On Fri, 2023-02-17 at 09:18 -0800, John Harrison wrote: > On 2/17/2023 00:39, Hogander, Jouni wrote: > > On Wed, 2023-02-15 at 17:10 -0800, John.C.Harrison@xxxxxxxxx wrote: > > > From: John Harrison <John.C.Harrison@xxxxxxxxx> > > > > > > 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@xxxxxxxxx> > Sweet! Out of interest, which platform was that? And how reproducible > was it? It would be interesting to know if an IGT was actually > regularly > showing the issue and we had just been ignoring it! It was Alderlake. It wasn't igt test. Opened several browser instances: https://webglsamples.org/aquarium/aquarium.html Took max. couple of minutes to reproduce. For some reason PSR2 DEEP_SLEEP entry/exit was some kind of trigger for this. Without PSR2 DEEP_SLEEP I couldn't reproduce the issue. BR, Jouni Högander > John. > > > > > > 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@xxxxxxxxx> > > > > > > > > > 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(-) > > > >
