linux-kernel - Re: [PATCH 2/2] cpu: intel, amd: mask cleared cpuid features

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Message-ID: <20120724101041.GA24739@aftab.osrc.amd.com>
Date:	Tue, 24 Jul 2012 12:10:41 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	Andre Przywara <andre.przywara@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
	Borislav Petkov <borislav.petkov@....com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>
Subject: Re: [PATCH 2/2] cpu: intel, amd: mask cleared cpuid features

On Tue, Jul 24, 2012 at 12:29:19PM +0400, Vladimir Davydov wrote:
> I guess that when the more advanced features become widely-used,
> vendors will offer new MSRs and/or CPUID faulting.

And this right there is the dealbreaker:

So what are you doing for cpus which have the advanced CPUID features
leafs but there are no MSRs to turn those bits off?

You surely need some software-only solution for the migration to work,
no?

If so, why not apply that solution to your hypervisor without touching
the kernel at all?

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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