Re: Announcement: Introducing UEFI Capsule Update Integration for coreboot with EDK II

Hi Sergii, Arthur,

On 13.09.24 16:43, Arthur Heymans wrote:
>>
>> No EFI_CAPSULE_LOADER needed, not Linux specific. EFI-aware OS'
>> are also aware of the EFI system partition, FWIW. And with the
>> Boot Loader Specification[3], we already try to make use of it
>> beyond UEFI.
>>
>> Modeling things with files is a good choice by the Linux kernel
>> developers. But the overall design seems to miss that the boot-
>> loaders are file-aware too! We already have a ubiquitous mecha-
>> nism to pass files (usually the kernel) to the firmware.  Often
>> also to validate their authenticity (secure boot).
>
>
> So basically instead of a runtime service, getting a file from a disk at
> boottime to update the flash?
> I think this is indeed dramatically simpler on both the firmware side as
> the OS side.
> I suppose this only works when there is a boot disk, but then again servers
> tend to have a BMC which takes care of firmware updates anyway.
> So this seems like a good trade-off.

I don't know how UEFI models network boot. But assuming that it's
also something like a "mounted" FS, it might work too?

If not doing EFI, one could ofc. define their own way to retrieve
updates.

>
> Not sure about exact considerations which went into the decision other than
>> on-disk capsules already working in EDK2, but use of in-RAM capsules looks
>> like a cleaner design to me:
>>  - no file-system writes by an OS

I don't think this is bad? Considering more than Linux, I think
it's actually better than having to implement things inside the
kernel.

>>  - no file-system writes by firmware to remove a processed capsule (not
>>    sure I want to trust EDK2 drivers doing that)
>>  - the capsule can be verified at the moment it's offered to the
>>    firmware, not in the middle of a boot
>
> - File system writes are way simpler than supporting an UEFI runtime
> service.
> - Does the firmware need to remove the capsule? Can't fwupd do that once it
> detects a successful update? What does the spec say about this?

It says the firmware should remove the file, however then states
that it may silently fail doing so :) I would also prefer to not
let the firmware write to file systems.

Nico

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