[Intel-gfx] [PATCH 11/11] drm/i915: add HAS_ALIASING_PPGTT parameter for userspace

[Ben Widawsky]

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+?

> 
> Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>