What happens on Linux after running the /sbin/shutdown command?

Question

linux

Ideally, after the /sbin/shutdown command, for example, with the -warm flag, it would be possible to start the warm-boot procedure in the form of loading the MBR sector from the zero sector of the hard drive, etc. That is, so that the reboot goes without cold-boot: without resetting the CPU, without entering the BIOS via jmp far ffff: 0. Thus, the speed of reloading would increase drastically.
By analyzing the kernel sources, it was not possible to establish - does the CPU return after the /sbin/shutdown command back to real mode? I think no. And since there is no real mode, it turns out that you can forget about loading the MBR sector at 0: 7c00h?
Upd1. It seems that this is not possible due to the need to re-initialize the hardware. But then two more questions arise:
1) The BIOS on the motherboard can do all this. Why is Linux worse?
2) What if I don't have sophisticated equipment?

Answer 1

kexec?