building in 32bit chroot on x86_64 host broken (was: Linux 4.17)

From: Thomas Backlund
Date: Tue Jun 05 2018 - 14:06:59 EST

I have a 32bit x86 and a 64bit x86_64 install on the system.

With linux source up to 4.16.x I could do:

setarch i686 (or use command linux32)
chroot /path/to/32bit/
(/dev, /proc, /sys, /run is bind mounted in the chroot)

Then I could build a 32bit kernel in the chroot without booting the 32bit system...

(host is running a 4.14 longterm kernel)

but building from 4.17 source in the chroot I get:

$ uname -m
$ make oldconfig
scripts/kconfig/conf --oldconfig Kconfig
* Restart config...
* Linux/x86 4.17.0 Kernel Configuration
64-bit kernel (64BIT) [Y/n/?] (NEW)

So it does not pick up 32bit anymore ...

Is this intentional ? If so, why ? If not, how can I fix it ?