Linux Virtualization - Mar 2017 - [PATCH] virtio_console: fix uninitialized variable use

We try to disable callbacks on c_ivq even without multiport
even though that vq is not initialized in this configuration.

Fixes: c743d09dbd01 ("virtio: console: Disable callbacks for virtqueues at
start of S4 freeze")
Suggested-by: Mike Galbraith <efault at gmx.de>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

Hi Mike
	if you like, pls send me your Signed-off-by and I'll
	change the patch to make you an author.
	More importantly, pls let me know whether this helps
	resolve the issues about hybernation for you!

 drivers/char/virtio_console.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5da4c8e..d0699c5 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -2202,14 +2202,16 @@ static int virtcons_freeze(struct virtio_device *vdev)
 
 	vdev->config->reset(vdev);
 
-	virtqueue_disable_cb(portdev->c_ivq);
+	if (use_multiport(portdev))
+		virtqueue_disable_cb(portdev->c_ivq);
 	cancel_work_sync(&portdev->control_work);
 	cancel_work_sync(&portdev->config_work);
 	/*
 	 * Once more: if control_work_handler() was running, it would
 	 * enable the cb as the last step.
 	 */
-	virtqueue_disable_cb(portdev->c_ivq);
+	if (use_multiport(portdev))
+		virtqueue_disable_cb(portdev->c_ivq);
 	remove_controlq_data(portdev);
 
 	list_for_each_entry(port, &portdev->ports, list) {
-- 
MST

On Wed, 2017-03-29 at 23:27 +0300, Michael S. Tsirkin wrote:
> Hi Mike
> 	if you like, pls send me your Signed-off-by and I'll
> 	change the patch to make you an author.
Nah, it's perfect as it is.  While I was pretty darn sure it was
generic, I intentionally posted it as diagnostic info.
> 	More importantly, pls let me know whether this helps
> 	resolve the issues about hybernation for you!
Well, it prevents kaboom with VIRTIO_CONSOLE_F_MULTIPORT turned off,
but no, it does nada wrt the warnings.

	-Mike