virtio-ccw has deadlock issues with reading the config space inside the
interrupt context, so we tweak the virtballoon_changed implementation
by moving the config read operations into the related workqueue contexts.
The config_read_bitmap is used as a flag to the workqueue callbacks
about the related config fields that need to be read.
Reported-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 81 +++++++++++++++++++++++++++--------------
1 file changed, 53 insertions(+), 28 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 728ecd1..35ee762 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -61,6 +61,10 @@ enum virtio_balloon_vq {
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;
@@ -77,6 +81,8 @@ struct virtio_balloon {
/* 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;
@@ -390,37 +396,31 @@ static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
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;
- 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_DONE) {
- /* Pass ULONG_MAX to give back all the free pages */
- return_free_pages_to_mm(vb, ULONG_MAX);
- } else 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);
- }
+ 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)
@@ -609,6 +609,16 @@ static int get_free_page_and_send(struct virtio_balloon *vb)
return 0;
}
+static void virtio_balloon_read_cmd_id_received(struct virtio_balloon *vb)
+{
+ if (!test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
+ &vb->config_read_bitmap))
+ return;
+
+ virtio_cread(vb->vdev, struct virtio_balloon_config,
+ free_page_report_cmd_id, &vb->cmd_id_received);
+}
+
static int send_free_pages(struct virtio_balloon *vb)
{
int err;
@@ -620,6 +630,7 @@ static int send_free_pages(struct virtio_balloon *vb)
* stop the reporting.
*/
cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
+ virtio_balloon_read_cmd_id_received(vb);
if (cmd_id_active != vb->cmd_id_received)
break;
@@ -637,11 +648,9 @@ static int send_free_pages(struct virtio_balloon *vb)
return 0;
}
-static void report_free_page_func(struct work_struct *work)
+static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
{
int err;
- struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
- report_free_page_work);
struct device *dev = &vb->vdev->dev;
/* Start by sending the received cmd id to host with an outbuf. */
@@ -659,6 +668,22 @@ static void report_free_page_func(struct work_struct *work)
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);
+
+ virtio_balloon_read_cmd_id_received(vb);
+ if (vb->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 (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
+ vb->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
--
2.7.4
