Hi!
With 4.18.1 and l1tf=full no problems so far and no noticeable performance-degradation in normal desktop-usage including a VirtualBox-VM. Compiling a kernel seems to take a bit longer, though.
4.9.120 and 4.14.63 also seem OK in cursory testing. CPU: Core i3.
Thanks and so long!
Rainer Fiebig