This has been an issue since before AM2+, but AM2+ is when I first started to deal with it. For AMD IOMMU does not fully work behind the DMI. If you break out IOMMU from the CPU lanes You can generally get it working anyway you want. But if you try and  break out DMI attached devices (PCIE, Onboard, other) the Groups are generally broken and do not work. Have tried this with many HyperVisors and some will just give up the ghost after a while due to sharing violations. So this is not exactly new and I wouldnt expect a proper fix.