virtio: console: Return -EPIPE to hvc_console if we lost the connection

hvc_console handles -EPIPE properly when the connection to the host is
lost.
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/virtio_console.c

@@ -653,7 +653,7 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 
 	port = find_port_by_vtermno(vtermno);
 	if (!port)
-		return 0;
+		return -EPIPE;
 
 	return send_buf(port, (void *)buf, count);
 }
@@ -669,9 +669,13 @@ static int get_chars(u32 vtermno, char *buf, int count)
 {
 	struct port *port;
 
+	/* If we've not set up the port yet, we have no input to give. */
+	if (unlikely(early_put_chars))
+		return 0;
+
 	port = find_port_by_vtermno(vtermno);
 	if (!port)
-		return 0;
+		return -EPIPE;
 
 	/* If we don't have an input queue yet, we can't get input. */
 	BUG_ON(!port->in_vq);