Minimum build config for boot messages

[Andre Schmidt]

Hello,

what is the minimum config to build a linux kernel that just prints boot messages/errors?

I was going through my old experiments/notes and found that we used to get kernel boot message with vanilla allnoconfig.

make ARCH=x86_64 allnoconfig
make all
qemu-system-x86_64 -kernel arch/x86/boot/bzImage

Those commands above used to be enough, but now the produced kernel doesn't print any messages on the qemu screen.

With some trial-and-error i was able to track down this commit
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/init/Kconfig?id=5d2acfc7b974bbd3858b4dd3f2cdc6362dd8843a
and if i add CONFIG_EMBEDDED=n to my KCONFIG_ALLCONFIG file, i can see kernel errors again.

I didn't investigate further cause i don't really know what i'm doing, but do wonder:

Can you reproduce this?
Is this (now) expected behavior?
(and it was luck before, to get kernel messages with vanilla allnoconfig)
Do we (now) need some specific option to enable kernel messages with allnoconfig?
(CONFIG_EMBEDDED=n sounds pretty generic and doesn't feel right)
Am i doing it all wrong? :D

Curiously,
Andre Schmidt

ps. i'm aware of defconfig, but i would like to experiment/learn from bottom-up, rather than top-down.