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 353392D3A75; Sun, 23 Nov 2025 11:12:35 +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=1763896356; cv=none; b=jYxILhmL8hPcmyyx6Lti1qdtGKkJTqQW8iAT+zO0ha6emvXEUNXuwoWNkJGuUVu+NgCMUPy27L+OcuQXT7s3YL8dAOrt4O6t26j8HCVHQ079YGizuyTk+TwsWXazII1ij6r3G7N5pMJowwkvEs2HFJas+rwhG0fMHzCj4vah514= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763896356; c=relaxed/simple; bh=Akr26sM3VEhR3kKN7o52n5Q0IG8yNVh9gdExmJrI8ek=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GVBt9oqwW6LsNEBgBTw4S0efT0AJw1W90CBI2rPCib8qbWIdVpKj+GjNQYmS++C19/YDjx680D80DJBdO8JBmozoI3BMoVCTT7GjFFaxZ3Xce178YUT0RgLk5ndQgWJxMHR0OA+/LX+2pDMjexMSnE0a2fDIwl6tFMta8thOASI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DD70297O; 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="DD70297O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E672EC113D0; Sun, 23 Nov 2025 11:12:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763896355; bh=Akr26sM3VEhR3kKN7o52n5Q0IG8yNVh9gdExmJrI8ek=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DD70297OscX5jW+1bL2L8Z5+6LxRLvMSuqNcQmzITuFPIzMzmkRtlD/mIf3T2D858 mLjthfkdI3QvX5wzmOddr/fDz3ZYEbjtxPo1YEND1/rowOhEwrqrpzC2boUYmSqpWC LJa9Y4iSUVo8vPl4T49RkU+H90guNy7wohSE0KXct5W8r9dxLkD1p0m6pifzJ+NS+d gQ4atTXM+NBkfw97j9VlyFdkIVV9vi3HLQHWP2WLZ7acpq+JnxntA0ebpsXBDISpJN uF6MX92LSt9PIFptSK1yfDhmlyBzzfbfcjg9RYfN9IA5CBhLECVurLPXjqk1yT2SZV LiaEhMRjyjibg== Date: Sun, 23 Nov 2025 13:12:11 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org Subject: Re: [PATCH v7 01/22] liveupdate: luo_core: Live Update Orchestrator Message-ID: References: <20251122222351.1059049-1-pasha.tatashin@soleen.com> <20251122222351.1059049-2-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251122222351.1059049-2-pasha.tatashin@soleen.com> On Sat, Nov 22, 2025 at 05:23:28PM -0500, Pasha Tatashin wrote: > Introduce LUO, a mechanism intended to facilitate kernel updates while > keeping designated devices operational across the transition (e.g., via > kexec). The primary use case is updating hypervisors with minimal > disruption to running virtual machines. For userspace side of hypervisor > update we have copyless migration. LUO is for updating the kernel. > > This initial patch lays the groundwork for the LUO subsystem. > > Further functionality, including the implementation of state transition > logic, integration with KHO, and hooks for subsystems and file > descriptors, will be added in subsequent patches. > > Create a character device at /dev/liveupdate. > > A new uAPI header, , will define the necessary > structures. The magic number for IOCTL is registered in > Documentation/userspace-api/ioctl/ioctl-number.rst. > > Signed-off-by: Pasha Tatashin > Reviewed-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) with a few nits below > --- > diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig > index a973a54447de..90857dccb359 100644 > --- a/kernel/liveupdate/Kconfig > +++ b/kernel/liveupdate/Kconfig > @@ -1,4 +1,10 @@ > # SPDX-License-Identifier: GPL-2.0-only > +# > +# Copyright (c) 2025, Google LLC. > +# Pasha Tatashin > +# > +# Live Update Orchestrator > +# If you are adding copyrights it should have Amazon and Microsoft as well. I believe those from kexec_handover.c would work. @Alex? > menu "Live Update and Kexec HandOver" > depends on !DEFERRED_STRUCT_PAGE_INIT > @@ -51,4 +57,25 @@ config KEXEC_HANDOVER_ENABLE_DEFAULT > The default behavior can still be overridden at boot time by > passing 'kho=off'. > > +config LIVEUPDATE > + bool "Live Update Orchestrator" > + depends on KEXEC_HANDOVER > + help > + Enable the Live Update Orchestrator. Live Update is a mechanism, > + typically based on kexec, that allows the kernel to be updated > + while keeping selected devices operational across the transition. > + These devices are intended to be reclaimed by the new kernel and > + re-attached to their original workload without requiring a device > + reset. > + > + Ability to handover a device from current to the next kernel depends > + on specific support within device drivers and related kernel > + subsystems. Sorry, somehow this slipped during v6 review. These days LUO is less about devices and more about file descriptors :) > + > + This feature primarily targets virtual machine hosts to quickly update > + the kernel hypervisor with minimal disruption to the running virtual > + machines. > + > + If unsure, say N. > + > endmenu -- Sincerely yours, Mike.