@@ -42,6 +42,14 @@
#define DEFAULT_BALLOON_PAGES_TO_SHRINK 256
#define VIRTBALLOON_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_FREE_PAGE_ORDER (MAX_ORDER - 1)
+/* The size of a free page block in bytes */
+#define VIRTIO_BALLOON_FREE_PAGE_SIZE \
+ (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
+
static unsigned long balloon_pages_to_shrink = DEFAULT_BALLOON_PAGES_TO_SHRINK;
module_param(balloon_pages_to_shrink, ulong, 0600);
MODULE_PARM_DESC(balloon_pages_to_shrink, "pages to free on memory presure");
@@ -50,9 +58,22 @@ MODULE_PARM_DESC(balloon_pages_to_shrink, "pages to free on memory presure");
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_MAX
+};
+
struct virtio_balloon {
struct virtio_device *vdev;
- struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
+ 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;
@@ -62,6 +83,16 @@ struct virtio_balloon {
spinlock_t stop_update_lock;
bool stop_update;
+ /* 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 cmd id received from host */
+ u32 cmd_id_received;
+ /* 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;
@@ -325,17 +356,6 @@ static void stats_handle_request(struct virtio_balloon *vb)
virtqueue_kick(vq);
}
-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);
- spin_unlock_irqrestore(&vb->stop_update_lock, flags);
-}
-
static inline s64 towards_target(struct virtio_balloon *vb)
{
s64 target;
@@ -352,6 +372,52 @@ static inline s64 towards_target(struct virtio_balloon *vb)
return target - vb->num_pages;
}
+static void virtballoon_changed(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb = vdev->priv;
+ unsigned long flags;
+ s64 diff = towards_target(vb);
+
+ if (diff) {
+ spin_lock_irqsave(&vb->stop_update_lock, flags);
+ if (!vb->stop_update)
+ queue_work(system_freezable_wq,
+ &vb->update_balloon_size_work);
+ spin_unlock_irqrestore(&vb->stop_update_lock, flags);
+ }
+
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+ virtio_cread(vdev, struct virtio_balloon_config,
+ free_page_report_cmd_id, &vb->cmd_id_received);
+ if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
+ vb->cmd_id_received !=
+ virtio32_to_cpu(vdev, vb->cmd_id_active)) {
+ spin_lock_irqsave(&vb->stop_update_lock, flags);
+ if (!vb->stop_update) {
+ queue_work(vb->balloon_wq,
+ &vb->report_free_page_work);
+ }
+ spin_unlock_irqrestore(&vb->stop_update_lock, flags);
+ }
+ }
+}
+
+static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb)
+{
+ struct page *page;
+ unsigned long num = 0;
+
+ spin_lock_irq(&vb->free_page_list_lock);
+ while ((page = balloon_page_pop(&vb->free_page_list))) {
+ free_pages((unsigned long)page_address(page),
+ VIRTIO_BALLOON_FREE_PAGE_ORDER);
+ num++;
+ }
+ spin_unlock_irq(&vb->free_page_list_lock);
+
+ return num;
+}
+
static void update_balloon_size(struct virtio_balloon *vb)
{
u32 actual = vb->num_pages;
@@ -394,26 +460,44 @@ static void update_balloon_size_func(struct work_struct *work)
static int init_vqs(struct virtio_balloon *vb)
{
- struct virtqueue *vqs[3];
- vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
- static const char * const names[] = { "inflate", "deflate", "stats" };
- int err, nvqs;
+ struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
+ vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
+ const char *names[VIRTIO_BALLOON_VQ_MAX];
+ int err;
/*
- * We expect two virtqueues: inflate and deflate, and
- * optionally stat.
+ * 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.
*/
- nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
- err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
+ 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";
+ names[VIRTIO_BALLOON_VQ_STATS] = NULL;
+ names[VIRTIO_BALLOON_VQ_FREE_PAGE] = 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;
+ }
+
+ err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
+ vqs, callbacks, names, NULL, NULL);
if (err)
return err;
- vb->inflate_vq = vqs[0];
- vb->deflate_vq = vqs[1];
+ 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[2];
+ vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
/*
* Prime this virtqueue with one buffer so the hypervisor can
@@ -431,9 +515,145 @@ static int init_vqs(struct virtio_balloon *vb)
}
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];
+
+ return 0;
+}
+
+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, vb->cmd_id_received);
+ 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_FREE_PAGE_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_FREE_PAGE_SIZE);
+ /* There is always one 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_FREE_PAGE_ORDER);
+ return err;
+ }
+ virtqueue_kick(vq);
+ spin_lock_irq(&vb->free_page_list_lock);
+ balloon_page_push(&vb->free_page_list, page);
+ 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_FREE_PAGE_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 (cmd_id_active != vb->cmd_id_received)
+ 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 report_free_page_func(struct work_struct *work)
+{
+ int err;
+ struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
+ report_free_page_work);
+
+ /* Start by sending the received cmd id to host with an outbuf. */
+ err = send_cmd_id_start(vb);
+ if (unlikely(err))
+ goto out_err;
+
+ err = send_free_pages(vb);
+ return_free_pages_to_mm(vb);
+ if (unlikely(err))
+ goto out_err;
+
+ /* End by sending a stop id to host with an outbuf. */
+ err = send_cmd_id_stop(vb);
+out_err:
+ if (err)
+ dev_err(&vb->vdev->dev, "%s: err = %d\n", __func__, err);
+}
+
#ifdef CONFIG_BALLOON_COMPACTION
/*
* virtballoon_migratepage - perform the balloon page migration on behalf of
@@ -523,6 +743,16 @@ static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+ pages_freed = return_free_pages_to_mm(vb) <<
+ VIRTIO_BALLOON_FREE_PAGE_ORDER;
+ }
+
+ if (pages_freed >= pages_to_free)
+ return pages_freed;
+
+ pages_to_free -= pages_freed;
+
/*
* One invocation of leak_balloon can deflate at most
* VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
@@ -530,8 +760,8 @@ static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
* balloon_pages_to_shrink pages.
*/
while (vb->num_pages && pages_to_free) {
- pages_to_free = balloon_pages_to_shrink - pages_freed;
pages_freed += leak_balloon(vb, pages_to_free);
+ pages_to_free -= pages_freed;
}
update_balloon_size(vb);
@@ -541,6 +771,7 @@ static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
struct shrink_control *sc)
{
+ unsigned long count;
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);
@@ -551,8 +782,18 @@ static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
return 0;
- return min_t(unsigned long, vb->num_pages, balloon_pages_to_shrink) /
- VIRTIO_BALLOON_PAGES_PER_PAGE;
+ count = min_t(unsigned long, vb->num_pages, balloon_pages_to_shrink) /
+ VIRTIO_BALLOON_PAGES_PER_PAGE;
+
+ /*
+ * Just add one block of free pages for the count estimation. We will
+ * release all of them in shrinker_scan regardless of the count
+ * returned here.
+ */
+ if (!list_empty(&vb->free_page_list))
+ count += 1 << VIRTIO_BALLOON_FREE_PAGE_ORDER;
+
+ return count;
}
static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
@@ -615,13 +856,38 @@ static int virtballoon_probe(struct virtio_device *vdev)
err = PTR_ERR(vb->vb_dev_info.inode);
kern_unmount(balloon_mnt);
vb->vb_dev_info.inode = NULL;
- goto out_del_vqs;
+ goto out_del_balloon_wq;
}
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_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 = 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);
+ }
+
err = virtio_balloon_register_shrinker(vb);
if (err)
- goto out_del_vqs;
+ goto out_del_balloon_wq;
virtio_device_ready(vdev);
@@ -629,6 +895,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
virtballoon_changed(vdev);
return 0;
+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:
@@ -662,6 +931,11 @@ static void virtballoon_remove(struct virtio_device *vdev)
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)
@@ -713,6 +987,7 @@ 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,
};
static struct virtio_driver virtio_balloon_driver = {
@@ -34,15 +34,19 @@
#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
#define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
+#define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
+#define VIRTIO_BALLOON_CMD_ID_STOP 0
struct virtio_balloon_config {
/* Number of pages host wants Guest to give up. */
__u32 num_pages;
/* Number of pages we've actually got in balloon. */
__u32 actual;
+ /* Free page report command id, readonly by guest */
+ __u32 free_page_report_cmd_id;
};
#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */