linux-kernel - Re: [PATCH] x86_64: make amd quad core 8 socket system not be clustered

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Date:	Mon, 25 Feb 2008 20:05:41 -0800
From:	Ravikiran Thirumalai <kiran@...lemp.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	shai@...lemp.com
Subject: Re: [PATCH] x86_64: make amd quad core 8 socket system not be clustered_box v2

On Tue, Feb 26, 2008 at 04:46:25AM +0100, Andi Kleen wrote:
>> I don't quite understand the purpose of the patch to begin with.  Looking at
>> the current x86 git tree, apic_is_clustered_box is used only to determine if
>> tsc is synchronized on the platform.  The AMD docs  imply that TSC's are not
>> guaranteed to be synced across cores between nodes -- Opteron BKDG for
>> family 10h, Section 2.9.4:
>
>After long discussions with AMD they determined the CPUID flag
>for sync RDTSC will imply synchronization between nodes.

Ah!

>
>If you can't support that in your hardware you're supposed
>to clear it.

Hmm! How would a hardware vendor do that? That doesn't seem to be clear in
the BKDG. (Well, this is the problem with undocumented features :()

Thanks,
Kiran
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