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

[Chen Zhou]

Hi Catalin,

Sorry to ping you.
What's your suggestion about this patch series? I am looking forward to your replay.

Thanks,
Chen Zhou


On 2019/5/16 11:19, Chen Zhou wrote:
> Hi Bhupesh,
> 
> On 2019/5/15 13:06, Bhupesh Sharma wrote:
>> +Cc kexec-list.
>>
>> Hi Chen,
>>
>> I think we are still in the quiet period of the merge cycle, but this is a change which will be useful for systems like HPE Apollo where we are looking at reserving crashkernel across a larger range.
>>
>> Some comments inline and in respective patch threads..
>>
>> On 05/07/2019 09:20 AM, Chen Zhou wrote:
>>> This patch series enable reserving crashkernel on high memory in arm64.
>>
>> Please fix the patch subject, it should be v5.
>> Also please Cc the kexec-list (kexec@xxxxxxxxxxxxxxxxxxx) for future versions to allow wider review of the patchset.
>>
>>> We use crashkernel=X to reserve crashkernel below 4G, which will fail
>>> when there is no enough memory. Currently, crashkernel=Y@X can be used
>>> to reserve crashkernel above 4G, in this case, if swiotlb or DMA buffers
>>> are requierd, capture kernel will boot failure because of no low memory.
>>
>> ... ^^ required
>>
>> s/capture kernel will boot failure because of no low memory./capture kernel boot will fail because there is no low memory available for allocation.
>>
>>> 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. Then
>>> 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]>.
>>
>> Please use consistent naming for the second kernel, better to use crash dump kernel.
>>
>> I have tested this on my HPE Apollo machine and with crashkernel=886M,high syntax, I can get the board to reserve a larger memory range for the crashkernel (i.e. 886M):
>>
>> # dmesg | grep -i crash
>> [    0.000000] kexec_core: Reserving 256MB of low memory at 3560MB for crashkernel (System low RAM: 2029MB)
>> [    0.000000] crashkernel reserved: 0x0000000bc5a00000 - 0x0000000bfd000000 (886 MB)
>>
>> kexec/kdump can also work also work fine on the board.
>>
>> So, with the changes suggested in this cover letter and individual patches, please feel free to add:
>>
>> Reviewed-and-Tested-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
>>
>> Thanks,
>> Bhupesh
>>
> 
> Thanks for you review and test. I will fix these later.
> 
> Thanks,
> Chen Zhou
> 
>>> Besides, we need to modify kexec-tools:
>>>    arm64: support more than one crash kernel regions(see [1])
>>>
>>> I post this patch series about one month ago. The previous changes and
>>> discussions can be retrived from:
>>>
>>> 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/2019-April/022792.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
>>>
>>> Chen Zhou (3):
>>>    x86: kdump: move reserve_crashkernel_low() into kexec_core.c
>>>    arm64: kdump: support reserving crashkernel above 4G
>>>    kdump: update Documentation about crashkernel on arm64
>>>
>>> Mike Rapoport (1):
>>>    memblock: extend memblock_cap_memory_range to multiple ranges
>>>
>>>   Documentation/admin-guide/kernel-parameters.txt |  6 +--
>>>   arch/arm64/include/asm/kexec.h                  |  3 ++
>>>   arch/arm64/kernel/setup.c                       |  3 ++
>>>   arch/arm64/mm/init.c                            | 72 +++++++++++++++++++------
>>>   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, 157 insertions(+), 103 deletions(-)
>>>
>>
>>
>> .
>>
> 
> 
> .
>