Re: [RFC PATCH 0/3] efi: Implement generic zboot support
From: Mario Limonciello
Date: Thu Apr 20 2023 - 08:30:09 EST
On 4/20/23 02:54, Ard Biesheuvel wrote:
On Thu, 20 Apr 2023 at 08:07, Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
Hi,
Realistically, the second option is unlikely to ever be used on x86,
What would be needed to do so? Teach kexec-tools and grub2 parse and
load zboot kernels I guess?
I already implemented this for mach-virt here, so we can load Fedora
kernels without firmware:
https://gitlab.com/qemu-project/qemu/-/commit/ff11422804cd03494cc98691eecd3909ea09ab6f
On arm64, this is probably more straight-forward, as the bare metal
image is already intended to be booted directly like that. However,
the x86 uncompressed image requires surprisingly little from all the
boot_params/setup_header cruft to actually boot, so perhaps there it
is easy too.
For existing boot loaders like grub I'd expect it being easy
to code up, all the setup header code exists already, grub also
has support for uncompressing stuff, so it should really be only
zboot header parsing and some plumbing to get things going (i.e.
have grub boot efi zboot kernels in bios mode).
Disclaimer: didn't actually check grub source code.
I have :-(
I suspect the bigger problem wrt. grub is that getting patches merged
upstream is extremely slow and every distro carries a huge stack of
patches ...
Yeah, Daniel has been asking me about LoadFile2 initrd loading support
for x86, so I think getting things merged is not going to be a problem
(although it will still take some time) - I can just implement it and
send it out at the same time.
If zboot ends up being the way to go there would be quite a bit
of pressure to land the GRUB stuff in distros because of the NX
requirements being pushed into the EFI ecosystem.
They wouldn't be able to work on a system that enforces NX which
is anticipated to balloon.
But hacking/building/running GRUB is a rather painful experience, so I
have been kicking this can down the road.