port-amd64/60631: Intel N150 cpu hang leading to kernel panic in heartbeat

["phil.netbsd%ashbysoft.com@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60631
>Category:       port-amd64
>Synopsis:       Intel N150 cpu hang leading to kernel panic in heartbeat
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 22 08:50:00 +0000 2026
>Originator:     Phil Ashby
>Release:        NetBSD 11.0 (GENERIC)
>Organization:
>Environment:
NetBSD timmy-iv 11.0 NetBSD 11.0 (GENERIC) #0: Thu Jul 30 15:23:12 UTC 2026  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
On a Beelink ME Pro NAS, which uses the Intel N150 SoC and associated Intel PCH chipset, I find the following with current NetBSD 11.0 (GENERIC):

1/ USB image installer works OK
2/ Single user boot (boot -s) works OK
3/ Multi user boot (boot) hangs during /etc/rc execution
  3.1/ Further execution appears to stop (no visible progress)
  3.2/ heartbeat(9) triggers a kernel panic after 15s (1501 beats)

>How-To-Repeat:
The problem is completely repeatable on every default multi user boot
>Fix:
After experimenting with boot options (thanks to Stephen Borill) I have discovered that avoiding ACPI (boot -2) provides a reliable solution. Sometimes a uniprocessor boot (boot -1) works, but not always.

Further information:

DDB shows that the stuck cpu is asleep in x86_stihlt() at the point when the heartbeat panic fires.

I am happy to collect crash dumps for analysis.