Question about passthru

alextulu · July 23, 2018, 10:18am

When using PCI-E passthrough to pass a dedicated GPU to a VM, can I use the integrated GPU for the host, so that I can do it with just one graphics card? (or maybe try it on a laptop with Nvidia Optimus)

Also, when I want to play native linux games, and I shut down the VM, can the host use the dedicated GPU, since it’s not used by the VM anymore?

Hobnob · July 23, 2018, 12:40pm

I’m by no means an expert, but I’m using a gtx 1070 passed through to a windows vm with the igpu from an i7-6700k as the gpu for my linux host.

Play games in Windows on Linux! PCI passthrough quick guide Linux

Hello all! I am Gray from GrayWolfTech. I make videos on Linux and other interesting technology. Wendell has given me permission to post my written guides here for my videos. This is great for two reasons: First it helps grow this community and second my videos reach a wider audience to share what I have learned. I look forward to posting all my guides and videos here, and I am more than happy to answer any questions about the guide you may have. – Onward! – Now it’s time for one of the coolest and more advanced capabilities of Linux. KVM, or kernel virtual machines. We are going to go through step by step, how to setup PCI pass-through to a Windows virtual machine on a Debian host to play games! Thanks to Redhat, KVM can run virtual machines with almost bare metal performance and supports a wide variety of other neat features. The one we are going to focus on in this video is of course, PCI pass-through. The process of allowing a virtual machine full access to a PCI express graphics card for gaming, CAD, or 3D rendering. With this neat capability, you can run Linux as your host OS, and then pass your GPU (or one of your GPUs if you have multiple) to a virtual machine to play games. Let’s go over the requirements for this project: First and most important, you should backup any data you have on your PC. If you know what you are doing then you will not lose anything, but accidentally selecting the wrong drive when installing can lead you to be very sad when you figure out the drive you wiped had all your really good porn on it. Second, this process will take time. For someone who is an experienced Linux user it should take about 20 minutes (not counting time to install Debian or recompile the kernel). For someone who is new it might take longer. Make sure you allow yourself an entire afternoon or a good chunk of 4-5 hours where you could potentially not have a working PC. Third, follow the instructions I lay out in the video. I will answer questions down belo…

I followed this nice guide step by step with little issue, and got it working in about half an hour.
(I had trouble with LibVirt, so switched to using just qemu and a bash script as I’m more familiar with that)

so short answer, it depends on what cpu you have, and if it supports it, but yes, it is possible.

imhigh.today · July 23, 2018, 3:44pm

When using PCI-E passthrough to pass a dedicated GPU to a VM, can I use the integrated GPU for the host, so that I can do it with just one graphics card?

Yes. This is actually a dual GPU setup, and one of the reason I went with a Ryzen 2600.

You can not currently pass through the integrated graphics to the virtual machine, but if you pass the dedicated GPU, you’ll be able to use your integrated one just fine.

Also, when I want to play native linux games, and I shut down the VM, can the host use the dedicated GPU, since it’s not used by the VM anymore?

This depends a little on how you set up the passthrough, but yes. Worst case, it’s doable but you have to script the loading and unloading of some kernel modules when you switch.

Some methods of VFIO passthrough “stub” out the video card. There’s an older module ‘pci_stub’ and a newer one “vfio-pci” the both do (basically) the same thing. They load at boot time in place of your GPU’s kernel modules, so that when the VM is booted, they don’t have to unload.

The “you might have to script something” part comes in here. To hand the GPU back to the host, you’ll need to initialize the GPU with the right modules. This should be fairly sane; unload the vfio-pci module, load the nvidia/amdgpu module, and launch. Check out the man pages or an online wiki for “modprobe” invocation commands.

tkoham · July 23, 2018, 4:21pm

here’s a guide for exactly what you’re talking about: