[PATCH v2 0/8] Rate limit AER logs

[Jon Pan-Doh <pandoh@google.com>]

Proposal
========

When using native AER, spammy devices can flood kernel logs with AER errors
and slow/stall execution. Add per-device per-error-severity ratelimits
for more robust error logging. Allow userspace to configure ratelimits
via sysfs knobs.

Motivation
==========

Several OCP members have issues with inconsistent PCIe error handling,
exacerbated at datacenter scale (myriad of devices).
OCP HW/Fault Management subproject set out to solve this by
standardizing industry:

- PCIe error handling best practices
- Fault Management/RAS (incl. PCIe errors)

Exposing PCIe errors/debug info in-band for a userspace daemon (e.g.
rasdaemon) to collect/pass on to repairability services is part of the
roadmap.

Background
==========

AER error spam has been observed many times, both publicly (e.g. [1], [2],
[3]) and privately. While it usually occurs with correctable errors, it can
happen with uncorrectable errors (e.g. during new HW bringup). 

There have been previous attempts to add ratelimits to AER logs ([4],
[5]). The most recent attempt[5] has many similarities with the proposed
approach.

Patch organization
==================
1-4 AER logging cleanup
5-8 Ratelimits and sysfs knobs

Outstanding work
================
Cleanup:
- Consolidate aer_print_error() and pci_print_error() path

Roadmap:
- IRQ ratelimiting

v2:
- Rebased on top of pci/aer (6.14.rc-1)
- Split series into log and IRQ ratelimits (defer patch 5)
- Dropped patch 8 (Move AER sysfs)
- Added log level cleanup patch[6] from Karolina's series
- Fixed bug where dpc errors didn't increment counters
- "X callbacks suppressed" message on ratelimit release -> immediately
- Separate documentation into own patch

[1] https://bugzilla.kernel.org/show_bug.cgi?id=215027
[2] https://bugzilla.kernel.org/show_bug.cgi?id=201517
[3] https://bugzilla.kernel.org/show_bug.cgi?id=196183
[4] https://lore.kernel.org/linux-pci/20230606035442.2886343-2-grundler@chromium.org/
[5] https://lore.kernel.org/linux-pci/cover.1736341506.git.karolina.stolarek@oracle.com/
[6] https://lore.kernel.org/linux-pci/edd77011aafad4c0654358a26b4e538d0c5a321d.1736341506.git.karolina.stolarek@oracle.com/

Jon Pan-Doh (7):
  PCI/AER: Remove aer_print_port_info
  PCI/AER: Move AER stat collection out of __aer_print_error
  PCI/AER: Rename struct aer_stats to aer_report
  PCI/AER: Introduce ratelimit for error logs
  PCI/AER: Add ratelimits to PCI AER Documentation
  PCI/AER: Add AER sysfs attributes for log ratelimits
  PCI/AER: Update AER sysfs ABI filename

Karolina Stolarek (1):
  PCI/AER: Use the same log level for all messages

 ...es-aer_stats => sysfs-bus-pci-devices-aer} |  20 ++
 Documentation/PCI/pcieaer-howto.rst           |  13 +-
 drivers/pci/pci-sysfs.c                       |   1 +
 drivers/pci/pci.h                             |   4 +-
 drivers/pci/pcie/aer.c                        | 194 ++++++++++++------
 drivers/pci/pcie/dpc.c                        |   3 +-
 include/linux/pci.h                           |   2 +-
 7 files changed, 169 insertions(+), 68 deletions(-)
 rename Documentation/ABI/testing/{sysfs-bus-pci-devices-aer_stats => sysfs-bus-pci-devices-aer} (85%)

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