virtio: console: return -ENODEV on all read operations after unplug

If a port gets unplugged while a user is blocked on read(), -ENODEV is
returned.  However, subsequent read()s returned 0, indicating there's no
host-side connection (but not indicating the device went away).

This also happened when a port was unplugged and the user didn't have
any blocking operation pending.  If the user didn't monitor the SIGIO
signal, they won't have a chance to find out if the port went away.

Fix by returning -ENODEV on all read()s after the port gets unplugged.
write() already behaves this way.

CC: <>
Signed-off-by: Amit Shah <>
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 3435348..2b68075 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -749,6 +749,10 @@
 	port = filp->private_data;
+	/* Port is hot-unplugged. */
+	if (!port->guest_connected)
+		return -ENODEV;
 	if (!port_has_data(port)) {
 		 * If nothing's connected on the host just return 0 in
@@ -765,7 +769,7 @@
 		if (ret < 0)
 			return ret;
-	/* Port got hot-unplugged. */
+	/* Port got hot-unplugged while we were waiting above. */
 	if (!port->guest_connected)
 		return -ENODEV;