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Re: [Xen-devel] How to get guest PTEs info of a HVM with EPT

from [Tim Deegan]

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To:	KennyChen <windtracekimo@xxxxxxxxxxxx>
Subject:	Re: [Xen-devel] How to get guest PTEs info of a HVM with EPT
From:	Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date:	Thu, 20 Jan 2011 09:44:37 +0000
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At 02:50 +0000 on 20 Jan (1295491817), KennyChen wrote:
> When EPT is enabled for a HVM guest, is that possible for hypervisor
> to get the PTE information of guest page table? e.g, R/W, Supervisor
> flags? 

Yes, of course - you know the guest's CR3 value and you can map all its
memory so you can read its pagetables.  Look at hap_gva_to_gfn() and 
how it calls guest_walk_tables().  You can even do it from userspace 
in dom0 - see xc_translate_foreign_address().

What you can't do easily without shadow paging is _control_ the
pagetable values.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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