They have to be same as the maximum addressable bit, i.e. in the case of 48 bit virtual address size the 48th bit. This is actually kind of a cute way of divid

They have to be same as the maximum addressable bit, i.e. in the case of 48 bit virtual address size the 48th bit. This is actually kind of a cute way of dividing kernel and userland space as you just set the upper bit to 1 for kernel addresses and 0 for userland. EDIT: Specifically talking about x86-64 here. https://github.com/lorenzo-stoakes/linux-mm-notes/blob/master/virt_layout.md#virtual-address-layout https://github.com/lorenzo-stoakes/linux-mm-notes/blob/maste...