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

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Message-ID: <CACGkMEtfzcCzdCCFWKup2d417_OtpBgiWRf2bu1Qh=SQnD7Jcw@mail.gmail.com>
Date: Mon, 26 May 2025 09:01:21 +0800
From: Jason Wang <jasowang@...hat.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Willem de Bruijn <willemdebruijn.kernel@...il.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>
Subject: Re: [PATCH net-next 4/8] virtio_net: add supports for extended offloads

On Wed, May 21, 2025 at 6:33 PM Paolo Abeni <pabeni@...hat.com> 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>
> ---
>  drivers/net/virtio_net.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e53ba600605a5..71a972f20f19b 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -35,6 +35,29 @@ 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 49
> +#define VIRTIO_FEATURES_MAP_MIN        65
> +#define VIRTIO_O2F_DELTA       (VIRTIO_FEATURES_MAP_MIN - VIRTIO_OFFLOAD_MAP_MIN)

Instead of doing this, I wonder if it's simple to just have an array
for the mapping from all guest offload features to guest controllable
offload bits?

> +
> +static bool virtio_is_mapped_offload(unsigned int obit)
> +{
> +       return obit >= VIRTIO_OFFLOAD_MAP_MIN &&
> +              obit <= VIRTIO_OFFLOAD_MAP_MAX;
> +}
> +
> +#define VIRTIO_FEATURE_TO_OFFLOAD(fbit)        \
> +       ({                                                              \
> +               unsigned int __f = fbit;                                \
> +               __f >= VIRTIO_FEATURES_MAP_MIN ? __f - VIRTIO_O2F_DELTA : __f; \
> +       })
> +#define VIRTIO_OFFLOAD_TO_FEATURE(obit)        \
> +       ({                                                              \
> +               unsigned int __o = obit;                                \
> +               virtio_is_mapped_offload(__o) ? __o + VIRTIO_O2F_DELTA :\
> +                                               __o;                    \
> +       })
> +
>  /* FIXME: MTU in config. */
>  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
>  #define GOOD_COPY_LEN  128
> @@ -7037,9 +7060,13 @@ 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();
> --
> 2.49.0
>

Thanks