Call model-class from view

[eluser]juan1904[/eluser]
So basically I need to to do something like this in every Controller:
$data['welcome_info'] = $this->login_model->welcome();

But if the login fails I want the validation_errors(); to show the errors in the view. But I can only do this if I call a view in the controller that the form calls for (in my case class user, function login).

How do I know which contentpage I need to load?