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.

Getting here required more than writing an RFC. The PHP License gives the PHP Group the authority to change it, which meant tracking down each of the original PHP Group members and getting their written consent. Each approved the proposal. Perforce Software, the successor to Zend Technologies, needed to sign off on the Zend Engine side, as well. They provided a formal letter confirming their full authority and support for the change. I hired an attorney to review the proposal and provide advice on any legal questions that might surface during the discussion period. Speaking of which, I allowed for a six-month community discussion period preceding the vote, which passed unanimously.

LWN covered the license-change process back in March.