In addition, it is managed by an ASC, the “ANS”, which needs to be brought up before NVMe can work, and that also relies on a companion “SART” driver, which is like a minimal IOMMU. The NVMe hardware in the M1 is quite peculiar: it breaks the spec in multiple ways, requiring patches to the core NVMe support in Linux, and it also is exposed as a platform device instead of PCIe.
