Perhaps I misunderstood. Here is the logic flow I followed:
(1) Apple has a virtualization framework that can "...boot and run a Linux-based operating system on an Apple silicon or Intel-based Mac computer."
(2) The virtualization framework for arm-based Macs will virtualize arm-Linux and x86-based macs would virtualize x86-linux. There maybe a semantic issue here if you believe that this api would also allow the "virtualization" of x86-linux on arm. That would not be considered virtualization to my best understanding of the definition.
(3) Looking at Apple's VZVirtualMachineConfiguration, VZVirtualMachine and "Virtualization Constants" there is nothing apparently exposing the underlying virtualization mechanism. So we don't know if Apple uses hardware (ring -1 in x86 parlance) or software virtualization (almost always para-virtualization) under the hood. Likely it uses both depending on the context.
(4) We know that Apple's current dev kit hardware (A12z) doesn't support hardware virtualization. Hardware virtualization is commonly referred to as the "Virtualization Host Extension" in arm64 parlance.
(5) We know that Apple demoed virtualization on arm with what appeared to be a arm64 ubuntu guest.
(6) Your original message said that you believed they weren't using an a12z for the demo, likely because its aforementioned lack of hardware virtualization.
(7) The comment below yours suggest that "One can certainly write software that virtualizes another machine". They were more than likely referring to para-virtualzation in their comment. I don't know any other blanket type of software virtualization.
(8) You responded saying you didn't know what software virtualization was, it is almost always para-virtualization. Para-virtualziation does not require a hardware hypervisor and predates all hardware virtualization technologies.
While there is full-hardware virtualization, it basically never a thing that happens anymore because of the rather large overhead. I don't know of any modern virtualization software that offers full software virtualization. Especially if your guest is Linux.
