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Ard Biesheuvel
aa9695157f
kmap_atomic() is used to create short-lived mappings of pages that may not be accessible via the kernel direct map. This is only needed on 32-bit architectures that implement CONFIG_HIGHMEM, but it can be used on 64-bit other architectures too, where the returned mapping is simply the kernel direct address of the page. However, kmap_atomic() does not support migration on CONFIG_HIGHMEM configurations, due to the use of per-CPU kmap slots, and so it disables preemption on all architectures, not just the 32-bit ones. This implies that all scatterwalk based crypto routines essentially execute with preemption disabled all the time, which is less than ideal. So let's switch scatterwalk_map/_unmap and the shash/ahash routines to kmap_local() instead, which serves a similar purpose, but without the resulting impact on preemption on architectures that have no need for CONFIG_HIGHMEM. Cc: Eric Biggers <ebiggers@kernel.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "Elliott, Robert (Servers)" <elliott@hpe.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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.