Enable IOMMU in GRUB
Most Linux distros do not enable IOMMU by default.
You will need to update your grub bootloader config to support IOMMU.
sudo nano /etc/default/grub
and add following to the GRUB_CMDLINE_LINUX_DEFAULT line:
A) for Intel CPU:
iommu=pt iommu=1 intel_iommu=on
B) for AMD CPU:
iommu=pt iommu=1 amd_iommu=on
so it looks like this: (in my case, i put amd_iommu, cuz i am on AMD platform)
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash iommu=pt iommu=1 amd_iommu=on"
result:
save file (ctrl + x, y, ENTER) and run:
update-grub
REBOOT
If your GPUs are in the same IOMMU group after you have completed this section of a guide, continue here: https://forum.level1techs.com/t/elementary-os-5-0-beta-vfio-pcie-passthrough-guide-tutorial/131420/17 , then proceed with next section (“Check if IOMMU is working”)