[libvirt PATCH 00/28] Improve firmware autoselection

[Gerd Hoffmann]

On Thu, Jun 23, 2022 at 06:14:12PM +0200, Andrea Bolognani wrote:
> The main motivation behind this series was making it as simple as
> possible ("one click") to enable Secure Boot for a VM.

Heads up, and sort-of follow-up to the recent secure boot and smm (x86)
and tz (arm) discussion.

We'll most likely get a new secure boot variant soon.  This will not
require smm, but it will also not support persistent variables.  The
underlying idea is to simply re-initialize the variable store from
known-good ROM on each boot to compensate for the varstore not being
protected against the guest OS tampering with it.

Which of course implies some drawbacks:  The guest can't add keys (via
mokutil) for example, and turning off secure boot in firmware setup
wouldn't work either.  There are enough use cases (like just booting
cloud images in secure boot mode) where this doesn't matter, so I
consider this useful nevertheless, but maybe a separate feature flag
like 'stateless-secure-boot' makes sense for that.

Not sure yet how to package that up, best is probably as stateless image
because that'll reduce the chances of getting it wrong, i.e. something
like this:

{
    "description": "OVMF with secure boot, no persistent vars",
    "interface-types": [
        "uefi"
    ],
    "mapping": {
        "device": "flash",
        "mode": "stateless",
        "executable": {
            "filename": "/usr/share/edk2/ovmf/OVMF.secboot.fd",
            "format": "raw"
        }
    },
    "targets": [
        {
            "architecture": "x86_64",
            "machines": [
                "pc-i440fx-*"
                "pc-q35-*"
            ]
        }
    ],
    "features": [
        "secure-boot",
        "enrolled-keys",
    ]
}

The idea idea should work for aarch64 too and remove the trustzone support
requirement.

take care,
  Gerd