krunkit integration with crc/crc-ng

[vyasgun]

Component

None

Task description

Description

krunkit integration with crc/crc-ng

Background

• macadam already supports krunkit (--provider libkrun)
• Provides an alternative to vfkit for macOS virtualization

Requirements

• Allow users to start CRC with krunkit
• Support running self-sufficient CRC bundles on krunkit
• Integrate with crc daemon for networking
• Test coverage for krunkit usage (VM lifecycle, networking, resource management)

[vyasgun]

Running CRC Bundle with macadam using --provider libkrun

Related Issue: #4968

Tested on: macOS (26.0) ARM64 (Apple Silicon)
Bundle: crc_vfkit_4.20.1_arm64 (RHCOS-based)

Commands Used

./bin/macadam-darwin-arm64 init \
  /Users/gvyas/.crc/cache/crc_vfkit_4.20.1_arm64/crc.img \
  --provider libkrun --cpus 4 --memory 16384 --disk-size 35 \
  --name crc --ssh-identity-path /Users/gvyas/scripts/keys/id_ed25519 \
  --username core --cloud-init /Users/gvyas/scripts/user-data --log-level debug

./bin/macadam-darwin-arm64 start crc --provider libkrun --log-level debug

Startup and Authentication Behaviour:

The VM successfully reaches the running state despite initial debug logs showing SSH connection errors. --cloud-init is ignored and the provided public key is not installed during startup. The machine transitions into running state and can be accessed using the key inside the bundle.

VM State Check:

./bin/macadam-darwin-arm64 list --provider libkrun
NAME        VM TYPE     CREATED         LAST UP            CPUS        MEMORY      DISK SIZE
crc         libkrun     24 minutes ago  Currently running  4           16GiB       35GiB
curl -s --output - http://localhost:62726/vm/state
{"state": "VirtualMachineStateRunning"}

To manually access the VM:

ssh core@localhost -p 60277 -i /Users/gvyas/.crc/cache/crc_vfkit_4.20.1_arm64/id_ecdsa_crc

GPU Passthrough:

[core@crc ~]$ ls -l /dev/dri/
total 0
drwxr-xr-x. 2 root root         80 Nov 11 02:34 by-path
crw-rw----. 1 root video  226,   0 Nov 11 02:34 card0
crw-rw-rw-. 1 root render 226, 128 Nov 11 02:34 renderD128

Comparison with vfkit:
The default provider on macos is applehv which means that it starts a vfkit VM. Both krunkit and vfkit have similar startup times and same resource utilization (CPU and RAM). The key difference is the GPU access which is only available in krunkit.

Conclusion:

macadam can successfully start CRC bundles using the --provider libkrun on macOS ARM64, and the VM provides working GPU access, which is the key advantage over the default vfkit provider for LLM workloads. SSH access requires the pre-baked id_ecdsa_crc key from the bundle, as standard methods for injecting a custom key (--ssh-identity-path and --cloud-init) are ineffective in both provider configurations with this bundle.