[SOLVED] Modern UEFI vs Legacy boot issue

[Randomhero]

I find myself running in circles here and hoping someone can help me out. I have a modern Unraid server running on an i5 13500, Asus H770 D-4 mobo and 32GB of ram. I have a 6700XT passed through on a windows VM and working perfectly in Legacy boot mode. The issue I am encountering is I completely lose video output of my iGPU in legacy mode but cant seem to get the 6700XT working in UEFI mode as I encounter code 43 and the windows VM dumps the driver. VM is running Q35 7.1 machine and OMVF Bios.

 

I mostly want the iGPU for Plex transcodes. I have no /dev/dri folder on boot, modprobe i915 gives no errors but even with a script set to pull drivers on boot Im left with no /dri folder. This is all in legacy mode which I assume is the current culprit but I need the GPU passthrough more than the transcode and just hope someone has a fix for this that Im missing. Mobo has IOMMU groups enabled and VT-d enabled as well. 

 

Thanks for any tips you guys can give I'm in a pickle here.

Edited May 26, 2023 by Randomhero

[Randomhero]

Clearly iGPU in legacy is not an option. Anyone get an AMD GPU product to work using UEFI boot?

[dairnu_unraid]

Have the same motherboard with an RX570.

I tried heaps of combinations so I'm not 100% sure what got it working but try the below:

- UEFI Boot (in BIOS)

- Set the motherboard to use iGPU (in BIOS)

- Allow multi monitor support (in BIOS)

- Disable fast boot (in BIOS)

- Install a fresh Windows VM. Don't pass through the AMD GPU. Before you add any drivers, shut the VM down from within the VM and then boot it from Unraid. Then you can add all the drivers etc. I had a copy of the AMD drivers downloaded so I could install the AMD GPU driver first. This stops Windows from trying to install one.

- I bound the GPU to VFIO at Boot

 

Had my W11 VM up and running for a few days now and everything seems fine. Performance seems great (for my hardware anyway).

Edited May 25, 2023 by dairnu_unraid

[Vr2Io]

I haven't PT GPU, but first time hear just bound to vfio then work.

 

May be because you have iGPU.

Edited May 25, 2023 by Vr2Io

[Randomhero]

Sorry guys I forgot that I had started this topic since it was a week of radio silence. I  actually sorted it out a little while ago. The culprit actually ended up being Resizable Bar. 

So multi monitor on, resize bar off, UEFI boot enabled as well as the usual suite of VM magic and it is now working smoothly alongside my Intel iGPU that is running Plex transcodes.

Edited May 25, 2023 by Randomhero
Spelling

[Derek_]

Hiya, i'm doing research as i'm about to change my hardware, so i'm trying to see what gotcha's there might be.

 

What's "Resizable Bar"?

[Randomhero]

10 minutes ago, Derek_ said:

Hiya, i'm doing research as i'm about to change my hardware, so i'm trying to see what gotcha's there might be.

 

What's "Resizable Bar"?

It’s a modern motherboard/GPU feature that can offload VRAM duties to motherboard RAM if you exceed capacity or the system seems it more efficient. For GPU pass through in a VM it appears to confuse the system as the ram it’s looking for is outside of the VM. Only an issue for AMD GPU it seems as I never see it mentioned on NVIDIA

Edited May 26, 2023 by Randomhero

[Derek_]

1 minute ago, Randomhero said:

It’s a modern motherboard/GPU feature that can offload VRAM duties to motherboard RAM if you exceed capacity or the system seems it more efficient. For GPU pass through in a VM it appears to confuse the system as the ram it’s looking for is outside of the VM. Only an issue for AMD GPU it seems as I never see it mentioned on NVIDIA

 

Thanks, where does one check for that setting?

[Randomhero]

1 minute ago, Derek_ said:

 

Thanks, where does one check for that setting?

It’s motherboard specific but most seem to have it visible on the bios main page. It’s usually on the top or bottom of the page near the shortcut keys are (F9 for Search, F10 to Save etc).It would be unlikely that a server board has this option if you are using server hardware. 

[Derek_]

Interesting, i don't remember seeing it. I have an AMD Ryzen 2700X PC and a new (just about to build) Intel 12th gen for unRAID. Maybe this is new? Or maybe i've just not noticed it.

 

Thanks for the info