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

[Yu, Fenghua]

> From: Borislav Petkov [mailto:bp@xxxxxxxxx]
> On Tue, Dec 06, 2011 at 04:55:02PM +0530, Srivatsa S. Bhat wrote:
> > By the way, this problem is not tied to CPU0 alone, it exists for any
> > CPU! (as long as we are talking about plugging in/out CPUs
> physically).
> 
> Just a reminder: before you guys go and wander off into the woods of
> hypothetical with this, please make sure this use case is relevant
> enough for the trouble. The only real reason given so far AFAICT was
> RAS
> and to be able to offline BSP in order to prolong system life before
> maintenance.
> 
> When you take it down for maintenance eventually, you don't need to
> suspend but simply poweroff.

Agree with you. To maintain a system with a bad CPU, either you hot plug or hot replace the CPU, or you power off then replace the CPU. Replacing the CPU between suspend and resume doesn't seem a normal RAS behavior.

If you choose hotplug or hot replace the CPU, then this patchset is useful.

CPU0 offline/online is a must-have if you want to replace a socket which has the BSP in it for any errors in uncore or a sibling CPU. Not mention that CPU0 itself is bad and you want to hot unplug it.

Thanks.

-Fenghua
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