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Re: [Xen-devel] Passing a grant reference to another domain!

To: "Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx>
Subject: Re: [Xen-devel] Passing a grant reference to another domain!
From: Daniel Stodden <stodden@xxxxxxxxxx>
Date: Mon, 18 Aug 2008 13:41:58 -0700
Cc: Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Tue, 2008-08-19 at 03:27 +0800, Jayaraman, Bhaskar wrote:
> Hi can anyone point me to the code which passes grant reference between 
> domains?

>  In Mini-OS it doesn't seem to be used and I'm a little clueless where to 
> look for passing of reference.
> I am aware of the way a grant table is mapped, how to use the ring buffer 
> once you map the shared memory page 

> into your domain using the reference and the domain id, and how to read and 
> write into the xenstored database.

>  However, I'm struggling to understand how we pass the grant reference to a 
> particular domain once 

> you share a page after setting necessary access permissions on the page.

XenStore's typically used for bootstrapping shared memory. For generic
I/O rings, it's sufficient to set up sharing of the ring itself. In that
case, a frontend allocates the shared page and puts that reference into
an xs location watched by the backend.

Beyond that, further references would be typically be sent as messages,
but when and how many clearly depends on the application and protocol.
See e.g. the sector segment descriptors in
xen/include/public/io/blkif.h. Similarly for io/netif.h, but blkif is


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
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B

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