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b4401403af
FEAT_SPEv1p4 (optional from Armv8.8) adds some new filter bits and also makes some previously available bits unavailable again e.g: E[30], bit [30] When FEAT_SPEv1p4 is _not_ implemented ... Continuing to hard code the valid filter bits for each version isn't scalable, and it also doesn't work for filter bits that aren't related to SPE version. For example most bits have a further condition: E[15], bit [15] When ... and filtering on event 15 is supported: Whether "filtering on event 15" is implemented or not is only discoverable from the TRM of that specific CPU or by probing PMSEVFR_EL1. Instead of hard coding them, write all 1s to the PMSEVFR_EL1 register and read it back to discover the RES0 bits. Unsupported bits are RAZ/WI so should read as 0s. For any hardware that doesn't strictly follow RAZ/WI for unsupported filters: Any bits that should have been supported in a specific SPE version but now incorrectly appear to be RES0 wouldn't have worked anyway, so it's better to fail to open events that request them rather than behaving unexpectedly. Bits that aren't implemented but also aren't RAZ/WI will be incorrectly reported as supported, but allowing them to be used is harmless. Testing on N1SDP shows the probed RES0 bits to be the same as the hard coded ones. The FVP with SPEv1p4 shows only additional new RES0 bits, i.e. no previously hard coded RES0 bits are missing. Tested-by: Leo Yan <leo.yan@arm.com> Signed-off-by: James Clark <james.clark@linaro.org> Signed-off-by: Will Deacon <will@kernel.org> |
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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.