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When the kernel mapping was moved outside of the linear mapping, the
kernel memory reservation was increased, to take into account mapping
granularity. However, this is done unconditionally, regardless of
whether the kernel memory is mapped read-only or not.
If this extension is not needed, up to 2 MiB may be lost, which has a
big impact on e.g. Canaan K210 (64-bit nommu) platforms with only 8 MiB
of RAM.
Reclaim the lost memory by only extending the reserved region when
needed, i.e. depending on a simplified version of the conditional logic
around the call to protect_kernel_linear_mapping_text_rodata().
Fixes: 2bfc6cd81b ("riscv: Move kernel mapping outside of linear mapping")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.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 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.