PCI/AER: Support Advisory Non-Fatal Errors

Per PCIe r7.0 sec 6.2.4.3, certain Non-Fatal Errors may be signaled using
ERR_COR instead of ERR_NONFATAL.  These "Advisory Non-Fatal Errors" are
listed in sec 6.2.7 and explained in detail in sec 6.2.3.2.4.

Advisory Non-Fatal Errors set bits in the Uncorrectable Error Status
Register as well as one bit in the Correctable Error Status Register
(Advisory Non-Fatal Error Status, bit 13).  The latter is masked by
default, hence these errors are currently not signaled at all (except on
non-compliant products which choose to unmask the bit).

Unmask Advisory Non-Fatal Errors on device enumeration.

Some Non-Fatal Errors are always Advisory, others may be Advisory at the
discretion of the detecting agent.  If multiple errors occur, the agent
may qualify a portion as non-Advisory and signal ERR_NONFATAL in addition
to ERR_COR.  In this case, there's no way to determine which Non-Fatal
Error was Advisory.  Assume none is to ensure that the Uncorrectable Error
code path is taken to recover from the errors.

Introduce aer_compute_anfe_status() to compute Advisory Non-Fatal Error
bits from AER registers, based on this policy.  Use it for Firmware First
error handling in pci_print_aer(), which receives an AER register dump
from the platform (UEFI r2.11 sec N.2.7).

Introduce aer_get_anfe_status() to read AER registers from a device and
feed them to aer_compute_anfe_status().  Use it for native error handling
in aer_get_device_error_info(), which gathers registers from the device
and caches the computed Advisory Non-Fatal Error bits in a new anfe_status
field in struct aer_err_info.

Regardless whether error handling is native or Firmware First, the AER
driver needs to increment error counters, signal a trace event and log
each error.  When Advisory Non-Fatal Errors occur, these steps must be
performed for Correctable Errors and for Uncorrectable Errors.  Achieve
this through a recursive invocation of aer_print_error() (for native error
handling) and pci_print_aer() (for Firmware First error handling).  The
recursive invocation reports the (Advisory) Uncorrectable Errors after
reporting the Correctable Errors.

Note that the First Error Pointer and TLP Prefix Log is only meaningful
for Uncorrectable Errors, but when Advisory Non-Fatal Errors occur,
aer_get_device_error_info() has to populate the first_error and
tlp_header_valid fields in struct aer_err_info for a Correctable Error.
Avoid incorrectly logging those fields for Correctable Errors by amending
__aer_print_error() and aer_print_error() with conditionals.

Sample log output for an Advisory Unsupported Request Error:

  pcieport 0001:00:00.4: AER: Multiple Correctable Error messages received, first one from 0001:0e:00.0
  idxd 0001:0e:00.0: PCIe Bus Error: severity=Correctable
  idxd 0001:0e:00.0:   device [8086:1216] error status/mask=00002000/00000000
  idxd 0001:0e:00.0:   [13] NonFatalErr       |             |
  idxd 0001:0e:00.0: PCIe Bus Error: severity=Uncorrectable (Non-Fatal)
  idxd 0001:0e:00.0:   device [8086:1216] error status/mask=00100000/00000000
  idxd 0001:0e:00.0:   [20] UnsupReq          | Receiver    | Transaction Layer (First)
  idxd 0001:0e:00.0: AER:   TLP Header (Flit): 0x01000104 0x00000000 0x0000080e 0x0f800001

This commit takes inspiration (but differs significantly) from an earlier
submission by Zhenzhong Duan, which in turn was based on a submission by
Qingshun Wang:

  https://lore.kernel.org/r/20240620025857.206647-1-zhenzhong.duan@intel.com/

Prior attempts at supporting Advisory Non-Fatal Errors were submitted by
Yicong Yang and Dio Sun:

  https://lore.kernel.org/r/1614689994-10925-1-git-send-email-yangyicong@hisilicon.com/
  https://lore.kernel.org/r/BJXPR01MB0614C01A9523786117B1F1CBCEC8A@BJXPR01MB0614.CHNPR01.prod.partner.outlook.cn/

Signed-off-by: Lukas Wunner <lukas@wunner.de>
[bhelgaas: fold in https://lore.kernel.org/all/amdnMg_J6T3Sys45@wunner.de,
https://lore.kernel.org/all/120da0565eac0157ffd913423c7cfa66e985ff59.1786800931.git.lukas@wunner.de]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20240620025857.206647-1-zhenzhong.duan@intel.com/
Link: https://lore.kernel.org/r/1614689994-10925-1-git-send-email-yangyicong@hisilicon.com/
Link: https://lore.kernel.org/r/BJXPR01MB0614C01A9523786117B1F1CBCEC8A@BJXPR01MB0614.CHNPR01.prod.partner.outlook.cn/
Link: https://patch.msgid.link/1b62915ffe06ee5b08e846531c42392e5f244337.1784905909.git.lukas@wunner.de

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