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According to PCIe spec, Enable Relaxed Ordering value in the VF's PCI config space is wired to 0 and PF relaxed ordering (RO) setting should be applied to the VF. In QEMU (and maybe others), when assigning VFs, the RO bit in PCI config space is not emulated properly and is always set to 0. Therefore, pcie_relaxed_ordering_enabled() always returns 0 for VFs and VMs and thus MKeys can't be created with RO read even if the PF supports it. pcie_relaxed_ordering_enabled() check was added to avoid a syndrome when creating a MKey with relaxed ordering (RO) enabled when the driver's relaxed_ordering_read_pci_enabled HCA capability is out of sync with FW. With the new relaxed_ordering_read capability this can't happen, as it's set regardless of RO value in PCI config space and thus can't change during runtime. Hence, to allow RO read in VFs and VMs, use the new HCA capability relaxed_ordering_read without checking pcie_relaxed_ordering_enabled(). The old capability checks are kept for backward compatibility with older FWs. Allowing RO in VFs and VMs is valuable since it can greatly improve performance on some setups. For example, testing throughput of a VF on an AMD EPYC 7763 and ConnectX-6 Dx setup showed roughly 60% performance improvement. Signed-off-by: Avihai Horon <avihaih@nvidia.com> Reviewed-by: Shay Drory <shayd@nvidia.com> Reviewed-by: Aya Levin <ayal@nvidia.com> Link: https://lore.kernel.org/r/e7048640d66c341a8fa0465e099926e7989184bc.1681131553.git.leon@kernel.org Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Signed-off-by: Leon Romanovsky <leon@kernel.org>
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.