[phil-opp]

It is possible to access other address spaces, it is just a bit more complicated:

- Set the recursive entry of the active level 4 table to the (recursive) level 4 table of the other address space. - Now the recursive addresses point to the other address space, so you can access its tables freely. - The difficult part is to switch back to the active address space again because can no longer access the original level 4 entry. This can be solved with a temporary mapping to the active level 4 table or by using different level 4 entries for the recursive mapping of active and inactive address spaces.

However, I'm no longer sure whether recursive page tables are a good choice for the blog since they're complicated, difficult to learn and not portable. See my reply to DSMan.