It’s doable, really depends on which GPU you get, but it’s not ideal.
It’s easiest with Nvidia GPUs because their drivers (despite being closed source) are built more or less properly. (fully featured)
Could I switch the passed through GPU between different guests?.. i.e. shotdown the Windows guest and fire up a Linux guest with the GPU passed through?
Yes, absolutely. This is as easy as shutting down one guest, and starting up the other.
As long as I can switch the GPU between guests, host access isn’t too much of a big deal. I do have a follow up question regarding switching the guest GPU back to the host but I’ll save that for a later post if I may.
Red vs. Evil… I mean Green
For the “host gpu” (the one you use on the Linux os on the Metal) you can go with whatever, but Nvidia is going to be the best option for actually passing it through.
That’s helpful to knnow because I was under the impression that AMD was easier but Nvidia had better performance.
So, AMD cards are great if you undervolt them a bit. AMD should have really done that from the factory, but they didn’t.
But, again, AMD isn’t the brand you want to go with for passing through. Their compatibility is hit or miss, and Nvidia is as close to a sure thing as you can get.
As much as I’d like a fully FOSS system, sometimes it’s just not pratical or worth the comprimise… why do I feel like I’m slipping down a slope when I say that?
Nope, I’m using a 1070ti on my host and a 1080ti on my guest. (typing from the host right now) and it works just fine.
Furthermore, if I do upgrade the Host GPU, it’d likely be a low end Nvidia GPU for the same reasons described above. Is there anything I need to be aware of other than not using identical cards?
You actually can use identical cards, but it’s not quite as easy.
But, there are some super-low-end gpus that just don’t have the power to do what you’re trying to do, so my recommendation is to not go any lower than a 1050ti class card.
Even though Looking Glass does the rendering of the game to your VM and the passed-through GPU, you still need a little bit of horsepower to render the looking glass client on your Linux machine. While it’s doable, even with an iGPU, your best experience will come from a slightly more beefy GPU.
That’s a very good point, I hadn’t considered the host GPU doing much other than high bitrate video playback. I had initially considered a GT 1030 but I’ve pretty much ruled it out as I’d like 3 video outputs, which means more the GTX 1050 range.
So given the questions you asked already, it seems like there’s a few other gotchas that you might bump into, so I’ll try to educate you about them ahead of time.
I will. The point of this thread was basically to confirm whether or not I’d be making a mistake going the Nvidia route and whether I could pass the GPU from one guest to another. Any other gotchas, as long as they’re not total deal breakers or they stop me from doing what I described in my previous post, then I don’t mind working around them.
What sort of system specs do you currently have for your other components? Certain motherboards are more compatible with passthrough than others. Certain CPUs obviously work better than others. I typically recommend at least 16GB of ram to get this done.
My current specs:
Ryzen 7 1700x
Gigabyte AX370 Gaming 5*
32 GB of RAM
500GB NVMe disk for Debian (Root on ZFS)
+a variety of SSDs at my disposal
*I did have it’s IOMMU groups somewhere but I can’t find it at the moment. I’m just about to eat dinner so I’ll get a copy of them and report back tomorrow if that’s okay.
If you’ve got more questions, I can definitely help you, feel free to ask.
Thank you. You’ve been very helpful so far but I’d be happy to pick your brain in the next few days.
One question that springs to mind, and I’m guessing you won’t be able to answer with any degree of certainty until I get the IOMMU groups output, is how I’ll address the question of audio. I use an Asus Xonar DGX sound card but if at all possible, my motherboard has two audio chips, on for the front i/o and one for rear i/o. I’d like to be able to pass just one of them through to the guest. Have you ever heard of that being done?.. is it just a matter of them being in differnt IOMMU groups or seperating them with the ACS(?) patch?
(worst case scenario, I pass the sound card through or buy a USB DAC)
I have got more questions but dinner is on the table.
Thanks again sgtawsomesauce!