linux-kernel - Re: [patch 4/4] x86: apic_is_clustered_box to indicate unsynched TSC's on multiboard vSMP systems

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Date:	Thu, 20 Mar 2008 00:53:25 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Ravikiran G Thirumalai" <kiran@...lex86.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	"Glauber de Oliveira Costa" <gcosta@...hat.com>,
	"Andi Kleen" <ak@...e.de>, shai@...lex86.org
Subject: Re: [patch 4/4] x86: apic_is_clustered_box to indicate unsynched TSC's on multiboard vSMP systems

On Thu, Mar 20, 2008 at 12:45 AM, Ravikiran G Thirumalai
<kiran@...lex86.org> wrote:
> Indicate TSCs are unreliable as time sources if the platform is
>  a multi chassi ScaleMP vSMPowered machine.
>
>  Signed-off-by: Ravikiran Thirumalai <kiran@...lex86.org>
>
>  Index: linux.git.trees/arch/x86/kernel/apic_64.c
>  ===================================================================
>  --- linux.git.trees.orig/arch/x86/kernel/apic_64.c      2008-03-19 20:42:28.187659497 -0700
>  +++ linux.git.trees/arch/x86/kernel/apic_64.c   2008-03-19 21:24:17.705515003 -0700
>  @@ -1208,7 +1208,7 @@ __cpuinit int apic_is_clustered_box(void
>          * will be [4, 0x23] or [8, 0x27] could be thought to
>          * vsmp box still need checking...
>          */
>  -       if (!is_vsmp_box() && (boot_cpu_data.x86_vendor == X86_VENDOR_AMD))
>  +       if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
>                 return 0;

why?

>
>         bios_cpu_apicid = x86_bios_cpu_apicid_early_ptr;
>  @@ -1248,6 +1248,12 @@ __cpuinit int apic_is_clustered_box(void
>                         ++zeros;
>         }
>
>  +       /* ScaleMP vSMPowered boxes have one cluster per board and TSCs are
>  +        * not guaranteed to be synced between boards
>  +        */
>  +       if (is_vsmp_box() && clusters > 1)
>  +               return 1;

you still call that for intel box.

YH
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