Two VMs each with its own GPU-passthru

[matthei]

I am already using Proxmox 7 with a Windows VM which has a GPU passed through, so I'm successfully using it as a workstation. I'd like to add another such VM, then switch the monitors input between the two - basically having 2 computers in one machine.

But I have a problem: when I add the second GPU, only one is visible/listed in the list of PCI-E devices. Perhaps relevant: If i switch them around, the same GPU is still listed.

From what I gathered, this could be a problem of the IOMMU groups of this motherboard - and it's just not possible?
Is there anything I can try to attempt to get this working?

Hardware: AsRock rack X470D4U2-2T
GPUs: GTX950 and GTX1050Ti

Btw, it's the GTX950 that is shown in the list, regardless of which PCI-E slot I put it in. So if i put GTX950 in the first slot and GTX1050 in the second slot, or switch them around, only the GTX950 is displayed on the list of PCI-E devices.
Also BTW: the motherboard only has 2 slots that can accept the GPU (an x16, and an x8, it's a uATX board)

Thanks for your help in advance!

 

[dcsapak]

what is the exact output (can you post a screenshot) ?
also the output of 'lspci' would be helpful .

 

[matthei]

Thanks! I found the problem in the bios setting, but learning that command and knowing that there's someone to help, sure did help a lot!

I assumed that adding the second GPU immediately adjusts the PCIE lanes to enable both devices. There was a setting in the GPU called "PCIE6/PCIE4 Link Width" it was set to "x16" and I've changed it to "x8x8", rebooted and now both GPUs are visible, both in the "lspci" output as well as Proxmox web GUI.

(I still don't understand why only the GTX950 was detected whether I've put it in the top slot and the 1050 in the bottom, or the other way around, but since it works I'll leave it at that)