Re: [Xen-devel] Sharing machine pages among domains

["Haifeng He" <hehaifeng2nd@xxxxxxxxx>]

On 11/20/07, Daniel Stodden <stodden@xxxxxxxxxx> wrote:
>
> On Tue, 2007-11-20 at 20:26 -0700, Haifeng He wrote:
> > Hi,
> >
> > I have another question about memory sharing among domains(domUs). I know
> that
> > grant table can be used for memory sharing. But my question is if it is
> possible
> > to setup memory sharing before domain starts. For example, suppose
> > I have 2 domUs: A and B. Before A and B are booted, is it possible to map
> > certain physical pages of A and B into the same machine pages? Any
> comment?
>
> yes, this is possible. quite a number of pages get 'shared' that way,
> e.g. the console and xenstore mfns. see e.g. the definition of the
> start_info struct in the xen headers and see e.g. the domain builder
> code (tools/libxc/xc_(linux|*)_build.c) on how this is set up from dom0.
> you might just need to add a few lines to get what you want.
>

Thank you for your reply. I checked the above code.
If I understand correctly, the page sharing of console and xenstore is
between dom0 and domU instead of between domUs. Secondly,
the mapping is one to one, i.e., one mfn page allocated to domU
is mapped to dom0. However, what I am looking for is, probably one to many
mapping. That is, one mfn page can be mapped into physical page in
multiple domUs and shared by them. Any idea?

Thanks

Haifeng

> regards,
> daniel
>
> --
> Daniel Stodden
> LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
> Institut für Informatik der TU München             D-85748 Garching
> http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
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>
>
>

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