[PATCH v1 1/2] virtio-balloon: tweak config_changed implementation

Wei Wang
2019-01-03T05:31:01Z

virtio-ccw has deadlock issues with reading config registers inside the
interrupt context, so we tweak the virtballoon_changed implementation
by moving the config read operations into the related workqueue contexts.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
drivers/virtio/virtio_balloon.c | 54 ++++++++++++++++++++---------------------
1 file changed, 26 insertions(+), 28 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 728ecd1..9a82a11 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -394,33 +394,15 @@ 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);
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+ queue_work(vb->balloon_wq, &vb->report_free_page_work);
}
+ spin_unlock_irqrestore(&vb->stop_update_lock, flags);
}

static void update_balloon_size(struct virtio_balloon *vb)
@@ -637,11 +619,9 @@ 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 +639,24 @@ 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_cread(vb->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(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