When a Root Port or Root Complex Event Collector receives an error Message
e.g., ERR_COR, it sets PCI_ERR_ROOT_COR_RCV in the Root Error Status
register and logs the Requester ID in the Error Source Identification
register.  If it receives a second ERR_COR Message before software clears
PCI_ERR_ROOT_COR_RCV, hardware sets PCI_ERR_ROOT_MULTI_COR_RCV and the
Requester ID is lost.

In the following scenario, PCI_ERR_ROOT_MULTI_COR_RCV was never cleared:

  - hardware receives ERR_COR message
  - hardware sets PCI_ERR_ROOT_COR_RCV
  - aer_irq() entered
  - aer_irq(): status = pci_read_config_dword(PCI_ERR_ROOT_STATUS)
  - aer_irq(): now status == PCI_ERR_ROOT_COR_RCV
  - hardware receives second ERR_COR message
  - hardware sets PCI_ERR_ROOT_MULTI_COR_RCV
  - aer_irq(): pci_write_config_dword(PCI_ERR_ROOT_STATUS, status)
  - PCI_ERR_ROOT_COR_RCV is cleared; PCI_ERR_ROOT_MULTI_COR_RCV is set
  - aer_irq() entered again
  - aer_irq(): status = pci_read_config_dword(PCI_ERR_ROOT_STATUS)
  - aer_irq(): now status == PCI_ERR_ROOT_MULTI_COR_RCV
  - aer_irq() exits because PCI_ERR_ROOT_COR_RCV not set
  - PCI_ERR_ROOT_MULTI_COR_RCV is still set

The same problem occurred with ERR_NONFATAL/ERR_FATAL Messages and
PCI_ERR_ROOT_UNCOR_RCV and PCI_ERR_ROOT_MULTI_UNCOR_RCV.

Fix the problem by queueing an AER event and clearing the Root Error Status
bits when any of these bits are set:

  PCI_ERR_ROOT_COR_RCV
  PCI_ERR_ROOT_UNCOR_RCV
  PCI_ERR_ROOT_MULTI_COR_RCV
  PCI_ERR_ROOT_MULTI_UNCOR_RCV

See the bugzilla link for details from Eric about how to reproduce this
problem.

[bhelgaas: commit log, move repro details to bugzilla]
Fixes: e167bfca ("PCI: aerdrv: remove magical ROOT_ERR_STATUS_MASKS")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215992
Link: https://lore.kernel.org/r/20220418150237.1021519-1-sathyanarayanan.kuppuswamy@linux.intel.comReported-by: Eric Badger <ebadger@purestorage.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>