Pausing VCPUs is useful in crosvm so the host system can properly go through a suspend/resume without triggering the soft lockup watchdog in the guest kernel.

With this feature, an external process can tell a running crosvm process to pause all VCPUs. After resuming, crosvm can inform the kvmclock with KVM_KVMCLOCK_CTRL that a suspend/resume cycle was trigger, which will prevent the guest's soft lockup from being triggered.