The Khyber pass is a region where plants drugs are made of grow. Despite the drugs being the main topic of the film, this song is about anal sex (it's also showed during the anal sex scene in the movie).
"Up the khyber" is slang, and, like k3boyle said, it means "Up the arse".
Compare "Ummagumma", which is 60's/70's slang for sex.
The Khyber pass is a region where plants drugs are made of grow. Despite the drugs being the main topic of the film, this song is about anal sex (it's also showed during the anal sex scene in the movie). "Up the khyber" is slang, and, like k3boyle said, it means "Up the arse".
Compare "Ummagumma", which is 60's/70's slang for sex.