> On Jan 30, 2020, at 4:24 AM, Xiaoyao Li <xiaoyao.li@xxxxxxxxx> wrote: > > There are two types of #AC can be generated in Intel CPUs: > 1. legacy alignment check #AC; > 2. split lock #AC; > > Legacy alignment check #AC can be injected to guest if guest has enabled > alignemnet check. > > When host enables split lock detection, i.e., split_lock_detect!=off, > guest will receive an unexpected #AC when there is a split_lock happens in > guest since KVM doesn't virtualize this feature to guest. > > Since the old guests lack split_lock #AC handler and may have split lock > buges. To make guest survive from split lock, applying the similar policy > as host's split lock detect configuration: > - host split lock detect is sld_warn: > warning the split lock happened in guest, and disabling split lock > detect around VM-enter; > - host split lock detect is sld_fatal: > forwarding #AC to userspace. (Usually userspace dump the #AC > exception and kill the guest). A correct userspace implementation should, with a modern guest kernel, forward the exception. Otherwise you’re introducing a DoS into the guest if the guest kernel is fine but guest userspace is buggy. What’s the intended behavior here?
