Re: [PATCH v2 0/16] Support for custom EFI firmware

[Fiona Ebner <f.ebner@proxmox.com>]

Hi Christian,

Am 28.09.26 um 7:48 AM schrieb Christian Ludwig:
> Hi,
> 
> here is an updated patch series that brings support for custom UEFI
> firmware images. You can find the v1 series at [1] for reference.
> 
> In Confidential Computing the aim is to not trust the hypervisor, yet it
> runs its bundled firmware in each VM. Some VM appliances also ship their
> own firmware images. This series allows to bring your own firmware for
> OVMF based VMs.
> 
> Today the Proxmox-VE API allows to import a custom efidisk0 (EFIVAR)
> already. EFI firmware and EFIVAR data have to match. Otherwise, the VM
> might not boot anymore. Therefore, with this series you can set a custom
> EFI firmware via the API, along with a custom efidisk. But these are two
> steps. And there is no safety net. The GUI is missing a way to set a
> custom EFIVAR. So this series only allows to set a custom firmware image
> for confidential computing VMs that do not need EFIVAR storage. The
> defaults do not change.
> 

Looks mostly good to me (haven't looked at UI/docs yet). Apart from
comments on the individual patches, I do have two design
questions/considerations:

Format Extensions
=================

Would it be an issue to require/restrict file extensions here, i.e. only
allow names ending with '.fd', '.raw' and '.img' or similar?

1. It would protect against potential confusion, e.g. otherwise, there
can be a filename ending in '.qcow2'. While the code will look at the
returned format which is hard-coded/enforced to be 'raw', such a name
would still be confusing.

2. It would also allow us to extend support to non-raw formats in the
future. For example, we probably want to support IGVM [0] files as well
at some point. Have you already looked at that this format and what do
you think about it regarding your use case?

[0]: https://www.qemu.org/docs/master/system/igvm.html

'bios' as property string
=========================

I wonder if we should turn 'bios' into a property string with the
firmware file as a sub-property? This would couple the properties more
tightly.

===

Happy to hear opinions about these from you and also other developers!

Best Regards,
Fiona