[PATCH v2 0/2] PCI/CXL: Guard MMIO accesses during reset recovery

[Richard Cheng <icheng@nvidia.com>]

PCI reset recovery may proceed with state restoration and driver
reset_done() callbacks even when a device has not recovered.
Accessing device MMIO in that state can cause additional errors, including
DPC containment.

This series adds checks before two MMIO access paths: MSI-X table
resoration and CXL HDM decoder checking.

Patch 1 checks the existing PCI Command register read in
__pci_restore_msix_state(). If the read fails or returns all ones,
warn and return before accessing the MSI-X table.

Patch 2 guards CXL decoder accesses after reset.
The CXL reset_done() callback independently accesses HDM decoder
MMIO to check whether decoder state was lost during reset.

Changes since v1 [1]:
- Dropped v1 patch 1, since commit e8df1d194c39
  ("PCI: Don't treat ~0 as ready in pci_dev_wait() with RRS SV")
  already addresses the issue.
- Dropped v1 patch 2, following Benjamin Cheatham's review.
  That some devices rely on the existing fallback behavior.
- Reworked v1 patch 3 into v2 patch 1. Instead of skipping all PCI
  state restoration, check config accessibility before MSI-X restoration.
  This reduces the impact on other restoration paths.
- Retained v1 patch 4 as v2 patch 2.


Richard Cheng (2):
  PCI/MSI: Skip MSI-X restoration when configuration is inaccessible
  cxl/pci: Guard decoder accesses after reset

 drivers/cxl/pci.c     | 6 ++++++
 drivers/pci/msi/msi.c | 6 +++++-
 2 files changed, 11 insertions(+), 1 deletion(-)


base-commit: f66469d9905b39d2c260a15d7d6db450f4db67c1
-- 
2.43.0