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virtio-net: add feature bit for any header s/g

PATCH New Michael S. Tsirkin 1 participant 1 message Sep 28, 2012

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Michael S. Tsirkin

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PATCH 1/1 virtio-net: add feature bit for any header s/g

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 <[email protected]>
---
 hw/virtio-net.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
hw/virtio-net.h +3 -1
index 36aa463..e7187e4 100644
@@ -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
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