I found this article with the diagram that you mention: https://wccftech.com/ibm-worlds-first-dual-architecture-proc...

The diagram is the last picture, and according to it you choose the ISA at the VM level: either Linux on s390x or Linux on arm64, but not both on the same VM.

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rbanffy 6 hours ago | parent [-]

Interesting that z/VM doesn't seem to support spinning up ARM Linux VMs, at least according to this diagram, but it does support bringing up s390x Linux VMs (the LinuxONE Community Cloud creates Linux VMs under z/VM). Also, it looks like z/OS is running directly on the LPAR, which wasn't common the last time I looked (a decade ago, more or less).

	▲	dfox an hour ago \| parent [-]
		I suspect that is not an inherent limitation of the dual-ISA design (the HotChips slides mention some sort of bidirectional thread state mapping between arm and z), but just about there not being z/VM release that supports that (building such a thing is probably SMoP, but another question is whether that makes business sense).