32-bit architectures have to share a small 4GiB address space between
privileged and non-privileged modes. Picking the address to split the
address space at affects how much virtual memory userlevel can use, and
how much physical memory the kernel can turn into untypeds. This is
something that should be configurable policy as different divisions make
sense for different applications. For now we only add the config
option to qemu-arm-virt to try it out before potentially adding it to
all 32-bit platforms.
Signed-off-by: Kent McLeod <kent@kry10.com>