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Re: [Xen-devel] update_va_mapping_otherdomain

To: <mhines@xxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] update_va_mapping_otherdomain
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sun, 09 Sep 2007 09:17:11 +0100
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There is currently no way to modify active page tables of another domain.

 -- Keir


On 8/9/07 19:27, "Michael R. Hines" <mhines@xxxxxxxxxxxxxxxxx> wrote:

> 
> So, if I would like to use dom0 to modify a specific L1 PTE belonging
> to another unprivileged domain, what's the best way to go about it?
> 
> Grant references? (on L1 page tables?)
> 
> Might I be able to get a quick pointer on the right sequence of hypercalls?
> 
> Much appreciated,
> - Michael
> 
> Michael R. Hines wrote:
>> ooooh, ok. I understand now.
>> 
>> Thank you very much for your response. =)
>> 
>> - Michael
>> 
>> Keir Fraser wrote:
>>> On 8/9/07 02:29, "Michael R. Hines" <mhines@xxxxxxxxxxxxxxxxx> wrote:
>>> 
>>>> Upon successful return from update_va_mapping (i.e. return code == zero),
>>>> my problem involves the last step mentioned above. The present bit still
>>>> remains unchanged (is still one), although update_va_mapping return true.
>>>> 
>>>> What might cause such a strange problem to occur?
>>> That hypercall allows you to update a *local* va mapping to map *another*
>>> domain's memory page. So you've mapped the guest's page somewhere random in
>>> your own address space.
>>> 
>>>  -- Keir
>>> 
>>> 
>>> 
>>> 
>>> _______________________________________________
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>>> 
>> 
>> 
>> ------------------------------------------------------------------------
>> 
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