Re: [dpdk-dev] [PATCH] virtio: fix the vq size issue

["Ouyang, Changchun" <changchun.ouyang@intel.com>]

> -----Original Message-----
> From: Ouyang, Changchun
> Sent: Wednesday, July 1, 2015 3:49 PM
> To: dev@dpdk.org
> Cc: Cao, Waterman; Xu, Qian Q; Ouyang, Changchun
> Subject: [PATCH] virtio: fix the vq size issue
> 
> This commit breaks virtio basic packets rx functionality:
>   d78deadae4dca240e85054bf2d604a801676becc
> 
> The QEMU use 256 as default vring size, also use this default value to
> calculate the virtio avail ring base address and used ring base address, and
> vhost in the backend use the ring base address to do packet IO.
> 
> Virtio spec also says the queue size in PCI configuration is read-only, so virtio
> front end can't change it. just need use the read-only value to allocate space
> for vring and calculate the avail and used ring base address. Otherwise, the
> avail and used ring base address will be different between host and guest,
> accordingly, packet IO can't work normally.
> 
> Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index fe5f9a1..d84de13 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -263,8 +263,6 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev,
>  	 */
>  	vq_size = VIRTIO_READ_REG_2(hw, VIRTIO_PCI_QUEUE_NUM);
>  	PMD_INIT_LOG(DEBUG, "vq_size: %d nb_desc:%d", vq_size,
> nb_desc);
> -	if (nb_desc == 0)
> -		nb_desc = vq_size;
>  	if (vq_size == 0) {
>  		PMD_INIT_LOG(ERR, "%s: virtqueue does not exist",
> __func__);
>  		return -EINVAL;
> @@ -275,15 +273,9 @@ int virtio_dev_queue_setup(struct rte_eth_dev
> *dev,
>  		return -EINVAL;
>  	}
> 
> -	if (nb_desc < vq_size) {
> -		if (!rte_is_power_of_2(nb_desc)) {
> -			PMD_INIT_LOG(ERR,
> -				     "nb_desc(%u) size is not powerof 2",
> -				     nb_desc);
> -			return -EINVAL;
> -		}
> -		vq_size = nb_desc;
> -	}
> +	if (nb_desc != vq_size)
> +		PMD_INIT_LOG(ERR, "Warning: nb_desc(%d) is not equal to
> vq size (%d), fall to vq size",
> +			nb_desc, vq_size);
> 
>  	if (queue_type == VTNET_RQ) {
>  		snprintf(vq_name, sizeof(vq_name), "port%d_rvq%d",
> --
> 1.8.4.2

Any more comments for this patch?

Thanks
Changchun