Kernel panic when using initramfs instead of initrd

Hello everyone! Briefly, I'm creating a dummy distribution which boots from CD (using VirtualBox for testing purposes) and lives in RAM. It's a very minimalistic kernel which has almost nothing enabled except from core facilities, virtual terminal, framebuffer and serial port. I'm trying to

when to remount sysfs ?

Hi: As i know , when kernel is booting , sysfs is mounted at /sys before the real root fs is mounted . Then , after the real root fs is mounted , when does i need to remount sysfs at the new /sys location ? I know the devfs is remounted by do_mount (none, /dev, devfs, 0, ) ,