Hi,

systemd carries 80-hotplug-cpu-mem.rules which basically encodes the onlining
policy for the newly added memory/cpu.

This was a temporary solution but now it seems that the kernel gained some
support to handle memory onlining eventually:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=31bc3858ea3ebcc3157b3f5f0e624c5962f5a7a6

So it would be nice if we could make use of that and drop the bits from
systemd/udev.

Unfortunately there doesn't seem to be a counter part for cpus but this rule
should probably be hosted by one of the packages maintained by the kernel team.

Thanks.