[PATCH v18 09/10] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ

[Wei Wang]

Negotiation of the VIRTIO_BALLOON_F_FREE_PAGE_VQ feature indicates the
support of reporting hints of guest free pages to host via virtio-balloon.

Host requests the guest to report free pages by sending a new cmd
id to the guest via the free_page_report_cmd_id configuration register.

When the guest starts to report, the first element added to the free page
vq is the cmd id given by host. When the guest finishes the reporting
of all the free pages, VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID is added
to the vq to tell host that the reporting is done. Host may also requests
the guest to stop the reporting in advance by sending the stop cmd id to
the guest via the configuration register.

Signed-off-by: Wei Wang 
Signed-off-by: Liang Li 
Cc: Michael S. Tsirkin 
Cc: Michal Hocko 
---
 drivers/virtio/virtio_balloon.c | 202 +---
 include/uapi/linux/virtio_balloon.h |   4 +
 2 files changed, 167 insertions(+), 39 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 2c21c5a..035bd3a 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -55,7 +55,12 @@ static struct vfsmount *balloon_mnt;
 
 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;
@@ -65,6 +70,13 @@ struct virtio_balloon {
spinlock_t stop_update_lock;
bool stop_update;
 
+   /* Start to report free pages */
+   bool report_free_page;
+   /* Stores the cmd id given by host to start the free page reporting */
+   uint32_t start_cmd_id;
+   /* Stores STOP_ID as a sign to tell host that the reporting is done */
+   uint32_t stop_cmd_id;
+
/* Waiting for host to ack the pages we released. */
wait_queue_head_t acked;
 
@@ -159,7 +171,8 @@ static void send_one_desc(struct virtio_balloon *vb,
  uint64_t addr,
  uint32_t len,
  bool inbuf,
- bool batch)
+ bool batch,
+ bool wait)
 {
int err;
unsigned int size;
@@ -178,8 +191,12 @@ static void send_one_desc(struct virtio_balloon *vb,
BUG_ON(err);
 
/* If batching is requested, we batch till the vq is full */
-   if (!batch || !vq->num_free)
-   kick_and_wait(vq, vb->acked);
+   if (!batch || !vq->num_free) {
+   if (wait)
+   kick_and_wait(vq, vb->acked);
+   else
+   virtqueue_kick(vq);
+   }
 }
 
 /*
@@ -212,11 +229,11 @@ static void tell_host_sgs(struct virtio_balloon *vb,
addr = pfn_start << PAGE_SHIFT;
len = (pfn_end - pfn_start) << PAGE_SHIFT;
while (len > max_len) {
-   send_one_desc(vb, vq, addr, max_len, true, true);
+   send_one_desc(vb, vq, addr, max_len, true, true, true);
addr += max_len;
len -= max_len;
}
-   send_one_desc(vb, vq, addr, len, true, true);
+   send_one_desc(vb, vq, addr, len, true, true, true);
pfn_start = pfn_end + 1;
}
 
@@ -401,7 +418,7 @@ static unsigned int leak_balloon_sg_oom(struct 
virtio_balloon *vb)
list_add(>lru, );
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
send_one_desc(vb, vq, virt_to_phys(page_address(page)),
- PAGE_SIZE, true, true);
+ PAGE_SIZE, true, true, true);
release_pages_balloon(vb, );
}
 
@@ -491,17 +508,6 @@ 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(>stop_update_lock, flags);
-   if (!vb->stop_update)
-   queue_work(system_freezable_wq, >update_balloon_size_work);
-   spin_unlock_irqrestore(>stop_update_lock, flags);
-}
-
 static inline s64 towards_target(struct virtio_balloon *vb)
 {
s64 target;
@@ -518,6 +524,36 @@ static inline s64 towards_target(struct virtio_balloon *vb)
return target - vb->num_pages;
 }
 
+static void virtballoon_changed(struct virtio_device *vdev)
+{
+

[PATCH v18 09/10] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ

[Wei Wang]

Negotiation of the VIRTIO_BALLOON_F_FREE_PAGE_VQ feature indicates the
support of reporting hints of guest free pages to host via virtio-balloon.

Host requests the guest to report free pages by sending a new cmd
id to the guest via the free_page_report_cmd_id configuration register.

When the guest starts to report, the first element added to the free page
vq is the cmd id given by host. When the guest finishes the reporting
of all the free pages, VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID is added
to the vq to tell host that the reporting is done. Host may also requests
the guest to stop the reporting in advance by sending the stop cmd id to
the guest via the configuration register.

Signed-off-by: Wei Wang 
Signed-off-by: Liang Li 
Cc: Michael S. Tsirkin 
Cc: Michal Hocko 
---
 drivers/virtio/virtio_balloon.c | 202 +---
 include/uapi/linux/virtio_balloon.h |   4 +
 2 files changed, 167 insertions(+), 39 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 2c21c5a..035bd3a 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -55,7 +55,12 @@ static struct vfsmount *balloon_mnt;
 
 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;
@@ -65,6 +70,13 @@ struct virtio_balloon {
spinlock_t stop_update_lock;
bool stop_update;
 
+   /* Start to report free pages */
+   bool report_free_page;
+   /* Stores the cmd id given by host to start the free page reporting */
+   uint32_t start_cmd_id;
+   /* Stores STOP_ID as a sign to tell host that the reporting is done */
+   uint32_t stop_cmd_id;
+
/* Waiting for host to ack the pages we released. */
wait_queue_head_t acked;
 
@@ -159,7 +171,8 @@ static void send_one_desc(struct virtio_balloon *vb,
  uint64_t addr,
  uint32_t len,
  bool inbuf,
- bool batch)
+ bool batch,
+ bool wait)
 {
int err;
unsigned int size;
@@ -178,8 +191,12 @@ static void send_one_desc(struct virtio_balloon *vb,
BUG_ON(err);
 
/* If batching is requested, we batch till the vq is full */
-   if (!batch || !vq->num_free)
-   kick_and_wait(vq, vb->acked);
+   if (!batch || !vq->num_free) {
+   if (wait)
+   kick_and_wait(vq, vb->acked);
+   else
+   virtqueue_kick(vq);
+   }
 }
 
 /*
@@ -212,11 +229,11 @@ static void tell_host_sgs(struct virtio_balloon *vb,
addr = pfn_start << PAGE_SHIFT;
len = (pfn_end - pfn_start) << PAGE_SHIFT;
while (len > max_len) {
-   send_one_desc(vb, vq, addr, max_len, true, true);
+   send_one_desc(vb, vq, addr, max_len, true, true, true);
addr += max_len;
len -= max_len;
}
-   send_one_desc(vb, vq, addr, len, true, true);
+   send_one_desc(vb, vq, addr, len, true, true, true);
pfn_start = pfn_end + 1;
}
 
@@ -401,7 +418,7 @@ static unsigned int leak_balloon_sg_oom(struct 
virtio_balloon *vb)
list_add(>lru, );
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
send_one_desc(vb, vq, virt_to_phys(page_address(page)),
- PAGE_SIZE, true, true);
+ PAGE_SIZE, true, true, true);
release_pages_balloon(vb, );
}
 
@@ -491,17 +508,6 @@ 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(>stop_update_lock, flags);
-   if (!vb->stop_update)
-   queue_work(system_freezable_wq, >update_balloon_size_work);
-   spin_unlock_irqrestore(>stop_update_lock, flags);
-}
-
 static inline s64 towards_target(struct virtio_balloon *vb)
 {
s64 target;
@@ -518,6 +524,36 @@ 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;
+