I just confirmed the two requested patches are in the Ubuntu-4.15.0-29 kernel:
eeada334156f powerpc: use NMI IPI for smp_send_stop
4190e27bf0ee powerpc: Fix smp_send_stop NMI IPI handling
Can you confirm the kernel posted in comment #5 fixes this bug on the same machine?
I just confirmed the two requested patches are in the Ubuntu-4.15.0-29 kernel:
eeada334156f powerpc: use NMI IPI for smp_send_stop
4190e27bf0ee powerpc: Fix smp_send_stop NMI IPI handling
Can you confirm the kernel posted in comment #5 fixes this bug on the same machine?