From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [Patch v5 1/4] Remove SMEP bit from CR4_RESERVED_BITS
Date: Mon, 30 May 2011 10:52:32 +0200
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Cc: "Yang, Wei Y" <wei.y.yang@intel.com>,
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To: Avi Kivity <avi@redhat.com>
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* Avi Kivity <avi@redhat.com> wrote:

> > Another option would be to try to set the SMEP bit *before* we 
> > enable paging. In theory this should not confuse a Linux guest - 
> > and while i have not tested it i *think* we let it survive in the 
> > saved_cr4_features shadow variable. That would make guest 
> > suspend/resume work out of box as well.
> 
> Is there any reason not to do it in a hidden way in kvm?  Why must 
> we play tricks?

So do you have a suggestion of how to do this cleaner?

Add an ioctl that allows a VCPU to be configured in a way to set a 
cr4 feature without the guest actually seeing that bit? [Assuming 
both cr4 reads and writes are fully captured by KVM and thus guest 
behavior is controllable.]

Thanks,

	Ingo