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AJvYcCUfLziRVcp1F139LvwTyENNA6MEaZ70lUnJeabSCOBC/CakR4LzSUSEXeozSYrhRpzpiL611iXNRQ==@kvack.org X-Gm-Message-State: AOJu0Yx6YnKgISqNvcAt9Giqeb9A1jxbIrGWkh7SCyui1aKODqvcGZtB xr9yhRSb51QB6A6DHm42U8EF2tGkkP2etnm3w3SxVKEEsjF6J/LLxiHvG23dXvdAFRY66UHYPE7 hZXvziN3xttVrUpMeXNJ9wndJaaedHCMsjwHzGlKQAA== X-Gm-Gg: ASbGncvnETx0i4ztdC2yoppA23X+y+hUhbdOgH7ToVXAwfu6g6nD5SpozODK8KyHRtl av/3ayyvC7QRdU76rGq9YjYh60rrhUMnfdLd5VMYuWyW73BLxQnbnjneNs2JmPq5tC3FLArCoVj I2wGcEfZNTaNwzk9fpmK8z/3+gOQWW4fJHYD5q1LAts3XYFdTOvkeBVRRp7pUeGEjkO0Q1UGt/y yZ7zUdbKVzJDGEKCsHkCokvV5gfMRl2cKNir4z0EMHP5mc8ZceGZyf1pQ== X-Google-Smtp-Source: AGHT+IGfpzw30I50uzhP4zU1mSQ9H6EkikBegZxPU5LLVKtN3RM+oen2ff0GDhVd9BnhapB0BApwf174qkOpARMYJRI= X-Received: by 2002:a05:6402:2688:b0:640:c3c4:45fd with SMTP id 4fb4d7f45d1cf-6415dc00b0bmr10748897a12.5.1762874834355; Tue, 11 Nov 2025 07:27:14 -0800 (PST) MIME-Version: 1.0 References: <20251101142325.1326536-1-pasha.tatashin@soleen.com> <20251101142325.1326536-2-pasha.tatashin@soleen.com> <029090cf-9a4d-4f79-b857-04c3ada83323@linux.dev> <442fa82e-16ef-4bde-84eb-743450222468@linux.dev> <0735e1ef-2b65-4a54-b4d5-964fb875cd09@linux.dev> In-Reply-To: <0735e1ef-2b65-4a54-b4d5-964fb875cd09@linux.dev> From: Pasha Tatashin Date: Tue, 11 Nov 2025 10:26:38 -0500 X-Gm-Features: AWmQ_bnTJun9_-b7oKykqWTYNLwDN30PScTynxGQ0sII17gfGixQqv4sWCWauz0 Message-ID: Subject: Re: [PATCH v9 1/9] kho: make debugfs interface optional To: Zhu Yanjun Cc: Pratyush Yadav , akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 4r8esfnpwpuwaw5as9b1x3fk1peqcnow X-Rspam-User: X-Rspamd-Queue-Id: 3411814000A X-Rspamd-Server: rspam10 X-HE-Tag: 1762874836-83040 X-HE-Meta: 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 NdIKqyO1 CEHqomgcyzn315nQ7LzFmJCUe4iIAUCM3VDqsOyjktMIX1bacP1NuJ5abe4dUe9S5xuxkFP3ehV/VqQ3wugxzm2Wx4U9RywaahJdpE5OABLygEOEwUe3SiQcBgnjm7IycmcTy30oEy+F/K1nVtdx531TAHXaim7m8qWHGDKzgUge1OcE0C02dBoD+ZOwnMkvEtkYXSjLwlJPEFmSj/iWBShe17onUOMQq0FscTW8PQHv/Mvl0UWUeYxy7uzn9wnZdISdH2ENLs0tthiAigRAmlEraiwsS1RifXRGP93FcCTRj7Ds7axqORPM4ZbKDLv0+LK64D5aJdTnLphDX/qecLH9GczXATyMl04JrJPWZ0jFzxynqiUvlUkkukowsmDjJPFs3 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Nov 10, 2025 at 11:11=E2=80=AFPM Zhu Yanjun = 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=3D[initramfs] [kernel] Pasha > > The call trace is in the attachment. > > Yanjun.Zhu > > =E5=9C=A8 2025/11/10 7:26, Pasha Tatashin =E5=86=99=E9=81=93: > > On Mon, Nov 10, 2025 at 8:16=E2=80=AFAM Pratyush Yadav wrote: > >> On Sun, Nov 09 2025, Zhu Yanjun wrote: > >> > >>> =E5=9C=A8 2025/11/8 10:13, Pasha Tatashin =E5=86=99=E9=81=93: > >>>> On Fri, Nov 7, 2025 at 6:36=E2=80=AFPM Yanjun.Zhu wrote: > >>>>> On 11/7/25 4:02 AM, Pasha Tatashin wrote: > >>>>>> On Fri, Nov 7, 2025 at 7:00=E2=80=AFAM Pasha Tatashin 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 ad= ding a > >>>>>>>> variable in debugfs to keep track of this count. > >>>>>>>> However, since debugfs is now optional, where would be an approp= riate > >>>>>>>> place to store this variable? > >>>>>>> It is an optional config and can still be enabled if the live upd= ate > >>>>>>> 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 dur= ing > >>>>>>> boot and also store it in the incoming LUO FDT tree, which can al= so 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=E2=80=99ve carefully read this commit: > >>>>> https://github.com/soleen/linux/commit/60205b9a95c319dc9965f119303a= 1d83f0ff08fa. > >>>>> > >>>>> To be honest, I=E2=80=99d like to run some tests with who/luo, incl= uding 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=3Dy" > >>> > >>> # ./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=3Dy > >>> /boot/config-next-20251107-luo+:11985:CONFIG_LIVEUPDATE_TEST=3Dy > >>> > >>> I made tests on FC42. But /dev/liveupdate is missing. > >> You need to add liveupdate=3D1 to your kernel cmdline to enable LUO an= d > >> get /dev/liveupdate. > > +1, kernel parameters require: kho=3D1 liveupdate=3D1 > > > >> Pasha, your LUO series doesn't add the liveupdate parameter to > >> kernel-parameters.txt. I think it should be done in the next version t= o > >> 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