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* [PATCH v3 0/1] platform/x86/intel/pmt: Notify userspace when crashlogs complete
@ 2026-11-12  2:08 David E. Box
  2026-11-12  2:08 ` [PATCH v3 1/1] " David E. Box
                   ` (4 more replies)
  0 siblings, 5 replies; 7+ messages in thread
From: David E. Box @ 2026-11-12  2:08 UTC (permalink / raw)
  To: ilpo.jarvinen, david.e.box, linux-kernel, platform-driver-x86,
	rodrigo.vivi, michael.j.ruhl, ayaz.siddiqui,
	syed.abdul.muqthyar.ahmed, intel-xe, hansg

This patch adds a uevent so userspace can find out when an Intel PMT
crashlog is available without polling.

It emits a KOBJ_CHANGE uevent on the crashlog<x> device carrying
INTEL_PMT_CRASHLOG_COMPLETE. The value is 1 when a completed crashlog is
found at probe, or when a manually triggered capture completes. The value
is 0 when a manual trigger does not complete within the 5 second poll
window. The ABI documentation is updated to match.

The main change in v3 is that the probe-time check no longer reads the
crashlog registers from probe. The register access callbacks added by
Michael's "platform/x86/intel/pmt: Add register access callbacks"
(7fdfccf87676) are there for the upcoming xe support for Crescent Island
(CRI). That support implements read_reg() and holds the lock it takes
across intel_vsec_register() when it registers late, after its firmware
is ready. With pmt_crashlog already loaded, crashlog probe runs
synchronously inside that call, and the v2 probe-time read deadlocked on
the lock its own caller held. Michael found this on CRI. In v3 the check
runs from a work item, which waits for registration to finish.

One rule follows from this and is noted in the code: a parent must not
hold its read_reg() lock while removing the crashlog device, because
remove waits for these work items. The CRI xe code only removes the
device under that lock if devm_add_action_or_reset() fails inside
intel_vsec_add_aux().

Testing: Michael tested v3 on CRI hardware. It was also tested in QEMU
on a kernel with CONFIG_PROVE_LOCKING, covering the cases listed for v2
plus disabling the crashlog during the trigger poll. A test parent
driver modelled the CRI late-bind path: read_reg() callbacks under a
mutex held across intel_vsec_register(), a slow registration that keeps
the lock held after the device appears, and a trigger that reaches
control_mutex before the probe-time check.

Tool use: an LLM coding assistant was used to analyze the deadlock,
draft the changes and the QEMU tests, and review the patch with
sashiko. I reviewed and tested the result.

V3 changes:
  - Run the probe-time check from a work item queued at the end of
    probe instead of from probe, so a read_reg() callback is never
    called from a synchronous probe that may run under the parent's
    lock (reported and tested by Michael on CRI).
  - Queue the probe-time check on the freezable workqueue, like the
    poll (sashiko).
  - Enable triggers once probe has created every entry, rather than per
    entry, so abort_probe never waits on a work item blocked on its
    caller's lock.
  - If a trigger is accepted before the probe-time check runs, the
    check skips its notification. The trigger's poll reports the
    capture, so it is not also reported as found at probe.
  - Disabling the crashlog while the trigger poll runs ends the poll
    without an event, like clear and rearm (sashiko).
  - ABI: note that events may be merged, list writing 0 to trigger and
    disabling as ending the poll, and update Date and KernelVersion.
  - Rebased onto review-ilpo-next. The patch also applies cleanly to
    for-next.

v2: https://lore.kernel.org/all/cover.1792721526.git.david.e.box@linux.intel.com/
v1: https://lore.kernel.org/all/20261001220351.1592138-1-david.e.box@linux.intel.com/

David E. Box (1):
  platform/x86/intel/pmt: Notify userspace when crashlogs complete

 .../ABI/testing/sysfs-class-intel_pmt         |  35 ++++
 drivers/platform/x86/intel/pmt/crashlog.c     | 180 +++++++++++++++++-
 2 files changed, 209 insertions(+), 6 deletions(-)


base-commit: 5680519168f65666d2c03cc6ed8fe2b7052aee12
-- 
2.53.0


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-- links below jump to the message on this page --
2026-11-12  2:08 [PATCH v3 0/1] platform/x86/intel/pmt: Notify userspace when crashlogs complete David E. Box
2026-11-12  2:08 ` [PATCH v3 1/1] " David E. Box
2026-11-12  2:19   ` sashiko-bot
2026-11-12  2:14 ` ✗ CI.checkpatch: warning for platform/x86/intel/pmt: Notify userspace when crashlogs complete (rev2) Patchwork
2026-11-12  2:17 ` ✓ CI.KUnit: success " Patchwork
2026-11-12  2:50 ` ✓ Xe.CI.BAT: " Patchwork
2026-11-12  9:09 ` ✗ Xe.CI.FULL: failure " Patchwork

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