Re: [PATCH 2.6.21 review I] [11/25] x86: default to physical mode on hotplug CPU kernels

[Eric W. Biederman]

Andi Kleen <ak@xxxxxxx> writes:

> From: Ingo Molnar <mingo@xxxxxxx>
>
> Default to physical mode on hotplug CPU kernels.  Furher simplify and clean up
> the APIC initialization code.

Where is the code that the subject describes?

I have two problems here.

- I don't see anything handling the hotplug case, and forcing us to
  physical mode.
- Ingo's other patch asserts that hotplug should be made to handle
  logical deliver mode.

With logical deliver mode the experimental evidence is that the
destination cpu is a hint, and you can arrive at a cpu that is not
in your cpu mask.  Now I only saw that problem on hyperthreaded cpus
but we didn't have the code enabled long enough to see it in other
cases.

Maybe if I can finish getting irq migration back into process context,
and someone verifies that the cpu disable in the hotplug path actually
disables the cpu/hyperthread instead of sitting in a hlt loop.  We
won't have a problem.  But broadcast ipis and irqs that don't go where
you tell them to are things we need to be very careful with.

Eric
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