Can some one explain Xen and KVM

Hello
I just purchased a new xps 15 which will have a GeForce gt750m. I was playing with the idea of running Linux on it but I want to game and I need certain windows apps. I came across the idea of type I hypervisor (i.e. xen) which I would use to run a windows 8 and Linux environment (Kubuntu). After a lot of looking, I'm really confused about the graphics card compatibility. Ideally, I would like to use bumblebee in Linux and Optimus in the windows environment; however, if this is not possible, then I would not mind sacrificing the extra power in Linux and run both the NVidia chip and integrated graphics in windows with Optimus?

 

I don't know about KVM*, but first of all if you're thinking of making use of VT-d GPU passthrough with Xen, you need either an AMD graphics card or a fairly high-end Quadro. Geforces and entry-level Quadros do not work with GPU passthrough - it's believed that Nvidia purposely blocks it in the video BIOS.

Secondly, your CPU, chipset, and motherboard all have to support VT-d, regardless of what hypervisor you choose. I don't know about the XPS 15, but VT-d is rarely available on consumer notebooks.

Thirdly, I hate to say this, but it ultimately may not work. At least with Xen, GPU passthrough passes through the entire GPU. I know that sounds really obvious, but you'd be surprised at how many people don't fully realize that the entire GPU includes things like the DVI/HDMI output ports and what the implications of that are, so I'll state it explicitly just in case: when you pass the GPU through, you need to connect a display directly to the GPU in order to see anything on the VM. On a desktop computer, this just means reaching behind your PC and moving the VGA/DVI/HDMI/DisplayPort cable from your integrated graphics to your discrete GPU, but on an Optimus/Enduro laptop where there might not even be a physical connection between the discrete GPU and the outside world, there might not be anything to connect to, if you get what I mean.

Finally, just so that I don't completely crush your hopes, Citrix has a Xen-derived product called XenClient for precisely this kind of scenario. It's not free, though.

* I've heard that KVM has better support for Geforce passthrough than Xen nowadays, but this is just hearsay for you to follow up on, if you wish. I've never used KVM before so I can't help you there.

 

VGA Passthrough with KVM

You will probably have more success with KVM rather than XEN VGA passthrough with an Nvidia card.

Some tips for running a Windows Guest under KVM.