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Re: [Xen-devel] Can't map the page referenced by HVM-DomU CR3 in Dom0

To: david <david_n@xxxxxx>
Subject: Re: [Xen-devel] Can't map the page referenced by HVM-DomU CR3 in Dom0
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Mon, 18 Apr 2011 10:34:09 +0100
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At 14:45 +0100 on 15 Apr (1302878734), david wrote:
> I'm trying to access the page containing the paging information for a 
> DomU from Dom0.
> I'm doing that by translating the address contained in the DomU CR3 
> register with xc_translate_foreign_address (libxc) and try to map the
> returned frame number with xc_map_foreign_range.
> The problem is, that the return value from xc_translate_foreign_address 
> is 0 (guest cr3 is 0x002f3000 in my case), which indicates an error 
> (corresponding to the code comments). After some debugging I have 
> discovered, that pte becomes 0 when level=2 and therefore the function 
> returns 0 on line 79:

How often does this happen?  On every attempt or only from time to time?
Have you checked (say, from inside the guest) that the level-2 PTE isn't
actually zero?



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

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