- Fix bug in `KvmRunWrapper`. The memory for `kvm_run` struct was
  not unmapped after the `KvmRunWrapper` object got out of scope.
- Return proper value when receiving the EOI KVM exit.
- Add support for KVM_ENABLE_CAP.
- Add support for KVM_SIGNAL_MSI.
- Mark `set_user_memory_region` as unsafe.