linux-kernel - Re: [PATCH] x86: Fix AMD K6 indirect call check v2

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Message-ID: <517469BD.3060406@zytor.com>
Date:	Sun, 21 Apr 2013 15:35:41 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] x86: Fix AMD K6 indirect call check v2

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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