netdev - Re: [net-next rfc v7 2/3] virtio

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Date:	Mon, 03 Dec 2012 12:34:08 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jason Wang <jasowang@...hat.com>, mst@...hat.com,
	krkumar2@...ibm.com, virtualization@...ts.linux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, bhutchings@...arflare.com,
	jwhan@...ewood.snu.ac.kr, shiyer@...hat.com,
	Jason Wang <jasowang@...hat.com>
Subject: Re: [net-next rfc v7 2/3] virtio_net: multiqueue support

Jason Wang <jasowang@...hat.com> writes:
> +static const struct ethtool_ops virtnet_ethtool_ops;
> +
> +/*
> + * Converting between virtqueue no. and kernel tx/rx queue no.
> + * 0:rx0 1:tx0 2:cvq 3:rx1 4:tx1 ... 2N+1:rxN 2N+2:txN
> + */
> +static int vq2txq(struct virtqueue *vq)
> +{
> +	int index = virtqueue_get_queue_index(vq);
> +	return index == 1 ? 0 : (index - 2) / 2;
> +}
> +
> +static int txq2vq(int txq)
> +{
> +	return txq ? 2 * txq + 2 : 1;
> +}
> +
> +static int vq2rxq(struct virtqueue *vq)
> +{
> +	int index = virtqueue_get_queue_index(vq);
> +	return index ? (index - 1) / 2 : 0;
> +}
> +
> +static int rxq2vq(int rxq)
> +{
> +	return rxq ? 2 * rxq + 1 : 0;
> +}
> +

I thought MST changed the proposed spec to make the control queue always
the last one, so this logic becomes trivial.

> +static int virtnet_set_queues(struct virtnet_info *vi)
> +{
> +	struct scatterlist sg;
> +	struct virtio_net_ctrl_rfs s;
> +	struct net_device *dev = vi->dev;
> +
> +	s.virtqueue_pairs = vi->curr_queue_pairs;
> +	sg_init_one(&sg, &s, sizeof(s));
> +
> +	if (!vi->has_cvq)
> +		return -EINVAL;
> +
> +	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RFS,
> +				  VIRTIO_NET_CTRL_RFS_VQ_PAIRS_SET, &sg, 1, 0)){
> +		dev_warn(&dev->dev, "Fail to set the number of queue pairs to"
> +			 " %d\n", vi->curr_queue_pairs);
> +		return -EINVAL;
> +	}

Where do we check the VIRTIO_NET_F_RFS bit?

>  static int virtnet_probe(struct virtio_device *vdev)
>  {
> -	int err;
> +	int i, err;
>  	struct net_device *dev;
>  	struct virtnet_info *vi;
> +	u16 curr_queue_pairs;
> +
> +	/* Find if host supports multiqueue virtio_net device */
> +	err = virtio_config_val(vdev, VIRTIO_NET_F_RFS,
> +				offsetof(struct virtio_net_config,
> +				max_virtqueue_pairs), &curr_queue_pairs);
> +
> +	/* We need at least 2 queue's */
> +	if (err)
> +		curr_queue_pairs = 1;

Huh?  Just call this queue_pairs.  It's not curr_ at all...

> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
> +		vi->has_cvq = true;
> +
> +	/* Use single tx/rx queue pair as default */
> +	vi->curr_queue_pairs = 1;
> +	vi->max_queue_pairs = curr_queue_pairs;

See...

Cheers,
Rusty.
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