Re: [PATCH -tip] x86: do_boot_cpu - check if we have ESR register

From: Maciej W. Rozycki
Date: Wed Oct 22 2008 - 11:41:20 EST


On Wed, 22 Oct 2008, Ingo Molnar wrote:

> i'm wondering - is the server there really that old, that it has no
> integrated lapic? I.e. it's an i486 SMP box or so? Or perhaps some
> other, weird SMP box?

I've been wondering about that too, though the fix is correct either way.

Note that all the discrete APIC boxes we have ever supported were
Pentium-based, either the original P5 (i.e. 60/66MHz) chips which had no
APIC on chip at all or P54C ones but with the integrated APIC disabled
(because the systems were 4-way SMP or suchlike and there was no suitable
chipset component to provide a compatible I/O APIC).

All the documentation for i486 SMP boxes I was able to track down
indicated that even if APIC chips were used with them, the whole setup did
not support the MP table as defined by the MultiProcessor Specification
and therefore could not be supported by Linux as it is. And I have never
come across a specimen to look into it any further.

Maciej
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