Turns out it is actually set:
rover [~] % fgrep CONFIG_RCU_NOCB_CPU /boot/config-$(uname -r) CONFIG_RCU_NOCB_CPU=y
Turns out it is actually set:
rover [~] % fgrep CONFIG_RCU_NOCB_CPU /boot/config- $(uname -r) RCU_NOCB_ CPU=y
CONFIG_