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Tsirkin" To: Jiri Pirko Cc: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org Subject: Re: [patch net-next] net: virtio_net: implement exact header length guest feature Message-ID: <20230217072032-mutt-send-email-mst@kernel.org> References: <20230217121547.3958716-1-jiri@resnulli.us> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230217121547.3958716-1-jiri@resnulli.us> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Feb 17, 2023 at 01:15:47PM +0100, Jiri Pirko wrote: > From: Jiri Pirko > > 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 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