virtio_net: Add a virtqueue for outbound control commands

This will be used for RX mode, MAC filter table, VLAN filtering, etc...

The control transaction consists of one or more "out" sg entries and
one or more "in" sg entries.  The first out entry contains a header
defining the class and command.  Additional out entries may provide
data for the command.  The last in entry provides a status response
back from the command.

Virtqueues typically run asynchronous, running a callback function
when there's data in the channel.  We can't readily make use of this
in the command paths where we need to use this.  Instead, we kick
the virtqueue and spin.  The kick causes an I/O write, triggering an
immediate trap into the hypervisor.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index d8e362d52fd..245eda829aa 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -23,6 +23,7 @@
 #define VIRTIO_NET_F_HOST_UFO	14	/* Host can handle UFO in. */
 #define VIRTIO_NET_F_MRG_RXBUF	15	/* Host can merge receive buffers. */
 #define VIRTIO_NET_F_STATUS	16	/* virtio_net_config.status available */
+#define VIRTIO_NET_F_CTRL_VQ	17	/* Control channel available */
 
 #define VIRTIO_NET_S_LINK_UP	1	/* Link is up */
 
@@ -59,4 +60,21 @@ struct virtio_net_hdr_mrg_rxbuf {
 	__u16 num_buffers;	/* Number of merged rx buffers */
 };
 
+/*
+ * Control virtqueue data structures
+ *
+ * The control virtqueue expects a header in the first sg entry
+ * and an ack/status response in the last entry.  Data for the
+ * command goes in between.
+ */
+struct virtio_net_ctrl_hdr {
+	__u8 class;
+	__u8 cmd;
+} __attribute__((packed));
+
+typedef __u8 virtio_net_ctrl_ack;
+
+#define VIRTIO_NET_OK     0
+#define VIRTIO_NET_ERR    1
+
 #endif /* _LINUX_VIRTIO_NET_H */