Raspberry Pi no network after PXE boot with flatcar due to missing kernel

[wernerb]

Description

Support has already been added for RPI4 network in #227 . However, when using PXE booting, we need an additional flag called CONFIG_MDIO_BCM_UNIMAC. More details can be found here https://bugzilla.redhat.com/show_bug.cgi?id=1943983

Impact

No ethernet adapter when network booting (either PXE or UEFI HTTP).

Environment and steps to reproduce

boot http://boot.netboot.xyz/ipxe/netboot.xyz-arm64.efi manually through the HTTP Network boot gui with the UEFI firmware for
RPI4.
Then when booted into the menu.
Select Execute iPXE shell

Type in the following:

kernel https://alpha.release.flatcar-linux.net/arm64-usr/current/flatcar_production_pxe.vmlinuz initrd=flatcar_production_pxe_image.cpio.gz flatcar.config.url=http://urldoesntmatter flatcar.first_boot=yes console=tty0 console=ttyS0 flatcar.autologin
initrd https://alpha.release.flatcar-linux.net/arm64-usr/current/flatcar_production_pxe_image.cpio.gz
boot

You will see messages such as:

[  133.316150] Unable to find mii
[  133.319239] bcmgenet BCM6E4E:00 enabcm6e4ei0: failed to connect to PHY

Expected behavior
The network driver comes up.

Additional information
Enabling the flag would fix the support for PXE alongside the support already #227

[dongsupark]

Thanks for the PR flatcar-archive/coreos-overlay#929.
From my understanding, we would have to also update dracut to >= 0.52, to fix the rpi4 issue.
Though Gentoo does not seem to have its stabilized ebuild. Well.

[wernerb]

Thanks for the PR kinvolk/coreos-overlay#929.
From my understanding, we would have to also update dracut to >= 0.52, to fix the rpi4 issue.
Though Gentoo does not seem to have its stabilized ebuild. Well.

Yes, but not just for rpi4. Per my understanding all net/mdio modules are currently not working since kernel 5.10.

[t-lo]

To summarise, we would need to:

• merge Enable MDIO_BCM_UNIMAC for arm64 flatcar-archive/coreos-overlay#929
• update dracut to 053 (upstream gentoo ebuild available, even though it's masked currently [i.e. unstable])

Adding a label "good first issue" for users who want to accustom themselves with building custom images, assuming that both the kernel config change as well as the dracut version bump will be straightforward.

[dongsupark]

Fortunately Gentoo stablized dracut 053.
amd64: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=6a934a75bbc054b3ae7c14948df6a4ac6d69e643
arm64: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=a35bed081b36613d414a7a24534a4706e11fb2b0

[jepio]

The effect of the dracut fix still needs to be tested.

[raballew]

@jepio I used the latest version of the alpha channel on Raspberry Pi 4 and it seems that the issue is still present causing the same error as described in #227 (comment) when using iPXE to netboot. I will build a custom image later today and rerun the test.

[jepio]

I saw that same error (failed to connect to PHY) even without iPXE and netboot. I will try to push my WIP dracut update PR, that allows the network to be configured on my RPI4, you could test and see if that also solves the issue when netbooting.

[raballew]

@jepio That would speed up the entire process! I will test your WIP PR once pushed.

[jepio]

@raballew try flatcar-archive/coreos-overlay#1105.

[raballew]

@jepio My machine is currently rebuilding everything. This will take a while and now I am wondering how both flatcar_production_pxe.vmlinuz and flatcar_production_pxe_image.cpio.gz are generated. Could you point me in the right direction?

EDIT: I guess it is something similar to ./image_to_vm.sh --from=../build/images/arm64-usr/developer-latest --format=pxe

[raballew]

@jepio Have a look at https://github.com/raballew/picar/blob/03df9c5dd370ca31104f1cf78b768787c27d2c18/Makefile#L14 where I try to build your WIP PR. The build succeeds, but I still see the same issue occuring everytime when PXE booting even with the new build.

[jepio]

./build_image builds a generic image, that is then converted to platform (or deployment) specific images by running ./image_to_vm.sh. You have the right command.

There is currently something wrong with dependencies and the initramfs does not get rebuilt when dracut is updated, sorry about that. You need to run an explicit emerge-arm64-usr coreos-kernel between build_packages and build_image to force the kernel to be rebuilt.

[raballew]

@jepio Thanks for the hint! Manually forcing a rebuild of the coreos-kernel did the trick and I can confirm that the issue is solved for PXE environments as well. The build artifact that I used for testing is available here and can be pulled with oras.

[jmgilman]

For context, I'm pretty confident this issue is not strictly related to PXE but rather more likely to UEFI booting in general (which I suspect is being done in this case?). Either way, I'm seeing similar errors when UEFI booting from a raw image to my RPi4. If I get some time I'll try to manually build the same image as above - otherwise, I'll wait and see if the next release resolves the issue.

[jepio]

@jmgilman I agree with you (not related to PXE), I use UEFI on my RPI4. The fix is in main and will be part of the next alpha release.

[raballew]

@jmgilman I am using EFI as well on my set of RPi 4s.