RE: [PATCH v4 0/7] x86: BSP or CPU0 online/offline

[Yu, Fenghua]

> We need a debug feature for this: CONFIG_DEBUG_BOOT_CPU_OFF=y or
> such (disabled by default): this feature would offline the boot
> CPU as soon as possible, and boot up userspace with the boot CPU
> offlined.

I would think the earliest time when CPU0 can be offline is right after do_initcalls() because do_initcalls() installs some cpu hotplug notifier.

But this will change generic code (e.g. add arch hook in init/main.c or add a new initcall level which is after level 7s).

Another way is to offline CPU0 (or any CPU) in /etc/rc.local. By this way, we don't change kernel. And this is safe, but a bit later than in kernel.

Any comment?

Thanks.

-Fenghua
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