Re: [RFC v4 PATCH 2/5] powerpc/crash hp: introduce a new config option CRASH_HOTPLUG

[Laurent Dufour <ldufour@linux.ibm.com>]

On 11/04/2022, 10:43:54, Sourabh Jain wrote:
> The option CRASH_HOTPLUG enables, in kernel update to kexec segments on
> hotplug events.
> 
> All the updates needed on the capture kernel load path in the kernel for
> both kexec_load and kexec_file_load system will be kept under this config.
> 
> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> Reviewed-by: Eric DeVolder <eric.devolder@oracle.com>

Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>

> ---
>  arch/powerpc/Kconfig | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index b779603978e1..777db33f75b5 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -623,6 +623,17 @@ config FA_DUMP
>  	  If unsure, say "y". Only special kernels like petitboot may
>  	  need to say "N" here.
>  
> +config CRASH_HOTPLUG
> +	bool "kernel updates of crash kexec segments"
> +	depends on CRASH_DUMP && (HOTPLUG_CPU) && KEXEC_FILE
> +	help
> +	  An efficient way to keep the capture kernel up-to-date with CPU
> +	  hotplug events. On CPU hotplug event the kexec segments of capture
> +	  kernel becomes stale and need to be updated with latest CPU data.
> +	  In this method the kernel performs minimal update to only relevant
> +	  kexec segments on CPU hotplug event, instead of triggering full
> +	  capture kernel reload from userspace using udev rule.
> +
>  config PRESERVE_FA_DUMP
>  	bool "Preserve Firmware-assisted dump"
>  	depends on PPC64 && PPC_POWERNV && !FA_DUMP