Trouble using second GPU for PVE

[devellis]

I'm currently trying to dedicate my AMD RX 580 8GB to an Arch VM for gaming and I'm trying to basically disable it's output on the host and force my secondary GPU(a GTX 1650) as the output for everything on the host. The RX 580 is in the main 16x slot on my motherboard as it needs the bandwidth more than the GTX 1650 which sits in a measly 4x slot. I disabled the Radeon driver loading by blacklisting it in /etc/modprobe.d and I have the motherboard's "initial display output" to the secondary PCIe 16x(logically 4x) slot and it does output to the 1650 but as soon as Proxmox starts booting it switches to the RX 580.

How do I stop Proxmox from loading the drivers to my RX 580, disable it's video output and force the 1650 as the output for PVE-Host?

 

[leesteken]

Most motherboard don't allow you to choose. Sometimes changing CSM from Enabled to Disable or the other way around will switch the boot GPU. I know many Gigabyte Ryzen motherboard allow you to select the PCIe slot for the primary GPU but I don't know your motherboard.
If you want to passthrough the boot GPU then use this work-around for recent Proxmox versions, but you'll lose the Proxmox host console and boot messages.

 

[leesteken]

I'm on a gigabyte board and I have that option enabled AND the 1650 does seem to work in Proxmox for a few seconds until it switches to the primary GPU and freezes the image on the 1650.

Sorry, I did not realize. Make sure to early bind the GPU to vfio-pci to prevent Proxmox from using the device.

I disabled the Radeon driver loading by blacklisting it in /etc/modprobe.d and I have the motherboard's "initial display output" to the secondary PCIe 16x(logically 4x) slot and it does output to the 1650 but as soon as Proxmox starts booting it switches to the RX 580.

Please note that the RX580 uses the amdgpu driver (Radeon RX 2xx and later) and not the radeon driver (Radeon HD 7xxx and earlier). Blacklisting is usually not necessary as early binding to vfio-pci in combination with a softdep is more specific.

 

[leesteken]

And they all still freeze the 1650 and switch back to the 580 mid-boot. Do you have an example blacklist.conf file you can show me?

No, because I don't blacklist amdgpu and I also don't early bind to vfio-pci, because I use pve-kernel-6.1 and vendor-reset and my boot RX570 reset properly that way (and can even bind it back to the host).