Random reboots and freezes solution for 11th gen Intel i5-11400F with B560M (yes, the C-states)

I've recently installed Unraid 6.11.15 on my new home server with an 11th generation Intel i5-11400F and MSI B560M PRO-VDH (MS-7D18) motherboard.
I've been experiencing random reboots and freezes.

I've managed to reproduce the problem (after several attempts over a couple of weeks). Copying large amounts of data via SCP (using WinSCP for example) has always resulted in a reboot.

I won't mention any other hardware in my server as I've tried replacing and disabling all of it. 

I've of course updated the BIOS to the latest version.

Usually it's been a kernel panic with a message on the screen (nothing in the logs of course) something like this:

mce: [Hardware Error!: CPU 0: Machine Check Exception: 5 Bank 10: be0000000100110a
...
[Hardware Error]: Machine check: Processor context corrupt
Kernel panic - not syncing: Fatal machine check
Kernel Offset: disabled

The reboots disappeared when I replaced the CPU with a 10th gen Intel, but that's not a great solution.

After googling around, I've found that C-states might be the problem.

So I added "intel_idle.max_cstate=1" to the kernel boot options and the problem disappeared. 

You can do this using the Unraid Web UI. Go to the main tab, click on "Flash", scroll down to Syslinux Configuration, the "Unraid OS" section should look like this:

kernel /bzimage
append initrd=/bzroot intel_idle.max_cstate=1

You can probably disable it completely in the BIOS, but I haven't tried that.

Probably newer kernels will not have such problems, but we should wait for the Unraid OS update to try it.

I've read about C-states problem on this forum but usually it was about AMD Ryzen CPU.