This won't work in the presence of CPU hotplug (which Android uses for power management), because some of the CPUs might not be online when you do it. The API

This won't work in the presence of CPU hotplug (which Android uses for power management), because some of the CPUs might not be online when you do it. The API for "tell me this info" is "read the CTR_EL0 register"; it's a hardware bug that it doesn't do the right thing on this particular chip.