The invention pertains to a memory management unit for a microprocessor system, the memory management unit being connected or connectable to at least one processor core of the microprocessor system and being connected or connectable to a physical memory of the microprocessor system. The memory management unit is adapted to selectively operate in a hypervisor mode or in a supervisor mode, the hypervisor mode and the supervisor mode having different privilege levels of access to hardware The memory management unit comprises a first register table indicating physical address information for mapping at least one logical physical address and at least one actual physical address onto each other; a second register table indicating an allowed address range of physical addresses accessible to a process running in or under supervisor mode; wherein the memory management unit is adapted to prevent write access to the second register table by a process not in hypervisor mode. The memory management unit is further adapted to allow write access to the first register table of a process running in or under supervisor mode to reconfigure the physical address information indicated in the first register table with memory mapping information relating to at least one physical address, if the at least one physical address is in the allowed address range, and to prevent write access to the first register table of the process running in or under supervisor mode if the at least one physical address is not in the allowed address range. The invention also pertains to a microprocessor system and a method for managing memory.