xen-netback: add control ring boilerplate

My recent patch to include/xen/interface/io/netif.h defines a new shared
ring (in addition to the rx and tx rings) for passing control messages
from a VM frontend driver to a backend driver.

This patch adds the necessary code to xen-netback to map this new shared
ring, should it be created by a frontend, but does not add implementations
for any of the defined protocol messages. These are added in a subsequent
patch for clarity.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 69 insertions, 10 deletions

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index bd182cd55dda..6a31f2610c23 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -38,7 +38,8 @@ struct backend_info {
 	const char *hotplug_script;
 };
 
-static int connect_rings(struct backend_info *be, struct xenvif_queue *queue);
+static int connect_data_rings(struct backend_info *be,
+			      struct xenvif_queue *queue);
 static void connect(struct backend_info *be);
 static int read_xenbus_vif_flags(struct backend_info *be);
 static int backend_create_xenvif(struct backend_info *be);
@@ -367,6 +368,12 @@ static int netback_probe(struct xenbus_device *dev,
 	if (err)
 		pr_debug("Error writing multi-queue-max-queues\n");
 
+	err = xenbus_printf(XBT_NIL, dev->nodename,
+			    "feature-ctrl-ring",
+			    "%u", true);
+	if (err)
+		pr_debug("Error writing feature-ctrl-ring\n");
+
 	script = xenbus_read(XBT_NIL, dev->nodename, "script", NULL);
 	if (IS_ERR(script)) {
 		err = PTR_ERR(script);
@@ -457,7 +464,8 @@ static void backend_disconnect(struct backend_info *be)
 #ifdef CONFIG_DEBUG_FS
 		xenvif_debugfs_delif(be->vif);
 #endif /* CONFIG_DEBUG_FS */
-		xenvif_disconnect(be->vif);
+		xenvif_disconnect_data(be->vif);
+		xenvif_disconnect_ctrl(be->vif);
 	}
 }
 
@@ -825,6 +833,48 @@ static void hotplug_status_changed(struct xenbus_watch *watch,
 	kfree(str);
 }
 
+static int connect_ctrl_ring(struct backend_info *be)
+{
+	struct xenbus_device *dev = be->dev;
+	struct xenvif *vif = be->vif;
+	unsigned int val;
+	grant_ref_t ring_ref;
+	unsigned int evtchn;
+	int err;
+
+	err = xenbus_gather(XBT_NIL, dev->otherend,
+			    "ctrl-ring-ref", "%u", &val, NULL);
+	if (err)
+		goto done; /* The frontend does not have a control ring */
+
+	ring_ref = val;
+
+	err = xenbus_gather(XBT_NIL, dev->otherend,
+			    "event-channel-ctrl", "%u", &val, NULL);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "reading %s/event-channel-ctrl",
+				 dev->otherend);
+		goto fail;
+	}
+
+	evtchn = val;
+
+	err = xenvif_connect_ctrl(vif, ring_ref, evtchn);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "mapping shared-frame %u port %u",
+				 ring_ref, evtchn);
+		goto fail;
+	}
+
+done:
+	return 0;
+
+fail:
+	return err;
+}
+
 static void connect(struct backend_info *be)
 {
 	int err;
@@ -861,6 +911,12 @@ static void connect(struct backend_info *be)
 	xen_register_watchers(dev, be->vif);
 	read_xenbus_vif_flags(be);
 
+	err = connect_ctrl_ring(be);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "connecting control ring");
+		return;
+	}
+
 	/* Use the number of queues requested by the frontend */
 	be->vif->queues = vzalloc(requested_num_queues *
 				  sizeof(struct xenvif_queue));
@@ -896,11 +952,12 @@ static void connect(struct backend_info *be)
 		queue->remaining_credit = credit_bytes;
 		queue->credit_usec = credit_usec;
 
-		err = connect_rings(be, queue);
+		err = connect_data_rings(be, queue);
 		if (err) {
-			/* connect_rings() cleans up after itself on failure,
-			 * but we need to clean up after xenvif_init_queue() here,
-			 * and also clean up any previously initialised queues.
+			/* connect_data_rings() cleans up after itself on
+			 * failure, but we need to clean up after
+			 * xenvif_init_queue() here, and also clean up any
+			 * previously initialised queues.
 			 */
 			xenvif_deinit_queue(queue);
 			be->vif->num_queues = queue_index;
@@ -935,15 +992,17 @@ static void connect(struct backend_info *be)
 
 err:
 	if (be->vif->num_queues > 0)
-		xenvif_disconnect(be->vif); /* Clean up existing queues */
+		xenvif_disconnect_data(be->vif); /* Clean up existing queues */
 	vfree(be->vif->queues);
 	be->vif->queues = NULL;
 	be->vif->num_queues = 0;
+	xenvif_disconnect_ctrl(be->vif);
 	return;
 }
 
 
-static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
+static int connect_data_rings(struct backend_info *be,
+			      struct xenvif_queue *queue)
 {
 	struct xenbus_device *dev = be->dev;
 	unsigned int num_queues = queue->vif->num_queues;
@@ -1007,8 +1066,8 @@ static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
 	}
 
 	/* Map the shared frame, irq etc. */
-	err = xenvif_connect(queue, tx_ring_ref, rx_ring_ref,
-			     tx_evtchn, rx_evtchn);
+	err = xenvif_connect_data(queue, tx_ring_ref, rx_ring_ref,
+				  tx_evtchn, rx_evtchn);
 	if (err) {
 		xenbus_dev_fatal(dev, err,
 				 "mapping shared-frames %lu/%lu port tx %u rx %u",