Port backlog from cocoon: multi-disk, VFIO passthrough, console attach, hot-NIC, virtiofs, vsock exec, logs, export/import

[CMGS]

Tracking issue for cocoon capabilities not yet ported to cocoon-macos (QEMU/macOS on x86 Linux).

Already done (context): full network port (CNI/bridge auto-TAP, same plane as cocoon CH/FC), snapshot/restore/clone (offline qcow2-internal + CoW + unique cold-boot identity), image store (cocoon cloudimg, qcow2-only), shared <state-dir>/firmware store + per-VM CoW OpenCore overlay, display-sleep fix (pmset baked).

All Linux-runtime ports should follow the *_linux.go + *_other.go build-tag split so GOOS=darwin go build ./... stays green; reuse cocoon types/utils where possible.

P0 — bypass / hardware

• Multi-disk / data disks. Port cocoon types.DataDiskSpec + types.StorageRole (data/cow/layer/cidata) + a --data-disk flag (parsed into VMConfig.DataDisks). QEMU mapping: one extra -drive id=dN,if=none,format=…,file=… + -device virtio-blk-pci,drive=dN per disk; create + attach/detach lifecycle. Types are darwin-clean; the qcow2/format work is pure qemu-img.
• PCI device passthrough (VFIO). Port cocoon extend/vfio (vfio.Spec/Attacher/Lister, BDF + SysfsPCIPrefix) and a vm device attach/detach surface. QEMU mapping: -device vfio-pci,host=<BDF> (host device bound to vfio-pci). Linux-only, build-tagged like the network port. Runtime-only (gone after stop/clone/restore), don't snapshot a VM holding one.

P1 — lifecycle parity

• vm console real attach. Today it only prints a VNC 127.0.0.1:590N / SSH … hint (cmd/vm/handler.go Console). Options: add -serial (unix socket / pty) + attach via socat (note: macOS has no serial login — only OpenCore/early-boot log), and/or vm console --vnc that launches a viewer against the framebuffer. For macOS the real console is VNC + SSH, so decide whether "attach" means serial-log or VNC.
• NIC hot-resize. cocoon vm net --nics N (add/remove NICs on a running VM). QEMU mapping: netdev_add/netdev_del + device_add/device_del virtio-net-pci over QMP, paired with cocoon network Add/Remove for the host TAP. (CH has hot-plug; QEMU does too.)
• vm logs [-f --tail]. Capture per-VM qemu stdout/stderr to a logfile under the VM dir (currently inherits the launcher's stdout/stderr) and tail it.
• Human-readable CLI output by default + -o json. vm list / image list / vm inspect currently print raw json.MarshalIndent as the default (machine output). Add a default table/columnar view (e.g. vm list: NAME · STATE · CPU · MEM · VNC · SSH · SERIAL · IMAGE; image list: NAME · SIZE · DIGEST · CREATED) and gate JSON behind -o json / --format json, matching cocoon's vm list -o json.
• Streaming status / watch interface. Port cocoon's vm status [--event --format json] event stream (consumed by vk-cocoon): emit per-VM lifecycle / state-change events (created → running → stopped/exited, SSH-ready) as a line-delimited JSON stream so a consumer can watch the fleet. For cocoon-macos: a vm status --watch / --event that polls qemu liveness + the record and emits state transitions.

P2 — advanced

• virtiofs share (vm fs attach). cocoon vhost-user-fs. QEMU mapping: virtiofsd + -chardev socket + -device vhost-user-fs-pci (+ -object memory-backend-file,share=on). Verify Tahoe has a working virtiofs driver first — may not, in which case this is blocked guest-side.
• vsock vm exec. Run an in-guest command over vsock (cocoon uses cocoon-agent). QEMU mapping: -device vhost-vsock-pci,guest-cid=…; needs an in-guest agent on macOS (none today — SSH is the current exec path).
• Cross-node snapshot export/import. cocoon snapshot export/import (plain tar, not OCI). For QEMU: tar the VM dir (disk overlay + OVMF_VARS + injected OpenCore + vm.json), rebase onto the same content-addressed base blob on import. Reuse cocoon snapshot/localfile envelope concept.

Notes

• Metering / tenant accounting / network policy stay with the consumer — cocoon (and cocoon-macos) are the mechanism layer, not policy.
• vm snapshot is intentionally offline/disk-state only: -cpu +invtsc makes the macOS guest non-migratable, so live savevm/resume-from-RAM is out (would also be an App-Store-identity risk for clones).