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Since commit:bad1e1c663("arm64: mte: switch GCR_EL1 in kernel entry and exit") we saved/restored the user GCR_EL1 value at exception boundaries, and update_gcr_el1_excl() is no longer used for this. However it is used to restore the kernel's GCR_EL1 value when returning from a suspend state. Thus, the comment is misleading (and an ISB is necessary). When restoring the kernel's GCR value, we need an ISB to ensure this is used by subsequent instructions. We don't necessarily get an ISB by other means (e.g. if the kernel is built without support for pointer authentication). As __cpu_setup() initialised GCR_EL1.Exclude to 0xffff, until a context synchronization event, allocation tag 0 may be used rather than the desired set of tags. This patch drops the misleading comment, adds the missing ISB, and for clarity folds update_gcr_el1_excl() into its only user. Fixes:bad1e1c663("arm64: mte: switch GCR_EL1 in kernel entry and exit") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210714143843.56537-2-mark.rutland@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.