IOMMU can't be enabled

[dorarosi]

Hello,
I am trying to passthrough a GPU and tried using the manual. At the point where you test if iommu is enabled I don't get the enabled msg. I am using a Ryzen 5 3600 on an Asus X570 E-Gaming mainboard. I just updated the Bios and tried to turn on diffrent things. Nothing works...
I have read somewhere it could be a Problem with AGESA, not sure what the problem here is.
Thanks in advance

 

[leesteken]

What enabled message are you looking for? The one on the PCI passthrough wiki is more for Intel than AMD. For Ryzen, just set IOMMU to Enabled (not Auto) in the BIOS. Some BIOS versions (with certain AGESA versions) break PCI passthrough but this is not detectable in a message (it fails when starting a VM). Also some BIOS version have better IOMMU grouping than other verions, sometimes older version are better for certain CPU generations.
You can check your IOMMU groups using this command (on the Proxmox host): for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done
This will also show if IOMMU is enabled (otherwise everything is in a single group) and show which devices can be passed through securely: devices in the same group cannot be split over VMs and/or the Proxmox host.