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podvm-mkosi: support to build s390x fedora image #1753

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merged 1 commit into from
Mar 21, 2024

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genjuro214
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According to #1640 , there are 2 problems for mkosi to build s390x images:

  • The nix OS does not support s390x, but we can use the mkosi ToolsTree feature defined in mkosi.conf to download latest tools automatically:
[Host]
ToolsTree=default
  • s390x does not support UEFI, so mkosi cannot build a bootable s390x image. Instead, we can first use mkosi to build non-bootable system files, then use zipl to generate the bootloader (podvm-mkosi/build-s390x-image.sh)

We need run mkosi from the repository:

git clone -b v21 https://github.com/systemd/mkosi
ln -s $PWD/mkosi/bin/mkosi /usr/local/bin/mkosi
mkosi --version

For the new mkosi release, there is an issue to set environment (#1746). Instead, we try to use profile as suggested in mkosi community (systemd/mkosi#2500).

I tested the s390x qcow2 image in libvirt environment, and it should work.


I try to avoid impacts to x86 images, which can still be run with nix, and s390x changes will not be picked up for the Match rules.

I also build a new x86 image, but I don't have AWS environment to verify it. Since UEFI is enabled, I can start the VM with following command on ubuntu 22.04 host:

virt-install --name podvm --memory 2048 --vcpus 1 --disk path=/var/lib/libvirt/images/podvm.qcow2,device=disk,bus=scsi --import --os-variant fedora38 --network default --graphics none --machine q35 --boot loader=/usr/share/OVMF/OVMF_CODE.secboot.fd,loader.readonly=yes,loader.type=pflash,loader_secure=yes --features smm.state=on

However, it seems current libvirt provider cannot support UEFI image on a host with Intel processor. I noticed we can configure LIBVIRT_LAUNCH_SECURITY and LIBVIRT_FIRMWARE for UEFI, but it requires SEV (AMD Secure Encrypted Virtualization) support on the host, but I don't have an AMD host.

2024/03/19 09:32:37 [adaptor/cloud/libvirt] failed to create an instance : error building the libvirt XML, cause: SEV is not supported for this domain

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Very cool! Since the rootfs is modified in the later build steps, I assume we don't use verity?

I assume that's ok, but it would good to point that out in the readme section. I'm also not seeing anything in config files that indicate that verity is not being used, can you elaborate how this works?

@@ -0,0 +1,92 @@
#!/bin/bash

set -eu
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Suggested change
set -eu
set -euo pipefail

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Sure, add pipefail.

Because we set Bootable=no and output Format=directory for s390x, mkosi will skip partition settings as well as verity.

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thanks, can we add this context to the Readme?

@@ -75,3 +75,27 @@ reduce complexity of configuration and CI and shall not be seen as open to-dos.

- Deployed images cannot be customized with cloud-init. Runtime configuration data is retrieved
from IMDS via the project's `process-user-data` tool.

## Build s390x image
Since the [nix OS](https://nixos.org/download/#download-nix) does not support s390x, we can use the mkosi **ToolsTree** feature defined in `mkosi.conf` to download latest tools automatically:
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ToolsTree is interesting. could this be replacement for the nix flake on all architectures? It would be good to have a common way, and if it supports reproducible builds that could be an option.

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I looked into it, mkosi still needs certain tools to be present on the host, so a py virtualenv + ToolsTree cannot fully replace nix yet

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If it's doable, I like the idea to also use ToolsTree for x86 for alignment. Maybe worth to try.

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I just tried ToolsTree on ubuntu host to build the fedora image

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On my side it was lacking the yum/rpm tools that are used to bootstrap a ToolsTree, but it might be due to an outdated local env. we should look into this, but it doesn't have to be in the scope of this PR.

podvm-mkosi/build-s390x-image.sh Outdated Show resolved Hide resolved
Comment on lines 61 to 67
chroot $dst_mnt systemctl enable cloud-init-local.service
chroot $dst_mnt systemctl enable cloud-init.service
chroot $dst_mnt systemctl enable cloud-config.service
chroot $dst_mnt systemctl enable cloud-final.service

# disable this service since we already have "NetworkManager-wait-online.service"
chroot $dst_mnt systemctl disable systemd-networkd-wait-online.service
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why do we perform those systemctl enable steps here? (instead of using a preset file like ./podvm-mkosi/mkosi.skeleton/usr/lib/systemd/system-preset/20-coco-sys.preset?

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mkosi.postinst would also be a good candidate

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I tried to use mkosi.postinst.chroot, but not sure why, the changes are revert in steps "Applying presets…".

Anyway, I try to use mkosi.finalize.chroot, and it works well.

podvm-mkosi/build-s390x-image.sh Outdated Show resolved Hide resolved
podvm-mkosi/build-s390x-image.sh Outdated Show resolved Hide resolved
Package system with mkosi and generate bootloader
with zipl

Signed-off-by: Lei Li <genjuro214@gmail.com>
Signed-off-by: Lei Li <cdlleili@cn.ibm.com>
@genjuro214
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@mkulke , thanks for your comments. I tried to address them and update the commit.

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LGTM, great work.

nit: it would a useful to add a sentence or two about the specific of this image since it doesn't use a verity protected rootfs and is running cloud-init. both have some implications for the integrity of the image (compared to the x86 images).

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LGTM,
I like the idea to use ToolsTree for x86 also and we can investigate/change it in new PR. thanks! @genjuro214

@huoqifeng huoqifeng merged commit 91f8d73 into confidential-containers:main Mar 21, 2024
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3 participants