https://bugs.freedesktop.org/show_bug.cgi?id=104082
--- Comment #17 from Michel Dänzer michel@daenzer.net --- (In reply to Matthew Scheirer from comment #16)
I get this as well with a 290 on 4.15 ONLY when DC is enabled. Its a dirty enough taint to leave btrfs volumes in inconsistent states so its straight crashing the kernel.
The swiotlb messages this report is about are harmless (though a fix is on the way anyway), the other issues you mention are probably not directly related.