(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.