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Re: [Xen-devel] dom0 and apicid not equal to cpuid

To: "Langsdorf, Mark" <mark.langsdorf@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] dom0 and apicid not equal to cpuid
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 08 Feb 2008 21:19:39 +0000
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On 8/2/08 21:05, "Langsdorf, Mark" <mark.langsdorf@xxxxxxx> wrote:

> Some AMD processor systems assign the boot processor
> (cpu 0) to apicid 4.  Standard Linux handles this
> cleanly by keeping track of the correspondences amongst
> cpu id, apic id, and acpi id.  dom0 Xen does not have
> the code to do that, and AMD is seeing some strange
> behavior on our 4 socket quad-core systems.
> Specifically, when we try to get ACPI information for
> cpu 0, the correspondences break down and the request
> fails.
> I know some of the code needs to be added to mpparse-xen.c,
> but it looks like the relevant code was #ifdef'd out in
> the first place.  Does anyone know why the code to match
> cpuids to apicids was removed and what would need to be
> done to restore it?

Probably most of the things that depend on it are actually managed by Xen
itself. Possibly this assumption is wrong and the code needs to be re-added,
or perhaps the problem is actually within Xen?

Can you point out the specific troubling code in our Linux tree (e.g., the
specific #if0'ed code, and also the place where the kernel ultimately gets
confused and the request fails)?

 -- Keir

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