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From: Jung-uk Kim <jkim@FreeBSD.org>
To: Colin Percival <cperciva@FreeBSD.org>
Date: Mon, 24 Apr 2006 17:31:37 -0400
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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/amd64/amd64 mp_machdep.c src/sys/i386/i386
	mp_machdep.c
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On Monday 24 April 2006 05:17 pm, Colin Percival wrote:
> cperciva    2006-04-24 21:17:02 UTC
>
>   FreeBSD src repository
>
>   Modified files:
>     sys/amd64/amd64      mp_machdep.c
>     sys/i386/i386        mp_machdep.c
>   Log:
>   Adjust dangerous-shared-cache-detection logic from "all shared
> data caches are dangerous" to "a shared L1 data cache is
> dangerous".  This is a compromise between paranoia and performance:
> Unlike the L1 cache, nobody has publicly demonstrated a
> cryptographic side channel which exploits the L2 cache -- this is
> harder due to the larger size, lower bandwidth, and greater
> associativity -- and prohibiting shared L2 caches turns Intel Core
> Duo processors into Intel Core Solo processors.
>
>   As before, the 'machdep.hyperthreading_allowed' sysctl will allow
> even the L1 data cache to be shared.
>
>   Discussed with: jhb, scottl
>   Security:       See FreeBSD-SA-05:09.htt for background material.
>
>   Revision  Changes    Path
>   1.272     +2 -2      src/sys/amd64/amd64/mp_machdep.c
>   1.265     +2 -2      src/sys/i386/i386/mp_machdep.c

Cool!  I was working on the same thing. :-)

http://www.freebsd.org/cgi/query-pr.cgi?pr=96203

Jung-uk Kim