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Re: [Xen-devel] Why CR0.WP is always set in HVM domain

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Why CR0.WP is always set in HVM domain
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 08 Nov 2007 14:43:57 +0000
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Thread-topic: [Xen-devel] Why CR0.WP is always set in HVM domain
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It's necessary because we need to trap guest writes to pagetables,
regardless of setting of guest CR0.WP. If it turns out we need to properly
emulate CR0.WP then we'll need to come up with a scheme that does not
require us to run the guest with real CR0.WP set. Possibly it will require
us to emulate certain memory accesses.

 -- Keir

On 8/11/07 14:23, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> In "arch/x86/hvm/vmx/vmx.c", vmx_update_guest_cr(), the CR0.WP is always
> set as following code:
>         v->arch.hvm_vcpu.hw_cr[0] =
>             v->arch.hvm_vcpu.guest_cr[0] |
>             X86_CR0_PE | X86_CR0_NE | X86_CR0_PG | X86_CR0_WP;
> 
> I'm wondering are there any special reason for this? I try to check
> shadow code and didn't find any clue.
> Can anyone give me some hints?
> 
> Thanks
> Yunhong Jiang
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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