On Tue, 6 Dec 2011 09:39:39 -0800, Ben Widawsky <ben at bwidawsk.net> wrote: > On Mon, Nov 28, 2011 at 10:24:55PM +0100, Daniel Vetter wrote: > > On Sanybridge a few MI read/write commands only work when ppgtt is > > enabled. Userspace therefore needs to be able to check whether ppgtt > > is enabled. For added hilarity, you need to reset the "use global GTT" > > bit on both snb/ivb when ppgtt is enabled, otherwise it won't work. > > Despite what bspec says about automatically using ppgtt ... > > > > Luckily PIPE_CONTROL (the only write cmd current userspace uses) is > > not affected by all this, as tested by tests/gem_pipe_control_store_loop. > > Since this is all SNB only, and we have no good benchmarks to show > performance gains, can we not just enable this for IVB+? Don't we have the same basic problem with IVB, that we need to adjust the commands in the batchbuffer depending on whether HAS_ALIASING_PPGTT is true? Or do you mean that we should just assume that IVB uses the ppgtt and so kernel 3.3+, which will be around March... -Chris -- Chris Wilson, Intel Open Source Technology Centre
