linux-kernel - Re: AVX "Sandy Bridge" hardware issue?

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Message-ID: <4E1DC535.1030000@genband.com>
Date:	Wed, 13 Jul 2011 10:17:57 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	MK <mk@...nitivedissonance.ca>, linux-kernel@...r.kernel.org
Subject: Re: AVX "Sandy Bridge" hardware issue?

On 07/12/2011 06:49 PM, Andi Kleen wrote:
> MK<mk@...nitivedissonance.ca>  writes:
>>
>> In which Andreas Schwab points out (rightly or wrongly) that according
>> to the /proc/cpuinfo from the slice, the processor actually does not
>> support AVX.  However,  the "model name", "Intel(R) Xeon(R) CPU
>> E31230", is according to this a Sandy Bridge processor with AVX:
>
> If it's in a VM then the VM may not expose AVX to the guest
> (the VMs have to do that explicitely because AVX has additional state).
> If it's not in /proc/cpuinfo on the guest that's likely the case.

The OP mentioned that he's using OpenVZ, so it's running in a container 
(chroot on steroids), not a "true" VM.

Each instance runs the same kernel, they're isolated from the other 
instances using filesystem/process/network namespaces.

That said, /proc/cpuinfo is virtualized somehow by the containerization 
since it shows only the cpus assigned to the container--it seems 
plausible that they screwed up the cpu flags while doing it.

I think your suggestion of talking to the vendor is the correct next step.

Chris

-- 
Chris Friesen
Software Developer
GENBAND
chris.friesen@...band.com
www.genband.com
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