linux-kernel - Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

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Message-ID: <20110726183721.GF32536@aftab>
Date:	Tue, 26 Jul 2011 20:37:21 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Borislav Petkov <bp@...64.org>, Avi Kivity <avi@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Przywara, Andre" <Andre.Przywara@....com>,
	"Pohlack, Martin" <Martin.Pohlack@....com>
Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

On Tue, Jul 26, 2011 at 02:16:56PM -0400, H. Peter Anvin wrote:
> >> Is it possible to derive the bit positions (and the need to mask them) 
> >> from the cpuid description of the cache topology and sizes?
> > 
> > As far as I understand your question, there's no need for deriving the
> > bit positions because they're not special. You just have to have bits
> > [14:12] the same across all processes - we simply opted for clearing
> > them in order to keep the patch as simple as possible. But we could just
> > as well hashed the library name and generated the bits from it and thus
> > keep them same per library (we have that version too, btw. :)).
> > 
> > FWIW, in both cases, the patch should fix even the virtualization
> > scenario with and without KSM.
> > 
> > Does that answer your question?
> > 
> 
> I think the question was the width (and position) for the mask... i.e.
> your [14:12] above which *is* magic.

Oh, that's easy: family 15h means bits [14:12] - those bits are used for
I$ index generation.

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Boris.

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