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
--
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