Re: [Intel-gfx] [PATCH v3 0/2] Don't use stolen memory or BAR mappings for ring buffers

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Wed, 2023-02-15 at 17:10 -0800, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> Instruction from hardware arch is that stolen memory and BAR mappings
> are unsafe for use as ring buffers. There can be issues with cache
> aliasing due to the CPU access going to memory via the BAR. So, don't
> do it.

Tested these patches for GPU Hang I was debugging. Seem to fix that one
as well:

Tested-by: Jouni Högander <jouni.hogander@intel.com>

> 
> v2: Dont use BAR mappings either.
> Make conditional on LLC so as not to change platforms that don't need
> to change (Daniele).
> Add 'Fixes' tags (Tvrtko).
> v3: Fix dumb typo.
> 
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> 
> 
> John Harrison (2):
>   drm/i915: Don't use stolen memory for ring buffers with LLC
>   drm/i915: Don't use BAR mappings for ring buffers with LLC
> 
>  drivers/gpu/drm/i915/gt/intel_ring.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>