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Gerd Bayer 84af732af4 PCI: Enable AtomicOps only if Root Port supports them 
[ Upstream commit 1ae8c4ce15 ]

When inspecting the config space of a Connect-X physical function in an
s390 system after it was initialized by the mlx5_core device driver, we
found the function to be enabled to request AtomicOps despite the Root Port
lacking support for completing them:

  00:00.1 Ethernet controller: Mellanox Technologies MT2894 Family [ConnectX-6 Lx]
          Subsystem: Mellanox Technologies Device 0002
          DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-
                   AtomicOpsCtl: ReqEn+

On s390 and many virtualized guests, the Endpoint is visible but the Root
Port is not.  In this case, pci_enable_atomic_ops_to_root() previously
enabled AtomicOps in the Endpoint even though it can't tell whether the
Root Port supports them as a completer.

Change pci_enable_atomic_ops_to_root() to fail if there's no Root Port or
the Root Port doesn't support AtomicOps.

Fixes: 430a23689d ("PCI: Add pci_enable_atomic_ops_to_root()")
Reported-by: Alexander Schmidt <alexs@linux.ibm.com>
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
[bhelgaas: commit log, check RP first to simplify flow]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260330-fix_pciatops-v7-2-f601818417e8@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-06-01 17:35:32 +02:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.