Do I need another Chinese visa to enter Sanya and return to Mainland China?

Hi there, I have a double entry one for PRC but I have already used both entries and it allows me to remain in Mainland China until October 17th. Do I need another one to enter Sanya and return to Mainland China or does my current one enable me to go to Sanya and return to Mainland China without having to apply for another one; I am a Canadian passport holder.