Re: GRUB2 PXE chainloading and EFI handles

[Andrei Borzenkov]

On 14.04.2024 14:24, kitzman wrote:
> Dear all,
>
> I'm here to ask for some help - I'm not an EFI expert so brace
> yourselves.
>
> I have the following situation: I PXE boot EFI GRUB2, which has menu
> entries for some operating systems.
> One of the operating systems requires chainloading its bootloader. That
> bootloader checks if it should/can
> boot from PXE, ISO, or local disk (in this order). The way the PXE check
> is done, is that it loads EFI
> handles related to PXE, and, if it can, it initiates a PXE boot (which
> uses other EFI handles, for networking).
>
> My problem is that: once GRUB2 chainloads, and the second bootloader is
> running, some EFI handles
> are not there. So it falls back to local disk boot.

It is possible. grub only supports SNP and exclusively opens network 
card that will close any layered protocols on top of it.

> Is there a way to tell GRUB to leave the handles there as if it's a
> regular PXE boot? 

Someone needs to add support for MNP to grub UEFI network driver.

> Maybe it's not GRUB2
> deciding if those handles should be there anymore? I don't know.
>
> Kind regards,
> kitzman