On Thu, Mar 28, 2013 at 04:58:33PM +0530, Amit Shah wrote:
> 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 <xfu@xxxxxxxxxx>
> Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
So, probably this will not apply on virtio-next because of the
virtqueue_add_outbuf change.
Anyway, Reviewed-by: Asias He <asias@xxxxxxxxxx>
> ---
> drivers/char/virtio_console.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7e9bc1d..410866c 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -150,6 +150,7 @@ struct ports_device {
>
> /* To protect the vq operations for the control channel */
> spinlock_t c_ivq_lock;
> + spinlock_t c_ovq_lock;
>
> /* The current config space is stored here */
> struct virtio_console_config config;
> @@ -569,11 +570,14 @@ static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id,
> vq = portdev->c_ovq;
>
> sg_init_one(sg, &cpkt, sizeof(cpkt));
> +
> + spin_lock_irq(&portdev->c_ovq_lock);
> if (virtqueue_add_buf(vq, sg, 1, 0, &cpkt, GFP_ATOMIC) == 0) {
> virtqueue_kick(vq);
> while (!virtqueue_get_buf(vq, &len))
> cpu_relax();
> }
> + spin_unlock_irq(&portdev->c_ovq_lock);
> return 0;
> }
>
> @@ -1987,6 +1991,7 @@ static int virtcons_probe(struct virtio_device *vdev)
> unsigned int nr_added_bufs;
>
> spin_lock_init(&portdev->c_ivq_lock);
> + spin_lock_init(&portdev->c_ovq_lock);
> INIT_WORK(&portdev->control_work, &control_work_handler);
>
> nr_added_bufs = fill_queue(portdev->c_ivq,
> --
> 1.8.1.4
>
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--
Asias
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