A recent patch set from Steffen Eiden and others has set the groundwork for allowing hardware-assisted emulation of Arm CPUs on s390 CPUs. Version two of the posting fixes a handful of smaller problems, but does not differ much. The patches were welcomed by the Arm maintainers, pending some discussion of how the collaboration between the architectures could be structured to prevent maintainability problems on the Arm side. When those details are resolved, the patches could pave the way for transparently running Arm-based virtual machines (VMs) on s390 hosts at native or near-native speeds.