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Once a mkey is created it can be modified using UMR. This is desirable for performance reasons. However, different hardware has restrictions on what modifications are possible using UMR. Make sense of these checks: - mlx5_ib_can_reconfig_with_umr() returns true if the access flags can be altered. Most cases create MRs using 0 access flags (now made clear by consistent use of set_mkc_access_pd_addr_fields()), but the old logic here was tormented. Make it clear that this is checking if the current access_flags can be modified using UMR to different access_flags. It is always OK to use UMR to change flags that all HW supports. - mlx5_ib_can_load_pas_with_umr() returns true if UMR can be used to enable and update the PAS/XLT. Enabling requires updating the entity size, so UMR ends up completely disabled on this old hardware. Make it clear why it is disabled. FRWR, ODP and cache always requires mlx5_ib_can_load_pas_with_umr(). - mlx5_ib_pas_fits_in_mr() is used to tell if an existing MR can be resized to hold a new PAS list. This only works for cached MR's because we don't store the PAS list size in other cases. To be very clear, arrange things so any pre-created MR's in the cache check the newly requested access_flags before allowing the MR to leave the cache. If UMR cannot set the required access_flags the cache fails to create the MR. This in turn means relaxed ordering and atomic are now correctly blocked early for implicit ODP on older HW. Link: https://lore.kernel.org/r/20200914112653.345244-6-leon@kernel.org Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
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.