linux-kernel - Re: ABI change for device drivers using future AVX instruction set

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Message-ID: <4862ECAB.1040402@zytor.com>
Date:	Wed, 25 Jun 2008 18:11:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Agner Fog <agner@...er.org>, linux-kernel@...r.kernel.org
Subject: Re: ABI change for device drivers using future AVX instruction set

Arjan van de Ven wrote:
> 
> Let me repeat this loud and clear:
> 
> It is not allowed to use floating point, SSE of AVX in device drivers.
> 
> (there are few places that very carefully do this anyway, the raid5
> code being the most obvious one, but we should not add more)
> 

Sadly, AVX repeats the mistakes of SSE1, and doesn't implement proper 
wide support for integer operations.  It has the basic bitwide stuff, 
which makes it usable for RAID-5, but it doesn't extend MMX (which SSE2 
eventually got around to), so it's not usable for RAID-6.  I'd hoped to 
find a VPERM-style instruction, like SSE5 has :(

	-hpa
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