netdev - Re: [RFC PATCH v2 4/8] virtio_net: add supports for extended offloads

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Message-ID: <a8d56434-da4b-466a-8225-3c6b64596b23@daynix.com>
Date: Sat, 31 May 2025 15:18:58 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Jason Wang <jasowang@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, "Michael S. Tsirkin" <mst@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
 <eperezma@...hat.com>, Yuri Benditovich <yuri.benditovich@...nix.com>
Subject: Re: [RFC PATCH v2 4/8] virtio_net: add supports for extended offloads

On 2025/05/30 23:49, Paolo Abeni wrote:
> The virtio_net driver needs it to implement GSO over UDP tunnel
> offload.
> 
> The only missing piece is mapping them to/from the extended
> features.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> v1 -> v2:
>   - drop unused macro
>   - restrict the offload remap range as per latest spec update
> ---
>   drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++--
>   1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e53ba600605a..ec638b4aa1c1 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -35,6 +35,24 @@ module_param(csum, bool, 0444);
>   module_param(gso, bool, 0444);
>   module_param(napi_tx, bool, 0644);
>   
> +#define VIRTIO_OFFLOAD_MAP_MIN	46
> +#define VIRTIO_OFFLOAD_MAP_MAX	47
> +#define VIRTIO_FEATURES_MAP_MIN	65
> +#define VIRTIO_O2F_DELTA	(VIRTIO_FEATURES_MAP_MIN - VIRTIO_OFFLOAD_MAP_MIN)
> +
> +static bool virtio_is_mapped_offload(unsigned int obit)
> +{
> +	return obit >= VIRTIO_OFFLOAD_MAP_MIN &&
> +	       obit <= VIRTIO_OFFLOAD_MAP_MAX;
> +}
> +
> +#define VIRTIO_OFFLOAD_TO_FEATURE(obit)	\
> +	({								\
> +		unsigned int __o = obit;				\
> +		virtio_is_mapped_offload(__o) ? __o + VIRTIO_O2F_DELTA :\
> +						__o;			\
> +	})

I wonder why this is a macro while virtio_is_mapped_offload() is a function.

> +
 >   /* FIXME: MTU in config. */>   #define GOOD_PACKET_LEN (ETH_HLEN + 
VLAN_HLEN + ETH_DATA_LEN)
>   #define GOOD_COPY_LEN	128
> @@ -7037,9 +7055,13 @@ static int virtnet_probe(struct virtio_device *vdev)
>   		netif_carrier_on(dev);
>   	}
>   
> -	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
> -		if (virtio_has_feature(vi->vdev, guest_offloads[i]))
> +	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++) {
> +		unsigned int fbit;
> +
> +		fbit = VIRTIO_OFFLOAD_TO_FEATURE(guest_offloads[i]);
> +		if (virtio_has_feature(vi->vdev, fbit))
>   			set_bit(guest_offloads[i], &vi->guest_offloads);
> +	}
>   	vi->guest_offloads_capable = vi->guest_offloads;
>   
>   	rtnl_unlock();