On 3/15/2023 00:51, Greg KH wrote:
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.... (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 :)
I'm still working through the backlog of them.
Note that these patches must all be applied as a pair. The 'don't use stolen' can be applied in isolation but won't totally fix the problem. However, applying 'don't use BAR mappings' without applying the stolen patch first will results in problems such as the failure to boot that was recently reported and resulted in a revert in one of the trees.
John.
thanks,
greg k-h