[PATCH v2 0/4] PCI/AER: Handle Advisory Non-Fatal properly

Wang, Qingshun
2024-01-25T06:28:36Z

According to PCIe Base Specification Revision 6.1, Sections 6.2.3.4
and 6.2.4.3, certain uncorrectable errors will signal ERR_COR instead
of ERR_NONFATAL, logged as Advisory Non-Fatal Error, and set bits in
both Correctable Error Status register and Uncorrectable Error Status
register. Currently, when handling AER events the kernel will only look
at CE status or UE status, but never both. In the Advisory
Non-Fatal Error case, bits set in the UE status register will not be
reported and cleared until the next Fatal/Non-Fatal error arrives.

For instance, previously, when the kernel receives an ANFE with Poisoned
TLP in OS native AER mode, only the status of CE will be reported and
cleared:

AER: Corrected error received: 0000:b7:02.0
PCIe Bus Error: severity=Corrected, type=Transaction Layer, (Receiver ID)
device [8086:0db0] error status/mask=00002000/00000000
[13] NonFatalErr

If the kernel receives a Malformed TLP after that, two UE will be
reported, which is unexpected. The Malformed TLP Header was lost since
the previous ANFE gated the TLP header logs:

PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, (Receiver ID)
device [8086:0db0] error status/mask=00041000/00180020
[12] TLP (First)
[18] MalfTLP

To handle this case properly, add additional fields in aer_err_info to
track both CE and UE status/mask, UE severity, and Device Status.
Use this information to determine the status bits that need to be cleared.

Now, in the previous scenario, both CE status and related UE status will
be reported and cleared after ANFE:

AER: Corrected error received: 0000:b7:02.0
PCIe Bus Error: severity=Corrected, type=Transaction Layer, (Receiver ID)
device [8086:0db0] error status/mask=00002000/00000000
[13] NonFatalErr
Uncorrectable errors that may cause Advisory Non-Fatal:
[18] TLP

Additionally, add more data to aer_event tracepoint, which would help
to better understand ANFE and other errors for external observation.

Note:
checkpatch.pl will produce following errors and warnings on PATCH 4:

ERROR: space prohibited after that open parenthesis '('
#103: FILE: include/ras/ras_event.h:319:
+ __field( u16, link_status )

...similar errors omitted...

WARNING: quoted string split across lines
#126: FILE: include/ras/ras_event.h:342:
+ TP_printk("%s PCIe Bus Error: severity=%s, %s, TLP Header=%s, "
+ "Correctable Error Status=0x%08x, "

...similar warnings omitted...

For readability reasons, these errors and warnings are not fixed,
following the code style of existing examples in the kernel source tree.

Change log:
v2:
- Reference to the latest PCIe Specification in both commit messages
and comments, as suggested by Bjorn Helgaas.
- Describe the reason for storing additional information in
aer_err_info in the commit message of PATCH 1, as suggested by Bjorn
Helgaas.
- Add more details of behavior changes in the commit message of PATCH
2, as suggested by Bjorn Helgaas.

v1: https://lore.kernel.org/linux-pci/20240111073227.31488-1-qingshun.wang@linux.intel.com/

Wang, Qingshun (4):
PCI/AER: Store more information in aer_err_info
PCI/AER: Handle Advisory Non-Fatal properly
PCI/AER: Fetch information for FTrace
RAS: Trace more information in aer_event

drivers/acpi/apei/ghes.c | 16 ++-
drivers/cxl/core/pci.c | 15 ++-
drivers/pci/pci.h | 12 ++-
drivers/pci/pcie/aer.c | 191 +++++++++++++++++++++++++++-------
include/linux/aer.h | 6 +-
include/linux/pci.h | 27 +++++
include/ras/ras_event.h | 48 ++++++++-
include/uapi/linux/pci_regs.h | 1 +
8 files changed, 269 insertions(+), 47 deletions(-)

base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
--
2.42.0