Debugging a custom kernel

Hello, I am working on a custom kernel, and I would like to add the necessary support to enable it to boot with qemu. In order to achieve that I am trying to debug it inside qemu by attaching a gdb to it. I still can't figure where the boot process is getting stuck with step-by-step execution, but it seems that the last function called is "delay_loop" from arch/x86/lib/delay.c. That function contains some assembly code, does someone know what it is supposed to do ? Beside, do you have any advice on the way I should proceed to get the necessary information to port the kernel ? Thanks. -- Apelete