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Message-ID: <a1aa7736-d014-477f-a516-2281a70fc8c1@linux.dev> Date: Wed, 12 Nov 2025 18:11:45 -0800 From: "Yanjun.Zhu" <yanjun.zhu@...ux.dev> To: Pasha Tatashin <pasha.tatashin@...een.com> Cc: Pratyush Yadav <pratyush@...nel.org>, akpm@...ux-foundation.org, brauner@...nel.org, corbet@....net, graf@...zon.com, jgg@...pe.ca, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-mm@...ck.org, masahiroy@...nel.org, ojeda@...nel.org, rdunlap@...radead.org, rppt@...nel.org, tj@...nel.org Subject: Re: [PATCH v9 1/9] kho: make debugfs interface optional On 11/12/25 5:41 PM, Yanjun.Zhu wrote: > > On 11/11/25 7:26 AM, Pasha Tatashin wrote: >> On Mon, Nov 10, 2025 at 11:11 PM Zhu Yanjun <yanjun.zhu@...ux.dev> >> wrote: >>> In FC42, when I run "./luo_multi_session" >>> >>> # ./luo_multi_session >>> # [STAGE 1] Starting pre-kexec setup for multi-session test... >>> # [STAGE 1] Creating state file for next stage (2)... >>> # [STAGE 1] Creating empty sessions 'multi-test-empty-1' and >>> 'multi-test-empty-2'... >>> # [STAGE 1] Creating session 'multi-test-files-1' with one memfd... >>> # [STAGE 1] Creating session 'multi-test-files-2' with two memfds... >>> # [STAGE 1] Executing kexec... >>> >>> Then the system hang. And via virt-viewer, a calltrace will appear. >> Looks like mountroot fails, are you passing the same kernel parameters >> as the during cold boot? >> i.e. kexec -l -s --reuse-cmdline --initrd=[initramfs] [kernel] > > > Thanks a lot. It can work now. The logs are as below: > > " > > # [STAGE 2] Starting post-kexec verification... > # [STAGE 2] Retrieving all sessions... > # [STAGE 2] Verifying contents of session 'multi-test-files-1'... > # [STAGE 2] Verifying contents of session 'multi-test-files-2'... > # [STAGE 2] Test data verified successfully. > # [STAGE 2] Finalizing all test sessions... > # [STAGE 2] Finalizing state session... > # > --- MULTI-SESSION KEXEC TEST PASSED --- > " > > Yanjun.Zhu Hi, Pasha In my tests, I found that luo_kexec_simple and luo_multi_session currently depend on the glibc-static library. If this library is not installed, build errors occur. By making the following changes, luo_kexec_simple and luo_multi_session would no longer depend on glibc-static, reducing external library dependencies. I am not sure whether you agree with these proposed changes. diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile index 6ee6efeec62d..b226b9976150 100644 --- a/tools/testing/selftests/liveupdate/Makefile +++ b/tools/testing/selftests/liveupdate/Makefile @@ -3,7 +3,6 @@ KHDR_INCLUDES ?= -I../../../../usr/include CFLAGS += -Wall -O2 -Wno-unused-function CFLAGS += $(KHDR_INCLUDES) -LDFLAGS += -static OUTPUT ?= . # --- Test Configuration (Edit this section when adding new tests) --- Yanjun.Zhu > > >> >> Pasha >> >>> The call trace is in the attachment. >>> >>> Yanjun.Zhu >>> >>> 在 2025/11/10 7:26, Pasha Tatashin 写道: >>>> On Mon, Nov 10, 2025 at 8:16 AM Pratyush Yadav >>>> <pratyush@...nel.org> wrote: >>>>> 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@...ux.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@...een.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/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. >>>> +1, kernel parameters require: kho=1 liveupdate=1 >>>> >>>>> 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. >>>> Yeah, that is missing, I will update that in a standalone patch, or in >>>> a next version. >>>> >>>> Thanks, >>>> Pasha >>> -- >>> Best Regards, >>> Yanjun.Zhu
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