linux: enable EFI_ZBOOT for generic compression support

[RaitoBezarius]

Description of changes

Starting 6.1, it is possible to have generic compression for aarch64 and riscv64 via CONFIG_EFI_ZBOOT which implements apparently its own decompression.

https://lwn.net/Articles/907679/

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[RaitoBezarius]

I am testing this by cross compiling a RISCV64 kernel first.

[alyssais]

aarch64 and riscv64

And loongarch!

[alyssais]

Needs unixtools.hexdump in nativeBuildInputs, at least for 6.3+.

[RaitoBezarius]

@alyssais Were you able to measure the reduced size? I don't know if I'm holding this wrong but I cannot see anything else than Image being produced for aarch64 or riscv64 with the same size.

[arianvp]

I think we also need to change the target here to bzImage (or zImage ?):

nixpkgs/lib/systems/platforms.nix

Line 379 in df70846

target = "Image";

[RaitoBezarius]

I think we also need to change the target here to bzImage (or zImage ?):

nixpkgs/lib/systems/platforms.nix

Line 379 in df70846

target = "Image";

Yeah, actually, I am planning for a bigger refactor of that.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/pi4-broken-on-23-11-uefi-zfs-root/36375/4

[ius]

@alyssais Were you able to measure the reduced size? I don't know if I'm holding this wrong but I cannot see anything else than Image being produced for aarch64 or riscv64 with the same size.

For reference, some numbers for my Aarch64 cross compiled kernel:

• Image: 56M
• vmlinuz.efi 15M

This would be really useful for undersized /boot partitions.

[zzywysm]

Commenting because this is important and shouldn't be marked stale.

[flokli]

I'm also interested in this, as rust-hypervisor is not happy with the too large kernels we currently produce. I summarized the situation in https://b.tvl.fyi/issues/407.

[flokli]

I'm also interested in this, as rust-hypervisor is not happy with the too large kernels we currently produce. I summarized the situation in https://b.tvl.fyi/issues/407.

I was just dumb, and used the wrong kernel output (from the dev output). ${myKernel}/${stdenv.hostPlatform.linux-kernel.target} actually has a somewhat reasonable size on aarch64-linux too. This is probably still important to get the number down further?

[fpletz]

I've been successfully EFI booting my Pinebook Pro with Tow-Boot, systemd-boot and zboot. 🚀 These were the changes needed if somebody wants to test on another aarch64 machine: master...fpletz:nixpkgs:arm64-zboot

To get this PR through the the door, I have fixed the formatting issue, rebased and added a commit restricting EFI_ZBOOT to aarch64 for now since I have tested the kernel builds correctly both the Image and the vmlinuz.efi. This is needed since otherwise the x86 build breaks. We should add new systems when they have been tested and thus not inadvertently break kernel builds of non-release architectures.

Current file sizes for aarch64:

70M	/boot/EFI/nixos/jvs0n8skfvzxixbaw74qmjz3df6m0znf-linux-6.9.7-Image.efi
17M	/boot/EFI/nixos/qgx88i268aq4ra1sd6xjzhdmsmxybny3-linux-6.9.7-vmlinuz.efi.efi

The extra .efi is added by systemd-boot-builder.py. 😏

[flokli]

Thanks for carrying this over the finish line! 🎉

[arianvp]

But this PR as is doesn't do anything as we still make install the uncompressed kernel I think? We need to make sure we do make vmlinuz.efi as opposed to make Image on aarch64

#287122 fixes that iirc

[arianvp]

Ah #324419 is the follow-up. I missed that