For Windows guest - KVM or XEN and which distro for host?

two boxes

Would never ever use a box for working AND games, especially if somebody else is fiddling with it.

Also I am not convinced that an virtual machine can run a game smoothly enough, no matter what hardware used.

I think I would use a dedicated Linux box with the needed hadware, store it safely where no one can get to it and access it cheap and dirty via VNC...

I would suggest staying away from KVM and going for Xen instead. KVM a crap support when it comes to USB as far as my experience is concerned. KVM is the most resource efficient, but Xen is a lot more stable and mature. It also works a lot better for USB and PCI devices.

Be very careful on what hardware you get and make sure you research it's support for PCI sharing, as this will be the most difficult bit and is what will make or break your rig, so to speak.

ATI as the lousiest support for visualization in the world, so I'd suggest sticking to Nvidia cards for graphics.

Sounds to me like Robolinux may be your answer

I don't know much about http://robolinux.org/, but I have installed it with the view of testing it out.

Solution to the Space problems

I Think you should opt for the two machine solution.

Having kids have access to a production machine is suboptimal (to say the least).

Regarding your no-space-for-a-second-machine-problem: Just strap it under the ceiling. Two U or Z shaped brackets should do the trick.

The way you don't need to worry. Your kids can toy with your windows machine. Your linux-machine is safe and sound out of their reach.

KVM is your best option, if you insist on your requirements

Whilst I'd suggest Linux on Windows is your best option overall, if you insist on your requirements KVM is the best option.

Xen is a great piece of software, but in the region of VGA passthrough it is decidedly inferior to KVM. Yl not get any support if it does not work.

Xen supports only Quadro devices for reliable passthrough. KVM supports AMD and Intel, but you will need a very recent Linux kernel (3.12+) and patches, plus a recent, patched Qemu. Google 'vfio VGA reset'

Be very careful with your hardware choices and read around the subject first. Also, read the motherboard manual cover to cover before purchase. My motherboard, for instance, supports graphics cards at 4x PCIe speed in only one slot - all others are limited to 1x by the chipset.

Also be careful of USB passthrough. In Linux/Windows it mostly works. In BSD it does not - you have to do a VTd passthrough rather than a single device passthrough in Qemu. You cannot usually pass through a single port due to iommu groups. USB works through allocating a pool of resources to a certain number of ports. Again, on my motherboard I have five USB ports. These can be passed through in two iommu groups - so 2/3 or similar? Wrong! 1/4, or 4/1!

I'm doing this because I'm enjoying fiddling with low level Linux, virtualisation and I'm stubborn. It's still leading edge stuff and you can expect to encounter pain. Be very familiar with iommu groups, PCIe bridges, FLR, VT-d and if your cards support various types of reset before you buy any hardware.

It does work, incidentally!

Just beware you'll have issues. On Windows Catalyst must be installed manually by selecting the driver, then installing the CCC MSI. Running the install always results in a blue screen.

It is fast enough to run games. You'll have to fiddle to get the best disk performance - use the virtio drivers. If anyone is trying to run older OS, be aware that KVM/Qemu creates a VM which is quite similar to a Q35 chipset, but with differences. With ancient OS you may need to use the Qemu 'pc' architecture (440LX). It may also be necessary to use a CPU type of qemu64 or qemu32 in some cases rather than 'host' or enabling KVM

Remember that the VFIO or pcistub driver is separate from KVM. Passthrough works without it. KVM only provides acceleration, which is usually (but not always) faster.

The virtual PC that KVM, Qemu and Xen create is similar to a real PC but it is not the same. OS/2, for instance, does Weird Shit(TM) on install (to be precise, non mainstream OS may tickle VMs in a way that's entirely valid on real hardware but freaks out the VM).

If I was doing this professionally, I'd use Xen and stick to a released version ideally without VGA passthrough. Xenserver is now free and a nice piece of kit.

What I really should have done is to buy a dual Xeon system, with a quadro and run Xen. What can I say, I'm waiting for Haswell-E before upgrading and spending lots of money. In the meantime I'm running an unusual Core2Quad system with a 6950 (pre Nehalem VTd works, but has no interrupt remapping).

Avoid btrfs

It's not really ready yet. I tried it out for a while but went back to ext4 after and unrecoverable filesysten corruption (and there's still no fsck tool).

No objective

If you aren't clear about what it is to do how can you make a choice?

It seems to be about trying this or trying that.

Maybe a simpler solution,

If you have limited disk space, but are happy to spend on hardware, then the solutions is to have a box under the desk running a headless Linux configuration and then replace the keyboard, monitor and mouse with a laptop with windows running on it, and make sure that the laptop is good enough to run your games. If desk space is at too much of a premium move the laptop to somewhere else in the house with more space?

always go with as simple solution as possible, as if there is a problem with hardware you could loose both systems!

By the way PCI passthrough works fine with ESXi. I'm using ESXi as my host machine, and passing through the Video Card to a Windows VM. Setup the VM to auto start when ESXi starts up, so as soon as it loads it automatically starts the VM and on screen you see the windows VM. Also passing through USB ports to plug in keyboard, mouse, and an external hard drive. All has been working perfectly for the last year or so.

Cloud?

How about build yourself a small gaming rig. Mid range CPU and a fast graphics card.

Get yourself an account with your Cloud vendor of choice with a nice Linux build on there.

2 Box solution

A late entry but I'd support the two box solution. You say you don't have space for two boxes, you could easily fix a bracket under the back of your desk to mount a netbook running ubuntu server, it'll just sit there out of the way. Even wall mount it, it's only the space of a book. I've been running such a setup for quite few years. Your family get a full blown windows machine and you get a decent linux server. Quite honestly I don't understand why you would even consider all the faffing about trying to do this with one box.

Space

If space for a 2-box solution seems problematic, how about something that will hang on the VESA mount on the back of the monitor:

http://www.fit-pc.com/web/products/mintbox/

http://www.solid-run.com/

etc etc etc

Specifics

When you say you want to be able to play games on the Windows side of things, is there any chance you could give an example of the sorts of games being played, and how well (graphically,) do you want to run them?

Also how big of a space have you got for the computer? If you do decide to go down the two computer route, how about this case? http://www.mountainmods.com/u2-ufo-duality-mirror-black-powder-coat-solid-top-p-390.html

Would running Windows as the host with VMware being able to allocate physical memory and processors negate the issue you have with Windows taking resources away from the Linux install?

Are you looking at the problem the right way?

Correct me if I'm wrong, (I know I probably am ;o)) but I have been intrigued by this discussion since I first read it 12 hours ago.

What you basically want is:

1. A PC which is capable of running some windows software and allowing the OS to see "decent hardware".

2. You normally prefer to use Linux for a working platform but are happy to access it via SSL.

3. You have a serious space limitation which apparently precludes multiple computers.

4. Your budget for a perfect solution is potentially quite high.

Looking at the replies you've received there area lot of brighter people than me out there with good ideas about how you can do what you want with the technology available, but many are basically saying "Virtualisation isn't there yet". Also some of them are really saying - you need 2 computers.

I know this sounds strange but have you considered putting 2 complete computers in the same case? Even building them into your desk like the Power Desk concept from the early 90s might work.

Think about it, get a couple of cheap cases cut them up and fit them into the space available. Build computers in those cases, including appropriate hardware, clad exterior in metal, or even wood, paying particular attention to really good airflow. Get a KVM for those rare times when you actually want to log onto the Linux box directly.

Screw it to the desk to make it harder to nick, problem sorted.

Or am I talking b#@*@~ks?

There is an alternative.

If you had an AIO- All In One (built into the screen, so no more space required) computer running windows, and connected via network (wireless if desired) to the Linux computer to run ssh in a window from the windows box. This way, you would have your Linux stack running natively and your windows machine running natively. If required, you can connect the Linux video via HDMI to your AIO monitor and use ur wiress keyboard and mouse. However, it does still seem the long way home (more expensive).

Again, the specifications seem arbitrary. If you could state specific objectives (compile whole linux distro and build into package over night or in 4 hours.

The more I read this thread the OP is hell bent on having linux run as close to bare metal as possible. This solution achieves that desire. What I would do and I agree with most posts saying run Windows (2000 - 8.1-depending on task) and then Linux in a VM such as Virtual Box. That is the easiest and most usable route. I like having an XP VM just in case. Since it doesn't get any more updates, it is very stable for private a network.

The reason so many advocate this solution is that windows graphics run best on a windows machine. The VM video interface just works better for that combination with windows as the host. Most video cards/ devices are designed to run DX* (windows API). Using DX* to emulate OpenGL is easier as more info is available. Since the GPL conflicts with IP ownership to most graphics companies, they are not real keen on supplying chip level commands/access/ documentation. Without access to the hardware documentation, Linux drivers have trouble supporting the windows DX* graphic API. Yes I heard Nvidia say they are going to play nicer. Wake me up when you see a finished combination. Yes they support Open GL, which is great.

You've got two mutually conflicting issues. By far the simplest way to solve it is to have two machines. Bit of lateral thinking.. literally. Bolt the linux box to a wall shelf, side on, out of the way.

http://www.overclock.net/t/1205216/guide-create-a-gaming-virtual-machine

Personally,CPU wise the Core i7 3960X seems best [Supports VT-d (C2 STEPPING ONLY)], which is probs what i'd go for.

6 cores/ 12 threads and 3.3/3.9ghz{boost}

whatever you decide, Sandy Bridge-E/EN or EP is the way to go imo, If you opt for Ivy Bridge read up on the overclocking problems associated with the cheap TIM paste they used!

Update

So, the hardware is ordered.

All should work well with VGA passthrough and even if virtualisation turns out to be too difficult, it's going to be some nice Linux server (and a GPU for my old PC)

* SuperMicro X9DA7

* 2x Xeon E5-2630V2

* Kingston DDR3 PC-1600, Registered ECC

* Sapphire Tri-X R9 290X

I guess, if I really have to make this Linux a separate server; I can always put in into 2U rack case and slide under a bed ;D

I have no experience with xen, but at least the kvm information says that while device passthrough is supported, video card passthrough is NOT. A few people have managed to get it to work with some patching work done.

I do see some documentation on it having been done successfully with xen however.

I agree with other people on BTRFS. The developers say it isn't ready for production use. Of course if your machine is just to run games and do some hobby work, then that might be good enough.

I too would avoid AMD graphics cards. I also personally am a Debian fan, and have no interest or appreciation for the commercial linux distributions.

what solution have you chosen in the end?

Bronek Kozicki - I have registered on this forum only to ask this: I am very curious, what solution have you chosen in the end? googling 'xen vs kvm for windows' gives this thread the first result! :)

Back in 2007 when I bought my current PC, having your exact identical needs (except that I don't patch gcc but run some programs on linux - proxy, firewall, other vms - and want a single box for energy costs) I wanted pci/vga pasthrough but it was in infant stage.

Now that pci passthrough seems more mature and I'd like to try it again. From the thread I've collected most opinions pro-Xen-based solution (xendesktop, xenserver, xen hdx, oracle jeos, centos, debian), one esxi and one kvm. I'm quite interested in the final choice.

lots of time have passed

.... for those who wonder what I've chosen in the end : I've been successfully running for nearly a year following stack:

• Arch Linux running as a headless hypervisor, where I configure, build & sign my own packages for software stack mentioned below, when and as I feel like upgrading them
• kernel build closely following current version from www.kernel.org , only little behind for sake of ZFS on Linux (currently 4.0.9, waiting for ZOL release 0.6.5 before upgrade to 4.1)
• ZFS on Linux, current release + occasionally a patch or two (currently 0.6.4.2 with single patch from pull request 3344)
• kvm with vfio GPU passthrough, AMD GPUs passed to Windows 7 (two GPUs, two Windows 7 VMs, plus some more VMs without GPU, all have qemu-agent installed). Linux console on serial port only (and of course ssh access). Linux radeon drivers are blacklisted
• qemu currently version 2.3.0 will upgrade soon to 2.4.0 (or perhaps 2.3.1, if I do not like it)
• libvirt with libvirt-guests to start and shutdown the VMs at the right moments. Patched libvirt-guests a little to use --mode=agent when shutting guests down
• VMs disks are setup as ZVOLs on ZFS, all VMs are snapshotted every now and then (alongside with user files, below)
• A filesystem on the same ZFS pool is shared under Samba as fileserver for user files
• Also using ZFS for Linux root, home and build directory (see top point)
• Samba 4.2.3 running on a separate pocket-size ("next unit of computing", as Intel calls this format) PC as an AD controller, to which both Samba running on host and Windows 7 guests are attached as members. A second AD controller (also Samba 4.2.3) is running under a VM, just in case
• zfs send | zfs receive, run occasionally to separate ZFS pool as backup (offline when not doing backup)

Right, it seems I failed to explain what I'm after. Added few more posts in the thread with explanations, hope it will start to make sense now.

Neither for your use case. Things that you can do that will make sense - Dual boot or run a hypervisor on a separate box ( which is what I do ) . I bought an Intel NUC PC which fits in the palm of your hand, and I installed VMWare ESXI (free version) on it, though you can install another hypervisor. This gives you a almost invisible box to run several VM's on at a pretty low cost. It's also very flexible so that you can erase the SSD and load windows/linux on it if you no longer need VM's.

I was thinking of a couple of boxes, Windows games machine and session client upstairs and Linux big box in the basement as OP likes his SSH and remote access.