Limitations¶
Honest scope notes for the current tree. These are intentional cuts and sequencing choices, not a backlog of unknown bugs.
Backends are asymmetric¶
| Track | Maturity |
|---|---|
| HVF / aarch64 | Platform layer live: Linux boot, virtio (blk/net/vsock/gpu), snapshot-fork, control plane, govern, observe, meter, SMP |
| KVM / x86-64 | PVH Linux boot, virtio-blk/net/vsock, SMP, IOAPIC; the platform layer (control plane, metering, govern, observe, watchdogs, slirp + egress firewall) and the cross-process snapshot fork (COW restore, SMP fork, __snapshot__/__park__, vmgenid reseed), all run-verified on bare metal. Remaining gap: virtio-gpu |
KVM parity is tracked in the roadmap.
Snapshot / restore¶
Snapshot save, COW restore (restore=1 / restore_from=), and the on-demand __snapshot__/__park__ capture work on both backends. The image formats differ (HVF vs KVM NSKV) and are same-host, same-build: a base is not portable across backends or machines. Still HVF-only: the rewind demo, GPU scanout capture, deflate-compressed durable bases, and incremental (diff) snapshots. See Running on KVM for the x86 flow.
Not a general-purpose VMM (yet)¶
- OVMF / UEFI is deferred. The edge path is PVH direct boot, not full firmware emulation.
- Windows guests are future scope (Phase 4+).
- Live migration and VFIO passthrough are roadmap items, not shipping.
- 3D virtio-gpu / virgl is explicitly out of core. 2D framebuffer only; 3D would be out-of-process.
Embedding¶
The shipping artifact is one swerver binary with embedded nether. The integration
contract (vsock spine, per-VM-per-worker, eventfd registration into IoRuntime) is
designed but not fully wired yet. The standalone nether executable remains for
dev and bringup only.
API stability¶
The library root (src/root.zig) and control protocol may change before 1.0. Downstream embedders should pin commits.
Platform¶
nether is the isolate + govern layer inside the swerver binary. It does not own routing, TLS, or billing — those stay in swerver and x402 above the embed boundary.
Roadmap¶
Phases, done-lines, and the platform track are in Roadmap. Architectural forks are recorded in Decisions.