On (Fri) 29 Mar 2013 [08:29:01], Asias He wrote:

On Thu, Mar 28, 2013 at 04:58:33PM +0530, Amit Shah wrote:

quoted

When multiple ovq operations are being performed (lots of open/close
operations on virtio_console fds), the __send_control_msg() function can
get confused without locking.

A simple recipe to cause badness is:
* create a QEMU VM with two virtio-serial ports
* in the guest, do
  while true;do echo abc >/dev/vport0p1;done
  while true;do echo edf >/dev/vport0p2;done

In one run, this caused a panic in __send_control_msg().  In another, I
got

   virtio_console virtio0: control-o:id 0 is not a head!

This also results repeated messages similar to these on the host:

  qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
  qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0

Reported-by: FuXiangChun <redacted>
Signed-off-by: Amit Shah <redacted>

So, probably this will not apply on virtio-next because of the
virtqueue_add_outbuf change.

Yes, one-line context change.

Anyway,  Reviewed-by: Asias He [off-list ref]

Thanks!

		Amit