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By VMSA rules, using Normal Non-Cacheable type with a shareability attribute of anything other than Outer Shareable is liable to lead into unpredictable territory: | Overlaying the shareability attribute (B3-1377, ARM DDI 0406C.c) | | A memory region with a resultant memory type attribute of Normal, and | a resultant cacheability attribute of Inner Non-cacheable, Outer | Non-cacheable, must have a resultant shareability attribute of Outer | Shareable, otherwise shareability is UNPREDICTABLE Although the SMMU architectures seem to give some slightly stronger guarantees of Non-Cacheable output types becoming implicitly Outer Shareable in most cases, we may as well be explicit and not take any chances. It's also weird that LPAE attribute handling is currently split between prot_to_pte() and init_pte() given that it can all be statically determined up-front. Thus, collect *all* the LPAE attributes into prot_to_pte() in order to logically pick the shareability based on the incoming IOMMU API prot value, and tweak the short-descriptor code to stop setting TTBR0.NOS for Non-Cacheable walks. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will@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.