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Re: [Xen-devel] [PATCH] Proper use of VMX execution controls MSR.

To: "Li, Xin B" <xin.b.li@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Proper use of VMX execution controls MSR.
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 29 Mar 2007 08:41:17 +0100
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Thread-topic: [Xen-devel] [PATCH] Proper use of VMX execution controls MSR.
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Okay, I see. Well, that makes sense but I think we should have two masks for
each control word -- the bits we would like to set, and the bits we must be
able to set. Also your previous patch added an unnecessary AND with 'msr_hi
XOR msr_lo'.

This is pretty trivial to fix up. I'll do a patch.

 -- Keir

On 29/3/07 07:22, "Li, Xin B" <xin.b.li@xxxxxxxxx> wrote:

> But we have lots of
> hardware features,
> with new features being added to hareware, and I really don't like to
> add the almost
> same code just for another new feature detection.  The idea here is to
> use the control MSR
> to adjust the input controls we _hardcoded_ in Xen, for the features
> we've supported in Xen,
> we always set to 1 in the input control, like in
> then on processors supporting this feature, We get 1, while on
> processors not supporting this
> feature, we get 0.  This adjusted output control value can be also used
> to choose code
> path on different processors, and the attached patch can be an example.

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