Buildroot and Qemu

I'm using buildroot to compile a minimalistic linux with a 4.19-rt kernel. It is supposed to run on a raspberry pi 3b (arm processor). Additionally I want to run it on a x86_64 linux computer and found qemu as an emulation solution for that.

1. Building linux and kernel and running it on the raspi works. It boots, I can login and use it.

2. To test qemu I followed this instruction [1]. A recent raspbian with 4.19 kernel is booting fine so qemu seems to be installed correctly.

sudo qemu-system-arm -kernel ./qemu-rpi-kernel/kernel-qemu-4.19.50-buster -hda 2019-09-26-raspbian-buster-lite.img -cpu arm1176 -m 256 -M versatilepb -no-reboot -serial stdio -append "root=/dev/sda2 panic=1 rootfstype=ext4 rw" -dtb qemu-rpi-kernel/versatile-pb.dtb

3. Bringing 1. and 2. together fails. When I try to emulate any self build linux, qemu only shows a black screen and one CPU is using 100%.

I used the same sdcard.img that works on the real hardware. I also tried to recompile the whole system with a normal 4.19 kernel (without real time). And I tried to build a versatile system (make qemu_arm_versatile_defconfig && make). None of it works.

Command to start the emulation:

sudo qemu-system-arm -kernel zImage -drive format=raw,file=sdcard.img -cpu arm1176 -m 256 -M versatilepb -no-reboot -append "root=/dev/mmcblk0p2 panic=1 rootfstype=ext4 rw" -serial stdio

My main problem is, that there is absolutly no useful output. The command outputs the following

ALSA lib pulse.c:242:(pulse_connect) PulseAudio: Unable to connect: Connection refused

sdl: SDL_OpenAudio failed
sdl: Reason: ALSA: Couldn't open audio device: Connection refused
ALSA lib pulse.c:242:(pulse_connect) PulseAudio: Unable to connect: Connection refused

sdl: SDL_OpenAudio failed
sdl: Reason: ALSA: Couldn't open audio device: Connection refused
audio: Failed to create voice `lm4549.out'

and opens a window for the graphics output (that does not show anything). The message also appears when emulating raspbian so it does not seem to be the reason.

When I run qemu with the prebuild raspbian but without the -dtb argument, I get a message like "Error: invalid dtb and unrecognized/unsupported machine ID". I would at least expect something like this with my self build code. But because there is no output I'm out of ideas what even to google for.

Does someone maybe have an idea what I'm doing wrong or how I get qemu to provide me any useful information on what went wrong?

Thanks in advance

[1] https://blog.agchapman.com/using-qemu-to-emulate-a-raspberry-pi/