efivars

[FMDF]

On Thu, 23 Sep 2021, 09:11 FMDF, <fmdefrancesco at gmail.com> wrote:

> On Wed, 22 Sep 2021, 08:22 Ruben Safir, <ruben at mrbrklyn.com> wrote:
>
>> What is this for?
>>
>> efivarfs on /sys/firmware/efi/efivars type efivarfs
>>
>> why would the OS need to know anything about the UEFI
>> boot loader once it is up and running?
>>
>
> I think you are still making confusion: UEFI bootloaders and UEFI are two
> different entities.
>
> UEFI bootloaders (like Grub2) serve the purpose to locate, pass kernel
> options  and platform information to the kernel that themselves are going
> to boot.
>
> Instead the UEFI is an interface between the running OS and the platform
> firmware.
>
> UEFI defines two types of services: boot services and runtime services.
>
> After booting is done, via UEFI boot services and eventually UEFI
> bootloaders, the OS does not need anymore the bootloader and the UEFI boot
> services.
>
> Instead the OS needs UEFI runtime services to talk to the platform
> firmware. For example, if OS cannot talk to the platform via UEFI, it
> cannot even shutdown the system (obviously there is much more than simply
> shutting down). How can an OS know that you've attached a plug and play
> device if it cannot talk to the platform firmware?
>
> Fabio
>

For sake of completeness and for better understanding that OS need UEFI,
but not necessarily EFI bootloaders, please read the following document:

https://www.kernel.org/doc/html/latest/admin-guide/efi-stub.html

Linux can boot without bootloaders, but it still needs to use UEFI at
runtime.

Fabio

>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20210923/2200b20d/attachment.html>