Message-ID: <517469BD.3060406@zytor.com>
Date: Sun, 21 Apr 2013 15:35:41 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Borislav Petkov <bp@alien8.de>
CC: Andi Kleen <andi@firstfloor.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH] x86: Fix AMD K6 indirect call check v2
References: <1366562995-20530-1-git-send-email-andi@firstfloor.org> <51741CB2.3090209@zytor.com> <20130421174456.GA4559@pd.tnic>
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On 04/21/2013 10:44 AM, Borislav Petkov wrote:
> 
> But I have hard time understanding what that test with the 10^6 loop
> iterations is supposed to achieve. And what makes sure that the RDTSCs
> don't get reordered? Or maybe K6 wasn't reordering that aggressively...
> 
> Erratum says "unpredictable system behavior" but it seems it wasn't that
> unpredictable after all - otherwise the fix would've been "HLT" right
> then and there. :)
> 

Looks like it is just trying to sense the bug... but then it doesn't
actually do anything about it.  At least it should taint the kernel.

	-hpa


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