virtio: console: Add freeze and restore handlers to support S4

Remove all vqs and associated buffers in the freeze callback which
prepares us to go into hibernation state.  On restore, re-create all the
vqs and populate the input vqs with buffers to get to the pre-hibernate
state.

Note: Any outstanding unconsumed buffers are discarded; which means
there's a possibility of data loss in case the host or the guest didn't
consume any data already present in the vqs.  This can be addressed in a
later patch series, perhaps in virtio common code.

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

1 files changed, 58 insertions, 0 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 9681ffd79904..614b84d38d7a 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1844,6 +1844,60 @@ static unsigned int features[] = {
         VIRTIO_CONSOLE_F_MULTIPORT,
 };
 
+#ifdef CONFIG_PM
+static int virtcons_freeze(struct virtio_device *vdev)
+{
+        struct ports_device *portdev;
+        struct port *port;
+
+        portdev = vdev->priv;
+
+        vdev->config->reset(vdev);
+
+        cancel_work_sync(&portdev->control_work);
+        remove_controlq_data(portdev);
+
+        list_for_each_entry(port, &portdev->ports, list) {
+                /*
+                 * We'll ask the host later if the new invocation has
+                 * the port opened or closed.
+                 */
+                port->host_connected = false;
+                remove_port_data(port);
+        }
+        remove_vqs(portdev);
+
+        return 0;
+}
+
+static int virtcons_restore(struct virtio_device *vdev)
+{
+        struct ports_device *portdev;
+        struct port *port;
+        int ret;
+
+        portdev = vdev->priv;
+
+        ret = init_vqs(portdev);
+        if (ret)
+                return ret;
+
+        if (use_multiport(portdev))
+                fill_queue(portdev->c_ivq, &portdev->cvq_lock);
+
+        list_for_each_entry(port, &portdev->ports, list) {
+                port->in_vq = portdev->in_vqs[port->id];
+                port->out_vq = portdev->out_vqs[port->id];
+
+                fill_queue(port->in_vq, &port->inbuf_lock);
+
+                /* Get port open/close status on the host */
+                send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
+        }
+        return 0;
+}
+#endif
+
 static struct virtio_driver virtio_console = {
         .feature_table = features,
         .feature_table_size = ARRAY_SIZE(features),
@@ -1853,6 +1907,10 @@ static struct virtio_driver virtio_console = {
         .probe =        virtcons_probe,
         .remove =       virtcons_remove,
         .config_changed = config_intr,
+#ifdef CONFIG_PM
+        .freeze =       virtcons_freeze,
+        .restore =      virtcons_restore,
+#endif
 };
 
 static int __init init(void)