Comment 29 for bug 1749040

Found && fixed.

https://git.launchpad.net/~p-pisati/ubuntu/+source/linux/log/?h=artful-master-next-arm64-kpti-414-backport

I pushed two fixes on top of it:

1) 'syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check' fixes a FTBFS for armhf
2) 'arm64: mm: fix thinko in non-global page table attribute check' fixes this kvm boot race

We probably need to test it again on all arm64 boards now...