From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 609E31397; Mon, 10 Nov 2025 13:16:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762780601; cv=none; b=newxeKB1HlO9mwxLbWK196lAMMX3SBvIFn6qbUuHFh8coBZDzQlXctD8kFYH9XxaiUg/wth9c3MlKKD6Fs5zlXmMOlI4bpUwxmbjqvjNAT6oE5yM0GP7fEz+mdJ5Bxfirf5AACe4yHW28uFl+U2r4TtsndO5M6ASLMLeBibhFDM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762780601; c=relaxed/simple; bh=f0dZjtcP0vxUJBo4nfnO1ah3073NhYiLonrdArYUsXw=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=F5WBqcLl9JgVZvbQ3WANezJldCU2j9BOBHcxxCRQlRfveKS2B04S14EFqkMguqft4WBv9QQY6yQ5lPD2Oi+OzSJPlRIj/vwg2I3GIuDvEyTB7gjnkec55OYSO+Un+Btya9wtXtnPDEOanVvdpdnuLD35MdLX3ztqtj0q93lXSjs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PS38d2F+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PS38d2F+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78A7FC4CEF5; Mon, 10 Nov 2025 13:16:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762780601; bh=f0dZjtcP0vxUJBo4nfnO1ah3073NhYiLonrdArYUsXw=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=PS38d2F+HD6yJ+cCZ27VfTyu/Xb5ZNzr80MqBwuo05yeFYAXUJdvjE5nUUkXYcFFD +5183EI4m7vKpS3ZZwa7ynwmCHyhTwcz+iEuPcYXMSWAvc3cub34I6kp/Cnbduib2k O2om8Jm3FT/iufyjmHEZqTttkvC6e+bBJbYB2icy6vI5KYYdvLq6XlDk1bKyZZ9tZh roMVdrRyxyw38iwxO2aGZ2XNKX9DBFV8xK31IMNliK86ajR/C3rW3abM/BOELVQbfR C0M8uOI3syHk24+OYOUanJp+f96ijtCAJSGZ55L2Ur8Kc8x9HzduLTQ+LWWXzdhMpq ipF5HIEmgZ2pA== From: Pratyush Yadav To: Zhu Yanjun Cc: Pasha Tatashin , 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, pratyush@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Subject: Re: [PATCH v9 1/9] kho: make debugfs interface optional In-Reply-To: <442fa82e-16ef-4bde-84eb-743450222468@linux.dev> (Zhu Yanjun's message of "Sun, 9 Nov 2025 16:20:56 -0800") 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> Date: Mon, 10 Nov 2025 14:16:37 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 t= imes >>>>>> 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=E2=80=99ve carefully read this commit: >>> https://github.com/soleen/linux/commit/60205b9a95c319dc9965f119303a1d83= f0ff08fa. >>> >>> To be honest, I=E2=80=99d like to run some tests with who/luo, includin= g 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 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. --=20 Regards, Pratyush Yadav