If by faith you mean belief without evidence, or belief despite the evidence (which is what I think you mean, Nailit) then no virtue at all.
But if you think of faith in moral terms as in commitment to an ideal, or in terms of personal loyalties (trust and confidence in a person, or an institution, or a country) then you can see that "keeping the faith", that is not forsaking it at the first sign of difficulty, is a virtuous quality, and the more so when it incurs personal cost and risk to yourself.