[PATCH v5 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
==========

Inconsistent PCIe error handling, exacerbated at datacenter scale (myriad
of devices), affects repairabilitiy flows for fleet operators.

Exposing PCIe errors/debug info in-band for a userspace daemon (e.g.
rasdaemon) to collect/pass on to repairability services will allow for
more predictable repair flows and decrease machine downtime.

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
==================
1-5 AER logging cleanup
6-8 Ratelimits and sysfs knobs

Outstanding work
================
Cleanup:
- Consolidate aer_print_error() and pci_print_error() path[6]

Roadmap:
- IRQ ratelimiting

v5:
- Handle multi-error AER by evaluating ratelimits once and storing result
- Reword/rename commit messages/functions/variable
v4:
- Fix bug where trace not emitted with malformed aer_err_info
- Extend ratelimit to malformed aer_err_info
- Update commit messages with patch motivation
- Squash AER sysfs filename change (Patch 8)
v3:
- Ratelimit aer_print_port_info() (drop Patch 1)
- Add ratelimit enable toggle
- Move trace outside of ratelimit
- Split log level (Patch 2) into two
- More descriptive documentation/sysfs naming
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[7] 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/8bcb8c9a7b38ce3bdaca5a64fe76f08b0b337511.1742202797.git.karolina.stolarek@oracle.com/
[7] https://lore.kernel.org/linux-pci/edd77011aafad4c0654358a26b4e538d0c5a321d.1736341506.git.karolina.stolarek@oracle.com/

Jon Pan-Doh (6):
  PCI/AER: Move AER stat collection out of __aer_print_error()
  PCI/AER: Rename aer_print_port_info() to aer_printrp_info()
  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 sysfs attributes for log ratelimits

Karolina Stolarek (2):
  PCI/AER: Check log level once and propagate down
  PCI/AER: Make all pci_print_aer() log levels depend on error type

 ...es-aer_stats => sysfs-bus-pci-devices-aer} |  34 +++
 Documentation/PCI/pcieaer-howto.rst           |  16 +-
 drivers/pci/pci-sysfs.c                       |   1 +
 drivers/pci/pci.h                             |   6 +-
 drivers/pci/pcie/aer.c                        | 282 +++++++++++++-----
 drivers/pci/pcie/dpc.c                        |   3 +-
 include/linux/pci.h                           |   2 +-
 7 files changed, 270 insertions(+), 74 deletions(-)
 rename Documentation/ABI/testing/{sysfs-bus-pci-devices-aer_stats => sysfs-bus-pci-devices-aer} (77%)

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2.49.0.395.g12beb8f557-goog