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Re: [vfio-users] GPU Passthrough Artifacts

As far as single GPU goes, it appears it's not impossible. I won't be trying it for probably another month, but from what I've gathered, you need to boot with UEFI, need to unbind all VTs, unload any drivers like nouveau, nvidia and/or efifb (which needs to be compiled in as module), so that nothing holds onto the device, then you should be good to go to pass it through. Once QEMU quits, you have to revert all that.

I had a discussion with someone else about it on /r/vfio (on Reddit) a while ago, he eventually managed to get it to work.

Personally, I have this script bookmarked as reference for the VT business, for whenever I'm going to give it an attempt (it's about switching between nvidia and nouveau at runtime, but it does all the VT binding stuff, too). Maybe it'll help you experimenting:



On Sun, Mar 27, 2016 at 10:50 PM, Eduardo <eduardomanuel1512 gmail com> wrote:

I am having a weird problem with GPU passthrough.

I am running Arch Linux, and these are my (relevant) specs:

- Intel(R) Xeon(R) CPU E3-1270 v5
- GeForce 9500GT (to have a GPU on the Linux host - this CPU does not have an iGPU, so I needed to place this GPU as a workaround as I wasn't able to grab the GTX 970 when it was the primary GPU. I do not need a screen on this machine, it's headless)
- ASUS Strix GeForce GTX970 (to pass through to the Windows guest)

Using this build, I can pass the GPU just fine, Nvidia drivers install fine, everything is great, except for one fact - either randomly on boot, or when trying to run a very GPU intensive game, I get weird artifacts on the guest GPU (by artifacts, I mean my screen gets filled with flickering white lines). Some seconds after getting those artifacts, if I continue trying to play games, the Nvidia driver starts to continuously crash and my system gets unusable.

This does not happen when I boot Windows natively with only this GPU on the machine.

This is the script I am using to boot QEMU: http://pastebin.com/fKNsDMLQ

I tried messing around with the CPU flags and the addr flag on the PCI device to no avail.

Does anyone have an idea of what might be the cause of this problem?

Also, kind of unrelated question, but: I don't need a display on this machine. Is there a way to not have the kernel grab the GPU when it is the only one and remove the need of having the 9500GT?

Eduardo Almeida

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