[ubuntu] dmesg error: Unable to read/write to IOMMU perf counter

Hello all.

I'm trying to set up PCI passthrough using this guide however I've hit a snag (I think).

I've got as far as enabling the required options in the BIOS - SVM module and IOMMU - as well as setting the "amd_iommu=on" and "iommu=pt" parameters in /etc/default/grub. Also I have isolated my GPU and it's sound 'thingy' (controller?)

However when I run 'dmesg | grep AMD-Vi' I get the following error...all the rest of the output suggests everything else is working. I'd love to know what the IOMMU 'perf counter' is, cant find anything online about that. Loads of people have had the same error when trying to install various distros with many threads suggesting setting 'iommu=soft' in /etc/default/grub, however when I tried this I just got a dmesg error saying IOMMU wasn't available, or some similar message.

I've posted the specs of my computer below, I believe all my hardware supports what I'm trying to do (in theory)

Ubuntu 20.04.1 LTS
Kernel 5.4.0-54-generic
Asus ROG Strix X570-I
AMD Ryzen 3400G

Any advice would be much appreciated!