Hello Joerg,
We are seeing a kdump kernel boot failure in test on an HP DL325 Gen10 and it was tracked down to 387caf0b759a ("iommu/amd: Treat per-device exclusion ranges as r/w unity-mapped regions"). Reproduced on 5.9-rc5 and goes away with revert of the commit. There is a follow on commit that depends on this that was reverted as well 2ca6b6dc8512 ("iommu/amd: Remove unused variable"). I'm working on getting system access and want to see what the IVRS table looks like, but thought I'd give you heads up. Regards, Jerry