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78de91b458
LoongArch already supports two crashkernel regions in kexec-tools, so we
can directly use the common interface to support crashkernel=X,[high,low]
after commit 0ab97169aa ("crash_core: add generic function to do
reservation").
With the help of newly changed function parse_crashkernel() and generic
reserve_crashkernel_generic(), crashkernel reservation can be simplified
by steps:
1) Add a new header file <asm/crash_core.h>, then define CRASH_ALIGN,
CRASH_ADDR_LOW_MAX and CRASH_ADDR_HIGH_MAX and in <asm/crash_core.h>;
2) Add arch_reserve_crashkernel() to call parse_crashkernel() and
reserve_crashkernel_generic();
3) Add ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION Kconfig in
arch/loongarch/Kconfig.
One can reserve the crash kernel from high memory above DMA zone range
by explicitly passing "crashkernel=X,high"; or reserve a memory range
below 4G with "crashkernel=X,low". Besides, there are few rules need to
take notice:
1) "crashkernel=X,[high,low]" will be ignored if "crashkernel=size" is
specified.
2) "crashkernel=X,low" is valid only when "crashkernel=X,high" is passed
and there is enough memory to be allocated under 4G.
3) When allocating crashkernel above 4G and no "crashkernel=X,low" is
specified, a 128M low memory will be allocated automatically for
swiotlb bounce buffer.
See Documentation/admin-guide/kernel-parameters.txt for more information.
Following test cases have been performed as expected:
1) crashkernel=256M //low=256M
2) crashkernel=1G //low=1G
3) crashkernel=4G //high=4G, low=128M(default)
4) crashkernel=4G crashkernel=256M,high //high=4G, low=128M(default), high is ignored
5) crashkernel=4G crashkernel=256M,low //high=4G, low=128M(default), low is ignored
6) crashkernel=4G,high //high=4G, low=128M(default)
7) crashkernel=256M,low //low=0M, invalid
8) crashkernel=4G,high crashkernel=256M,low //high=4G, low=256M
9) crashkernel=4G,high crashkernel=4G,low //high=0M, low=0M, invalid
10) crashkernel=512M@2560M //low=512M
11) crashkernel=1G,high crashkernel=0M,low //high=1G, low=0M
Recommended usage in general:
1) In the case of small memory: crashkernel=512M
2) In the case of large memory: crashkernel=1024M,high crashkernel=128M,low
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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.