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[ Upstream commit86ad60a65f] The XTS asm helper arrangement is a bit odd: the 8-way stride helper consists of back-to-back calls to the 4-way core transforms, which are called indirectly, based on a boolean that indicates whether we are performing encryption or decryption. Given how costly indirect calls are on x86, let's switch to direct calls, and given how the 8-way stride doesn't really add anything substantial, use a 4-way stride instead, and make the asm core routine deal with any multiple of 4 blocks. Since 512 byte sectors or 4 KB blocks are the typical quantities XTS operates on, increase the stride exported to the glue helper to 512 bytes as well. As a result, the number of indirect calls is reduced from 3 per 64 bytes of in/output to 1 per 512 bytes of in/output, which produces a 65% speedup when operating on 1 KB blocks (measured on a Intel(R) Core(TM) i7-8650U CPU) Fixes:9697fa39ef("x86/retpoline/crypto: Convert crypto assembler indirect jumps") Tested-by: Eric Biggers <ebiggers@google.com> # x86_64 Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Sasha Levin <sashal@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.