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Re: [Xen-devel] Is it possible that Xen starts without Domain0

To: "Hu Jia Yi" <jyhu@xxxxxxxxx>
Subject: Re: [Xen-devel] Is it possible that Xen starts without Domain0
From: "pradeep singh rautela" <rautelap@xxxxxxxxx>
Date: Fri, 7 Sep 2007 10:13:55 +0530
Cc: kevin.tian@xxxxxxxxx, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, eddie.dong@xxxxxxxxx
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On 9/7/07, Hu Jia Yi <jyhu@xxxxxxxxx> wrote:
> Hi,
> Dom0 itself is a virtual domain. I think the function of HVM should not

yes it is but it is a special domain which enjoys priviliges like
creating and controling other domUs and direct access to hardware
through device drivers. In short hypervisor trusts dom0 and grants
exclusive hardware access to it.

> depend
> on the dom0. So the question is if without any interference from dom0,
> how Xen
> helps HVM to function, such as creating a virtual disk for HVM, PCI,
> VGA, etc.

But still someone need to communicate with the actual hardware
devices. Who will do it then if there is no privileged domain which is
trusted by hypervisor?
All the preliminary setup a HVM needs is done by the dom0.

In short yes you may need heavy modifications to the hypervisor if you
want HVM to directly boot without any dom0. And i guess that would
mean moving a lot of stuff from dom0 to hypervisor just to make sure a
HVM boots directly :-/. Too much of overkill i think.

May be somebody else(Keir, Matt??) explain it in a correct way.

> Does this need modification of xen?
> Best regards,
> Hu Jia Yi
> Ext: 20430
> Tel: 65-67510430
> -----Original Message-----
> From: pradeep singh rautela [mailto:rautelap@xxxxxxxxx]
> Sent: Friday, September 07, 2007 12:18 PM
> To: Hu Jia Yi
> Cc: xen-devel
> Subject: Re: [Xen-devel] Is it possible that Xen starts without Domain0
> On 9/7/07, Hu Jia Yi <jyhu@xxxxxxxxx> wrote:
> > I have a question which may sound stupid.
> >
> > Is the dom0 mainly responsible for administration of other VMs?
> > If a PC only needs running HVM and doesn't need any administration, is
> > it possible that Xen doesn't start dom0 but setup VM environment and
> > start-up HVM image?
> I am not sure if that is possible, but i doubt possible atleast right
> now.
> hypervisor itself is pretty thin and minimal and does not contain most
> of the drivers.Directly booting a HVM(e.g a linux kernel on XYZ
> distro) means giving hardware control to that HVM drivers which is not
> something intended. What happens if there are two HVM?
> Thanks
> --psr
> >
> > What modification do I need, such as drivers, memory management, file
> > systems?
> >
> > Best regards,
> > Hu Jia Yi
> > Ext: 20430
> > Tel: 65-67510430
> >
> --
> --
> pradeep singh rautela
> "question = ( to ) ? be : ! be;"
>                 -- Wm. Shakespeare

pradeep singh rautela

"question = ( to ) ? be : ! be;"
                -- Wm. Shakespeare

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