Bug 15525

Summary: Sometimes wrong kernel selected on QEmu when bundling an InitRamFS
Product: [Build System, Metadata & Runtime] OE-Core Reporter: pasweistorz <Pascal.Weisser.ext>
Component: coreAssignee: pasweistorz <Pascal.Weisser.ext>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: Medium CC: meta.mr.watcher, meta.watcher, Pascal.Weisser.ext, randy.macleod
Version: 5.0   
Target Milestone: 5.2   
Hardware: x86   
OS: Multiple   
Whiteboard:
OS type for building Yocto: --- Type of Regression: ---
Verified: Documentation change: No (bug/feature does not impact docs)

Description pasweistorz 2024-06-21 08:48:02 UTC 
Hi,

we're having an issue when using QEmu and an InitRamFS bundled into the kernel. We're using the following additional lines in local.conf:

INITRAMFS_IMAGE_BUNDLE = "1"
INITRAMFS_IMAGE = "core-image-minimal-initramfs"

When we build the core-image-full-cmdline image the first time everything works as expected. But when we make a change in a script of the initramfs-framework which is packaged into the InitRamFS afterwards and build again the wrong kernel is selected (the kernel without the InitRamFS).

I think the reason is the following:

When building the first time the file core-image-full-cmdline-qemux86-64.rootfs.qemuboot.conf is poining to contains a line like this:

qb_default_kernel = bzImage-initramfs--6.6.23+git0+f7f00b22ef_2d01bc1d4e-r0-qemux86-64-20240614132425.bin

The reason is that the realpath instead of the symlink is written to the qemuboot.conf file [1].

When a change is made to a script of the initramfs-framework the core-image-minimal-initramfs is built again and bundled into the kernel. That creates a new kernel and the previous kernel referenced in the qemuboot.conf file of the core-image-full-cmdline image won't exist anymore. The qemuboot.conf file isn't adapted to that change.

When starting QEmu the qemuboot.conf file is evaluated. Since the kernel referenced by qb_default_kernel doesn't exist QEmu falls back to a kernel whose name is starting with bzImage. In our case a kernel that doesn't contain the InitRamFS is selected.

As the realpath of the kernel symlink is used as value for qb_default_kernel instead of the value of QB_DEFAULT_KERNEL itself a solution might be to make the do_write_qemuboot_conf task dependent on all variables that go into the value for qb_default_kernel which is written to qemuboot.conf. That way, the qemuboot.conf would be recreated when the realpath of the file QB_DEFAULT_KERNEL points to changes.

This issue might be related to https://bugzilla.yoctoproject.org/show_bug.cgi?id=14520.

[1]: https://git.yoctoproject.org/poky/tree/meta/classes-recipe/qemuboot.bbclass#n176
Comment 1 Randy MacLeod 2024-06-27 14:38:59 UTC 
You are on the right track with adding the missing dependencies variables.
Can you continue with that and send a patch to the email list or ask for help there if you get stuck?
Comment 2 pasweistorz 2024-07-03 10:59:24 UTC 
I've submitted a patch today to the openembedded-core@lists.openembedded.org mailing list.
Comment 3 Randy MacLeod 2024-10-31 15:09:23 UTC 
Bulk move of 5.1 bugs to 5.2. -- YP bug review (Randy)
Comment 4 Randy MacLeod 2025-06-05 15:27:00 UTC 
❯ git show 2e9e8f6fb3
commit 2e9e8f6fb3415f9aac6b5f96e8e7c8d9ced5beb5
Author: Weisser, Pascal.ext <Pascal.Weisser.ext@karlstorz.com>
Date:   Wed Jul 3 06:56:03 2024

    qemuboot: Trigger write_qemuboot_conf task on changes of kernel image realpath
    
    The qemuboot.conf file contains the realpath of the kernel image
    referenced by QB_DEFAULT_KERNEL. So, it must be recreated in case the
    realpath of the referenced kernel image changes.
    
    The variables KERNEL_IMAGE_NAME and KERNEL_IMAGE_BIN_EXT determine the
    realpath of the kernel image relative to DEPLOY_DIR_IMAGE. Adding both of
    them to the vardeps of the write_qemuboot_conf task triggers the
    write_qemuboot_conf task in case the realpath of the kernel image
    referenced by QB_DEFAULT_KERNEL changes.
    
    Fixes: [YOCTO 15525]
    
    (From OE-Core rev: f8b3975a9ce36ea7af5fd76243a823da2842415b)