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Re: [Xen-devel] [PATCH] Implement rdtscp emulation and rdtscp_aux "suppo

To: Jan Beulich <JBeulich@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Implement rdtscp emulation and rdtscp_aux "support"
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 26 Nov 2009 09:31:36 +0000
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On 26/11/2009 08:15, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> I realize that my comment really applies to your earlier patch introducing
> rdtsc emulation, but somehow that aspect slipped my attention back
> then: Linux has, as a security option, a mechanism to disable rdtsc for
> apps, but your emulation code doesn't honor the guest setting of
> CR4.TSD.

I'll fix this. While I'm at it, I think our PV emulation of MOV CR4,reg is
broken -- should just return v->arch.guest_context.ctrlreg[4], would you
agree? Otherwise guest's CR4.TSD isn't returned.

 -- Keir

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