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On Arm CCA, with RMM-v1.0, all MMIO regions are shared. However, in the future, an Arm CCA-v1.0 compliant guest may be run in a lesser privileged partition in the Realm World (with Arm CCA-v1.1 Planes feature). In this case, some of the MMIO regions may be emulated by a higher privileged component in the Realm world, i.e, protected. Thus the guest must decide today, whether a given MMIO region is shared vs Protected and create the stage1 mapping accordingly. On Arm CCA, this detection is based on the "IPA State" (RIPAS == RIPAS_IO). Provide a helper to run this check on a given range of MMIO. Also, provide a arm64 helper which may be hooked in by other solutions. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Steven Price <steven.price@arm.com> Link: https://lore.kernel.org/r/20241017131434.40935-5-steven.price@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.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 reStructuredText 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.