From e7428e95a06fb516fac1308bd0e176e27c0b9287 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Thu, 25 Jul 2013 10:20:23 +0930 Subject: virtio-net: put virtio net header inline with data For small packets we can simplify xmit processing by linearizing buffers with the header: most packets seem to have enough head room we can use for this purpose. Since existing hypervisors require that header is the first s/g element, we need a feature bit for this. Signed-off-by: Michael S. Tsirkin Signed-off-by: Rusty Russell Signed-off-by: David S. Miller --- include/uapi/linux/virtio_net.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h index c520203fac2f..227d4ce84e79 100644 --- a/include/uapi/linux/virtio_net.h +++ b/include/uapi/linux/virtio_net.h @@ -70,7 +70,9 @@ struct virtio_net_config { __u16 max_virtqueue_pairs; } __attribute__((packed)); -/* This is the first element of the scatter-gather list. If you don't +/* This header comes first in the scatter-gather list. + * If VIRTIO_F_ANY_LAYOUT is not negotiated, it must + * be the first element of the scatter-gather list. If you don't * specify GSO or CSUM features, you can simply ignore the header. */ struct virtio_net_hdr { #define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 // Use csum_start, csum_offset -- cgit v1.2.3