1. A computer system for exiting a multithreaded guest virtual machine (VM), the computer system comprising: a configuration comprising a core that includes a machine enabled to operate in a single thread (ST) mode and a multithreading (MT) mode, the machine including physical threads; and the machine configured to perform a method comprising: executing a guest entity on the core in MT mode, the guest entity comprising all or a portion of a guest VM, and the guest entity comprising a plurality of logical threads executing on the physical threads; detecting, at the machine, an exit event; and based on the detecting: waiting until all of the logical threads that are currently executing on the physical threads have reached a synchronization point; saving a state including exit reason information of each of the logical threads; and initiating execution of a host in the ST mode on one of the physical threads.