Re: [PATCH v10 2/5] powerpc/crash: introduce a new config option CRASH_HOTPLUG

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 24/04/23 15:27, Laurent Dufour wrote:
> On 23/04/2023 12:52:10, Sourabh Jain wrote:
>> Due to CPU/Memory hot plug/unplug or online/offline events the system
>> resources changes. A similar change should reflect in the loaded kdump
>> kernel kexec segments that describes the state of the CPU and memory of
>> the running kernel.
>>
>> If the kdump kernel kexec segments are not updated after the CPU/Memory
>> hot plug/unplug or online/offline events and kdump kernel tries to
>> collect the dump with the stale system resource data then this might
>> lead to dump collection failure or an inaccurate dump collection.
>>
>> The current method to keep the kdump kernel kexec segments up to date is
>> by reloading the complete kdump kernel whenever a CPU/Memory hot
>> plug/unplug or online/offline event is observed in userspace. Reloading
>> the kdump kernel for every CPU/Memory hot plug/unplug or online/offline
>> event is inefficient and creates a large window where the kdump service
>> is not available. It can be improved by doing in-kernel updates to only
>> necessary kdump kernel kexec segments which describe CPU and Memory
>> resources of the running kernel to the kdump kernel.
>>
>> The kernel changes related to in-kernel updates to the kdump kernel
>> kexec segments are kept under the CRASH_HOTPLUG config option.
>>
>> Later in the series, a powerpc crash hotplug handler is introduced to
>> update the kdump kernel kexec segments on CPU/Memory hotplug events.
>> This arch-specific handler is triggered from a generic crash handler
>> that registers with the CPU/Memory add/remove notifiers.
>>
>> The CRASH_HOTPLUG config option is enabled by default.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
> I can't remember having sent a review-by on that patch earlier.
>
> Anyway, I can't find any issue with that one, so replace with:
> Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>

I apologies for mistakenly applying the "Reviewed-by" tag to the entire
patch series, when it was intended for only one patch. I will remove the
tag in next version.

- Sourabh Jain


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