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>, and define CRASH_ALIGN, CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX and DEFAULT_CRASH_KERNEL_LOW_SIZE in <asm/crash_core.h>; 2) Add arch_reserve_crashkernel() to call parse_crashkernel() and reserve_crashkernel_generic(), and do the ARCH specific work if needed. 3) Add ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION Kconfig in arch/x86/Kconfig. When adding DEFAULT_CRASH_KERNEL_LOW_SIZE, add crash_low_size_default() to calculate crashkernel low memory because x86_64 has special requirement. The old reserve_crashkernel_low() and reserve_crashkernel() can be removed. [bhe@redhat.com: move crash_low_size_default() code into <asm/crash_core.h>] Link: https://lkml.kernel.org/r/ZQpeAjOmuMJBFw1/@MiWiFi-R3L-srv Link: https://lkml.kernel.org/r/20230914033142.676708-7-bhe@redhat.com Signed-off-by: Baoquan He <bhe@redhat.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chen Jiahao <chenjiahao16@huawei.com> Cc: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>