These fix many GPU hangs for Eugeni, though not on my machine for some reason. Oddly, the register writes to UCGCTL2 and SQ_CHICKEN_MBCUNIT_CONFIG stick, but the writes to L3_CHICKEN_MODE, L3CNTLREG1, and COMMON_SLICE_CHICKEN1 don't seem to take effect. Currently no theories why. Manually writing these values with intel_reg_write /does/ fix the hangs for me. I'm fine with these going to -fixes. They seem to help some people, and I highly doubt they'll make anything worse. It'd be nice to understand why the register writes aren't sticking, though...
