Visa if our cruise stop in both Shanghai and Hong Kong

My wife and I are Canadian citizens. We are visiting Shanghai & Hong Kong in March 2015 on a cruise ship that stops in each port for 2 days and eventually sails on to Singapore. On my flight back from Singapore at the end of the cruise March 22,2015, we connect through Hong Kong for our Air Canada flight to Canada. Can you advise if I need a visa and if so what kind? How much will it cost?
What documentation is required?