[Intel-gfx] [PATCH] drm/i915: Enforce read order into the hardware status page csb

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Quoting Mika Kuoppala (2018-04-12 14:52:37)
>> Read ordering on cpu can be out of order and speculative.
>
> If it didn't include a barrier to prevent compiler mispeculation. rmb()
> only applies to other CPU cores and not the GPU so this is entirely
> hocus.

How I understand the Documentation/memory-barrier.txt/THE THINGS CPUS
GET UP TO, the compiler memory barrier is not enough.

> -Chris