Re: [PATCH v2] qemuarm-trixie: Workaround with missing drivers in qemuarm-trixie initramfs

[Zhihang Wei <wzh@ilbers.de>]

On 2/20/26 16:36, Jan Kiszka wrote:
> On 20.02.26 15:42, Zhihang Wei wrote:
>> This is a workaround to fix the current qemuarm-trixie image unbootable
>> issue.
>>
>> Starting with Debian Trixie, update-initramfs invokes "dracut-install"
>> to collect and install required drivers into the generated initramfs.
>> "dracut-install" relies on fts_open() / fts_read() from glibc to
>> traverse directories and locate drivers.
>>
>> Due to a long-standing bug [1] between qemu and glibc, the fts_*
>> functions may fail to find files on certain 32-bit architectures. As a
>> result, required modules such as virtio_blk are not detected and not
>> added to the initramfs. The produced image then fails to boot under
>> qemu because the block device driver is missing.
>>
>> A similiar dracut bug report was filed in 2024 [2], pointing to this
>> upstream glibc issue reported in 2018 [1]. No upstream fix has been
>> applied, and the issue appears to affect only qemu builds for specific
>> 32-bit targets.
>>
>> As a temporary workaround, use a customized initramfs-hook to append
>> the neccessary drivers that are currently missed from the initramfs.
>>
>> For a complete fix, we either need to push for an upstream glibc/qemu
>> fix, or convince dracut to avoid using these non-POSIX fts_* functions
>> and use opendir() / readdir() instead.
>>
>> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=23960
>> [2] https://bugs-devel.debian.org/cgi-bin/bugreport.cgi?bug=1079443
>>
>> Signed-off-by: Zhihang Wei <wzh@ilbers.de>
>> ---
>> Changes in v2:
>> - Use initramfs-hook to install the driver, instead of adding another
>>    variable
>>
>>   meta-isar/conf/multiconfig/qemuarm-trixie.conf            | 4 +++-
>>   .../initramfs-virtio-blk-hook_0.1.bb                      | 8 ++++++++
>>   2 files changed, 11 insertions(+), 1 deletion(-)
>>   create mode 100644 meta/recipes-initramfs/initramfs-virtio-blk-hook/initramfs-virtio-blk-hook_0.1.bb
>>
>> diff --git a/meta-isar/conf/multiconfig/qemuarm-trixie.conf b/meta-isar/conf/multiconfig/qemuarm-trixie.conf
>> index 5600ab23..20eecd92 100644
>> --- a/meta-isar/conf/multiconfig/qemuarm-trixie.conf
>> +++ b/meta-isar/conf/multiconfig/qemuarm-trixie.conf
>> @@ -1,7 +1,9 @@
>>   # This software is a part of Isar.
>> -# Copyright (C) 2024 ilbers GmbH
>> +# Copyright (C) 2024-2026 ilbers GmbH
>>   #
>>   # SPDX-License-Identifier: MIT
>>   
>>   MACHINE ?= "qemuarm"
>>   DISTRO ?= "debian-trixie"
>> +
>> +IMAGE_INSTALL += "initramfs-virtio-blk-hook"
> This covers the initramfs-tools based generation. What if someone
> enables dracut (kas/opt/dracut.yaml)?
A pure dracut generated initramfs for qemuarm-trixie cannot boot. It
surprisingly has virtio_blk, but still not bootable. Need to find the
reason.

Actually, there should be more drivers installed into initramfs by
initramfs-tools, but they are now missing due to the same bug. Adding
virtio-blk just makes this initramfs-tools generated initramfs
"minimally" bootable. My guess is that the dracut generated initramfs
is missing some other necessary drivers.

Zhihang
>> diff --git a/meta/recipes-initramfs/initramfs-virtio-blk-hook/initramfs-virtio-blk-hook_0.1.bb b/meta/recipes-initramfs/initramfs-virtio-blk-hook/initramfs-virtio-blk-hook_0.1.bb
>> new file mode 100644
>> index 00000000..229d91d6
>> --- /dev/null
>> +++ b/meta/recipes-initramfs/initramfs-virtio-blk-hook/initramfs-virtio-blk-hook_0.1.bb
>> @@ -0,0 +1,8 @@
>> +# This software is a part of Isar.
>> +# Copyright (C) 2026 ilbers GmbH
>> +#
>> +# SPDX-License-Identifier: MIT
>> +
>> +inherit initramfs-hook
>> +
>> +HOOK_ADD_MODULES = "virtio-blk"
> Jan
>

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