When crashkernel is reserved above 4G in memory, kernel should reserve some amount of low memory for swiotlb and some DMA buffers. So there may be two crash kernel regions, one is below 4G, the other is above 4G.
Crash dump kernel reads more than one crash kernel regions via a dtb property under node /chosen, linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]>. Besides, we need to modify kexec-tools: arm64: support more than one crash kernel regions(see [1]) Changes since [v4] - reimplement memblock_cap_memory_ranges for multiple ranges. Changes since [v3] - Add memblock_cap_memory_ranges for multiple ranges. - Split patch "arm64: kdump: support more than one crash kernel regions" as two. One is above "Add memblock_cap_memory_ranges", the other is using memblock_cap_memory_ranges to support multiple crash kernel regions. - Fix some compiling warnings. Changes since [v2] - Split patch "arm64: kdump: support reserving crashkernel above 4G" as two. Put "move reserve_crashkernel_low() into kexec_core.c" in a separate patch. Changes since [v1]: - Move common reserve_crashkernel_low() code into kernel/kexec_core.c. - Remove memblock_cap_memory_ranges() i added in v1 and implement that in fdt_enforce_memory_region(). There are at most two crash kernel regions, for two crash kernel regions case, we cap the memory range [min(regs[*].start), max(regs[*].end)] and then remove the memory range in the middle. [1]: http://lists.infradead.org/pipermail/kexec/2019-April/022792.html [v1]: https://lkml.org/lkml/2019/4/8/628 [v2]: https://lkml.org/lkml/2019/4/9/86 [v3]: https://lkml.org/lkml/2019/4/15/6 [v4]: https://lkml.org/lkml/2019/4/15/273 Chen Zhou (4): x86: kdump: move reserve_crashkernel_low() into kexec_core.c arm64: kdump: support reserving crashkernel above 4G memblock: extend memblock_cap_memory_range to multiple ranges kdump: update Documentation about crashkernel on arm64 Documentation/admin-guide/kernel-parameters.txt | 4 +- arch/arm64/include/asm/kexec.h | 3 ++ arch/arm64/kernel/setup.c | 3 ++ arch/arm64/mm/init.c | 59 ++++++++++++++++------ arch/x86/include/asm/kexec.h | 3 ++ arch/x86/kernel/setup.c | 66 +++---------------------- include/linux/kexec.h | 5 ++ include/linux/memblock.h | 2 +- kernel/kexec_core.c | 56 +++++++++++++++++++++ mm/memblock.c | 44 ++++++++--------- 10 files changed, 144 insertions(+), 101 deletions(-) -- 2.7.4
