Comment # 4 on bug 1227345 from Maxime Thirion

Thank you very much for your feedback.

I tried with :

The default kernel and the vanilla kernel in 6.9.7.

I tried the vanilla kernel 6.10 rc6.

The problem is still there, only one core is available.

On the other hand, for some reason, both my servers have the "noapic" option
enabled in the kernel parameters in grub, but I've never touched or added this
option.

Honestly, I don't even know exactly what she does.

By removing this option, all cores are initialized and operation is normal.

So, the problem comes from the 6.9 kernel with the noapic option, and the fact
that this option is "default" on my installations.

I'm guessing that Hetzner's rescue system doesn't have this option, which
explains why everything works with their system.