Re: [PATCH v9 2/6] powerpc/crash: introduce a new config option CRASH_HOTPLUG

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

On 13/03/23 21:16, Eric DeVolder wrote:
>
>
> On 3/12/23 13:11, Sourabh Jain wrote:
>> Due to CPU/Memory hotplug events the system resources changes. A similar
>> change should reflect in the loaded kdump kernel image that describes
>> the state of the CPU and memory of the running kernel.
>>
>> If the kdump kernel image is not updated after the CPU or Memory hotplug
>> events and it tries to collect the dump with the stale system resource
>> data this might lead to dump collection failure or an inaccurate dump
>> collection.
>>
>> The current method to keep the kdump kernel up to date is by triggering
>> reload (i.e unload and load) the entire kdump kernel image whenever a
>> CPU or Memory hotplug event is observed by udev in the userspace.
>> Reloading the complete kdump kernel image is an expensive task. It can
>> be easily avoided by doing the in-kernel updates to specific kdump
>> kernel image components which are responsible for describing CPU and
>> Memory resources of the running kernel to the kdump kernel.
>>
>> The kernel changes related to in-kernel update to the kdump kernel image
>> on CPU/Memory hotplug events are kept under the CRASH_HOTPLUG config
>> option.
>>
>> Later in the series, a powerpc crash hotplug handler is introduced to
>> update the kdump kernel image on CPU/Memory hotplug events. This arch
>> specific handler is trigger from a generic crash handler that registers
>> with the CPU and memory notifiers.
>>
>> The CRASH_HOTPLUG config option is enabled by default.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> ---
>>   arch/powerpc/Kconfig | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index a6c4407d3ec83..2f45b3f5175cb 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -681,6 +681,18 @@ config CRASH_DUMP
>>         The same kernel binary can be used as production kernel and dump
>>         capture kernel.
>>   +config CRASH_HOTPLUG
>> +    bool "Update crash capture system on CPU/Memory hotplug event"
> Fwiw, online/offline changes also flow through this infrastructure...
> eric
Yes I will update the CONFIG summary and commit message to convey
the same.

Thanks for the review.

Thanks,
Sourabh Jain