Hi Naruto,

> My question is why crashing kernel on a specific CPU (not CPU0) on a KVM guest, it cannot bring up that CPU? The problem is gone if the guest is rebooted again. The problem does not happen on a real HW.

My best bet would be to open a service request or to send your question to some KVM-specific mailing list. It is pretty specific and probably answered best by someone with developer-level knowledge of KVM.