For systems with 52-bit userspace VAs enabled, the kernel will attempt
to maintain compatibility with older software by providing 48-bit VAs
unless a hint is supplied to mmap.

This configuration option disables the 48-bit compatibility logic, and
forces all userspace addresses to be 52-bit on HW that supports it. One
should only enable this configuration option for stress testing userspace
memory management code. If unsure say N here.