Create a Manifest of microVM Capabilites

[raduweiss]

We need some kind of documentation, possibly in a programmatically consumable format, to express the device profile of the microVM to consumer. For example, those building minimal Guest OSs could use this manifest to customize device support.

[raduweiss]

@rn do you think this kind of thing would actually be useful?

[dianpopa]

It looks like #1883 fixes this, right @raduweiss ?

[bbros-dev]

If #1883 doesn't close this (I think it misses the "possibly in a programmatically consumable format"), I think it is closed by #923 and #1212.

@dianpopa if you think it adds value I could insert into #1883 a 'complete' example of the JSON 'document'?

Somthing like:

{
  "boot-source": {
    "kernel_image_path": "vmlinux.bin",
    "boot_args": "console=ttyS0 reboot=k panic=1 pci=off"
  },
  "logger": {
    "log_fifo": "log_fifo",
    "metrics_fifo": "metrics_fifo"
  },
  "drives": [
    {
      "drive_id": "rootfs",
      "path_on_host": "xenial.rootfs.ext4",
      "is_root_device": true,
      "is_read_only": false
    }
  ],
  "machine-config": {
    "vcpu_count": 2,
    "mem_size_mib": 1024,
    "ht_enabled": false
  }
}

[dianpopa]

Hi @bbros-dev , sorry for the late reply, it is just now that I saw your proposal. I think the method you suggested of inserting an example of a complete microvm config with all the required fields clearly adds value. Feel free to post a PR with the suggestion. Thanks for the contribution!

[bbros-dev]

My working assumption is that this JSON should be valid uVM configuration - that is if passed to Firecracker it will run without error.

Are there configuration elements that are mutually exclusive?

[dianpopa]

The only thing that comes to mind is the BootSource representation and DriveConfig, i.e specifying an initrd_path in the BootSource (https://github.com/firecracker-microvm/firecracker/blob/master/src/api_server/swagger/firecracker.yaml#L734) will not make sense with a DriveConfig that specifies a root device (https://github.com/firecracker-microvm/firecracker/blob/master/src/api_server/swagger/firecracker.yaml#L762) since the system will use the provided initrd_path to load the filesystem. What you could do is provide 2 microvm configs: one using initrd_path and one using DriveConfig with a root device. wdyt?

[dianpopa]

A manifest of microVM capabilities can be found in the https://github.com/firecracker-microvm/firecracker/blob/v1.0.0/tests/framework/vm_config.json. This can be programatically consumed to configure a microVM from commandline. See #1212.