virtio: console: Handle port hot-plug

If the 'nr_ports' variable in the config space is updated to a higher
value, that means new ports have been hotplugged.

Introduce a new workqueue to handle such updates and create new ports.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 72 insertions, 6 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5506ff8bdf03..7c53f58c87ba 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -105,6 +105,7 @@ struct ports_device {
          * notification
          */
         struct work_struct control_work;
+        struct work_struct config_work;
 
         struct list_head ports;
 
@@ -675,11 +676,6 @@ static void resize_console(struct port *port)
         }
 }
 
-static void virtcons_apply_config(struct virtio_device *vdev)
-{
-        resize_console(find_port_by_vtermno(0));
-}
-
 /* We set the configuration at this point, since we now have a tty */
 static int notifier_add_vio(struct hvc_struct *hp, int data)
 {
@@ -928,6 +924,24 @@ static void control_intr(struct virtqueue *vq)
         schedule_work(&portdev->control_work);
 }
 
+static void config_intr(struct virtio_device *vdev)
+{
+        struct ports_device *portdev;
+
+        portdev = vdev->priv;
+        if (use_multiport(portdev)) {
+                /* Handle port hot-add */
+                schedule_work(&portdev->config_work);
+        }
+        /*
+         * We'll use this way of resizing only for legacy support.
+         * For newer userspace (VIRTIO_CONSOLE_F_MULTPORT+), use
+         * control messages to indicate console size changes so that
+         * it can be done per-port
+         */
+        resize_console(find_port_by_id(portdev, 0));
+}
+
 static void fill_queue(struct virtqueue *vq, spinlock_t *lock)
 {
         struct port_buffer *buf;
@@ -1040,6 +1054,57 @@ fail:
         return err;
 }
 
+/*
+ * The workhandler for config-space updates.
+ *
+ * This is called when ports are hot-added.
+ */
+static void config_work_handler(struct work_struct *work)
+{
+        struct virtio_console_config virtconconf;
+        struct ports_device *portdev;
+        struct virtio_device *vdev;
+        int err;
+
+        portdev = container_of(work, struct ports_device, config_work);
+
+        vdev = portdev->vdev;
+        vdev->config->get(vdev,
+                          offsetof(struct virtio_console_config, nr_ports),
+                          &virtconconf.nr_ports,
+                          sizeof(virtconconf.nr_ports));
+
+        if (portdev->config.nr_ports == virtconconf.nr_ports) {
+                /*
+                 * Port 0 got hot-added.  Since we already did all the
+                 * other initialisation for it, just tell the Host
+                 * that the port is ready.
+                 */
+                struct port *port;
+
+                port = find_port_by_id(portdev, 0);
+                send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
+                return;
+        }
+        if (virtconconf.nr_ports > portdev->config.max_nr_ports) {
+                dev_warn(&vdev->dev,
+                         "More ports specified (%u) than allowed (%u)",
+                         portdev->config.nr_ports + 1,
+                         portdev->config.max_nr_ports);
+                return;
+        }
+        if (virtconconf.nr_ports < portdev->config.nr_ports)
+                return;
+
+        /* Hot-add ports */
+        while (virtconconf.nr_ports - portdev->config.nr_ports) {
+                err = add_port(portdev, portdev->config.nr_ports);
+                if (err)
+                        break;
+                portdev->config.nr_ports++;
+        }
+}
+
 static int init_vqs(struct ports_device *portdev)
 {
         vq_callback_t **io_callbacks;
@@ -1230,6 +1295,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
         if (multiport) {
                 spin_lock_init(&portdev->cvq_lock);
                 INIT_WORK(&portdev->control_work, &control_work_handler);
+                INIT_WORK(&portdev->config_work, &config_work_handler);
 
                 fill_queue(portdev->c_ivq, &portdev->cvq_lock);
         }
@@ -1266,7 +1332,7 @@ static struct virtio_driver virtio_console = {
         .driver.owner = THIS_MODULE,
         .id_table =     id_table,
         .probe =        virtcons_probe,
-        .config_changed = virtcons_apply_config,
+        .config_changed = config_intr,
 };
 
 static int __init init(void)