Re: [dpdk-dev] [PATCH v5 04/11] net/virtio: flush packed receive virtqueues

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

On 09/06/2018 08:19 PM, Jens Freimann wrote:
> Flush used descriptors in packed receive virtqueue. As descriptors
> can be chained we need to look at the stored number of used descriptors
> to find out the length of the chain.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>   drivers/net/virtio/virtqueue.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtqueue.c b/drivers/net/virtio/virtqueue.c
> index 56a77cc71..d0520dad1 100644
> --- a/drivers/net/virtio/virtqueue.c
> +++ b/drivers/net/virtio/virtqueue.c
> @@ -58,12 +58,29 @@ virtqueue_detach_unused(struct virtqueue *vq)
>   void
>   virtqueue_rxvq_flush(struct virtqueue *vq)
>   {
> +	struct vring_desc_packed *descs = vq->vq_ring.desc_packed;
>   	struct virtnet_rx *rxq = &vq->rxq;
>   	struct virtio_hw *hw = vq->hw;
>   	struct vring_used_elem *uep;
>   	struct vq_desc_extra *dxp;
>   	uint16_t used_idx, desc_idx;
>   	uint16_t nb_used, i;
> +	uint16_t size = vq->vq_nentries;
> +
> +	if (vtpci_packed_queue(vq->hw)) {
> +		i = vq->vq_used_cons_idx;
> +		while (desc_is_used(&descs[i], &vq->vq_ring) &&
> +			i < vq->vq_nentries) {
It may be preferable to ensure 'i' is within the ring size before using
it in desc_is_used(). And raise (at least) an error message if it isn't.

> +			dxp = &vq->vq_descx[i];
> +			if (dxp->cookie != NULL)
> +				rte_pktmbuf_free(dxp->cookie);
> +			vq->vq_free_cnt += dxp->ndescs;
> +			i = i + dxp->ndescs;
> +			i = i >= size ? i - size : i;
> +			dxp->ndescs = 0;
> +		}
> +		return;
> +	}
>   
>   	nb_used = VIRTQUEUE_NUSED(vq);
>   
>