[PATCH v7 0/3] PCI: AtomicOps: Fix pci_enable_atomic_ops_to_root()

[Gerd Bayer]

Hi Bjorn et al.

On s390, AtomicOp Requests are enabled on a PCI function that supports
them, despite the helper being ignorant about the root port's capability
to supporting their completion.

Patch 1: Do not enable AtomicOps Requests on RCiEPs
Patch 2: Fix the logic in pci_enable_atomic_ops_to_root()
Patch 3: Update references to PCIe spec in that function.

I did test that the issue is fixed with these patches. Also, I verified
that on a Mellanox/Nvidia ConnectX-6 adapter plugged straight into the
root port of a x86 system still gets AtomicOp Requests enabled.

Due to a lack of the required hardware, I did not test this with any PCIe
switches between root port and endpoint. So test exposure in other
environments is highly appreciated.

Signed-off-by: Gerd Bayer <gbayer@xxxxxxxxxxxxx>
---
Changes in v7:
- Prepend series with a patch to explicitly exclude RCiEPs from
  enablement of AtomicOps Requests
- Limit the core patch 2 to enforce a full check of the entire
  PCIe hierarchy for support of AtomicOps capabilities.
- Rebase to v7.0-rc6
- Link to v6: https://lore.kernel.org/r/20260325-fix_pciatops-v6-0-10bf19d76dd1@xxxxxxxxxxxxx

Changes in v6:
- Incorporate Ilpo's editorial comments.
- Correct logic in pci_is_atomicops_capable_rp() (annotated by Sashiko)
- Link to v5: https://lore.kernel.org/r/20260323-fix_pciatops-v5-0-fada7233aea8@xxxxxxxxxxxxx

Changes in v5:
- Introduce new pcibios_connects_to_atomicops_capable_rc() so arch's can
  declare AtomicOps support outside of PCIe config space. Defaults to
  "true" - except s390.
- rebase to 7.0-rc5
- Link to v4: https://lore.kernel.org/r/20260313-fix_pciatops-v4-0-93bc70a63935@xxxxxxxxxxxxx

Changes in v4:
- drop patch 1 - it will become the base of a new series
- previous patch 2, now 1: reword commit message
- add a new patch to update references to PCI spec within
  pci_enable_atomic_ops_to_root()
- rebase to latest master
- Link to v3: https://lore.kernel.org/r/20260306-fix_pciatops-v3-0-99d12bcafb19@xxxxxxxxxxxxx

Changes in v3:
- rebase to 7.0-rc2
- gentle ping
- add netdev and rdma lists for awareness
- Link to v2: https://lore.kernel.org/r/20251216-fix_pciatops-v2-0-d013e9b7e2ee@xxxxxxxxxxxxx

Changes in v2:
- rebase to 6.19-rc1
- otherwise unchanged to v1
- Link to v1: https://lore.kernel.org/r/20251110-fix_pciatops-v1-0-edc58a57b62e@xxxxxxxxxxxxx

---
Gerd Bayer (3):
      PCI: AtomicOps: Do not enable requests by RCiEPs
      PCI: AtomicOps: Do not enable without support in root port
      PCI: AtomicOps: Update references to PCIe spec

 drivers/pci/pci.c | 48 ++++++++++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 22 deletions(-)
---
base-commit: 7aaa8047eafd0bd628065b15757d9b48c5f9c07d
change-id: 20251106-fix_pciatops-7e8608eccb03

Best regards,
-- 
Gerd Bayer <gbayer@xxxxxxxxxxxxx>