Comment # 11 on bug 87023 from Alex Deucher

(In reply to Romy from comment #10)
> What do you mean bisect mesa? Did you mean I must installing mesa 10.1.3 and
> send you xorg log and dmesg output?

bisecting is a git feature you can use to identify what commit causes a
regression.  You just checkout the mesa git tree and mark what commits were
working and not-working and it will walk you hrough the rest to identify the
culprit.  Google for git bisect howto.