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

Bjorn Helgaas
2026-04-02T16:38:42Z

On Mon, Mar 30, 2026 at 03:09:43PM +0200, Gerd Bayer wrote:
> 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@linux.ibm.com>

Thanks, applied to pci/atomics for v7.1 with minor rework of 2/3.

> ---
> 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@linux.ibm.com
>
> 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@linux.ibm.com
>
> 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@linux.ibm.com
>
> 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@linux.ibm.com
>
> 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@linux.ibm.com
>
> 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@linux.ibm.com
>
> ---
> 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@linux.ibm.com>
>