Comment # 50 on bug 104082 from Michel Dänzer

The remaining issue should be fixed with
https://patchwork.freedesktop.org/patch/219765/ .

Anyway, the issues in 4.16 were swiotlb regressions, not directly related to
the issue originally reported here. If there's ever an issue again with the fix
above and Takashi-san's fix referenced in comment  40, please report it to the
swiotlb developers instead of here.