As mentioned in a previous post, after updating the BIOS on my MSI PRO B850M-A WIFI, PCIe passthrough stopped working in Proxmox. After a new BIOS version was released (which still resulted in the passthrough error) I thought i’d investigate more thoroughly.
The setting which most often came up was related to DMA protection. Looking through the UEFI configuration on this motherboard, these settings were apparently located under:
- Overclocking
- Advanced CPU Configuration
- AMD CBS
- Advanced CPU Configuration
.. however it wasn’t obvious where they were. The trick was that the IOMMU setting first needed to be changed (in this case from “Compatibility” but in other motherboards it could be called “Auto” apparently) to “Enabled” - this unlocked extra settings (but did not fix the error by itself).
The two settings which looked relevant were:
- Disable Pre-boot DMA Protection
- Disable Kernel DMA Protection Indicator
I was unsure if both of these neded to be enabled or only 1 (and if so which one) - the end result was enabling “Disable Kernel DMA Protection Indicator” by itself resolved the GPU passthrough.