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SubjectRe: [PATCH v17 00/10] support reserving crashkernel above 4G on arm64 kdump

On 2021/12/10 14:55, Zhen Lei wrote:
> There are following issues in arm64 kdump:
> 1. We use crashkernel=X to reserve crashkernel below 4G, which
> will fail when there is no enough low memory.
> 2. If reserving crashkernel above 4G, in this case, crash dump
> kernel will boot failure because there is no low memory available
> for allocation.
> To solve these issues, change the behavior of crashkernel=X.
> crashkernel=X tries low allocation in DMA zone and fall back to high
> allocation if it fails.
> We can also use "crashkernel=X,high" to select a high region above
> DMA zone, which also tries to allocate at least 256M low memory in
> DMA zone automatically and "crashkernel=Y,low" can be used to allocate
> specified size low memory.
> When reserving crashkernel in high memory, some low memory is reserved
> for crash dump kernel devices. So there may be two regions reserved for
> crash dump kernel.
> In order to distinct from the high region and make no effect to the use
> of existing kexec-tools, rename the low region as "Crash kernel (low)",
> and pass the low region by reusing DT property
> "linux,usable-memory-range". We made the low memory region as the last
> range of "linux,usable-memory-range" to keep compatibility with existing
> user-space and older kdump kernels.
> Besides, we need to modify kexec-tools:
> arm64: support more than one crash kernel regions(see [1])
> Another update is document about DT property 'linux,usable-memory-range':
> schemas: update 'linux,usable-memory-range' node schema(see [2])
> This patchset contains the following 10 patches:
> 0001-0004 are some x86 cleanups which prepares for making functionsreserve_crashkernel[_low]() generic.
> 0005 makes functions reserve_crashkernel[_low]() generic.
> 0006-0007 reimplements arm64 crashkernel=X.
> 0008-0009 adds memory for devices by DT property linux,usable-memory-range.
> 0010 updates the doc.
> Changes since [v16]
> - Because no functional changes in this version, so add
> "Tested-by: Dave Kleikamp <>" for patch 1-9
> - Add "Reviewed-by: Rob Herring <>" for patch 8
> - Update patch 9 based on the review comments of Rob Herring
> - As Catalin Marinas's suggestion, merge the implementation of
> ARCH_WANT_RESERVE_CRASH_KERNEL into patch 5. Ensure that the
> contents of X86 and ARM64 do not overlap, and reduce unnecessary
> temporary differences.

An Internal review has been done, so for this series,

Reviewed-by: Kefeng Wang <>

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