One Entry or multiple entry visa?

Hi
I arrive in Hong Kong from Ireland for two nights before boarding cruise ship to Taiwan, Japan, South Korea (3nights) and Beijing (also 3 nights). From Beijing I sail back to Shanghai where I stay for another 3 nights in a hotel.
The Chinese Embassy in Dublin tell me I only require a one-entry visa, although the cruise company tell me I need multiple entry one.
Can you tell me who is correct please? Thank you very much in advance
Kind Regards
Denise