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[Solved] KVM pass-through on X399 platform issues

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I have issues trying to pass-through two Windows 10 KVMs, each with it's own dedicated GPU on X399 platform. I've been successfully using a similar configuration with Z97 platform & i7 4970K for three years, now I've upgraded to X399. Notable difference between the platforms is that X399 does not have the on-board graphics.


I've set all BIOS settings that make sense to me (AMD-v/SVM, IOMMU, C-state...) and I can't seem to get both VMs to use GPUs simultaneously - only the KVM with GPU, that's not used by motherboard's default output seems to work. The other VM starts, the unraid console on it's display turns black and nothing happens. I can VNC to the VM, but the GPU is not present in the OS. If I change the initial display output in BIOS they the issue moves to the other GPU/VM.


Currently I am using ACS override = downstream + multi-function without any specific vfio instructions.

label unRAID OS
  menu default
  kernel /bzimage 
  append iommu=pt pcie_acs_override=downstream,multifunction initrd=/bzroot


  • Motherboard: X399 Gigabyte Designare EX (BIOS ver F11)
  • CPU: AMD Ryzen Threadripper 1950x
  • RAM: 4x 8GB Corsair Vengeance RGB Pro 3200 MHz
  • GPU 1: Nvidia GTX 970
  • GPU 2: Nvidia GTX 750 Ti
  • SSD cache: 1x 120GB SATA
  • SSD unassigned: 2x 250GB NVME, 1x 120GB SATA
  • HDD array: 6x 4TB, 2x 2TB
  • PCIe cards: SATA controller


PCIe slot configuration:

  • Slot 1: Nvidia GTX 970
  • Slot 2: /
  • Slot 3: SATA controller
  • Slot 4: Nvidia GTX 750 Ti
  • Slot 5: /



I've attached diagnostics. 

Does anybody have some idea what I have to do to make it work? vifo instead of ACS override? Disable Unraid console display output at boot?



Edited by Nihil
Marking solved

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You may need the rom file for the card that's not working. You could pull it using gpu-z in Windows or find it on the tech powerup site. I ran 2 vms with gpus on ryzen and it's the same deal. 

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The card in the first slot passing through a VM for me needs a bios rom file. Dump it yourself or download the exact one for your card from Techpowerup. Check SpaceInvaderOnes youtube channel and you will find a couple tutorials how to do it.

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I have the same issue and I tried it with 4 different GPUs each with two GPU BIOS dump (terminal and GPUz w/o NVheader) but on the X99 Platform maybe that is only a special problem with my Mainboard. Try to dump the vbios of your graphics card you have to listen carefully because every step and clue is important!


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Worked perfectly!

I ended up following the guide where you modify the Techpowerup file:


Thanks to all of you!

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