https://bugs.freedesktop.org/show_bug.cgi?id=108992
--- Comment #24 from Chí-Thanh Christopher Nguyễn chithanh@gentoo.org --- No problem here with amdgpu and iommu enabled, running kernel 4.20.0 on Dell Latitude 5495 (2700U). So BIOS issue maybe?
iommu=pt is however still needed for kfd (bug 107898).