RE: [Xen-devel] Grant Table Hyper Calls For Sharing Memory

["Kumar, Venkat" <Venkat.Kumar@xxxxxxx>]

I think that sharing page includes both offering the page and mapping the page. 
How can a foreign domain use the shared page without mapping the page from the 
obtained grant reference number? And for mapping a page you have to have a 
hypercall defined.

Thx,
Venkat

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Daniel Stodden
Sent: Wednesday, August 20, 2008 12:08 PM
To: Xen Developers
Subject: Re: [Xen-devel] Grant Table Hyper Calls For Sharing Memory

Hope I'm not mistaken, but I believe this discussion only revolves
around the fact that you don't need hypercalls to *share* pages. The
gnttab hypercall interface is only needed to *map* shared pages, not to
let other domains access a hvm's memory.

Sharing a page only requires the owner to set appropriate permissions in
her own grant table. That's just a bit of store and cmpxchg. No
hypercalling involved.

Cheers,
Daniel

On Wed, 2008-08-20 at 14:03 +0800, Kumar, Venkat wrote:
> I was following an email chain in the xen mailing list on HVM
> hypercalls on grant tables and the email chain link is below
>
> http://lists.xensource.com/archives/html/xen-devel/2007-03/msg00688.html
>
>
>
> This link says that we need not required hypercalls to share memory
> b/w HVM's.
>
>
>
> But as far as my understanding of sharing memory is concerned, I think
> the memory is shared using grant table mechanism and we would need
> Hypercall support related to grant tables to make this possible.
>
>
>
> Correct me if I am wrong.
>
>
>
> Or is there any other way of sharing memory or Inter domain
> communication?
>
>
>
> Thx,
>
> Venkat
>
> ================================
>
> Venkata Kumar Duvvuru,
>
> LSI Engenio,
>
> Adv. Development,
>
> Bangalore.
>
> Mob: +91-9880318542
>
> Off : +91-80-41978700 ( Extn : 3544 )
>
> ================================
>
>
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>
>
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--
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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