Re: [dpdk-dev] [PATCH] net/virtio: fix indirect descriptors reconnection

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

Hi Xuan,

On 8/19/21 07:35, Xuan Ding wrote:
> Since packed indirect descriptors are added and initialized when
> initializing vring, the reconnection path also needs to be considered.
> 
> Fixes: 381f39ebb78a ("net/virtio: fix packed ring indirect descricptors setup")
> Cc: stable@dpdk.org
> Cc: yong.liu@intel.com
> 
> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> ---
>   drivers/net/virtio/virtqueue.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtqueue.c b/drivers/net/virtio/virtqueue.c
> index 1f9af3c31b..47229f35c4 100644
> --- a/drivers/net/virtio/virtqueue.c
> +++ b/drivers/net/virtio/virtqueue.c
> @@ -208,6 +208,20 @@ virtqueue_txvq_reset_packed(struct virtqueue *vq)
>   			rte_pktmbuf_free(dxp->cookie);
>   			dxp->cookie = NULL;
>   		}

It makes me think we might save quite some bytes by not allocating
indirect descriptors when feature is not negotiated, but it might have
a cost in term of performance.

> +
> +		struct virtio_tx_region *txr;

Don't mix declarations within code.

> +		txr = txvq->virtio_net_hdr_mz->addr;
> +		/* first indirect descriptor is always the tx header */
> +		struct vring_packed_desc *start_dp =
> +			txr[desc_idx].tx_packed_indir;

Ditto.

> +		vring_desc_init_indirect_packed(start_dp,
> +		      RTE_DIM(txr[desc_idx].tx_packed_indir));
> +		start_dp->addr = txvq->virtio_net_hdr_mem
> +			+ desc_idx * sizeof(*txr)
> +			+ offsetof(struct virtio_tx_region,
> +				   tx_hdr);
> +		start_dp->len = vq->hw->vtnet_hdr_size;
> +
>   	}
>   
>   	vring_desc_init_packed(vq, size);
> 

Thanks,
Maxime