Rebooting causes a cold reboot instead of a normal reboot

So far I’ve only noticed this on OpenSUSE and Pop!_OS, not any other distro I’ve tried (which is a lot…but that’s beside the point). But when I reboot my laptop it does a full power cut, and POSTs again instead of just doing a warm reboot (gives me the “hit a key to get firmware menu” but fans keep spinning, no sign of a POST). My laptop is a Lenovo T530 if that matters.

I’ve tried changing the “reboot=” kernel parameters and it doesn’t make a difference, and I tried booting with “mitigations=off” just in case it had something to do with a hardware mitigation (I was grasping at straws), that didn’t do anything either.

Anyway, I realize this isn’t that important of an issue but I’m really curios as to why it is. Just wondering if anyone has any ideas of where to start looking.

Have you carefully checked BIOS settings, to see if those might be the cause?

More specifically ACPI settings, both in the BIOS and in the OS.

Another interesting try is to see what the following does in a terminal/console, which is what I often prefer to do (It’s a lot faster than any Desktop reboot if you already have a root console open)

systemctl reboot

TSU

BIOS settings haven’t changed from any of the other distros that don’t cause the problem but I could take a look around and see if there’s anything in the OS. Do you know where those setting would be?

If memory serves rebooting from the command line does the same thing, I’ll have to double check. It even occurs from within the installer.

IME, all Linux distros when told to reboot normally do a cold boot, even from using Ctrl-Alt-Del keys.

The type of reboot you wish can be specified via kernel cmdline option reboot=. Details are in https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt

I’ve tried the reboot= kernel command line parameter and it doesn’t seem to have any effect.

Most of the other distros (Debian, Ubuntu, Fedora, Solus, Arch) I’ve run on the exact same hardware don’t cold-reboot.

I did some more digging and I think this is what I’m dealing with: https://bugzilla.opensuse.org/show_bug.cgi?id=1108302

What I have is matching the behavior referenced at https://bugzilla.redhat.com/show_bug.cgi?id=1532058 which is mentioned in that bug.

This mitigation is enabled by default if I’m reading the kernel sources correctly.