Old qemu versions required that 1st s/g entry is the header. My recent patchset titled "virtio-net: iovec handling cleanup" removed this limitation but a feature bit is needed so guests know it's safe to lay out header differently. This patch applies on top and adds such a feature bit. virtio net header inline with the data is beneficial for latency and small packet bandwidth. Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> --- hw/virtio-net.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/hw/virtio-net.h b/hw/virtio-net.h index 36aa463..e7187e4 100644 --- a/hw/virtio-net.h +++ b/hw/virtio-net.h @@ -44,6 +44,7 @@ #define VIRTIO_NET_F_CTRL_RX 18 /* Control channel RX mode support */ #define VIRTIO_NET_F_CTRL_VLAN 19 /* Control channel VLAN filtering */ #define VIRTIO_NET_F_CTRL_RX_EXTRA 20 /* Extra RX mode control support */ +#define VIRTIO_NET_F_ANY_HEADER_SG 22 /* Host can handle any header s/g */ #define VIRTIO_NET_S_LINK_UP 1 /* Link is up */ @@ -186,5 +187,6 @@ struct virtio_net_ctrl_mac { DEFINE_PROP_BIT("ctrl_vq", _state, _field, VIRTIO_NET_F_CTRL_VQ, true), \ DEFINE_PROP_BIT("ctrl_rx", _state, _field, VIRTIO_NET_F_CTRL_RX, true), \ DEFINE_PROP_BIT("ctrl_vlan", _state, _field, VIRTIO_NET_F_CTRL_VLAN, true), \ - DEFINE_PROP_BIT("ctrl_rx_extra", _state, _field, VIRTIO_NET_F_CTRL_RX_EXTRA, true) + DEFINE_PROP_BIT("ctrl_rx_extra", _state, _field, VIRTIO_NET_F_CTRL_RX_EXTRA, true), \ + DEFINE_PROP_BIT("any_header_sg", _state, _field, VIRTIO_NET_F_ANY_HEADER_SG, true) #endif -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html