Re: [PATCH 5.4.y] drm/i915: Don't use BAR mappings for ring buffers with LLC

[Greg KH <greg@kroah.com>]

On Mon, Mar 13, 2023 at 07:22:11PM -0700, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> Direction from hardware is that ring buffers should never be mapped
> via the BAR on systems with LLC. There are too many caching pitfalls
> due to the way BAR accesses are routed. So it is safest to just not
> use it.
> 
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> Fixes: 9d80841ea4c9 ("drm/i915: Allow ringbuffers to be bound anywhere")
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v4.9+
> Tested-by: Jouni Högander <jouni.hogander@intel.com>
> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Link: https://patchwork.freedesktop.org/patch/msgid/20230216011101.1909009-3-John.C.Harrison@Intel.com
> (cherry picked from commit 65c08339db1ada87afd6cfe7db8e60bb4851d919)
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> (cherry picked from commit 85636167e3206c3fbd52254fc432991cc4e90194)
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Also queued up for 5.10.y, you forgot that one :)

thanks,

greg k-h