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@xxxxxxxxxxxxx> Reviewed-by: Laurent Dufour <laurent.dufour@xxxxxxxxxx> --- arch/powerpc/Kconfig | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index a6c4407d3ec83..ac0dc0ffe89b4 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 "In-kernel update to kdump kernel on system configuration changes" + default y + depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) + help + Quick and efficient mechanism to update the kdump kernel in the + event of CPU/Memory hot plug/unplug or online/offline events. This + approach does the in-kernel update to only necessary kexec segment + instead of unload-reload entire kdump kernel from userspace. + + If unsure, say Y. + config FA_DUMP bool "Firmware-assisted dump" depends on PPC64 && (PPC_RTAS || PPC_POWERNV) -- 2.39.2 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
