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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Sep 30, 2020 at 10:03:00AM +0800, xiangxia.m.yue@gmail.com wrote:
> From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> 
> Allow user configuring RXCSUM separately with ethtool -K,
> reusing the existing virtnet_set_guest_offloads helper
> that configures RXCSUM for XDP. This is conditional on
> VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.
> 
> If Rx checksum is disabled, LRO should also be disabled.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>

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


> ---
> v2:
> * LRO depends the rx csum
> * remove the unnecessary check
> ---
>  drivers/net/virtio_net.c | 49 ++++++++++++++++++++++++++++++----------
>  1 file changed, 37 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 21b71148c532..5407a0106771 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -68,6 +68,8 @@ static const unsigned long guest_offloads[] = {
>  				(1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
>  				(1ULL << VIRTIO_NET_F_GUEST_UFO))
>  
> +#define GUEST_OFFLOAD_CSUM_MASK (1ULL << VIRTIO_NET_F_GUEST_CSUM)
> +
>  struct virtnet_stat_desc {
>  	char desc[ETH_GSTRING_LEN];
>  	size_t offset;
> @@ -2522,29 +2524,49 @@ static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
>  	return 0;
>  }
>  
> +static netdev_features_t virtnet_fix_features(struct net_device *netdev,
> +					      netdev_features_t features)
> +{
> +	/* If Rx checksum is disabled, LRO should also be disabled.
> +	 * That is life. :)
> +	 */
> +	if (!(features & NETIF_F_RXCSUM))
> +		features &= ~NETIF_F_LRO;
> +
> +	return features;
> +}
> +
>  static int virtnet_set_features(struct net_device *dev,
>  				netdev_features_t features)
>  {
>  	struct virtnet_info *vi = netdev_priv(dev);
> -	u64 offloads;
> +	u64 offloads = vi->guest_offloads &
> +		       vi->guest_offloads_capable;
>  	int err;
>  
> -	if ((dev->features ^ features) & NETIF_F_LRO) {
> -		if (vi->xdp_queue_pairs)
> -			return -EBUSY;
> +	/* Don't allow configuration while XDP is active. */
> +	if (vi->xdp_queue_pairs)
> +		return -EBUSY;
>  
> +	if ((dev->features ^ features) & NETIF_F_LRO) {
>  		if (features & NETIF_F_LRO)
> -			offloads = vi->guest_offloads_capable;
> +			offloads |= GUEST_OFFLOAD_LRO_MASK;
>  		else
> -			offloads = vi->guest_offloads_capable &
> -				   ~GUEST_OFFLOAD_LRO_MASK;
> +			offloads &= ~GUEST_OFFLOAD_LRO_MASK;
> +	}
>  
> -		err = virtnet_set_guest_offloads(vi, offloads);
> -		if (err)
> -			return err;
> -		vi->guest_offloads = offloads;
> +	if ((dev->features ^ features) & NETIF_F_RXCSUM) {
> +		if (features & NETIF_F_RXCSUM)
> +			offloads |= GUEST_OFFLOAD_CSUM_MASK;
> +		else
> +			offloads &= ~GUEST_OFFLOAD_CSUM_MASK;
>  	}
>  
> +	err = virtnet_set_guest_offloads(vi, offloads);
> +	if (err)
> +		return err;
> +
> +	vi->guest_offloads = offloads;
>  	return 0;
>  }
>  
> @@ -2563,6 +2585,7 @@ static const struct net_device_ops virtnet_netdev = {
>  	.ndo_features_check	= passthru_features_check,
>  	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
>  	.ndo_set_features	= virtnet_set_features,
> +	.ndo_fix_features	= virtnet_fix_features,
>  };
>  
>  static void virtnet_config_changed_work(struct work_struct *work)
> @@ -3013,8 +3036,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	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))
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
> +		dev->hw_features |= NETIF_F_RXCSUM;
>  		dev->hw_features |= NETIF_F_LRO;
> +	}
>  
>  	dev->vlan_features = dev->features;
>  
> -- 
> 2.23.0