On 3/15/2023 00:51, Greg KH wrote:
On Mon, Mar 13, 2023 at 07:22:11PM -0700, John.C.Harrison@xxxxxxxxx wrote:
From: John Harrison <John.C.Harrison@xxxxxxxxx>
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@xxxxxxxxx>
Fixes: 9d80841ea4c9 ("drm/i915: Allow ringbuffers to be bound anywhere")
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v4.9+
Tested-by: Jouni Högander <jouni.hogander@xxxxxxxxx>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20230216011101.1909009-3-John.C.Harrison@xxxxxxxxx
(cherry picked from commit 65c08339db1ada87afd6cfe7db8e60bb4851d919)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
(cherry picked from commit 85636167e3206c3fbd52254fc432991cc4e90194)
Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
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
