Co-kernels cannot bear with the extra latency caused by memory access
faults involved in COW or
overcommit. __ipipe_disable_ondemand_mappings() force commits all
common memory mappings with physical RAM.

In addition, the architecture code is given a chance to pre-load page
table entries for ioremap and vmalloc memory, for preventing further
minor faults accessing such memory due to PTE misses (if that ever
makes sense for them).

Revisit: Further COW breaking in copy_user_page() and copy_pte_range()
may be useless once __ipipe_disable_ondemand_mappings() has run for a
co-kernel task, since all of its mappings have been populated, and
unCOWed if applicable.