| Message ID | 20230216011101.1909009-1-John.C.Harrison@Intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Don't use stolen memory or BAR mappings for ring buffers | expand |
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(-) >
On 2/17/2023 00:39, Hogander, Jouni wrote: > 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> 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! 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@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(-) >>
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@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> > 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@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(-) > > > >
On 16/02/2023 01:10, 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. > > 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(-) It is doing what it laid out as the problem statement so series looks good to me. Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Regards, Tvrtko