RE: [Xen-users] Xen as virtual KVM

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

> -----Original Message-----
> From: Brandon Reno [mailto:brandonreno@xxxxxxxxx] 
> Sent: 26 June 2007 17:14
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Xen as virtual KVM
> 
> 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 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!
> 

What I was saying is that I don't think Dom0 will be easily made
headless, because the hypervisor relies sets up the VGA mode, and "owns
it" until Dom0 comes up - you may be able to get round this, but I'm not
sure. 

Just so that you understand it: It's perfectly possible to use ALL
versions of OS's as HVM domains, so you could just set up your Linux and
Windows domains to use HVM all the way - the graphics may not be as
snappy as you get on real hardware, but it's definitely usable for
testing purposes. And the advantage here is that you don't need any
"messing about", and you can even leave all of them running at once and
just click on the task-bar for which one you want to run at any given
time (or run several in parallel - you just can't see all of them if you
don't have a HUGE display on Dom0). 

--
Mats
> 
> On 6/26/07, Petersson, Mats <Mats.Petersson@xxxxxxx> wrote:
> 
> 
> 
>       > -----Original Message-----
>       > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
>       > [mailto: 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
>       >
>       >
>       
>       
>       
> 
> 
> 



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