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

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Message-ID: <20120106014748.GS11715@one.firstfloor.org>
Date:	Fri, 6 Jan 2012 02:47:48 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, 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 Thu, Jan 05, 2012 at 03:22:52PM -0800, H. Peter Anvin wrote:
> On 01/05/2012 10:28 AM, Andi Kleen wrote:
> >>
> >> Otherwise, is there any rationale for this sort of lurking bug?
> > 
> > Most (all?) of the CPUs I cared about when writing that code had 
> > bugs with string instructions and >4GB.
> > 
> 
> 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.

Don't know the state on current CPUs.

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

-Andi
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