/* * 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 #include #include #include #include #include #include #include #include #include /* * 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 #define OOM_VBALLOON_DEFAULT_PAGES 256 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES; module_param(oom_pages, int, S_IRUSR | S_IWUSR); MODULE_PARM_DESC(oom_pages, "pages to free on OOM"); 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]; /* To register callback in oom notifier call chain */ struct notifier_block nb; }; 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. */ virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 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; adjust_managed_page_count(page, -1); } /* 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) { struct page *page = balloon_pfn_to_page(pfns[i]); adjust_managed_page_count(page, 1); put_page(page); /* balloon reference */ } } static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) { unsigned num_freed_pages; 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; } num_freed_pages = vb->num_pfns; /* * 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); return num_freed_pages; } 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)); virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); 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; virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &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); virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual, &actual); } /* * virtballoon_oom_notify - release pages when system is under severe * memory pressure (called from out_of_memory()) * @self : notifier block struct * @dummy: not used * @parm : returned - number of freed pages * * The balancing of memory by use of the virtio balloon should not cause * the termination of processes while there are pages in the balloon. * If virtio balloon manages to release some memory, it will make the * system return and retry the allocation that forced the OOM killer * to run. */ static int virtballoon_oom_notify(struct notifier_block *self, unsigned long dummy, void *parm) { struct virtio_balloon *vb; unsigned long *freed; unsigned num_freed_pages; vb = container_of(self, struct virtio_balloon, nb); if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) return NOTIFY_OK; freed = parm; num_freed_pages = leak_balloon(vb, oom_pages); update_balloon_size(vb); *freed += num_freed_pages; return NOTIFY_OK; } 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 (it can't be broken yet!). */ 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; } #ifdef CONFIG_BALLOON_COMPACTION /* * virtballoon_migratepage - perform the balloon page migration on behalf of * a compation thread. (called under page lock) * @vb_dev_info: the balloon device * @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 */ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, struct page *newpage, struct page *page, enum migrate_mode mode) { struct virtio_balloon *vb = container_of(vb_dev_info, struct virtio_balloon, vb_dev_info); unsigned long flags; /* * 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; get_page(newpage); /* balloon reference */ /* balloon's page migration 1st step -- inflate "newpage" */ spin_lock_irqsave(&vb_dev_info->pages_lock, flags); balloon_page_insert(vb_dev_info, newpage); vb_dev_info->isolated_pages--; __count_vm_event(BALLOON_MIGRATE); 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" */ 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); put_page(page); /* balloon reference */ return MIGRATEPAGE_SUCCESS; } #endif /* CONFIG_BALLOON_COMPACTION */ static int virtballoon_probe(struct virtio_device *vdev) { struct virtio_balloon *vb; int err; if (!vdev->config->get) { dev_err(&vdev->dev, "%s failure: config access disabled\n", __func__); return -EINVAL; } 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; balloon_devinfo_init(&vb->vb_dev_info); #ifdef CONFIG_BALLOON_COMPACTION vb->vb_dev_info.migratepage = virtballoon_migratepage; #endif err = init_vqs(vb); if (err) goto out_free_vb; vb->nb.notifier_call = virtballoon_oom_notify; vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY; err = register_oom_notifier(&vb->nb); if (err < 0) goto out_oom_notify; 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: unregister_oom_notifier(&vb->nb); out_oom_notify: vdev->config->del_vqs(vdev); 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; unregister_oom_notifier(&vb->nb); kthread_stop(vb->thread); remove_common(vb); kfree(vb); } #ifdef CONFIG_PM_SLEEP 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; virtio_device_ready(vdev); 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, VIRTIO_BALLOON_F_DEFLATE_ON_OOM, }; 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_SLEEP .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");