340.104-9: NVS 420 hangs on starting X 1.95.5 with Base Mosaic and IOMMU on

X hangs the whole machine (black screen) when both of these conditions (Base Mosaic + IOMMU) are true

-when IOMMU is off everything works
-when Base Mosaic is off everything works

Machine is: Intel i7-4820k running linux-4.14.3-1 64-bit
2x Quadro NVS 420 cards

This is probably an edge case that hasn’t been accounted for yet.
The only online result that seems remotely related was on this page:
https://us.download.nvidia.com/XFree86/Linux-x86/375.39/README/dma_issues.html

What solution is there for this?

-IOMMU is required for PCI pass-through to virtual machines (a device other than the 420s) so disabling it is not an option
-Base Mosaic is required for efficient use of 8 monitors so disabling this is also not an option.

I sincerely appreciate your time!
Thank you!

p.s. Tomorrow I will try to run the nvidia bug report script over ssh and will update as soon as I get it.
nvidia-bug-report.log.gz (135 KB)