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 <[email protected]> wrote: >>> >>> On 11/7/25 4:02 AM, Pasha Tatashin wrote: >>>> On Fri, Nov 7, 2025 at 7:00 AM Pasha Tatashin <[email protected]> >>>> 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/60205b9a95c319dc9965f119303a1d83f0ff08fa. >>> >>> 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. -- Regards, Pratyush Yadav
