(In reply to Stratos Zolotas from comment #20)
> Maybe it is a coincidence, for sure I'm not running out of memory when it is
> happening and started with kernel 4.15 and (or) Mesa 18.0 without any change
> on Virtualbox side. I'll wait for the fix to see what happens...

Well the message means that we ran out of memory to allocate a 2MB block and
instead use many small 4K blocks.

What could be is that there is a memory leak somewhere triggering both the
message and the VM faults you are seeing.