kernelconfig_penguin
CONFIG_3_LEVEL_PGTABLES is not available for the default architecture x86.
Result is shown for architecture um
default or selected kernelversion does not have config value CONFIG_3_LEVEL_PGTABLES.
Result is shown for kernelversion 3.1.9
depends
CONFIG_EXPERIMENTAL

Three-level pagetables (EXPERIMENTAL)

configname: CONFIG_3_LEVEL_PGTABLES

User Mode Linux/$SUBARCH $KERNELVERSION Kernel Configuration
└─> UML-specific options
└─> Three-level pagetables (EXPERIMENTAL)

Three-level pagetables will let UML have more than 4G of physical
memory. All the memory that can't be mapped directly will be treated
as high memory.

However, this it experimental on 32-bit architectures, so if unsure say
N (on x86-64 it's automatically enabled, instead, as it's safe there).