https://bugs.freedesktop.org/show_bug.cgi?id=108992
--- Comment #16 from Brian Schott briancschott@gmail.com --- I've tested a next-20181221 kernel with IOMMU_DEFAULT_PASSTHROUGH set, and I'm able to get the system to start properly. Still seeing some system lockups, when playing games, but it's better than crashing on the login screen.