(before the experts wake up...)
are you sure it's smoke? (black smoke?) could be just water condensation (more of a white steam). other than that, the GS seems to burn a pretty good amount of oil (run a search), although i don't know if 500ml is excessive....
Mine was using a quart in 300 miles or less on a 48K mile bike. I also made great compression as well as had excellent power and smoke on startup is a combination of condensation of water vapor in the exhaust as it comes out, and un burnt fuel due to choke. I was going to run mine till it will run no more, but then I got broke and sold it. But you may have rings or valve stem seals ... just as well ride it till it falls apart and then see what.
Cool.
Srinath.