GPU Native Output Passthrough Problems! (Linux Guest)


New Member
Jan 28, 2023
Hello, over the past week or two I've been trying to get GPU passthrough (EVGA 8400GS 01G-P3-1303-KR) working into a Linux guest (Linux Mint) and have only been partially successful. The goal is to just use this basic GPU as a native display output to my monitor over VGA however I can't seem to get it to work. I don't believe I've ever gotten the passthrough to work correctly as the VM would often freeze on Mint login before X launches using the nouveau driver or patched Nvidia driver. Any help would be appreciate and I can complete any suggested troubleshooting. Again the goal is to be able to use the VGA/HDMI out on the card to connect to a display in order to use it.

I have a rom file I pulled from a live boot on Mint using real hardware that I tried to test with without success. I also have tried disabling and enabling unsafe interrupt remapping (my board does support the remaps but tried it anyway with no success)

Below I have attached screenshots for all current settings and the 2 VMs I've been testing with BIOS/UEFI both Mint however I have tried different distributions which unsurprisingly has no change.

VM settings tried on both:

Primary GPU: on/off
Rom file from dump: used/unused
scsihw: single/PCI
Display: None, VGA (std), Spice


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Important note as long as I could login to the VM the guest GPU would show, just not display video out with any of the combined settings noted.
Please be aware that nofb nomodeset textonly video=vesafb:off video=efifb:off don't really do anything anymore. If you are doing passthrough of the GPU that is used during boot of the Proxmox host, you need this work-around. You probably have that BAR cannot reserve error in your system logs. Check with cat /proc/cmdline which kernel parameters are in effect.
After trying your suggestion and changing my /etc/default/grub and updating the config via 'update-grub' it seems the VM is booting a little more reliable however still no native display out with and without display set to none/vga(std) and with and without using my rom file.

BOOT_IMAGE=/boot/vmlinuz-5.15.74-1-pve root=/dev/mapper/pve-root ro intel_iommu=on iommu=pt pcie_acs_override=downstream,multifunction initcall_blacklist=sysfb_init


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