netdev - Re: [PATCH 2/2] virtio-net: ethtool configurable RXCSUM

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Date:   Mon, 28 Sep 2020 15:25:10 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     xiangxia.m.yue@...il.com
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] virtio-net: ethtool configurable RXCSUM

On Mon, Sep 28, 2020 at 11:39:15AM +0800, xiangxia.m.yue@...il.com wrote:
> From: Tonghao Zhang <xiangxia.m.yue@...il.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.
> 
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> ---
>  drivers/net/virtio_net.c | 40 ++++++++++++++++++++++++++++------------
>  1 file changed, 28 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 21b71148c532..2e3af0b2c281 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;
> @@ -2526,25 +2528,37 @@ 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;
>  	}
>  
> +	if (offloads == (vi->guest_offloads &
> +			 vi->guest_offloads_capable))
> +		return 0;

Hmm, what exactly does this do?

> +
> +	err = virtnet_set_guest_offloads(vi, offloads);
> +	if (err)
> +		return err;
> +
> +	vi->guest_offloads = offloads;
>  	return 0;
>  }
>  
> @@ -3013,8 +3027,10 @@ 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