Comment # 25 on bug 100239 from Michel Dänzer

(In reply to Bruno Jacquet (Xaapyks) from comment #23)
> So I'd say the issue is still there.

Maybe you have a ~/.drirc or other drirc file which gets picked up and disables
radeonsi_zerovram? (E.g. due to ever starting the old "driconf" application
with a driver which supported the option)