diff options
Diffstat (limited to 'drivers/virtio/virtio_balloon.c')
| -rw-r--r-- | drivers/virtio/virtio_balloon.c | 1132 |
1 files changed, 1132 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c new file mode 100644 index 000000000..2d5d252ef --- /dev/null +++ b/drivers/virtio/virtio_balloon.c @@ -0,0 +1,1132 @@ +// 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 <linux/virtio.h> +#include <linux/virtio_balloon.h> +#include <linux/swap.h> +#include <linux/workqueue.h> +#include <linux/delay.h> +#include <linux/slab.h> +#include <linux/module.h> +#include <linux/balloon_compaction.h> +#include <linux/oom.h> +#include <linux/wait.h> +#include <linux/mm.h> +#include <linux/page_reporting.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 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 +/* 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) + +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); + + /* + * Aligned up to guest page size to avoid inflating and deflating + * balloon endlessly. + */ + target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE); + 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; +} +#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 + vb->vb_dev_info.migratepage = virtballoon_migratepage; +#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_del_vqs; + } + vb->balloon_wq = alloc_workqueue("balloon-wq", + WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0); + if (!vb->balloon_wq) { + err = -ENOMEM; + goto out_del_vqs; + } + 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_del_vqs: + 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); + 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"); |