_operations virtio_balloon_aops = { |
| .migratepage = virtballoon_migratepage, |
| }; |
| #endif /* CONFIG_BALLOON_COMPACTION */ |
| |
| static int virtballoon_probe(struct virtio_device *vdev) |
| { |
| struct virtio_balloon *vb; |
| struct address_space *vb_mapping; |
| struct balloon_dev_info *vb_devinfo; |
| int err; |
| |
| vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); |
| if (!vb) { |
| err = -ENOMEM; |
| goto out; |
| } |
| |
| vb->num_pages = 0; |
| mutex_init(&vb->balloon_lock); |
| init_waitqueue_head(&vb->config_change); |
| init_waitqueue_head(&vb->acked); |
| vb->vdev = vdev; |
| vb->need_stats_update = 0; |
| |
| vb_devinfo = balloon_devinfo_alloc(vb); |
| if (IS_ERR(vb_devinfo)) { |
| err = PTR_ERR(vb_devinfo); |
| goto out_free_vb; |
| } |
| |
| vb_mapping = balloon_mapping_alloc(vb_devinfo, |
| (balloon_compaction_check()) ? |
| &virtio_balloon_aops : NULL); |
| if (IS_ERR(vb_mapping)) { |
| /* |
| * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP |
| * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off. |
| */ |
| err = PTR_ERR(vb_mapping); |
| if (err != -EOPNOTSUPP) |
| goto out_free_vb_devinfo; |
| } |
| |
| vb->vb_dev_info = vb_devinfo; |
| |
| err = init_vqs(vb); |
| if (err) |
| goto out_free_vb_mapping; |
| |
| vb->thread = kthread_run(balloon, vb, "vballoon"); |
| if (IS_ERR(vb->thread)) { |
| err = PTR_ERR(vb->thread); |
| goto out_del_vqs; |
| } |
| |
| return 0; |
| |
| out_del_vqs: |
| vdev->config->del_vqs(vdev); |
| out_free_vb_mapping: |
| balloon_mapping_free(vb_mapping); |
| out_free_vb_devinfo: |
| balloon_devinfo_free(vb_devinfo); |
| out_free_vb: |
| kfree(vb); |
| out: |
| return err; |
| } |
| |
| static void remove_common(struct virtio_balloon *vb) |
| { |
| /* There might be pages left in the balloon: free them. */ |
| while (vb->num_pages) |
| leak_balloon(vb, vb->num_pages); |
| update_balloon_size(vb); |
| |
| /* Now we reset the device so we can clean up the queues. */ |
| vb->vdev->config->reset(vb->vdev); |
| |
| vb->vdev->config->del_vqs(vb->vdev); |
| } |
| |
| static void virtballoon_remove(struct virtio_device *vdev) |
| { |
| struct virtio_balloon *vb = vdev->priv; |
| |
| kthread_stop(vb->thread); |
| remove_common(vb); |
| balloon_mapping_free(vb->vb_dev_info->mapping); |
| balloon_devinfo_free(vb->vb_dev_info); |
| kfree(vb); |
| } |
| |
| #ifdef CONFIG_PM |
| static int virtballoon_freeze(struct virtio_device *vdev) |
| { |
| struct virtio_balloon *vb = vdev->priv; |
| |
| /* |
| * The kthread is already frozen by the PM core before this |
| * function is called. |
| */ |
| |
| remove_common(vb); |
| return 0; |
| } |
| |
| static int virtballoon_restore(struct virtio_device *vdev) |
| { |
| struct virtio_balloon *vb = vdev->priv; |
| int ret; |
| |
| ret = init_vqs(vdev->priv); |
| if (ret) |
| return ret; |
| |
| fill_balloon(vb, towards_target(vb)); |
| update_balloon_size(vb); |
| return 0; |
| } |
| #endif |
| |
| static unsigned int features[] = { |
| VIRTIO_BALLOON_F_MUST_TELL_HOST, |
| VIRTIO_BALLOON_F_STATS_VQ, |
| }; |
| |
| static struct virtio_driver virtio_balloon_driver = { |
| .feature_table = features, |
| .feature_table_size = ARRAY_SIZE(features), |
| .driver.name = KBUILD_MODNAME, |
| .driver.owner = THIS_MODULE, |
| .id_table = id_table, |
| .probe = virtballoon_probe, |
| .remove = virtballoon_remove, |
| .config_changed = virtballoon_changed, |
| #ifdef CONFIG_PM |
| .freeze = virtballoon_freeze, |
| .restore = virtballoon_restore, |
| #endif |
| }; |
| |
| module_virtio_driver(virtio_balloon_driver); |
| MODULE_DEVICE_TABLE(virtio, id_table); |
| MODULE_DESCRIPTION("Virtio balloon driver"); |
| MODULE_LICENSE("GPL"); |