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Re: [Xen-devel] Mapping hvm guest pages in Dom0

To: Satya <satyakiran@xxxxxxxxx>
Subject: Re: [Xen-devel] Mapping hvm guest pages in Dom0
From: "pradeep singh rautela" <rautelap@xxxxxxxxx>
Date: Sat, 27 Sep 2008 03:55:24 +0530
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Sat, Sep 27, 2008 at 12:32 AM, Satya <satyakiran@xxxxxxxxx> wrote:
> hello,
> I would like to map (Read/Write) pages owned by a HVM guest from my Dom0
> Linux kernel module. I have access to the "machine frame numbers" of these
> pages.

Won't this make your HVM guest go boom?
After all you are changing the state of the pages *supposedly* owned
by a HVM domain.

> 1. What is the right interface to do this? kmap needs 'struct page' ptrs
> which I doubt exist for pages owned by a HVM guest. Is there a hypercall to
> do this then?

Do grant tables exist for HVM guests, I doubt it?
> 2. Do I need to modify the HVM behavior in any way for this? (e.g., load a
> driver in the guest that will setup grant tables?). I need to keep my guest
> "pure HVM".

pure HVM which knows that some pages are being used by the domain0
will essentially make them non pure I guess :).
BTW perhaps you can make sure that a HVM domain sees a region of
memory as shared with some other kernel. To do this you can write a
kernel module in the HVM domain( I hope it is linux ).

But this is all pure guess work, so please do not take my word. May be
you can think something better on similar lines. :)

> thanks,
> ./satya
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Pradeep Singh Rautela

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