RE: [Xen-users] Xen on AMD64 with Desktop on domU

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Samir Mishra
> Sent: 20 April 2006 13:03
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Xen on AMD64 with Desktop on domU
> 
> In one of the documents, I read, it indicated that, for 
> example, if I had 2 PCI network cards, and I wanted to have 
> domU manage one of the cards directly, there's a way of 
> telling Dom0 to not manage the card in question. Is it 
> possible to do something similar with the AGP adapter 
> bus/card? But, given I actually get this to work, how do I go 
> about getting desktop domU to gain control of tty7 (or 
> whatever, since all consoles are (I believe) controlled by 
> dom0. In other words, I'd like to have a direct pass-through.

Yes, that would work in theory - although you'd have to have two
different monitors (or a monitor switch or a monitor with two inputs to
switch between) as the video output would come out through two different
connectors. So your graphics would be out of the nVidia card and the PCI
graphics card would be your Dom0 output. 

However, I very much doubt this will work in actual practice [as I once
read: In theory, there's no difference between theory and practice - in
practice there is...] The difficulty would be to have a driver that is
"Xen-clean" or "Xen-aware". Since the low-level driver for the graphics
card is a kernel driver, it will have access to all sorts of
kernel-internal information, and some of this is managed by Xen and
should not be used directly by for instance a driver. Xen fixes this by
patching [changing some macros in header-files is the key part of this]
the kernel drivers that are included in the kernel itself. But the
nVidia drivers are closed source, so they are not patchable by this
method...

> 
> Could I achieve something similar by installing Xorg in dom0 
> and domU and running XDMCP to connect to domU? This would 
> mean a more complicated package management scenario. I guess 
> it all depends on how well the nvidia drivers play with Xen.

I'm not familiar with XDMCP, but you can certainly use any method that
uses networking to transmit the X drawing commands to your Dom0...

--
Mats
> 
> Any thoughts?
> 
> SM
> 
> Petersson, Mats wrote:
> >> -----Original Message-----
> >> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> >> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Samir 
> >> Mishra
> >> Sent: 20 April 2006 12:00
> >> To: xen-users@xxxxxxxxxxxxxxxxxxx
> >> Subject: [Xen-users] Xen on AMD64 with Desktop on domU
> >>
> >> Hello.
> >>
> >> I'm doing a fresh install of Xen on an AMD64 using Gentoo. 
> I have an 
> >> nvidia graphics card. Dom0 will be a minimal system 
> install without 
> >> Xorg or any other GUI applications. I'm hoping to set up 
> Xen with 3 
> >> guest domains -- one running servers for the network (ntp, dhcp, 
> >> bind, yp, etc.), one guest domain running my desktop with Xorg and 
> >> the third guest domain to be used for development & testing.
> >>
> >> What I'm hoping to find out is --
> >> 1. does the above make sense?
> >>     
> > In theory yes. In practice, it doesn't work. See below. 
> >
> >   
> >> 2. I want to access the X-server on the desktop domU directly on 
> >> tty7.
> >> Is this possible? If so, how can I do this?
> >>     
> > No. The X-server needs to be the OWNER of all the graphics 
> card, and 
> > your Dom0 takes ownership of the graphics card very early on.
> >
> > There is two solutions that come to mind:
> > You could perhaps use a simple PCI graphics card for the 
> Dom0 console, 
> > and then give the DomU the nvidia card, but any shared 
> hardware must 
> > be managed by one Domain only (and everyone else talking 
> through that 
> > domain to get access). Of coruse, this assumes that there 
> is an nVidia 
> > driver that works under Xen, which I don't think exists 
> (yet) - and I 
> > very much doubt that native kernel graphics drivers will 
> work "out of 
> > the box" - as they probably do all sorts of "nasty" things that Xen 
> > needs to be aware of.
> >
> > Or you can use vncserver/vncviewer to access your desktop machine.
> >
> >   
> >> 3. what are the things I need to watch out for?
> >>     
> >
> > See above. 
> >
> > [Snip other questions that I can't really answer anyways]
> >
> > --
> > Mats
> >
> >
> >   
> 
> 
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