Watch out for memory leaks as well.

When mesa drops the last reference to the BO by closing it's handle the VA
mapping should go away automatically. That's the reason why it works for X and
EGL.

What you see here is that you manually need to remove the VA mapping because
there is still a reference to the BO outside of mesa.

Could be intentional, but could be a bug as well.

Anyway Michels patch is clearly a good idea.