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john.newman
Tux's lil' helper
Joined: 17 Oct 2009
Posts: 85
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 Posted: Thu Feb 09, 2012 5:01 am Post subject: Any experience with Xen GPU passthrough |
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I've been using qemu-kvm for a long time now to run some "test server" VMs out of my desktop - to keep my development type work nice and separated from everything else, and avoid destroying my main install. This for the most part has been a great success.
Now just the other day, I find out that it's possible to pass a raw PCI device to a VM. I had no idea... this is [potentially] huge. What I'd like to do is pass a GPU through to a certain other operating system  , to run certain types of games etc that unfortunately do not yet work on linux. I refuse to dual boot and wine as usual just isn't cutting it.
At this point it looks like KVM is lagging a little bit behind with good support for passing a GPU over. Maybe in a year or two they'll get the patches in. Xen however has fully baked support for this. From what I am told the performance is "very good". So far I'm just not able to find many guides on how exactly this works and what the key capabilities and limitations really are. Just looking if anyone out there has done this with gentoo and can clearly state whether or not this is worth my time pursuing any further. I'd be looking to use Xen just for the VMs that need the GPU and leave my headless server VMs alone using KVM.
My ideal setup would be like this
| Code: | Primary big monitor secondary smaller monitor
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GPU1-GPU2 (sli) GPU3 (not as nice but still half decent) |
On boot, the host machine has full access to all 3 GPUs and both monitors, and runs separate X servers on each. This is really what I do today, just without the 3rd GPU..
I start the new Xen VM, and it takes over the first two GPUs and gets the first monitor as it's only primary. Host keeps the second monitor, so I can keep my web browser etc open over there.
Later, I suspend the job of the VM, the host picks the primary monitor back up and the previous state is somehow saved and restored. Then I resume the job of the VM and the monitor switches back over there and restores the previous state. Basically, is it possible to use job control as a kvm switch. ? I'm not too optimistic that will work today - if not i could buy a real kvm switch and figure something out
So .. anyone ever tried anything like that. any thoughts |
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Aquous
l33t
Joined: 08 Jan 2011
Posts: 700
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| Posted: Thu Feb 09, 2012 8:39 am Post subject: Re: Any experience with Xen GPU passthrough |
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| john.newman wrote: | | Later, I suspend the job of the VM, the host picks the primary monitor back up and the previous state is somehow saved and restored. Then I resume the job of the VM and the monitor switches back over there and restores the previous state. |
This is impossible. PCI-passthrough is incompatibe with saved states.
I have no experience with this either, but I do know that you need Intel VT-d/AMD Vi extensions on your memory controller, which not a lot of people have. Also, IOMMU needs to be enabled in the BIOS, while many BIOSes disable it. |
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