On Sun, Nov 09 2025, Zhu Yanjun wrote:
在 2025/11/8 10:13, Pasha Tatashin 写道:
On Fri, Nov 7, 2025 at 6:36 PM Yanjun.Zhu yanjun.zhu@linux.dev wrote:
On 11/7/25 4:02 AM, Pasha Tatashin wrote:
On Fri, Nov 7, 2025 at 7:00 AM Pasha Tatashin pasha.tatashin@soleen.com wrote:
Hi, Pasha
In our previous discussion, we talked about counting the number of times the kernel is rebooted via kexec. At that time, you suggested adding a variable in debugfs to keep track of this count. However, since debugfs is now optional, where would be an appropriate place to store this variable?
It is an optional config and can still be enabled if the live update reboot number value needs to be accessed through debugfs. However, given that debugfs does not guarantee a stable interface, tooling should not be built to require these interfaces.
In the WIP LUO [1] I have, I pr_info() the live update number during boot and also store it in the incoming LUO FDT tree, which can also be accessed through this optional debugfs interface.
The pr_info message appears like this during boot: [ 0.000000] luo: Retrieved live update data, liveupdate number: 17
Pasha
Forgot to add link to WIP LUOv5: [1] https://github.com/soleen/linux/tree/luo/v5rc04
Thanks a lot. I’ve carefully read this commit: https://github.com/soleen/linux/commit/60205b9a95c319dc9965f119303a1d83f0ff0....
To be honest, I’d like to run some tests with who/luo, including the selftest for kho/luo. Could you please share the steps with me?
If the testing steps have already been documented somewhere, could you please share the link?
Currently the test performs in-kernel tests for FLB data, it creates a number of FLB for every registered LUO file-handler, which at the moment is only memfd.
It works together with any of the kexec based live update tests. In v5, I introduce two tests: luo_kexec_simple luo_multi_session
For example, with luo_multi_session:
Hi, Pasha
I enabled "CONFIG_LIVEUPDATE=y"
# ./luo_multi_session 1..0 # SKIP Failed to open /dev/liveupdate. Is the luo module loaded?
# ls /dev/liveupdate ls: cannot access '/dev/liveupdate': No such file or directory
# grep "LIVEUPDATE" -inrHI /boot/config-`uname -r` /boot/config-next-20251107-luo+:349:CONFIG_LIVEUPDATE=y /boot/config-next-20251107-luo+:11985:CONFIG_LIVEUPDATE_TEST=y
I made tests on FC42. But /dev/liveupdate is missing.
You need to add liveupdate=1 to your kernel cmdline to enable LUO and get /dev/liveupdate.
Pasha, your LUO series doesn't add the liveupdate parameter to kernel-parameters.txt. I think it should be done in the next version to this parameter is discoverable.