RE: [PATCH] virtio-net: clarify guest offloads <> features mapping

Hi Paolo,

> From: Paolo Abeni <[email protected]>
> Sent: Monday, May 19, 2025 3:42 PM
> 
> The guest offloads, as specified by 'Setting Offloads State,' use a 64-bit wide
> space, while some of the corresponding virtio net features are in the upper 64
> bits of a 128-bit wide space.
> 
> Clarify the relevant mapping as somewhat implied by the current text.
> Also rename the offload definitions to avoid referring to different numeric
> values with the same name in the features table and in the offload table.
> 
> Signed-off-by: Paolo Abeni <[email protected]>
> ---
>  device-types/net/description.tex | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/device-types/net/description.tex b/device-
> types/net/description.tex
> index 1b6b54d..8c501bc 100644
> --- a/device-types/net/description.tex
> +++ b/device-types/net/description.tex
> @@ -2186,8 +2186,8 @@ \subsubsection{Control
> Virtqueue}\label{sec:Device Types / Network Device / Devi
>  #define VIRTIO_NET_F_GUEST_TSO6       8
>  #define VIRTIO_NET_F_GUEST_ECN        9
>  #define VIRTIO_NET_F_GUEST_UFO        10
> -#define VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO  46 -#define
> VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM 47
> +#define VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_MAPPED  46 #define
> +VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM_MAPPED 47
Since the offload command is defined only for the rx side, in the below 'Note' should it be only 65-66 map to 46-47?

>  #define VIRTIO_NET_F_GUEST_USO4       54
>  #define VIRTIO_NET_F_GUEST_USO6       55
> 
> @@ -2205,6 +2205,9 @@ \subsubsection{Control
> Virtqueue}\label{sec:Device Types / Network Device / Devi  negotiation
> corresponding offload gets enabled to preserve backward  compatibility.
> 
> +Note that device features bits in the [65 to 68] range correspond to
> +offload bits in the [46 to 49] range.
> +
>  \drivernormative{\subparagraph}{Setting Offloads State}{Device Types /
> Network Device / Device Operation / Control Virtqueue / Offloads State
> Configuration / Setting Offloads State}
> 
>  A driver MUST NOT enable an offload for which the appropriate feature
> --
> 2.49.0