Hi all,
On 12/18/25 20:50, Salvatore Bonaccorso wrote:
Hi all,
Roland Schwarzkopf reported to the Debian mailing list a problem which
he encountered once updating in Debian from 5.10.244 to 5.10.247. The
report is quoted below and found in
https://lists.debian.org/debian-kernel/2025/12/msg00223.html
Roland did bisect the changes between 5.10.244 to 5.10.247 and found
that the issue is introduced with 1550f3673972 ("net: rtnetlink: add
bulk delete support flag") which is the backport to the 5.10.y series.
On Thu, Dec 18, 2025 at 02:59:55PM +0100, Roland Schwarzkopf wrote:
Hi Salvatore,
On 12/17/25 20:28, Salvatore Bonaccorso wrote:
Hi Roland,
I'm CC'ing Ben Hutchings directly as well as he takes care of the
Debian LTS kernel updates. Idellly we make this as well a proper bug
for easier tracking.
On Wed, Dec 17, 2025 at 01:35:54PM +0100, Roland Schwarzkopf wrote:
Hi there,
after upgrading to the latest kernel on Debian 11
(linux-image-5.10.0-37-amd64) I have an issue using libvirt with qemu/kvm
virtual machines and macvtap networking. When a machine is shut down,
libvirt can not delete the corresponding macvtap device. Thus, starting the
machine again is not possible. After manually removing the macvtap device
using `ip link delete` the vm can be started again.
In the journal the following message is shown:
Dec 17 13:19:27 iblis libvirtd[535]: error destroying network device macvtap0:
Operation not supported
After downgrading the kernel to linux-image-5.10.0-36-amd64, the problem
disappears. I tested this on a fresh minimal install of Debian 11 - to
exclude that anything else on my production machines is causing this issue.
Since the older kernel does not have this issue, I assume this is related to
the kernel and not to libvirt?
I tried to check for bug reports of the kernel package, but the bug tracker
finds no reports and even states that the package does not exist (I used the
"Bug reports" link on
https://packages.debian.org/bullseye/linux-image-5.10.0-37-amd64). This left
me a bit puzzled. Since I don't have experience with the debian bug
reporting process, I had no other idea than writing to this list.
You would need to search for inhttps://bugs.debian.org/src:linux ,
but that said I'm not aware of any bug reports in that direction.
Would you be in the position of bisecting the problem as you can say
that 5.10.244 is good and 5.10.247 is bad and regressed? If you can do
that that would involve compiling a couple of kernels to narrow down
where the problem is introduced:
git clone --single-branch -b
linux-5.10.yhttps://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
cd linux-stable
git checkout v5.10.244
cp /boot/config-$(uname -r) .config
yes '' | make localmodconfig
make savedefconfig
mv defconfig arch/x86/configs/my_defconfig
# test 5.10.244 to ensure this is "good"
make my_defconfig
make -j $(nproc) bindeb-pkg
... install the resulting .deb package and confirm it successfully boots
/ problem does not exist
# test 5.10.247 to ensure this is "bad"
git checkout v5.10.247
make my_defconfig
make -j $(nproc) bindeb-pkg
... install the resulting .deb package and confirm it fails to boot /
problem exists
With that confirmed, the bisection can start:
git bisect start
git bisect good v5.10.244
git bisect bad v5.10.247
In each bisection step git checks out a state between the oldest
known-bad and the newest known-good commit. In each step test using:
make my_defconfig
make -j $(nproc) bindeb-pkg
... install, try to boot / verify if problem exists
and if the problem is hit run:
git bisect bad
and if the problem doesn't trigger run:
git bisect good
. Please pay attention to always select the just built kernel for
booting, it won't always be the default kernel picked up by grub.
Iterate until git announces to have identified the first bad commit.
Then provide the output of
git bisect log
In the course of the bisection you might have to uninstall previous
kernels again to not exhaust the disk space in /boot. Also in the end
uninstall all self-built kernels again.
I just did my first bisection \o/ (sorry)
Here are the results:
git bisect start
# bad: [f964b940099f9982d723d4c77988d4b0dda9c165] Linux 5.10.247
git bisect bad f964b940099f9982d723d4c77988d4b0dda9c165
# good: [863b76df7d1e327979946a2d3893479c3275bfa4] Linux 5.10.244
git bisect good f52ee6ea810273e527a5d319e5f400be8c8424c1
# good: [dc9fdb7586b90e33c766eac52b6f3d1c9ec365a1] net: usb: lan78xx: Add error
handling to lan78xx_init_mac_address
git bisect good dc9fdb7586b90e33c766eac52b6f3d1c9ec365a1
# bad: [2272d5757ce5d3fb416d9f2497b015678eb85c0d] phy: cadence: cdns-dphy:
Enable lower resolutions in dphy
git bisect bad 2272d5757ce5d3fb416d9f2497b015678eb85c0d
# bad: [547539f08b9e3629ce68479889813e58c8087e70] ALSA: usb-audio: fix control
pipe direction
git bisect bad 547539f08b9e3629ce68479889813e58c8087e70
# bad: [3509c748e79435d09e730673c8c100b7f0ebc87c] most: usb: hdm_probe: Fix
calling put_device() before device initialization
git bisect bad 3509c748e79435d09e730673c8c100b7f0ebc87c
# bad: [a6ebcafc2f5ff7f0d1ce0c6dc38ac09a16a56ec0] net: add ndo_fdb_del_bulk
git bisect bad a6ebcafc2f5ff7f0d1ce0c6dc38ac09a16a56ec0
# good: [b8a72692aa42b7dcd179a96b90bc2763ac74576a] hfsplus: fix KMSAN
uninit-value issue in __hfsplus_ext_cache_extent()
git bisect good b8a72692aa42b7dcd179a96b90bc2763ac74576a
# good: [2b42a595863556b394bd702d46f4a9d0d2985aaa] m68k: bitops: Fix
find_*_bit() signatures
git bisect good 2b42a595863556b394bd702d46f4a9d0d2985aaa
# good: [9d9f7d71d46cff3491a443a3cf452cecf87d51ef] net: rtnetlink: use BIT for
flag values
git bisect good 9d9f7d71d46cff3491a443a3cf452cecf87d51ef
# bad: [1550f3673972c5cfba714135f8bf26784e6f2b0f] net: rtnetlink: add bulk
delete support flag
git bisect bad 1550f3673972c5cfba714135f8bf26784e6f2b0f
# good: [c8879afa24169e504f78c9ca43a4d0d7397049eb] net: netlink: add NLM_F_BULK
delete request modifier
git bisect good c8879afa24169e504f78c9ca43a4d0d7397049eb
# first bad commit: [1550f3673972c5cfba714135f8bf26784e6f2b0f] net: rtnetlink:
add bulk delete support flag
Is there anything else I can do to help?
Is there soemthing missing?
Roland I think it would be helpful if you can test as well more recent
stable series versions to confirm if the issue is present there as
well or not, which might indicate a 5.10.y specific backporting
problem.
I tested this on some newer kernel versions: stable 6.18.2 and 6.17.13
as well as mainline 6.19-rc1. With all three kernel versions, a
different problem occurs: I can't even start the virtual machine.
The relevant journal entry is:
Dec 19 17:25:41 iblis libvirtd[438]: error creating macvtap interface
macvtap0@eno1 (08:00:27:25:16:0c): Operation not supported
I then searched in the commit log for the upstream commit of the one I
found when bisecting the issue. It is a6cec0bcd342, which git describe
says is v5.18-rc1-423-ga6cec0bcd342. Therefore I decided to also test
the two longterm versions before and after that commit was introduced:
5.15.197 and 6.1.159. With both kernel versions I found the same
behavior as with the stable and mainline versions.
So on all newer kernel versions I tested behave identical, but different
than the latest release in the 5.10.y branch.
I'm not sure if I caused this behaviour by making a mistake during
building the kernels - I don't have much experience in that area. I used
the same steps Salvatore gave me for bisecting the issue for the
different versions, i.e.,
cp /boot/config-$(uname -r) .config
yes '' | make localmodconfig
make savedefconfig
mv defconfig arch/x86/configs/my_defconfig
make my_defconfig
make -j $(nproc) bindeb-pkg
Best regards,
Roland
#regzbot introduced: 1550f3673972c5cfba714135f8bf26784e6f2b0f
Regards,
Salvatore
--
Dr. Roland Schwarzkopf <[email protected]>
Dept. of Mathematics and Computer Science, IT Solutions
University of Marburg, Hans-Meerwein-Str. 6, D-35032 Marburg, Germany
Tel: +4964212821523, Fax: +4964212821573
