I have been using GPU/HW passthrough, but at times these systems are not working. Thanks to these forums and Squid I've found out that my IOMMU is being disabled. If I go to Tools>System Devices it says "PCI Devices (No IOMMU Groups Available)". This is fixed by going into the bios and enabling IOMMU.  However, for some reason my system will disable it, and I will have to go into the bios to re-enable the IOMMU. Does anyone know why my bios would change this setting? Especially without me making the change.

 

I am using a X570 Phantom Gaming 4 motherboard.

 

 

Edited October 8, 20214 yr by bat2o

I'm having this exact same issue.  I'm using an ASrock X750 Steel Legend and Ryzen 9 3900x.

ASRock X570 Phantom Gaming 4S no problems here. Try to update your BIOS'es maybe?

This may help the OP but mine is up to date.  The problem has been a struggle to diagnose because it happens randomly and at random intervals.  The only consolation is that it only appears to happen every several months or so.

 

I'm also having issues where occasionally my server locks up when reading from the Blu-ray player; but that's a topic for another day.