netdev - [PATCH RFC 0/2] mlx5/pci: Fix enablement of PCIe AtomicOp Requests

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Message-Id: <20251105-mlxatomics-v1-0-10c71649e08d@linux.ibm.com>
Date: Wed, 05 Nov 2025 18:55:12 +0100
From: Gerd Bayer <gbayer@...ux.ibm.com>
To: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
        Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Jay Cornwall <Jay.Cornwall@....com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Alexander Schmidt <alexs@...ux.ibm.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Gerd Bayer <gbayer@...ux.ibm.com>
Subject: [PATCH RFC 0/2] mlx5/pci: Fix enablement of PCIe AtomicOp Requests

As I promised in
https://lore.kernel.org/linux-pci/9c7c4217171fb56c505dc90b8c73b2ce079207a9.camel@linux.ibm.com/#t
here's an RFC patch proposing to correct the usage of
pci_enable_atomic_ops_to_root() in the Ethernet and InfiniBand drivers
for Mellanox/NVidia devices.

With this fix, AtomicOp Requests would only be enabled if a root-port
correctly announced its capability to support all AtomicOps including
the optional 128bit CAS - as the drivers intend to.

That said, on the only x86 system that I can test this on, it appears
that UEFI is already enabling AtomicOp Requests for the ConnectX-6 Dx
card in that system.

Overall, both the enablement of PCIe AtomicOps by core PCI code, and
their usage by (very few) device drivers, appear to be in need of some
attention?

Thanks,
Gerd

Signed-off-by: Gerd Bayer <gbayer@...ux.ibm.com>
---
Gerd Bayer (2):
      net/mlx5: Request PCIe AtomicOps enabled for all 3 sizes
      ib/mlx5: Request PCIe AtomicOps enabled for all 3 sizes

 drivers/infiniband/hw/mlx5/data_direct.c       | 6 +++---
 drivers/net/ethernet/mellanox/mlx5/core/main.c | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)
---
base-commit: 6146a0f1dfae5d37442a9ddcba012add260bceb0
change-id: 20251024-mlxatomics-5729e8af60b9

Best regards,
-- 
Gerd Bayer <gbayer@...ux.ibm.com>