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When support for a crypto algorithm is enabled, the arch-optimized
implementation of that algorithm should be enabled too. We've learned
this the hard way many times over the years: people regularly forget to
enable the arch-optimized implementations of the crypto algorithms,
resulting in significant performance being left on the table.
Currently, BLAKE2s support is always enabled ('obj-y'), since random.c
uses it. Therefore, the arch-optimized BLAKE2s code, which exists for
ARM and x86_64, should be always enabled too. Let's do that.
Note that the effect on kernel image size is very small and should not
be a concern. On ARM, enabling CRYPTO_BLAKE2S_ARM actually *shrinks*
the kernel size by about 1200 bytes, since the ARM-optimized
blake2s_compress() completely replaces the generic blake2s_compress().
On x86_64, enabling CRYPTO_BLAKE2S_X86 increases the kernel size by
about 1400 bytes, as the generic blake2s_compress() is still included as
a fallback; however, for context, that is only about a quarter the size
of the generic blake2s_compress(). The x86_64 optimized BLAKE2s code
uses much less icache at runtime than the generic code.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250827151131.27733-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@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.