virtio_console: avoid config access from irq

commit eeb8a7e8bb123e84daeef84f5a2eab99ad2839a2 upstream.

when multiport is off, virtio console invokes config access from irq
context, config access is blocking on s390.
Fix this up by scheduling work from config irq - similar to what we do
for multiport configs.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 82650b4b62a1a4d1681ec960f3cdb7821ef93693..96f4a503ff9d165b72e1b1f17abb07b629fd110a 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -124,6 +124,7 @@ struct ports_device {
         * notification
         */
        struct work_struct control_work;
+       struct work_struct config_work;
 
        struct list_head ports;
 
@@ -1555,10 +1556,21 @@ static void config_intr(struct virtio_device *vdev)
 
        portdev = vdev->priv;
 
+       if (!use_multiport(portdev))
+               schedule_work(&portdev->config_work);
+}
+
+static void config_work_handler(struct work_struct *work)
+{
+       struct ports_device *portdev;
+
+       portdev = container_of(work, struct ports_device, control_work);
        if (!use_multiport(portdev)) {
+               struct virtio_device *vdev;
                struct port *port;
                u16 rows, cols;
 
+               vdev = portdev->vdev;
                vdev->config->get(vdev,
                                  offsetof(struct virtio_console_config, cols),
                                  &cols, sizeof(u16));
@@ -1752,6 +1764,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
        spin_lock_init(&portdev->ports_lock);
        INIT_LIST_HEAD(&portdev->ports);
 
+       INIT_WORK(&portdev->config_work, &config_work_handler);
        INIT_WORK(&portdev->control_work, &control_work_handler);
 
        if (multiport) {
@@ -1826,6 +1839,8 @@ static void virtcons_remove(struct virtio_device *vdev)
        /* Finish up work that's lined up */
        if (use_multiport(portdev))
                cancel_work_sync(&portdev->control_work);
+       else
+               cancel_work_sync(&portdev->config_work);
 
        list_for_each_entry_safe(port, port2, &portdev->ports, list)
                unplug_port(port);
@@ -1867,6 +1882,7 @@ static int virtcons_freeze(struct virtio_device *vdev)
 
        virtqueue_disable_cb(portdev->c_ivq);
        cancel_work_sync(&portdev->control_work);
+       cancel_work_sync(&portdev->config_work);
        /*
         * Once more: if control_work_handler() was running, it would
         * enable the cb as the last step.