[CentOS] A Blast from the past

Tue Aug 17 15:34:39 UTC 2021
Simon Matter <simon.matter at invoca.ch>

> Hello,
> Can you please help with an interesting problem.
> I have an Intel Haswell based processor with CentOS 7.0 with an early
> kernel
> booting and running perfectly.
> I changed the processor to an Ice Lake and I get the problem below when I
> boot the working Haswell disk.
> The boot process hangs almost immediately and when I remove the 'quiet'
> boot
> parameter I see that it hangs randomly, usually with a high CPU number,
> when
> SMPBOOT is starting up the cores.
> The only solution I have found is to boot with the 'nr_cpus=8 (could be
> any
> low number), update to the latest kernel then reboot with the 'nr_cpus=8'
> parameter removed.
> On examination there are no problems with CentOS 7.4 and above but there
> are
> with CentOS 7.3 and below.

I think the issue is quite clear here: the newer CPU is not handled
correctly by the old kernel - maybe it even doesn't know this CPU type and
doesn't know how to detect the number of cores it has.

I don't think there is a better solution than what you already did.