[Intel-gfx] [PATCH] drm/i915: Re-enable aliasing PPGTT mode.

[Chris Wilson]

On Mon, Feb 06, 2017 at 03:04:55PM +0800, Zhi Wang wrote:
> Aliasing PPGTT mode is broken due to recent changes. Mostly boot the
> system with i915.enable_ppgtt=1 will lead a kernel crash.
> 
> This patch fixes this problem by:
> 
> - PPGTT page table will not be shrinkable if working under aliasing
> PPGTT mode.

Not that keen on adding yet another special case into the code. In the
patches I sent, the idea was to keep the PD structure from the
aliasing_ppgtt preallocation by keeping the used_pte count positive (and
so keeping the entire tree marked as in-use).
 
> - Load the root pointers of the PPGTT page table during the context
> initialization, as currently the "LRI PDPs updating" magic only works
> under full PPGTT mode and also GVT-g doesn't support LRI PDP updating.

That is incorrect, they are loaded into the context image before
submission. If you want to make sure they are unchanging so that
lite-restore under g-GVT works, that is another matter.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre