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, 65 insertions, 3 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fe576e75a538..67bb583b7fc9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -37,10 +37,12 @@ module_param(gso, bool, 0444);
 #define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN   128
 
+#define VIRTNET_SEND_COMMAND_SG_MAX    0
+
 struct virtnet_info
 {
         struct virtio_device *vdev;
-        struct virtqueue *rvq, *svq;
+        struct virtqueue *rvq, *svq, *cvq;
         struct net_device *dev;
         struct napi_struct napi;
         unsigned int status;
@@ -589,6 +591,53 @@ static int virtnet_open(struct net_device *dev)
         return 0;
 }
 
+/*
+ * Send command via the control virtqueue and check status.  Commands
+ * supported by the hypervisor, as indicated by feature bits, should
+ * never fail unless improperly formated.
+ */
+static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
+                                 struct scatterlist *data, int out, int in)
+{
+        struct scatterlist sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
+        struct virtio_net_ctrl_hdr ctrl;
+        virtio_net_ctrl_ack status = ~0;
+        unsigned int tmp;
+
+        if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
+                BUG();  /* Caller should know better */
+                return false;
+        }
+
+        BUG_ON(out + in > VIRTNET_SEND_COMMAND_SG_MAX);
+
+        out++; /* Add header */
+        in++; /* Add return status */
+
+        ctrl.class = class;
+        ctrl.cmd = cmd;
+
+        sg_init_table(sg, out + in);
+
+        sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
+        memcpy(&sg[1], data, sizeof(struct scatterlist) * (out + in - 2));
+        sg_set_buf(&sg[out + in - 1], &status, sizeof(status));
+
+        if (vi->cvq->vq_ops->add_buf(vi->cvq, sg, out, in, vi) != 0)
+                BUG();
+
+        vi->cvq->vq_ops->kick(vi->cvq);
+
+        /*
+         * Spin for a response, the kick causes an ioport write, trapping
+         * into the hypervisor, so the request should be handled immediately.
+         */
+        while (!vi->cvq->vq_ops->get_buf(vi->cvq, &tmp))
+                cpu_relax();
+
+        return status == VIRTIO_NET_OK;
+}
+
 static int virtnet_close(struct net_device *dev)
 {
         struct virtnet_info *vi = netdev_priv(dev);
@@ -752,6 +801,14 @@ static int virtnet_probe(struct virtio_device *vdev)
                 goto free_recv;
         }
 
+        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
+                vi->cvq = vdev->config->find_vq(vdev, 2, NULL);
+                if (IS_ERR(vi->cvq)) {
+                        err = PTR_ERR(vi->svq);
+                        goto free_send;
+                }
+        }
+
         /* Initialize our empty receive and send queues. */
         skb_queue_head_init(&vi->recv);
         skb_queue_head_init(&vi->send);
@@ -764,7 +821,7 @@ static int virtnet_probe(struct virtio_device *vdev)
         err = register_netdev(dev);
         if (err) {
                 pr_debug("virtio_net: registering device failed\n");
-                goto free_send;
+                goto free_ctrl;
         }
 
         /* Last of all, set up some receive buffers. */
@@ -784,6 +841,9 @@ static int virtnet_probe(struct virtio_device *vdev)
 
 unregister:
         unregister_netdev(dev);
+free_ctrl:
+        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
+                vdev->config->del_vq(vi->cvq);
 free_send:
         vdev->config->del_vq(vi->svq);
 free_recv:
@@ -815,6 +875,8 @@ static void virtnet_remove(struct virtio_device *vdev)
 
         vdev->config->del_vq(vi->svq);
         vdev->config->del_vq(vi->rvq);
+        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
+                vdev->config->del_vq(vi->cvq);
         unregister_netdev(vi->dev);
 
         while (vi->pages)
@@ -834,7 +896,7 @@ static unsigned int features[] = {
         VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
         VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
         VIRTIO_NET_F_GUEST_ECN, /* We don't yet handle UFO input. */
-        VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS,
+        VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
         VIRTIO_F_NOTIFY_ON_EMPTY,
 };