linux-kernel - Re: x86-64: memset()/memcpy() not fully standards compliant

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Message-ID: <4F06566B.8080708@zytor.com>
Date:	Thu, 05 Jan 2012 18:03:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Jan Beulich <JBeulich@...e.com>, mingo@...e.hu, tglx@...utronix.de,
	linux-kernel@...r.kernel.org
Subject: Re: x86-64: memset()/memcpy() not fully standards compliant

On 01/05/2012 05:47 PM, Andi Kleen wrote:
>>
>> Is that still true, and do we even use string instructions still on
>> those old CPUs?  Jan's fixes don't introduce any additional delays in
>> the non-string-instruction paths.
> 
> Yes various of the CPUs with bugs used string instructions.
> 

Which CPUs are you talking about here?

> 
> Both string and non string instructions are used on modern CPUs,
> so making any of that slower is not a good idea.
> 

Obviously not, but I'm perfectly fine turning REP_GOOD off on old broken
CPUs.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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