[SLOF] [PATCH] virtio-net: fix ring handling in receive

[Thomas Huth]

On 20.06.2016 13:32, Nikunj A Dadhania wrote:
> A bug crept in while doing the virtio 1.0 enablement in
> commit 6e4d62c2 (virtio-net: enable virtio 1.0)
> 
> +       idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.used->idx);
> 
> [...]
> 
> -       vq_rx.avail->ring[vq_rx.avail->idx % vq_rx.size] = id - 1;
> +       vq_rx.avail->ring[idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
>         sync();
> -       vq_rx.avail->idx += 1;
> +       vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, idx + 1);
> 
> Should be using avail->idx in place of used->idx.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
> ---
>  lib/libvirtio/virtio-net.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/libvirtio/virtio-net.c b/lib/libvirtio/virtio-net.c
> index fc620a2..2573031 100644
> --- a/lib/libvirtio/virtio-net.c
> +++ b/lib/libvirtio/virtio-net.c
> @@ -266,6 +266,7 @@ static int virtionet_receive(char *buf, int maxlen)
>  {
>  	uint32_t len = 0;
>  	uint32_t id, idx;
> +	uint16_t avail_idx;
>  
>  	idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.used->idx);
>  
> @@ -304,9 +305,10 @@ static int virtionet_receive(char *buf, int maxlen)
>  	/* Move indices to next entries */
>  	last_rx_idx = last_rx_idx + 1;
>  
> -	vq_rx.avail->ring[idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
> +	avail_idx = virtio_modern16_to_cpu(&virtiodev, vq_rx.avail->idx);
> +	vq_rx.avail->ring[avail_idx % vq_rx.size] = virtio_cpu_to_modern16(&virtiodev, id - 1);
>  	sync();
> -	vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, idx + 1);
> +	vq_rx.avail->idx = virtio_cpu_to_modern16(&virtiodev, avail_idx + 1);
>  
>  	/* Tell HV that RX queue entry is ready */
>  	virtio_queue_notify(&virtiodev, VQ_RX);
> 

You're right, that looks better this way!

Reviewed-by: Thomas Huth <thuth at redhat.com>