netdev - Re: [PATCH net-next v2] virtio-net: ethtool configurable LRO

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Date:   Thu, 20 Dec 2018 17:34:23 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jasowang@...hat.com,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next v2] virtio-net: ethtool configurable LRO

On Thu, Dec 20, 2018 at 05:14:54PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> Virtio-net devices negotiate LRO support with the host.
> Display the initially negotiated state with ethtool -k.
> 
> Also allow configuring it with ethtool -K, reusing the existing
> virtnet_set_guest_offloads helper that configures LRO for XDP.
> This is conditional on VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.
> 
> Virtio-net negotiates TSO4 and TSO6 separately, but ethtool does not
> distinguish between the two. Display LRO as on only if any offload
> is active.
> 
> RTNL is held while calling virtnet_set_features, same as on the path
> from virtnet_xdp_set.
> 
> Changes v1 -> v2
>   - allow ethtool config (-K) only if VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>   - show LRO as enabled if any LRO variant is enabled
>   - do not allow configuration while XDP is active
>   - differentiate current features from the capable set, to restore
>     on XDP down only those features that were active on XDP up
>   - move test out of VIRTIO_NET_F_CSUM/TSO branch, which is tx only

This part shouldn't be in the commit log, right? Should be after "---".

> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/net/virtio_net.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ea672145f6a66..0237250860467 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -236,6 +236,7 @@ struct virtnet_info {
>  	u32 speed;
>  
>  	unsigned long guest_offloads;
> +	unsigned long guest_offloads_capable;
>  
>  	/* failover when STANDBY feature enabled */
>  	struct failover *failover;
> @@ -2479,6 +2480,31 @@ static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
>  	return 0;
>  }
>  
> +static int virtnet_set_features(struct net_device *dev,
> +				netdev_features_t features)
> +{
> +	struct virtnet_info *vi = netdev_priv(dev);
> +	u64 offloads;
> +	int err;
> +
> +	if ((dev->features ^ features) & NETIF_F_LRO) {
> +		if (vi->xdp_queue_pairs)
> +			return -EBUSY;
> +
> +		if (features & NETIF_F_LRO)
> +			offloads = vi->guest_offloads_capable;
> +		else
> +			offloads = 0;
> +
> +		err = virtnet_set_guest_offloads(vi, offloads);
> +		if (err)
> +			return err;
> +		vi->guest_offloads = offloads;
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct net_device_ops virtnet_netdev = {
>  	.ndo_open            = virtnet_open,
>  	.ndo_stop   	     = virtnet_close,
> @@ -2493,6 +2519,7 @@ static const struct net_device_ops virtnet_netdev = {
>  	.ndo_xdp_xmit		= virtnet_xdp_xmit,
>  	.ndo_features_check	= passthru_features_check,
>  	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
> +	.ndo_set_features	= virtnet_set_features,
>  };
>  
>  static void virtnet_config_changed_work(struct work_struct *work)
> @@ -2951,6 +2978,11 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	}
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
>  		dev->features |= NETIF_F_RXCSUM;
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> +	    virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
> +		dev->features |= NETIF_F_LRO;
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
> +		dev->hw_features |= NETIF_F_LRO;
>  
>  	dev->vlan_features = dev->features;
>  
> @@ -3080,6 +3112,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
>  		if (virtio_has_feature(vi->vdev, guest_offloads[i]))
>  			set_bit(guest_offloads[i], &vi->guest_offloads);
> +	vi->guest_offloads_capable = vi->guest_offloads;
>  
>  	pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
>  		 dev->name, max_queue_pairs);
> -- 
> 2.20.1.415.g653613c723-goog