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Heiko Carstens
b7e81efc24
Provide infrastructure which allows to generate machine_has_<feature>() functions, which are replacing the existing MACHINE_HAS_<feature> macros. Such function usages generate a static branch depending on <feature>. The static branch is patched using an alternative. Each <feature> correlates with a bit set in the machine_features bit field. If the corresponding bit is set, the branch will be patched. In order to have any effect on branch patching feature bits must be set with set_machine_features() in the decompressor before alternatives patching of the kernel image. It is possible to use clear_machine_feature() and test_machine_feature() for machine features which cannot be completely detected within the decompressor, e.g. if common code command line parameters allow to enable or disable certain features. In such cases test_machine_feature() instead of machine_has_feature() must be used within the kernel. This results in a runtime check and not a static branch. Reviewed-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.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.