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[Xen-devel] RE: [PATCH v2] Enable SMEP CPU feature support for XEN hype

To: Jan Beulich <jbeulich@xxxxxxxxxx>, "keir@xxxxxxx" <keir@xxxxxxx>
Subject: [Xen-devel] RE: [PATCH v2] Enable SMEP CPU feature support for XEN hypervisor
From: "Li, Xin" <xin.li@xxxxxxxxx>
Date: Sun, 5 Jun 2011 16:39:54 +0800
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Thread-index: AcwjU0w8vlsr1zIxRuCnN1Lck9yOlQAB+c7A
Thread-topic: [PATCH v2] Enable SMEP CPU feature support for XEN hypervisor
>I mean, I know we may as well just hide the feature from PV 64b guests
>totally. That's obvious. Let's stop talking about PV 64b guests already! The
>question is: what to do about PV 32b guests?

>Quite obviously we ought to allow 32-bit pv guests to control this for
>themselves (and hence see the feature).

That needs
1) inject SMEP faults back to the 32-bit pv guest.
2) let the guest see SMEP thru CPUID and config it in CR4 (actually it's 
already set, but just to let guest see it).

Anything else?

>Besides that, assuming Xin verified it's working, your latest patch
>looks great to me.

Yeah, verified, the system crashed from a SMEP fault from 64-bit pv kernel.

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