Re: [Minios-devel] [UNIKRAFT PATCH v3 4/4] drivers/virtio: Memory barrier before notifying host on virtqueue updates

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hello Simon,

This patch seems fine.

Reviewed-by: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>

Thanks & Regards
Sharan

On 1/31/19 1:04 AM, Simon Kuenzer wrote:
> Before notifying the virtio backend on the host we should make
> sure that the virtqueue index update operation actually happened.
>
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
>   plat/drivers/include/virtio/virtqueue.h | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/plat/drivers/include/virtio/virtqueue.h 
> b/plat/drivers/include/virtio/virtqueue.h
> index a4181f57..f8b36348 100644
> --- a/plat/drivers/include/virtio/virtqueue.h
> +++ b/plat/drivers/include/virtio/virtqueue.h
> @@ -233,6 +233,13 @@ static inline void virtqueue_host_notify(struct virtqueue 
> *vq)
>   {
>         UK_ASSERT(vq);
>   
> +	/*
> +        * Before notifying the virtio backend on the host we should make sure
> +        * that the virtqueue index update operation happened. Note that this
> +        * function is declared as inline.
> +        */
> +       mb();
> +
>         if (vq->vq_notify_host && virtqueue_notify_enabled(vq)) {
>                 uk_pr_debug("notify queue %d\n", vq->queue_id);
>                 vq->vq_notify_host(vq->vdev, vq->queue_id);
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