Re: [PATCH v3 3/7] efi: implemented LoadFile2 initrd loading protocol for Linux

[dann frazier]

On Thu, Oct 28, 2021 at 11:31:16PM +0300, Nikita Ermakov wrote:
> From: Ard Biesheuvel <ard.biesheuvel@arm.com>
> 
> Recent Linux kernels will invoke the LoadFile2 protocol installed on
> a well-known vendor media path to load the initrd if it is exposed by
> the firmware. Using this method is preferred for two reasons:
> - the Linux kernel is in charge of allocating the memory, and so it can
>   implement any placement policy it wants (given that these tend to
>   change between kernel versions),
> - it is no longer necessary to modify the device tree provided by the
>   firmware.
> 
> So let's install this protocol when handling the 'initrd' command if
> such a recent kernel was detected (based on the PE/COFF image version),
> and defer loading the initrd contents until the point where the kernel
> invokes the LoadFile2 protocol.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Signed-off-by: Nikita Ermakov <arei@altlinux.org>
> ---
>  grub-core/loader/arm64/linux.c | 117 ++++++++++++++++++++++++++++++++-
>  1 file changed, 116 insertions(+), 1 deletion(-)
> 

fyi, Ubuntu currently includes this patch in our in-devel release, but
we'll likely have to disable it for arm64 due to a regression. We found
that it casuse our PXE boot install tests to fail because
grub_net_fini_hw() is called before the TFTP transfer for the
initramfs is attempted. More info here:

  https://launchpad.net/bugs/1967562

 -dann