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Message-ID: <9e144e21-a5e7-4c12-b8b0-07172787ab37@linux.dev> Date: Thu, 13 Nov 2025 11:55:10 -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 11/11/25 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] > > Pasha Hi, Pasha Following your advice, the following can work well. I am not sure if we can merge this commit into selftests/liveupdate mainline? commit 44764c48a658987b7729c5bc2be9fd87832cfbdf (HEAD -> linux-next/master) Author: Zhu Yanjun <yanjun.zhu@...ux.dev> Date: Thu Nov 13 11:45:21 2025 -0800 selftests/liveupdate: Fix the error "Unable to mount root fs on unknown-block" If the initrd is not provide, the followings will appear. " Call Trace: <TASK> dump_stack_lvl+0x5d/0x80 vpanic+0x118/8x320 panic+0x6b/0x6b ? do_mount_root+0x115/0x130 mount_root_generic+0x1cf/0x270 prepare_namespace+0x1e1/0x230 kernel_init_freeable+0x136/8x140 ?_pfx_kernel_init+0x10/0x10 kernel_init+0x1a/0x140 ret_from_fork+0x130/0x1a8 ?_pfx_kernel_init+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </ TASK> Kernel Offset: 0x3000000 from Oxffffffff81000000 " Signed-off-by: Zhu Yanjun <yanjun.zhu@...ux.dev> diff --git a/tools/testing/selftests/liveupdate/do_kexec.sh b/tools/testing/selftests/liveupdate/do_kexec.sh index bb396a92c3b8..4ee59abd0dd4 100755 --- a/tools/testing/selftests/liveupdate/do_kexec.sh +++ b/tools/testing/selftests/liveupdate/do_kexec.sh @@ -2,5 +2,5 @@ # SPDX-License-Identifier: GPL-2.0 set -e -kexec -l -s --reuse-cmdline /boot/bzImage +kexec -l -s --reuse-cmdline /boot/bzImage --initrd /boot/initramfs-`uname -r`.img kexec -e Thanks a lot. Yanjun.Zhu >> 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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