Re: [PATCH v8 0/5] support reserving crashkernel above 4G on arm64 kdump

[chenzhou]

Hi Baoquan,


Thanks for your suggestions.

You are right, some details should be made in the commit log.


Thanks,

Chen Zhou


On 2020/5/26 9:42, Baoquan He wrote:
> On 05/21/20 at 05:38pm, Chen Zhou wrote:
>> This patch series enable reserving crashkernel above 4G in arm64.
>>
>> 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. Currently, crashkernel=Y@X can be used to reserve crashkernel above 4G,
>> in this case, if swiotlb or DMA buffers are required, crash dump kernel
>> will boot failure because there is no low memory available for allocation.
>>
>> To solve these issues, introduce crashkernel=X,low to reserve specified
>> size low memory.
>> Crashkernel=X tries to reserve memory for the crash dump kernel under
>> 4G. If crashkernel=Y,low is specified simultaneously, reserve spcified
>> size low memory for crash kdump kernel devices firstly and then reserve
>> memory above 4G.
>>
>> When crashkernel is reserved above 4G in memory, that is, crashkernel=X,low
>> is specified simultaneously, kernel should reserve specified size low memory
>> for crash dump kernel devices. So there may be two crash kernel regions, one
>> is below 4G, the other is above 4G.
>> In order to distinct from the high region and make no effect to the use of
>> kexec-tools, rename the low region as "Crash kernel (low)", and add DT property
>> "linux,low-memory-range" to crash dump kernel's dtb to pass the low region.
>>
>> Besides, we need to modify kexec-tools:
>> arm64: kdump: add another DT property to crash dump kernel's dtb(see [1])
>>
>> The previous changes and discussions can be retrieved from:
>>
>> Changes since [v7]
>> - Move x86 CRASH_ALIGN to 2M
>> Suggested by Dave and do some test, move x86 CRASH_ALIGN to 2M.
> OK, moving x86 CRASH_ALIGN to 2M is suggested by Dave. Because
> CONFIG_PHYSICAL_ALIGN can be selected from 2M to 16M. So 2M seems good.
> But, anyway, we should tell the reason why it need be changed in commit
> log.
>
>
> arch/x86/Kconfig:
> config PHYSICAL_ALIGN
>         hex "Alignment value to which kernel should be aligned"
>         default "0x200000"
>         range 0x2000 0x1000000 if X86_32
>         range 0x200000 0x1000000 if X86_64
>
>> - Update Documentation/devicetree/bindings/chosen.txt 
>> Add corresponding documentation to Documentation/devicetree/bindings/chosen.txt suggested by Arnd.
>> - Add Tested-by from Jhon and pk
>>
>> Changes since [v6]
>> - Fix build errors reported by kbuild test robot.
>>
>> Changes since [v5]
>> - Move reserve_crashkernel_low() into kernel/crash_core.c.
>> - Delete crashkernel=X,high.
> And the crashkernel=X,high being deleted need be told too. Otherwise
> people reading the commit have to check why themselves. I didn't follow
> the old version, can't see why ,high can't be specified explicitly.
>
>> - Modify crashkernel=X,low.
>> If crashkernel=X,low is specified simultaneously, reserve spcified size low
>> memory for crash kdump kernel devices firstly and then reserve memory above 4G.
>> In addition, rename crashk_low_res as "Crash kernel (low)" for arm64, and then
>> pass to crash dump kernel by DT property "linux,low-memory-range".
>> - Update Documentation/admin-guide/kdump/kdump.rst.
>>
>> Changes since [v4]
>> - Reimplement memblock_cap_memory_ranges for multiple ranges by Mike.
>>
>> Changes since [v3]
>> - Add memblock_cap_memory_ranges back for multiple ranges.
>> - 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/2020-May/025128.html
>> [v1]: https://lkml.org/lkml/2019/4/2/1174
>> [v2]: https://lkml.org/lkml/2019/4/9/86
>> [v3]: https://lkml.org/lkml/2019/4/9/306
>> [v4]: https://lkml.org/lkml/2019/4/15/273
>> [v5]: https://lkml.org/lkml/2019/5/6/1360
>> [v6]: https://lkml.org/lkml/2019/8/30/142
>> [v7]: https://lkml.org/lkml/2019/12/23/411
>>
>> Chen Zhou (5):
>>   x86: kdump: move reserve_crashkernel_low() into crash_core.c
>>   arm64: kdump: reserve crashkenel above 4G for crash dump kernel
>>   arm64: kdump: add memory for devices by DT property, low-memory-range
>>   kdump: update Documentation about crashkernel on arm64
>>   dt-bindings: chosen: Document linux,low-memory-range for arm64 kdump
>>
>>  Documentation/admin-guide/kdump/kdump.rst     | 13 ++-
>>  .../admin-guide/kernel-parameters.txt         | 12 ++-
>>  Documentation/devicetree/bindings/chosen.txt  | 25 ++++++
>>  arch/arm64/kernel/setup.c                     |  8 +-
>>  arch/arm64/mm/init.c                          | 61 ++++++++++++-
>>  arch/x86/kernel/setup.c                       | 66 ++------------
>>  include/linux/crash_core.h                    |  3 +
>>  include/linux/kexec.h                         |  2 -
>>  kernel/crash_core.c                           | 85 +++++++++++++++++++
>>  kernel/kexec_core.c                           | 17 ----
>>  10 files changed, 208 insertions(+), 84 deletions(-)
>>
>> -- 
>> 2.20.1
>>
>>
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>
> .
>