Issues with dual GPU passthrough

[Nora]

Hi there!

I'm attempting to configure dual GPU passhtrough to two guest Win10 VMs.

I managed to pass the first GPU to a Win10 guest just fine (GTX 750Ti). I then decided to add the second GPU (GTX980), so I included its IDs to "/etc/modprobe.d/vfio.conf" and rebooted the server as per the instructions (I've been following this really awesome guide). The server then hangs during boot once it checks the disk. I tried disabling fastboot to see whether that would make a difference, but then boot stops at "2 logical volume(s) in volume group "pve" now active.

The PC also has Intel interated graphics and I thought it wouldn't need much else than that to boot, and a GPU is not mentioned in the minimum requirements as far as I could tell.

Any ideas what the issue may be?

 

[dcsapak]

maybe the mainboard chooses the gtx980 as boot gpu? if yes, try to change it to the integrated one?

 

[Nora]

That was it! Thanks a bunch

 

[rifaterdemsahin]

maybe the mainboard chooses the gtx980 as boot gpu? if yes, try to change it to the integrated one?

how do we set this ?

any why do we set this ?

can we disable the boot GPU ?

 

[leesteken]

how do we set this ?

When the CPU has integrated graphics, then most motherboards allow choosing between iGPU and (the first) PCIe GPU. Very few motherboards have a setting to select between PCIe GPUs. Sometimes turing CSM on or off will switch which GPU is used for boot.

any why do we set this ?

Some GPUs don't reset properly and won't work in a VM when they have been used during boot. If the GPU resets properly (sometimes via a work-around), then it is not a problem and not necessary.

can we disable the boot GPU ?

Not from Proxmox (or any other operating system) as this is a BIOS thing. I don't know of any motherboard that does not initialize a GPU to display boot messages (if one or more GPUs are present).

 

[rifaterdemsahin]

thanks for the answers

When the CPU has integrated graphics, then most motherboards allow choosing between iGPU and (the first) PCIe GPU. Very few motherboards have a setting to select between PCIe GPUs. Sometimes turing CSM on or off will switch which GPU is used for boot.

Some GPUs don't reset properly and won't work in a VM when they have been used during boot. If the GPU resets properly (sometimes via a work-around), then it is not a problem and not necessary.

Not from Proxmox (or any other operating system) as this is a BIOS thing. I don't know of any motherboard that does not initialize a GPU to display boot messages (if one or more GPUs are present).

go i have radeon 7 and radeon 6900 xt
https://forum.proxmox.com/threads/proxmox-as-an-ultimate-desktop-setup-dual-gpu-pass.108793/

I want to pass those 2 cards to virtual machines

what should be my thought/implementation process?

should i set displays to none and set a primary gpu after implementing reset bug ?

 

[leesteken]

thanks for the answers


go i have radeon 7 and radeon 6900 xt
https://forum.proxmox.com/threads/proxmox-as-an-ultimate-desktop-setup-dual-gpu-pass.108793/

I want to pass those 2 cards to virtual machines

what should be my thought/implementation process?

should i set displays to none and set a primary gpu after implementing reset bug ?

Primary GPU is for NVidia cards and you don't need it.
You need to use vendor-reset for AMD Radeon VII.
The AMD RX 6xxx should not have reset issues, so you can probably use that as boot GPU as well. My best results are with not blacklisting amgdpu and no video=... kernel parameters.
Set Display to none and attach a physical monitor to the GPUs. You might want to passthrough a USB controller or at least a keyboard and mouse for input to those VMs.