On (Thu) 17 Nov 2011 [14:25:08], Michael S. Tsirkin wrote:

On Thu, Nov 17, 2011 at 05:27:42PM +0530, Amit Shah wrote:

quoted

Delete the vqs on the freeze callback to prepare for hibernation.
Re-create the vqs in the restore callback to resume normal function.

Signed-off-by: Amit Shah <redacted>
---
 drivers/virtio/virtio_balloon.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1ff3cf4..90149d1 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c

@@ -363,6 +363,22 @@ static void __devexit virtballoon_remove(struct virtio_device *vdev)
 	kfree(vb);
 }
 
+#ifdef CONFIG_PM
+static int virtballoon_freeze(struct virtio_device *vdev)
+{
+	/* Now we reset the device so we can clean up the queues. */
+	vdev->config->reset(vdev);
+

This is a weird thing to do. We normally delete vqs then reset.

No, all the drivers first reset, then delete.

For example, I don't know whether we guarantee what happens
to MSI-X vectors assigned meanwhile if you reset.
IIRC qemu doesn't use MSI-X for the balloon, but nothing
prevents it.

quoted

+	vdev->config->del_vqs(vdev);

What prevents requests being submitted at this point?
I see all kind of handling of freezing in the balloon thread ...
maybe that gives us some guarantees, but if yes
it makes sense to add a comment to point this out.

Once reset, the host won't write anything to the vqs anyway..

		Amit