How to see /sys/kernel/debug/kernel_page_tables

lfkd000

With stock kernel, file is not there. I websearched and found following info and followed instruction with no avail. That is problem with stackexchange, more often than need, information there is just noise and invalidated, wasted so much time. so I brought issue here.
https://stackoverflow.com/questions/20069620/print-kernels-page-table-entries

Basically built, installed and booted new kernel with CONFIG_X86_PTDUMP and after that file is nowhere to be seen:
cat: /sys/kernel/debug/kernel_page_tables: No such file or directory
Ubuntu 20.04.