Re: [RFC PATCH 0/3] drm/xe: diagnostics and workaround for GuC TLB invalidation ack stalls on ARL

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Aug 04, 2026 at 02:29:27PM -0700, Matthew Brost wrote:
> On Tue, Aug 04, 2026 at 01:34:19PM -0300, Tales A. Mendonça wrote:
> > Patchwork reports my address is not on the CI allowlist, so CI was not
> > triggered for this series:
> > 
> >     Series author address 'talesam@gmail.com' is not on the allowlist,
> > which prevents CI from being automatically triggered.
> > 
> >   Could one of the project owners click 'retest' on the series (and/or
> > add me to the allowlist)? Series URL:
> > 
> >     https://patchwork.freedesktop.org/series/171539/
> > 
> 
> We'd have to resend this ourselves. I can do this, but I've requested
> for you to be on our allow list as well. I'll ping here once that goes
> through.
> 

You are approved on our CI for future patches.

Also I came across this issue in the i915 for MTL [1] which seems to
indicate the same issue (ARL and MTL are very close and share same GuC
firmware), the suggestion there is turn off rc6. Unfortunately Xe
doesn't have a knob to do this but according to [1] you can turn off rc6
in the BIOS. Might be worth a try.

Matt

[1] https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/14469

> Matt 
> 
> >   Thanks!
> >   Tales
> > 
> > 
> > Em seg., 3 de ago. de 2026 às 23:14, Tales A. Mendonça
> > <talesam@gmail.com> escreveu:
> > >
> > > Hi,
> > >
> > > This series is a follow-up to the TLB invalidation ack stall I have
> > > been debugging on ARL, tracked in:
> > >
> > >   https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8678
> > >
> > > Summary of the issue: with GuC 70.53.0 on ARL (reproduced on 7d51 and
> > > 7dd1 machines here, plus an independent Arc Pro 130T report on the
> > > issue above), TLB invalidation acks intermittently stall for ~2.3s.
> > > The H2G request is consumed from the CTB immediately and the G2H CTB
> > > is empty the whole time - the firmware simply does not send the ack
> > > until much later. The fence timeout fires at 2.25s and the ack lands
> > > tens of ms after it. Userspace blocked on the invalidation (compositor
> > > buffer unmaps etc.) hitches for the full window.
> > >
> > > Patch 1 adds xe_devcoredump_gt() so this kind of hang - which has no
> > > exec queue or job to blame - leaves a devcoredump with the GuC log and
> > > CT state behind (Matt suggested capturing devcoredumps when we
> > > discussed the issue; devcoredumps from both machines are attached to
> > > the issue above).
> > >
> > > Patch 2 logs when the ack for a timed out invalidation finally
> > > arrives. This is what established that the acks are late rather than
> > > lost.
> > >
> > > Patch 3 is the RFC part: a delayed work that pokes the GuC (status
> > > register read, CT flush, doorbell ring) every 250ms while an ack is
> > > overdue. On my machines this converts the guaranteed 2.3s stall into a
> > > sub-500ms hiccup for the majority of occurrences; a minority of severe
> > > episodes ignore 8-9 consecutive doorbells, which points at the GuC
> > > firmware being internally blocked for the whole window. Full data on
> > > the issue. I am happy to rework the approach (different delay,
> > > tying it to the G2H handler, dropping the status read, etc.) - mainly
> > > I would like the firmware side investigated, since no host-side poke
> > > can fix the severe cases.
> > >
> > > Based on drm-tip. Tested for several days on both ARL machines under
> > > desktop and VM-heavy workloads.
> > >
> > > Thanks,
> > > Tales
> > >
> > > Tales A. Mendonça (3):
> > >   drm/xe: Capture devcoredump on TLB invalidation timeout
> > >   drm/xe: Log when a timed out TLB invalidation ack finally arrives
> > >   drm/xe: Kick GuC while TLB invalidation acks are overdue
> > >
> > >  drivers/gpu/drm/xe/xe_devcoredump.c     |  68 ++++++++++++
> > >  drivers/gpu/drm/xe/xe_devcoredump.h     |   6 ++
> > >  drivers/gpu/drm/xe/xe_tlb_inval.c       | 131 +++++++++++++++++++++++-
> > >  drivers/gpu/drm/xe/xe_tlb_inval_types.h |  42 ++++++++
> > >  4 files changed, 243 insertions(+), 4 deletions(-)
> > >
> > > --
> > > 2.55.0
> > >
> > 
> > 
> > -- 
> > Com os cumprimentos,
> > 
> > Tales A. Mendonça
> > talesam.org
> > communitybig.org