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Armv9.4/8.9 PMU adds optional support for a fixed instruction counter similar to the fixed cycle counter. Support for the feature is indicated in the ID_AA64DFR1_EL1 register PMICNTR field. The counter is not accessible in AArch32. Existing userspace using direct counter access won't know how to handle the fixed instruction counter, so we have to avoid using the counter when user access is requested. Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Rob Herring (Arm) <robh@kernel.org> Tested-by: James Clark <james.clark@linaro.org> Link: https://lore.kernel.org/r/20240731-arm-pmu-3-9-icntr-v3-7-280a8d7ff465@kernel.org 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 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.