CI systems often run their workloads in virtualization (for both security and ease of uniform deployment), but sometimes the jobs themselves use a VM to either run part of the build process (such as depending on a tool distributed using Docker, which relies on such due to the host kernel not being Linux) or run some of the unit/integration tests (whether to create a clean environment or to take advantage of the hypervisor to get fast emulation of a target device, such as an Android phone or whatever). Without nested virtualization, services such as GitHub Actions (or locally hosted options; FWIW, GitHub also lets you bring your own "runners") have thereby been somewhat crippled on Apple Silicon.