Re: [dpdk-dev] [PATCH] net/virtio: turn SW RxQ size to that of split vec. virtqueue

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 8/20/21 2:47 PM, Andrew Rybchenko wrote:
> From: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
> 
> Descriptors number may be set less than queue size for split queue
> vectorized Rx path. Pointers to mbufs for received packets are
> obtained from SW ring, that is initially filled with them in the end
> of queue setup in virtio_dev_rx_queue_setup_finish(). The begin of the
> SW ring filled up to the size of descriptors number. At queue size
> offset from the begin of the SW ring pointers to some fake mbuf are also
> set for wrapping purpose. So the ring may contains the hole of invalid
> pointers from descriptors number offset to queue size offset, and split
> vectorized Rx routines could write to the invalid addresses since they
> use the ring up to the queue size. Fix this by setting descriptors
> number to queue size on Rx queue setup.
> 
> Fixes: fc3d66212fed ("virtio: add vector Rx")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> ---
>  drivers/net/virtio/virtio_rxtx.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 18f03c9fc9..97ed69596a 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -706,8 +706,14 @@ virtio_dev_rx_queue_setup(struct rte_eth_dev *dev,
>  	}
>  	vq->vq_free_thresh = rx_free_thresh;
>  
> -	if (nb_desc > vq->vq_nentries)
> +	/*
> +	 * For split ring vectorized path descriptors number must be
> +	 * equal to the ring size.
> +	 */
> +	if (nb_desc > vq->vq_nentries ||
> +	    (!virtio_with_packed_queue(hw) && hw->use_vec_rx)) {
>  		nb_desc = vq->vq_nentries;
> +	}
>  	vq->vq_free_cnt = RTE_MIN(vq->vq_free_cnt, nb_desc);
>  
>  	rxvq = &vq->rxq;
> 

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime