> I'd scope this to mirror the i915 W/A. > > I don't know enough about the W/A offhand so say, but again I'd just do > whatever we did on the i915 in Xe.
Done - v2 is out with the Wa_22016122933 implementation mirroring i915: scoped via an OOB rule to the media GT on media version 13.00, with coverage modeled on intel_guc_allocate_vma() (CTBs, GuC log, ADS and SLPC shared data): https://lore.kernel.org/intel-xe/[email protected]/ Validated on both ARL machines here for several days - details in the cover letter. Thanks, Tales Em ter., 11 de ago. de 2026 às 21:52, Matthew Brost <[email protected]> escreveu: > > On Sat, Aug 08, 2026 at 06:04:25PM -0300, Tales A. Mendonça wrote: > > Results: the GT1 cache-line theory is confirmed. > > > > With XE_BO_FLAG_NEEDS_UC added to both CTB allocations (blunt version, > > all GTs), firmware back to stock 70.53.0, same kernel otherwise: > > > > ~6h of my normal workload (sustained load 4-6), ~480k TLB > > invalidations per GT processed (per gt stats), ZERO stall events, > > ZERO fence timeouts. > > Awesome. > > > > > For comparison, yesterday on the same workload (cached CTBs): 14 stalls > > in the first ~1h45 of use, 59 stalls / 20 timeouts over the day. Every > > previous kernel reproduced within the first hour, every day, for weeks. > > > > So the GuC was replying in time all along - the CPU was reading a stale > > cache line of the G2H CTB, and the near-constant 2.3s "stall" was just > > how long the line took to get evicted naturally. That explains the > > whole signature: H2G direction fine, G2H CTB "empty" at timeout, H2G > > interrupt kicks unsticking only some episodes, firmware version > > irrelevant. > > > > I am happy to send a proper Wa_22016122933 implementation for xe. Two > > questions on the preferred shape before I do: > > > > 1. Scoping: mirror i915 (media GT only on the affected platforms), or > > is there a reason to cover both GTs on MTL/ARL? My blunt test cannot > > distinguish - Daniele's decode showed failures only on GT1, but I > > applied UC everywhere. > > > > I'd scope this to mirror the i915 W/A. > > > 2. Coverage: is the CTB buffer enough, or should the descriptor and/or > > the GuC log buffer get the same treatment (wherever the CPU polls > > GuC-written memory)? > > I don't know enough about the W/A offhand so say, but again I'd just do > whatever we did on the i915 in Xe. > > Matt > > > > > I will keep running the UC kernel and report the full-day numbers, but > > after weeks of daily reproduction, six hours at zero with ~960k > > invalidations processed is already a very strong signal. > > > > Thanks, > > Tales > > > > Em qui., 6 de ago. de 2026 às 18:13, Daniele Ceraolo Spurio > > <[email protected]> escreveu: > > > > > > > > > > > > On 8/6/2026 10:36 AM, Tales A. Mendonça wrote: > > > >> 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). > > > > > > Do you happen to have the matching dmesg for those? I decoded the logs > > > but there are thousands of invalidation calls in them; I looked at the > > > last few but from the GuC POV they've all been handled quickly. Dmesg > > > error should log exactly which invalidations were delayed from the > > > driver POV so I can just look at what happens around those. > > > Also, I have noticed that the failures seems to all be on GT1. On MTL, > > > there is a caching bug on GT1 and we do not implement the WA for that in > > > Xe (Wa_22016122933). Not sure if this is the actual root cause, but the > > > fact that it only happens on GT1 makes me suspicious (i.e., it is > > > possible that the GuC is replying in time but CPU doesn't see the reply > > > because the cache-line is not correctly updated, or vice versa). Not > > > sure if there is an easy way to implement this in Xe to test, that's not > > > really my field of expertise; maybe adding XE_BO_FLAG_FORCE_WC or > > > XE_BO_FLAG_NEEDS_UC to the CTB allocation could work as a quick hack? > > > But I'd like either Matt or Thomas to confirm. > > > > > > Daniele > > > > > > > > > > >> 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 -- Com os cumprimentos, Tales A. Mendonça talesam.org communitybig.org
