virtio-serial: Bug fix, add stats for bytes transferred

index a4825b9..6838d73 100644
@@ -114,7 +114,8 @@ static size_t write_to_port(VirtIOSerialPort *port,
     return offset;
 }
 
-static void discard_vq_data(VirtQueue *vq, VirtIODevice *vdev)
+static void discard_vq_data(VirtIOSerialPort *port, VirtQueue *vq,
+                            VirtIODevice *vdev)
 {
     VirtQueueElement elem;
 

@@ -248,7 +249,7 @@ int virtio_serial_close(VirtIOSerialPort *port)
      * consume, reset the throttling flag and discard the data.
      */
     port->throttled = false;
-    discard_vq_data(port->ovq, &port->vser->vdev);
+    discard_vq_data(port, port->ovq, &port->vser->vdev);
 
     send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
 

@@ -473,7 +474,7 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
     info = port ? DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info) : NULL;
 
     if (!port || !port->host_connected || !info->have_data) {
-        discard_vq_data(vq, vdev);
+        discard_vq_data(port, vq, vdev);
         return;
     }
 

@@ -730,7 +731,7 @@ static void remove_port(VirtIOSerial *vser, uint32_t port_id)
 
     port = find_port_by_id(vser, port_id);
     /* Flush out any unconsumed buffers first */
-    discard_vq_data(port->ovq, &port->vser->vdev);
+    discard_vq_data(port, port->ovq, &port->vser->vdev);
 
     send_control_event(port, VIRTIO_CONSOLE_PORT_REMOVE, 1);
 }

index 6838d73..2c84398 100644
@@ -122,6 +122,10 @@ static void discard_vq_data(VirtIOSerialPort *port, VirtQueue *vq,
     if (!virtio_queue_ready(vq)) {
         return;
     }
+    if (port && port->elem.out_num) {
+        virtqueue_push(vq, &port->elem, 0);
+        port->elem.out_num = 0;
+    }
     while (virtqueue_pop(vq, &elem)) {
         virtqueue_push(vq, &elem, 0);
     }

index 2c84398..deefda4 100644
@@ -108,6 +108,7 @@ static size_t write_to_port(VirtIOSerialPort *port,
         offset += len;
 
         virtqueue_push(vq, &elem, len);
+        port->stats.bytes_sent += len;
     }
 
     virtio_notify(&port->vser->vdev, vq);

@@ -123,10 +124,24 @@ static void discard_vq_data(VirtIOSerialPort *port, VirtQueue *vq,
         return;
     }
     if (port && port->elem.out_num) {
+        port->stats.bytes_discarded += (iov_size(port->elem.out_sg,
+                                                 elem.out_num)
+                                        - iov_size(port->elem.out_sg,
+                                                   port->iov_idx)
+                                        - port->iov_offset);
         virtqueue_push(vq, &port->elem, 0);
         port->elem.out_num = 0;
     }
     while (virtqueue_pop(vq, &elem)) {
+        if (port) {
+            unsigned long size;
+
+            size = iov_size(elem.out_sg, elem.out_num);
+
+            /* We haven't counted these bytes in the received stats yet. */
+            port->stats.bytes_received += size;
+            port->stats.bytes_discarded += size;
+        }
         virtqueue_push(vq, &elem, 0);
     }
     virtio_notify(vdev, vq);

@@ -152,6 +167,8 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
             }
             port->iov_idx = 0;
             port->iov_offset = 0;
+            port->stats.bytes_received += iov_size(port->elem.out_sg,
+                                                   port->elem.out_num);
         }
 
         for (i = port->iov_idx; i < port->elem.out_num; i++) {

@@ -684,11 +701,14 @@ static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
 {
     VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);
 
-    monitor_printf(mon, "%*sport %d, guest %s, host %s, throttle %s\n",
+    monitor_printf(mon, "%*sport %d, guest %s, host %s, throttle %s, bytes_sent %lu, bytes_received %lu, bytes_discarded: %lu\n",
                    indent, "", port->id,
                    port->guest_connected ? "on" : "off",
                    port->host_connected ? "on" : "off",
-                   port->throttled ? "on" : "off");
+                   port->throttled ? "on" : "off",
+                   port->stats.bytes_sent,
+                   port->stats.bytes_received,
+                   port->stats.bytes_discarded);
 }
 
 /* This function is only used if a port id is not provided by the user */

index ab13803..34d36d7 100644
@@ -67,6 +67,10 @@ typedef struct VirtIOSerialBus VirtIOSerialBus;
 typedef struct VirtIOSerialPort VirtIOSerialPort;
 typedef struct VirtIOSerialPortInfo VirtIOSerialPortInfo;
 
+typedef struct {
+    unsigned long bytes_sent, bytes_received, bytes_discarded;
+} PortStats;
+
 /*
  * This is the state that's shared between all the ports.  Some of the
  * state is configurable via command-line options. Some of it can be

@@ -87,6 +91,13 @@ struct VirtIOSerialPort {
     VirtQueue *ivq, *ovq;
 
     /*
+     * Keep count of the bytes sent, received and discarded for
+     * this port for accounting and debugging purposes.  These
+     * counts are not reset across port open / close events.
+     */
+    PortStats stats;
+
+    /*
      * This name is sent to the guest and exported via sysfs.
      * The guest could create symlinks based on this information.
      * The name is in the reverse fqdn format, like org.qemu.console.0