Hi Bjorn et al.
this series addresses a few issues that have come up with the helper function that enables Atomic Op Requests to be initiated by PCI enpoints:
A. Most in-tree users of this helper use it incorrectly [0]. B. On s390, Atomic Op Requests are enabled, although the helper cannot know whether the root port is really supporting them. C. Loop control in the helper function does not guarantee that a root port's capabilities are ever checked against those requested by the caller.
Address these issue with the following patches: Patch 1: Make it harder to mis-use the enablement function, Patch 2: Addresses issues B. and C.
I did test that issue B is fixed with these patches. Also, I verified that Atomic Ops enablement on a Mellanox/Nvidia ConnectX-6 adapter plugged straight into the root port of a x86 system still gets AtomicOp Requests enabled. However, I did not test this with any PCIe switches between root port and endpoint.
Ideally, both patches would be incorporated immediately, so we could start correcting the mis-uses in the device drivers. I don't know of any complaints when using Atomic Ops on devices where the driver is mis-using the helper. Patch 2 however, is fixing an obseved issue.
[0]: https://lore.kernel.org/all/fbe34de16f5c0bf25a16f9819a57fdd81e5bb08c.camel@l... [1]: https://lore.kernel.org/all/20251105-mlxatomics-v1-0-10c71649e08d@linux.ibm....
Signed-off-by: Gerd Bayer gbayer@linux.ibm.com --- Gerd Bayer (2): PCI: AtomicOps: Define valid root port capabilities PCI: AtomicOps: Fix logic in enable function
drivers/pci/pci.c | 43 +++++++++++++++++++++---------------------- include/uapi/linux/pci_regs.h | 8 ++++++++ 2 files changed, 29 insertions(+), 22 deletions(-) --- base-commit: e9a6fb0bcdd7609be6969112f3fbfcce3b1d4a7c change-id: 20251106-fix_pciatops-7e8608eccb03
Best regards,