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Date: Tue, 17 May 2011 13:50:41 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Avi Kivity <avi@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Fenghua Yu <fenghua.yu@intel.com>,
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        linux-kernel <linux-kernel@vger.kernel.org>,
        Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH v2 0/4] Enable SMEP CPU Feature
Message-ID: <20110517115041.GF13475@elte.hu>
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* Avi Kivity <avi@redhat.com> wrote:

> On 05/17/2011 02:44 PM, Avi Kivity wrote:
> >On 05/17/2011 02:38 PM, Ingo Molnar wrote:
> >>>
> >>>  Depends if the guest uses a read-modify-write pattern or not.
> >>We could do it
> >>>  transparently in kvm.ko, since the real cr4 need not
> >>corresponds to the guest
> >>>  notion (for example, we often set cr0.wp or cr0.ts even
> >>though the guest
> >>>  wants them clear).
> >>
> >>Oh, being transparent is a nice touch when it comes to security measures
> >>(catching attackers who think there's no SMEP and such) - but
> >>that would need
> >>KVM support and a new ioctl to configure it, right?
> >
> >Yes.
> >
> 
> btw, KVM support is required anyway, you can't set random bits in
> cr4 (from either the guest or host userspace) - kvm needs to
> understand them.

Sure, that is the whole premise of this discussion.

I meant to say:

 "but that would need KVM ABI support via a new ioctl to configure it, right?"

Thanks,

	Ingo