Re: [OE-core] [PATCH 0/6] systemd based initrd and modular kernel support

[Mikko Rapeli <mikko.rapeli@linaro.org>]

Hi,

On Mon, Mar 17, 2025 at 11:37:29AM +0100, Alexander Kanavin wrote:
> Note that the feature freeze is now. This has to wait.

Yes, I'm aware. Just posted this out as it is 'done' on my side
and need feedback.

The kernel config change RFC is also out but that in current form
breaks things so need feedback how this could be fixed, for example
in specific machines configure features to compile as modules,
and/or which usecases must work with the single kernel binary
without initrd.

Cheers,

-Mikko

> Alex
> 
> On Fri, 14 Mar 2025 at 12:20, Mikko Rapeli via lists.openembedded.org
> <mikko.rapeli=linaro.org@lists.openembedded.org> wrote:
> >
> > systemd based initrd supports more security, encryption etc features
> > than custom shell script ones but oe-core lacks support for it.
> > Convert core-image-initramfs-boot to create systemd based initrd
> > if "systemd-initramfs" is set in DISTRO_FEATURES. Includes a test
> > for this initrd to mount rootfs via Unified Kernel Image uki.py.
> >
> > Sadly the boot time is really slow, e.g. over 30 seconds with
> > systemd based initrd. One of the major reasons is the large
> > amount of kernel modules built into the linux-yocto kernel and
> > processing of their udev events in userspace. Thus add
> > kernel-initrd-modules meta package to easily install
> > subset of all kernel modules to initrd. The subset
> > supports "mount rootfs from any block device" but
> > doesn't include graphics, UBS etc support. Without this
> > generated meta package, initrd recipe needs to manually define
> > which exact kernel modules to include which breaks if
> > those modules are built into the kernel. Thus the initrd
> > becomes machine and kernel config specific and hard to maintain.
> > With this meta package a generic initrd can be created.
> >
> > Separate changes to linux-yocto compile a lot more drivers
> > as modules but they depend on these initrd changes.
> >
> > Mikko Rapeli (6):
> >   systemd: use serial-getty-generator on genericarm64
> >   systemd: enable efi support if in MACHINE_FEATURES too
> >   uki.bbclass: drop serial console from kernel command line
> >   kernel.bbclass: add kernel-initrd-modules meta package
> >   core-image-initramfs-boot: add option to build systemd based initrd
> >   oeqa selftest uki.py: add aarch64/arm test with systemd based initrd
> >
> >  .../recipes-core/systemd/systemd_%.bbappend   |  3 +
> >  .../kernel-module-split.bbclass               | 46 +++++++++++
> >  meta/classes-recipe/kernel.bbclass            |  5 +-
> >  meta/classes-recipe/module.bbclass            | 37 +++++++++
> >  meta/classes-recipe/uki.bbclass               |  2 +-
> >  meta/lib/oeqa/selftest/cases/uki.py           | 76 +++++++++++++++++++
> >  .../images/core-image-initramfs-boot.bb       | 28 ++++++-
> >  meta/recipes-core/systemd/systemd_257.3.bb    |  1 +
> >  8 files changed, 193 insertions(+), 5 deletions(-)
> >  create mode 100644 meta-yocto-bsp/recipes-core/systemd/systemd_%.bbappend
> >
> > --
> > 2.43.0
> >
> >
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