> That would definitely help, because if the issue does not happen on i915 > it likely means that we're missing a WA or something like that in Xe.
Two data points on that, pulling in different directions: * My second ARL machine (7dd1) has been running i915 for 7 days now, with the same GuC 70.53.0, and there is not a single TLB invalidation timeout or GuC error in its logs. Caveat: i915's TLB invalidation timeout is longer than xe's 2.25s, so short stalls could be silent there. * However, Matt just pointed at i915 MTL issue 14469, which looks like the same problem on i915 - so it may not be xe-specific after all. If it helps I can also boot i915 on the primary machine (7d51), where I can compare against days of xe statistics on identical workloads. > Just a bit of a terminology update here, to make sure we're on the same > page: we usually refer to the notification you're sending to the GuC as > an H2G interrupt and not a doorbell. Thanks for the correction - I will use H2G interrupt from here on and fix the terminology in v2. > It feels like when the > issue occurs something is stuck in HW rather than GuC FW and triggering > the interrupt causes the HW to get unstuck. That fits a pattern I can now see clearly with more data. Since enabling the bigger GuC logs (~1.5 days, 35 stalls): 12 stalls were unstuck by one of the H2G interrupts within 0.3-1.5s, but 23 ignored 8-9 consecutive interrupts and ran to the end. And in those severe cases the request-to-ack time is nearly constant: 2.28-2.34s, every single time. It does not look like congestion - it looks like a fixed internal timeout expiring somewhere and releasing things. Related: an A/B experiment I ran earlier (holding forcewake across the whole GT, C6 residency pinned at 0ms for the whole window) still hit 9 timeouts in a row, so GT-level RC6 avoidance alone does not prevent it. > Also, would you be able to capture the GuC logs when the issue occurs? Done. I rebuilt with the debug-sized log buffers (8M event data / 1M crash dump / 1M state capture) and xe.guc_log_level=3, and the series' patch 1 (devcoredump on TLB invalidation timeout) captures the GuC log at the exact moment the timeout fires. I attached three devcoredumps (4-8.7MB each, containing the full GuC log around severe stalls that ignored 8-9 H2G interrupts) to the gitlab issue: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8678 I have more captures if useful (9 so far). > I have pushed the latest GuC FW for MTL here in case you want to give it > a go: Downloaded and staged - I will switch to 70.72.1 via xe.guc_firmware_path today and report back with a few days of data (this machine currently reproduces 20-35 stalls/day under my normal workload, so the signal should be quick). Thanks, Tales Em ter., 4 de ago. de 2026 às 20:50, Daniele Ceraolo Spurio <[email protected]> escreveu: > > > > On 8/4/2026 4:00 PM, Tales A. Mendonça wrote: > >> Are we seeing this on i915? > > I have not tested i915 on the affected machines yet - the > > instrumentation that measured the stalls (late-ack logging, kick > > results) is xe-only, so I have no comparable i915 data. I can boot one > > of the ARL machines with i915 for a few days and watch for TLB > > invalidation timeouts there, if that data helps. > > That would definitely help, because if the issue does not happen on i915 > it likely means that we're missing a WA or something like that in Xe. > > > > > More generally: both machines here reproduce reliably (~1 stall/hour > > on a desktop workload, much more under memory pressure), so I am happy > > to test anything on them - including any GuC build the firmware team > > would like data on. > > > > On Stuart's masking concern: fully agreed, that is why patch 3 is > > marked RFC. Patches 1-2 are pure diagnostics and stand on their own; I > > am fine holding patch 3 until the firmware side has been looked at. > > The data point it adds is that a doorbell ring unblocks the ack in the > > majority of episodes, while the severe ones ignore 8-9 consecutive > > rings - hopefully that narrows where to look inside the GuC. > > Just a bit of a terminology update here, to make sure we're on the same > page: we usually refer to the notification you're sending to the GuC as > an H2G interrupt and not a doorbell. I'm making this clarification > because the GuC supports a separate per-context notification mechanism > that is referred to as doorbell and which we currently do not implement > in neither i915 nor Xe. > > When receiving the H2G interrupt, the only thing that the GuC does is > look into the CTB and process anything in there; however, you've said > that the contents of the H2G CTB are processed immediately, so the > follow up interrupt should result in the GuC just bailing out and doing > nothing because there is no data to process. It feels like when the > issue occurs something is stuck in HW rather than GuC FW and triggering > the interrupt causes the HW to get unstuck. > > I have pushed the latest GuC FW for MTL here in case you want to give it > a go: > https://gitlab.com/dceraolo/drm-firmware/-/blob/f783b931555be057dafc2400b7eb4d445c953fec/i915/mtl_guc_70.72.1.bin > . You can override the GuC firmware used by the driver via the > xe.guc_firmware_path modparam; the path is relative to /lib/firmware/ > and the firmware needs to be in initramfs for the driver to find it at > boot. Note that we haven't tested this image on MTL, so it might have > unexpected results. > > Also, would you be able to capture the GuC logs when the issue occurs? > The default guc log size is relatively small, so you'd have to capture > right when the issue happens. However, you can make them bigger by > building the kernel with CONFIG_DRM_XE_DEBUG or by simply modifying the > xe_guc_log.h file to pick the bigger size by default. If you go with the > latter, please also set xe.guc_log_level=3 on the command line (this is > automatically added by the kconfig). > > Thanks, > Daniele > > > > > I will send a v2 addressing Matt's review comments (the > > __xe_devcoredump unification and the fixes on patch 2). > > > > Thanks, > > Tales > > > > Em ter., 4 de ago. de 2026 às 19:08, Daniele Ceraolo Spurio > > <[email protected]> escreveu: > >> > >> > >> On 8/4/2026 2:33 PM, Summers, Stuart wrote: > >>> On Tue, 2026-08-04 at 14:27 -0700, Matthew Brost wrote: > >>>> On Tue, Aug 04, 2026 at 03:02:44PM -0600, Summers, Stuart wrote: > >>>>> On Mon, 2026-08-03 at 23:14 -0300, Tales A. Mendonça wrote: > >>>>>> 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. > >>>>> Firstly, thanks for the patch! > >>>>> > >>>>> I haven't looked in to all the details of the sighting you were > >>>>> debugging, but we have had similar issues that were fixed in a > >>>>> later > >>>>> GuC version. I think around 70.60.0? It might be worth trying on > >>>>> something later than that to see if that helps... (+Daniele) > >>>>> > >>>> I think this would require an AR on our end to make a new firmware > >>>> version available. > >>>> > >>>> The upstream repo only has 70.53.0 available for ARL [1] (iirc, ARL > >>>> aliases to MTL for firmware). (+Julia too). > >>>> > >>>> Presumably, the GuC changelogs should indicate whether an issue > >>>> related > >>>> this has been fixed. If so, we need to update all GuC versions across > >>>> both i915 and Xe. > >>> Right... I guess I'd still like to see if we can test this in GuC (or > >>> get confirmation we can't for some reason) before committing something. > >>> My worry is we will prevent bug reports like this by working around it > >>> and miss critical bugs that need to be fixed in the right component. > >>> > >>>> [1] > >>>> https://gitlab.com/kernel-firmware/linux-firmware/-/blob/main/i915/mtl_guc_70.bin?ref_type=heads > >>>> > >>>>>> Patch 1 adds xe_devcoredump_gt() so this kind of hang - which has > >>>>>> no > >>>>> Is there a reason we don't just re-use the main xe_devcoredump()? > >>>>> > >>>> This is my suggestion: the main devcoredump infrastructure is job- > >>>> based, > >>>> so it cannot be used for hangs that are not associated with a job. > >>>> > >>>> In my opinion, this is a gap on our end. Introducing something like > >>>> `xe_devcoredump_gt()`, which can be used for non-job-based hangs > >>>> (e.g., > >>>> TLB invalidation timeouts like those addressed in this series, or > >>>> more > >>>> generally any GuC protocol hang), makes sense to me. > >>> Ok makes sense. We can do that here. It would be nice to have a more > >>> inclusive implementation that lets us call this from anywhere so we > >>> aren't duplicating things around for different use cases. But not a > >>> blocker here. > >>> > >>>> I haven't looked at the patch yet, but at a high level, adding > >>>> `xe_devcoredump_gt()` seems like a reasonable approach. > >>>> > >>>>>> 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 > >>>>> I'm a little worried we're just papering over something here that > >>>>> needs > >>>>> to be addressed in GuC, particularly around GT going to sleep or > >>>>> something around the time we're expecting a response, so the pings > >>>>> on > >>>>> registers might be prematurely waking things up which is something > >>>>> we'd > >>>>> want to happen in GuC, not the KMD. > >>>>> > >>>> In general, I agree with this. We should avoid papering over the > >>>> issue > >>>> and instead fix it properly in the GuC. That said, this workaround > >>>> provides a pretty strong data point, since it appears to get the TLB > >>>> invalidation unstuck. > >>> So if we hit this issue I guess we're already going to have some > >>> performance degredation and the workaround makes that better. I need to > >>> look at the implementation, but we could be potentially introducing > >>> performance penalties in other areas doing these pings. > >>> > >>> Again, I'd like to see if we can fix this in the right place before > >>> implementing a workaround for it. Hopefully Daniele or Julia can give > >>> some direction there. > >> Are we seeing this on i915 at all? Given that Xe does not officially > >> support MTL/ARL and is missing several critical WAs for those platforms, > >> the approach so far has been to only update the GuC FW if it is required > >> for i915. > >> Looking at the GuC release notes, there have been a couple of > >> TLB-related fixes after 70.53, but they're both marked as only affecting > >> PVC and Xe2+ platforms, so no fixes seem to be available for ARL (or at > >> least they're not listed in the release notes). > >> > >> Daniele > >> > >>> Thanks, > >>> Stuart > >>> > >>>> Matt > >>>> > >>>>> Thanks, > >>>>> Stuart > >>>>> > >>>>>> 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(-) > >>>>>> > > > -- Com os cumprimentos, Tales A. Mendonça talesam.org communitybig.org
