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Date: Tue, 09 Sep 2008 13:48:51 -0400
From: Mark Lord <lkml@rtr.ca>
Organization: Real-Time Remedies Inc.
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To: Andi Kleen <andi@firstfloor.org>
Cc: Krzysztof Halasa <khc@pm.waw.pl>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,
       Arjan van de Ven <arjan@infradead.org>,
       x86 maintainers <x86@kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [git pull] x86 fixes
References: <200809081752.m88Hq6tn005080@askone.hos.anvin.org>	<alpine.LFD.1.10.0809081056350.3117@nehalem.linux-foundation.org>	<48C56D60.7010405@zytor.com> <20080908114619.741b6786@infradead.org>	<48C57439.3040903@zytor.com> <20080908190249.GA21998@elte.hu>	<alpine.LFD.1.10.0809081213330.3117@nehalem.linux-foundation.org>	<m3vdx6xm68.fsf@maximus.localdomain> <87d4jdty5b.fsf@basil.nowhere.org> <48C6AFA4.1050206@rtr.ca>
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Mark Lord wrote:
> Andi Kleen wrote:
>> Krzysztof Halasa <khc@pm.waw.pl> writes:
>>
>>> Linus Torvalds <torvalds@linux-foundation.org> writes:
>>>
>>>>  - "modern 32-bit": PPro and better. Can take CMOV, MMX and TSC for 
>>>>    granted.
>>> VIA C3 (Samuel 2/Ezra, 600 - 1000 MHz?, common on VIA EPIA-*: home
>>> theatres etc) can't CMOV.
>>
>> AFAIK they fixed that in newer BIOS with a microcode update. It's 
>> slow, but it works.
> ..
> 
> Our firewall here uses a Via C3-600 CPU, and CMOV has never worked on it.
> But based upon your posting, I have today upgraded the BIOS to the
> latest (2004) version.
> 
> Now.. how can I check whether CMOV works or not?  It's not listed in 
> /proc/cpuinfo.
..

H. Peter Anvin wrote:
>
> Compile just about any C program with -march=i686.
..

Okay, done.  And the binary does indeed have a ton of CMOV instructions.
When running it, this appears immediately:

    Illegal instruction

So much for the "BIOS upgrade fixes CMOV microcode" theory.

Cheers