> Thanks for the info. I was unaware of the issue with PCI-passthrough and
> HVMs. As for the dom0 I don't think it would be a problem to leave it
> headless.
As it stands, dom0 is going to grab your primary graphics card when it comes
up. There's not any way to stop it at the moment, so to pass through
graphics you'd need another card.
Some folks are working on PCI passthrough to HVM domains without requiring
special hardware, but it's not available yet (and I'm not clear what
limitations there will be).
suspend / resume won't work reliably for a domain which has passed-through PCI
devices anyhow, so there's not a straightforward way to dedicate the graphics
hardware to a domain and still be easily able to switch to other OSes - even
if you could get graphics passthrough to work :-(
If you can get 3D working in dom0 then you'll be able to run Compiz Fusion in
dom0. I'd recommend you use the SDL / VNC interfaces to the various
domU's /virtual/ screens in order to interact with them. The performance
isn't as good as native, but it works and will be less hassle than trying to
do passthrough. For the moment you won't get particularly good graphics
performance out of them though (certainly no 3D, I'm not sure if playing
videos would work or not...).
Cheers,
Mark
> As for wanting to set up a keystroke for the switch, I'd like to
> be able to switch while the 'active' domain is locked, logged out, etc.
> But for now, it would probably be just as easy to set up a remote interface
> on the dom0 for switching.
> Adding the Windows VM's is a long-term goal of the project, and I'd be
> willing to wait for that feature. (My wife has an aging Windows desktop
> that I generally keep my hands off of)
> Again, I'll track my progress with this venture, and post my experiences on
> the wiki once I'm done.
> Thanks for your help!
>
> On 6/26/07, Petersson, Mats <Mats.Petersson@xxxxxxx> wrote:
> > > -----Original Message-----
> > > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> > > [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> > > Brandon Reno
> > > Sent: 26 June 2007 15:28
> > > To: xen-users@xxxxxxxxxxxxxxxxxxx
> > > Subject: [Xen-users] Xen as virtual KVM
> > >
> > > I'm looking at doing something that may seem a little bit
> > > odd, I would like to use xen to virtualize several desktop
> > > environments, with a specific keystroke configured to switch
> > > to that environment.
> > > I will have either gentoo or debian as a dom0. this will be
> > > used only for management of the virtual machines.
> > > I will have several full desktop environments for different users.
> > > For example, I will be using Gentoo with KDE/Beryl (soon to
> > > be Fusion or whatever they are changing their name to)
> > > I'd like to have a test environment for various trials of
> > > different other flavours and for development
> > > Additionally, I will be buying a new computer, supporting
> > > AMD-V, will want to have 3 additional environments, Windows
> > > XP and Vista, for application testing, and one Windows DE for my Wife.
> > >
> > > To accellerate as much as possible the different
> > > environments, I would need to setup the PCI video card to
> > > passthrough to whichever domU is active. It is not necessary
> > > for more than one environment to be active and running at any
> > > given time.
> > > My theory is to simply configure each environment to pass
> > > through the video card, and drop one environment (suspend?),
> > > and switch to the next. Do you see any problems with this
> > > configuration, or have any advice?
> >
> > You can do it with VNC/SDL in fully-virtual domains with a virtual
> > graphics card. That's a (nearly) no-brainer.
> >
> > But unless you have at least two graphics cards in the machine, Dom0
> > will need to own the graphics card - it uses the VGA as console during
> > startup at the very least. So you need a second graphics card to start
> > with. I've seen complaints that pass-through of graphics doesn't work,
> > but don't take my word for it.
> >
> > Using PCI passthrough, you would definitely have to suspend ("xm save")
> > the domain and resume another ("xm resstore") when switching from one
> > domain to another. Note that this takes several seconds per save/restore
> > cycle for any reasonable size domain - just writing 128MB to the disk at
> > 50MB/s takes 2.5s or so, and there is more work than this involved in
> > the save-process.
> >
> > HVM domains (Windows for example) can't use PCI passthrough, at all, at
> > this time (there's work to allow ONE instance of Windows to do that -
> > but that's still some way off, and I wouldn't rely on this for the next
> > 3-6 months at least, although I'm not sure how far off it really is).
> >
> > > Additionally, I would need to write a program or series of
> > > scripts to manage the switching of DEs, which doesn't seem to
> > > be too much of a problem, except that it would need to
> > > capture a few specific keystrokes (i.e. win+f1 thru win+f5)
> > > to actually call the switch.
> >
> > Why? What's wrong with clicking buttons/menus or typing into a window
> > someplace?
> >
> > > I'm not sure where I would need to start to do this should
> > > this program monitor /dev/input for the keypress, or would
> > > this need to go into the hypervisor?
> >
> > That's a good question - Dom0 doesn't (strictly) own the keyboard, but
> > you'd certainly have an easier task intercepting this in Dom0 than you'd
> > have in the Hypervisor, since the hypervisor won't actually be able to
> > make the switch happen anyways, so you NEED to get to Dom0 someway
> > anywyas to achieve this.
> >
> > --
> > Mats
> >
> > > I currently have a few VMs on my server computer running
> > > things like a webserver, samba share, Kerberos
> > > Authentication, etc. and have been very happy with xen. I'd
> > > like to take the chance to document my findings on this
> > > unique setup in case someone else would be interested.
> > >
> > > Any advice would be appreciated, or better yet, if someone
> > > has done something like this, I'd like to hear about their
> > > successes/failures.
> > > Thanks,
> > > Brandon Reno
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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