On Fri, Feb 17, 2023 at 01:15:47PM +0100, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@xxxxxxxxxx>
>
> virtio_net_hdr_from_skb() fills up hdr_len to skb_headlen(skb).
>
> Virtio spec introduced a feature VIRTIO_NET_F_GUEST_HDRLEN which when
> set implicates that the driver provides the exact size of the header.
>
> The driver already complies to fill the correct value. Introduce the
> feature and advertise it.
>
> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
Could you add a bit of motivation just for the record?
Does this improve performance for some card? By how much?
Expected to help some future card?
thanks!
> ---
> drivers/net/virtio_net.c | 6 ++++--
> include/uapi/linux/virtio_net.h | 1 +
> 2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index fb5e68ed3ec2..e85b03988733 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -62,7 +62,8 @@ static const unsigned long guest_offloads[] = {
> VIRTIO_NET_F_GUEST_UFO,
> VIRTIO_NET_F_GUEST_CSUM,
> VIRTIO_NET_F_GUEST_USO4,
> - VIRTIO_NET_F_GUEST_USO6
> + VIRTIO_NET_F_GUEST_USO6,
> + VIRTIO_NET_F_GUEST_HDRLEN
> };
>
> #define GUEST_OFFLOAD_GRO_HW_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
> @@ -4213,7 +4214,8 @@ static struct virtio_device_id id_table[] = {
> VIRTIO_NET_F_CTRL_MAC_ADDR, \
> VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
> - VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL
> + VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL, \
> + VIRTIO_NET_F_GUEST_HDRLEN
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index b4062bed186a..12c1c9699935 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -61,6 +61,7 @@
> #define VIRTIO_NET_F_GUEST_USO6 55 /* Guest can handle USOv6 in. */
> #define VIRTIO_NET_F_HOST_USO 56 /* Host can handle USO in. */
> #define VIRTIO_NET_F_HASH_REPORT 57 /* Supports hash report */
> +#define VIRTIO_NET_F_GUEST_HDRLEN 59 /* Guest provides the exact hdr_len value. */
> #define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */
> #define VIRTIO_NET_F_RSC_EXT 61 /* extended coalescing info */
> #define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device
> --
> 2.39.0
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