sushimaru you need to use OLCI (online check/in) see
http://www.qatarairways.com/dk/en/checking-in.page. You can print your boarding pass there.
According to a recent discussion the transfer desk at CMB handles all airlines including QR and can even re-check your baggage if required. However you should try to get AI check-in to label your luggage through to CAI..