// SPDX-License-Identifier: GPL-2.0-or-later /* * Virtio balloon implementation, inspired by Dor Laor and Marcelo * Tosatti's implementations. * * Copyright 2008 Rusty Russell IBM Corporation */ #include #include #include #include #include #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 int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 /* Maximum number of (4k) pages to deflate on OOM notifications. */ #define VIRTIO_BALLOON_OOM_NR_PAGES 256 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ __GFP_NOMEMALLOC) /* The order of free page blocks to report to host */ #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1) /* The size of a free page block in bytes */ #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \ (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT)) #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER) #ifdef CONFIG_BALLOON_COMPACTION static struct vfsmount *balloon_mnt; #endif enum virtio_balloon_vq { VIRTIO_BALLOON_VQ_INFLATE, VIRTIO_BALLOON_VQ_DEFLATE, VIRTIO_BALLOON_VQ_STATS, VIRTIO_BALLOON_VQ_FREE_PAGE, VIRTIO_BALLOON_VQ_REPORTING, VIRTIO_BALLOON_VQ_MAX }; enum virtio_balloon_config_read { VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, }; struct virtio_balloon { struct virtio_device *vdev; struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; /* Balloon's own wq for cpu-intensive work items */ struct workqueue_struct *balloon_wq; /* The free page reporting work item submitted to the balloon wq */ struct work_struct report_free_page_work; /* The balloon servicing is delegated to a freezable workqueue. */ struct work_struct update_balloon_stats_work; struct work_struct update_balloon_size_work; /* Prevent updating balloon when it is being canceled. */ spinlock_t stop_update_lock; bool stop_update; /* Bitmap to indicate if reading the related config fields are needed */ unsigned long config_read_bitmap; /* The list of allocated free pages, waiting to be given back to mm */ struct list_head free_page_list; spinlock_t free_page_list_lock; /* The number of free page blocks on the above list */ unsigned long num_free_page_blocks; /* * The cmd id received from host. * Read it via virtio_balloon_cmd_id_received to get the latest value * sent from host. */ u32 cmd_id_received_cache; /* The cmd id that is actively in use */ __virtio32 cmd_id_active; /* Buffer to store the stop sign */ __virtio32 cmd_id_stop; /* 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; __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; /* Memory statistics */ struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */ struct shrinker shrinker; /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */ struct notifier_block oom_nb; /* Free page reporting device */ struct virtqueue *reporting_vq; struct page_reporting_dev_info pr_dev_info; }; static const 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 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 int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, struct scatterlist *sg, unsigned int nents) { struct virtio_balloon *vb = container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); struct virtqueue *vq = vb->reporting_vq; unsigned int unused, err; /* We should always be able to add these buffers to an empty queue. */ err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN); /* * In the extremely unlikely case that something has occurred and we * are able to trigger an error we will simply display a warning * and exit without actually processing the pages. */ if (WARN_ON_ONCE(err)) return err; virtqueue_kick(vq); /* When host has read buffer, this completes via balloon_ack */ wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); return 0; } static void set_page_pfns(struct virtio_balloon *vb, __virtio32 pfns[], struct page *page) { unsigned int i; BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX); /* * 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] = cpu_to_virtio32(vb->vdev, page_to_balloon_pfn(page) + i); } static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) { unsigned int num_allocated_pages; unsigned int num_pfns; struct page *page; LIST_HEAD(pages); /* We can only do one array worth at a time. */ num = min(num, ARRAY_SIZE(vb->pfns)); for (num_pfns = 0; num_pfns < num; num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { struct page *page = balloon_page_alloc(); 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; } balloon_page_push(&pages, page); } mutex_lock(&vb->balloon_lock); vb->num_pfns = 0; while ((page = balloon_page_pop(&pages))) { balloon_page_enqueue(&vb->vb_dev_info, page); set_page_pfns(vb, vb->pfns + vb->num_pfns, page); vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) adjust_managed_page_count(page, -1); vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; } num_allocated_pages = vb->num_pfns; /* Did we get any? */ if (vb->num_pfns != 0) tell_host(vb, vb->inflate_vq); mutex_unlock(&vb->balloon_lock); return num_allocated_pages; } static void release_pages_balloon(struct virtio_balloon *vb, struct list_head *pages) { struct page *page, *next; list_for_each_entry_safe(page, next, pages, lru) { if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) adjust_managed_page_count(page, 1); list_del(&page->lru); put_page(page); /* balloon reference */ } } static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num) { unsigned int num_freed_pages; struct page *page; struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; LIST_HEAD(pages); /* We can only do one array worth at a time. */ num = min(num, ARRAY_SIZE(vb->pfns)); mutex_lock(&vb->balloon_lock); /* We can't release more pages than taken */ num = min(num, (size_t)vb->num_pages); 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, vb->pfns + vb->num_pfns, page); list_add(&page->lru, &pages); 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); release_pages_balloon(vb, &pages); mutex_unlock(&vb->balloon_lock); 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 = cpu_to_virtio16(vb->vdev, tag); vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val); } #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) static unsigned int update_balloon_stats(struct virtio_balloon *vb) { unsigned long events[NR_VM_EVENT_ITEMS]; struct sysinfo i; unsigned int idx = 0; long available; unsigned long caches; all_vm_events(events); si_meminfo(&i); available = si_mem_available(); caches = global_node_page_state(NR_FILE_PAGES); #ifdef CONFIG_VM_EVENT_COUNTERS 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]); #ifdef CONFIG_HUGETLB_PAGE update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC, events[HTLB_BUDDY_PGALLOC]); update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL, events[HTLB_BUDDY_PGALLOC_FAIL]); #endif #endif 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)); update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL, pages_to_bytes(available)); update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES, pages_to_bytes(caches)); return idx; } /* * 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 delegate the job to a freezable workqueue that will do the actual work via * stats_handle_request(). */ static void stats_request(struct virtqueue *vq) { struct virtio_balloon *vb = vq->vdev->priv; spin_lock(&vb->stop_update_lock); if (!vb->stop_update) queue_work(system_freezable_wq, &vb->update_balloon_stats_work); spin_unlock(&vb->stop_update_lock); } static void stats_handle_request(struct virtio_balloon *vb) { struct virtqueue *vq; struct scatterlist sg; unsigned int len, num_stats; num_stats = update_balloon_stats(vb); vq = vb->stats_vq; if (!virtqueue_get_buf(vq, &len)) return; sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); virtqueue_kick(vq); } static inline s64 towards_target(struct virtio_balloon *vb) { s64 target; u32 num_pages; /* Legacy balloon config space is LE, unlike all other devices. */ virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages, &num_pages); target = num_pages; return target - vb->num_pages; } /* Gives back @num_to_return blocks of free pages to mm. */ static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, unsigned long num_to_return) { struct page *page; unsigned long num_returned; spin_lock_irq(&vb->free_page_list_lock); for (num_returned = 0; num_returned < num_to_return; num_returned++) { page = balloon_page_pop(&vb->free_page_list); if (!page) break; free_pages((unsigned long)page_address(page), VIRTIO_BALLOON_HINT_BLOCK_ORDER); } vb->num_free_page_blocks -= num_returned; spin_unlock_irq(&vb->free_page_list_lock); return num_returned; } static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) { if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) return; /* No need to queue the work if the bit was already set. */ if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, &vb->config_read_bitmap)) return; queue_work(vb->balloon_wq, &vb->report_free_page_work); } static void virtballoon_changed(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; unsigned long flags; spin_lock_irqsave(&vb->stop_update_lock, flags); if (!vb->stop_update) { queue_work(system_freezable_wq, &vb->update_balloon_size_work); virtio_balloon_queue_free_page_work(vb); } spin_unlock_irqrestore(&vb->stop_update_lock, flags); } static void update_balloon_size(struct virtio_balloon *vb) { u32 actual = vb->num_pages; /* Legacy balloon config space is LE, unlike all other devices. */ virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual, &actual); } static void update_balloon_stats_func(struct work_struct *work) { struct virtio_balloon *vb; vb = container_of(work, struct virtio_balloon, update_balloon_stats_work); stats_handle_request(vb); } static void update_balloon_size_func(struct work_struct *work) { struct virtio_balloon *vb; s64 diff; vb = container_of(work, struct virtio_balloon, update_balloon_size_work); diff = towards_target(vb); if (!diff) return; if (diff > 0) diff -= fill_balloon(vb, diff); else diff += leak_balloon(vb, -diff); update_balloon_size(vb); if (diff) queue_work(system_freezable_wq, work); } static int init_vqs(struct virtio_balloon *vb) { struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX]; vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX]; const char *names[VIRTIO_BALLOON_VQ_MAX]; int err; /* * Inflateq and deflateq are used unconditionally. The names[] * will be NULL if the related feature is not enabled, which will * cause no allocation for the corresponding virtqueue in find_vqs. */ callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack; names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate"; callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack; names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL; names[VIRTIO_BALLOON_VQ_STATS] = NULL; callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; names[VIRTIO_BALLOON_VQ_REPORTING] = NULL; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { names[VIRTIO_BALLOON_VQ_STATS] = "stats"; callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request; } if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq"; callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; } if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq"; callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack; } err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs, callbacks, names, NULL); if (err) return err; vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { struct scatterlist sg; unsigned int num_stats; vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS]; /* * Prime this virtqueue with one buffer so the hypervisor can * use it to signal us later (it can't be broken yet!). */ num_stats = update_balloon_stats(vb); sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL); if (err) { dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n", __func__); return err; } virtqueue_kick(vb->stats_vq); } if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING]; return 0; } static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb) { if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID, &vb->config_read_bitmap)) { /* Legacy balloon config space is LE, unlike all other devices. */ virtio_cread_le(vb->vdev, struct virtio_balloon_config, free_page_hint_cmd_id, &vb->cmd_id_received_cache); } return vb->cmd_id_received_cache; } static int send_cmd_id_start(struct virtio_balloon *vb) { struct scatterlist sg; struct virtqueue *vq = vb->free_page_vq; int err, unused; /* Detach all the used buffers from the vq */ while (virtqueue_get_buf(vq, &unused)) ; vb->cmd_id_active = cpu_to_virtio32(vb->vdev, virtio_balloon_cmd_id_received(vb)); sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active)); err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL); if (!err) virtqueue_kick(vq); return err; } static int send_cmd_id_stop(struct virtio_balloon *vb) { struct scatterlist sg; struct virtqueue *vq = vb->free_page_vq; int err, unused; /* Detach all the used buffers from the vq */ while (virtqueue_get_buf(vq, &unused)) ; sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop)); err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL); if (!err) virtqueue_kick(vq); return err; } static int get_free_page_and_send(struct virtio_balloon *vb) { struct virtqueue *vq = vb->free_page_vq; struct page *page; struct scatterlist sg; int err, unused; void *p; /* Detach all the used buffers from the vq */ while (virtqueue_get_buf(vq, &unused)) ; page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG, VIRTIO_BALLOON_HINT_BLOCK_ORDER); /* * When the allocation returns NULL, it indicates that we have got all * the possible free pages, so return -EINTR to stop. */ if (!page) return -EINTR; p = page_address(page); sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES); /* There is always 1 entry reserved for the cmd id to use. */ if (vq->num_free > 1) { err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL); if (unlikely(err)) { free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); return err; } virtqueue_kick(vq); spin_lock_irq(&vb->free_page_list_lock); balloon_page_push(&vb->free_page_list, page); vb->num_free_page_blocks++; spin_unlock_irq(&vb->free_page_list_lock); } else { /* * The vq has no available entry to add this page block, so * just free it. */ free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); } return 0; } static int send_free_pages(struct virtio_balloon *vb) { int err; u32 cmd_id_active; while (1) { /* * If a stop id or a new cmd id was just received from host, * stop the reporting. */ cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active); if (unlikely(cmd_id_active != virtio_balloon_cmd_id_received(vb))) break; /* * The free page blocks are allocated and sent to host one by * one. */ err = get_free_page_and_send(vb); if (err == -EINTR) break; else if (unlikely(err)) return err; } return 0; } static void virtio_balloon_report_free_page(struct virtio_balloon *vb) { int err; struct device *dev = &vb->vdev->dev; /* Start by sending the received cmd id to host with an outbuf. */ err = send_cmd_id_start(vb); if (unlikely(err)) dev_err(dev, "Failed to send a start id, err = %d\n", err); err = send_free_pages(vb); if (unlikely(err)) dev_err(dev, "Failed to send a free page, err = %d\n", err); /* End by sending a stop id to host with an outbuf. */ err = send_cmd_id_stop(vb); if (unlikely(err)) dev_err(dev, "Failed to send a stop id, err = %d\n", err); } static void report_free_page_func(struct work_struct *work) { struct virtio_balloon *vb = container_of(work, struct virtio_balloon, report_free_page_work); u32 cmd_id_received; cmd_id_received = virtio_balloon_cmd_id_received(vb); if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) { /* Pass ULONG_MAX to give back all the free pages */ return_free_pages_to_mm(vb, ULONG_MAX); } else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP && cmd_id_received != virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) { virtio_balloon_report_free_page(vb); } } #ifdef CONFIG_BALLOON_COMPACTION /* * virtballoon_migratepage - perform the balloon page migration on behalf of * a compaction 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 */ /* * When we migrate a page to a different zone and adjusted the * managed page count when inflating, we have to fixup the count of * both involved zones. */ if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) && page_zone(page) != page_zone(newpage)) { adjust_managed_page_count(page, 1); adjust_managed_page_count(newpage, -1); } /* 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, vb->pfns, newpage); tell_host(vb, vb->inflate_vq); /* balloon's page migration 2nd step -- deflate "page" */ spin_lock_irqsave(&vb_dev_info->pages_lock, flags); balloon_page_delete(page); spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; set_page_pfns(vb, vb->pfns, page); tell_host(vb, vb->deflate_vq); mutex_unlock(&vb->balloon_lock); put_page(page); /* balloon reference */ return MIGRATEPAGE_SUCCESS; } static int balloon_init_fs_context(struct fs_context *fc) { return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM; } static struct file_system_type balloon_fs = { .name = "balloon-kvm", .init_fs_context = balloon_init_fs_context, .kill_sb = kill_anon_super, }; #endif /* CONFIG_BALLOON_COMPACTION */ static unsigned long shrink_free_pages(struct virtio_balloon *vb, unsigned long pages_to_free) { unsigned long blocks_to_free, blocks_freed; pages_to_free = round_up(pages_to_free, VIRTIO_BALLOON_HINT_BLOCK_PAGES); blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES; blocks_freed = return_free_pages_to_mm(vb, blocks_to_free); return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES; } static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) { struct virtio_balloon *vb = container_of(shrinker, struct virtio_balloon, shrinker); return shrink_free_pages(vb, sc->nr_to_scan); } static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc) { struct virtio_balloon *vb = container_of(shrinker, struct virtio_balloon, shrinker); return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; } static int virtio_balloon_oom_notify(struct notifier_block *nb, unsigned long dummy, void *parm) { struct virtio_balloon *vb = container_of(nb, struct virtio_balloon, oom_nb); unsigned long *freed = parm; *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) / VIRTIO_BALLOON_PAGES_PER_PAGE; update_balloon_size(vb); return NOTIFY_OK; } static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb) { unregister_shrinker(&vb->shrinker); } static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) { vb->shrinker.scan_objects = virtio_balloon_shrinker_scan; vb->shrinker.count_objects = virtio_balloon_shrinker_count; vb->shrinker.seeks = DEFAULT_SEEKS; return register_shrinker(&vb->shrinker, "virtio-balloon"); } 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 = kzalloc(sizeof(*vb), GFP_KERNEL); if (!vb) { err = -ENOMEM; goto out; } INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func); INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func); spin_lock_init(&vb->stop_update_lock); mutex_init(&vb->balloon_lock); init_waitqueue_head(&vb->acked); vb->vdev = vdev; balloon_devinfo_init(&vb->vb_dev_info); err = init_vqs(vb); if (err) goto out_free_vb; #ifdef CONFIG_BALLOON_COMPACTION balloon_mnt = kern_mount(&balloon_fs); if (IS_ERR(balloon_mnt)) { err = PTR_ERR(balloon_mnt); goto out_del_vqs; } vb->vb_dev_info.migratepage = virtballoon_migratepage; vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb); if (IS_ERR(vb->vb_dev_info.inode)) { err = PTR_ERR(vb->vb_dev_info.inode); goto out_kern_unmount; } vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops; #endif if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { /* * There is always one entry reserved for cmd id, so the ring * size needs to be at least two to report free page hints. */ if (virtqueue_get_vring_size(vb->free_page_vq) < 2) { err = -ENOSPC; goto out_iput; } vb->balloon_wq = alloc_workqueue("balloon-wq", WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); if (!vb->balloon_wq) { err = -ENOMEM; goto out_iput; } INIT_WORK(&vb->report_free_page_work, report_free_page_func); vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP; vb->cmd_id_active = cpu_to_virtio32(vb->vdev, VIRTIO_BALLOON_CMD_ID_STOP); vb->cmd_id_stop = cpu_to_virtio32(vb->vdev, VIRTIO_BALLOON_CMD_ID_STOP); spin_lock_init(&vb->free_page_list_lock); INIT_LIST_HEAD(&vb->free_page_list); /* * We're allowed to reuse any free pages, even if they are * still to be processed by the host. */ err = virtio_balloon_register_shrinker(vb); if (err) goto out_del_balloon_wq; } if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { vb->oom_nb.notifier_call = virtio_balloon_oom_notify; vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY; err = register_oom_notifier(&vb->oom_nb); if (err < 0) goto out_unregister_shrinker; } if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { /* Start with poison val of 0 representing general init */ __u32 poison_val = 0; /* * Let the hypervisor know that we are expecting a * specific value to be written back in balloon pages. * * If the PAGE_POISON value was larger than a byte we would * need to byte swap poison_val here to guarantee it is * little-endian. However for now it is a single byte so we * can pass it as-is. */ if (!want_init_on_free()) memset(&poison_val, PAGE_POISON, sizeof(poison_val)); virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, poison_val, &poison_val); } vb->pr_dev_info.report = virtballoon_free_page_report; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { unsigned int capacity; capacity = virtqueue_get_vring_size(vb->reporting_vq); if (capacity < PAGE_REPORTING_CAPACITY) { err = -ENOSPC; goto out_unregister_oom; } /* * The default page reporting order is @pageblock_order, which * corresponds to 512MB in size on ARM64 when 64KB base page * size is used. The page reporting won't be triggered if the * freeing page can't come up with a free area like that huge. * So we specify the page reporting order to 5, corresponding * to 2MB. It helps to avoid THP splitting if 4KB base page * size is used by host. * * Ideally, the page reporting order is selected based on the * host's base page size. However, it needs more work to report * that value. The hard-coded order would be fine currently. */ #if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES) vb->pr_dev_info.order = 5; #endif err = page_reporting_register(&vb->pr_dev_info); if (err) goto out_unregister_oom; } virtio_device_ready(vdev); if (towards_target(vb)) virtballoon_changed(vdev); return 0; out_unregister_oom: if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) unregister_oom_notifier(&vb->oom_nb); out_unregister_shrinker: if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) virtio_balloon_unregister_shrinker(vb); out_del_balloon_wq: if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) destroy_workqueue(vb->balloon_wq); out_iput: #ifdef CONFIG_BALLOON_COMPACTION iput(vb->vb_dev_info.inode); out_kern_unmount: kern_unmount(balloon_mnt); out_del_vqs: #endif 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); /* There might be free pages that are being reported: release them. */ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) return_free_pages_to_mm(vb, ULONG_MAX); /* Now we reset the device so we can clean up the queues. */ virtio_reset_device(vb->vdev); vb->vdev->config->del_vqs(vb->vdev); } static void virtballoon_remove(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) page_reporting_unregister(&vb->pr_dev_info); if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) unregister_oom_notifier(&vb->oom_nb); if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) virtio_balloon_unregister_shrinker(vb); spin_lock_irq(&vb->stop_update_lock); vb->stop_update = true; spin_unlock_irq(&vb->stop_update_lock); cancel_work_sync(&vb->update_balloon_size_work); cancel_work_sync(&vb->update_balloon_stats_work); if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { cancel_work_sync(&vb->report_free_page_work); destroy_workqueue(vb->balloon_wq); } remove_common(vb); #ifdef CONFIG_BALLOON_COMPACTION if (vb->vb_dev_info.inode) iput(vb->vb_dev_info.inode); kern_unmount(balloon_mnt); #endif kfree(vb); } #ifdef CONFIG_PM_SLEEP static int virtballoon_freeze(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; /* * The workqueue 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); if (towards_target(vb)) virtballoon_changed(vdev); update_balloon_size(vb); return 0; } #endif static int virtballoon_validate(struct virtio_device *vdev) { /* * Inform the hypervisor that our pages are poisoned or * initialized. If we cannot do that then we should disable * page reporting as it could potentially change the contents * of our free pages. */ if (!want_init_on_free() && !page_poisoning_enabled_static()) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); __virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM); return 0; } static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST, VIRTIO_BALLOON_F_STATS_VQ, VIRTIO_BALLOON_F_DEFLATE_ON_OOM, VIRTIO_BALLOON_F_FREE_PAGE_HINT, VIRTIO_BALLOON_F_PAGE_POISON, VIRTIO_BALLOON_F_REPORTING, }; 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, .validate = virtballoon_validate, .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");