From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D2750CFD318 for ; Mon, 24 Nov 2025 05:08:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A3DDA6B000D; Mon, 24 Nov 2025 00:08:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A157C6B0010; Mon, 24 Nov 2025 00:08:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 92B0D6B0011; Mon, 24 Nov 2025 00:08:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 7F41F6B000D for ; Mon, 24 Nov 2025 00:08:20 -0500 (EST) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 04F25C021A for ; Mon, 24 Nov 2025 05:08:14 +0000 (UTC) X-FDA: 84144319350.24.7490873 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf17.hostedemail.com (Postfix) with ESMTP id 4089740013 for ; Mon, 24 Nov 2025 05:08:13 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PGWFz4wk; spf=pass (imf17.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763960893; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Kv5lKNyggtv57Xj6HWNXD5q3wcps9XYvZ+5HDRbjZNg=; b=EAEE82Xgoy/Rkf4ll+xHVPd7MfKq6uBWYMzyXTh8Qpl8yaGN9Lp3NSe5fenyOP6MyFAEuc XZHozETfTFpIKV1GVbV4nsAlsEZsni+8oOJCA/oispuWyeYbJI2gdItXE1UCb/zIhu0FMT IhAUwnrpPhRtayYP2+fu47pWb4eHeNI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763960893; a=rsa-sha256; cv=none; b=lGqDjr0j1BZlNzh5in4T+5HAS61aSu7CU4+7P2qrwkLhVo5B3hAi/jTWF0RZrH9U5N8xO/ dIvaQkZwMOlZGoSe/0wIMEMv+znt3fvo7U2QCn6lyvzCPPQihqmFhHJuERjSrVMPufW6IQ l4duGqyPGyzK6hEZaziZ033MG6H+/4A= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PGWFz4wk; spf=pass (imf17.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id B9904406F6; Mon, 24 Nov 2025 05:08:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 463A1C4CEF1; Mon, 24 Nov 2025 05:07:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763960891; bh=hieoIPxIhRSooVrU3/2wVozJyRs1qMXLmzpW8xV1wzY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PGWFz4wkyghWCM5P7ckMfeF1ztZvSWtS2QEwkzMCzyzCVgtFKGEkLgJqy/viT440v yaLEfYvDaQKnLSy6uR+9I+i+ZINn7SDTB+/qX8KrflY1cjgOHRmknnXDOV/u0/FvGu NNUNwqZ/xrD2U3CUlUTED32zlbalE8ApcvCTVV7fCZM+JTWXoXtS4lzsdcfGlmNLAZ /qzpXLU7vNgOw/YDtFTUPhAuvbAOle9zzBCqJRbhAWlNE1Pbz9cKm2a0gIDY1NPbmC 0aQfUTilZ7Bh0ou+L5xM7SHml4e2W0OPll/Ctzpic/zP4fsRsIy5pDrE+VWMcYh228 +PoEtTeYVePdw== Date: Mon, 24 Nov 2025 07:07:47 +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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 4089740013 X-Stat-Signature: 7ucastgo31hxocy96zqmd4hq3gattjo7 X-HE-Tag: 1763960893-465882 X-HE-Meta: U2FsdGVkX1/D3h+CWaVoMAoem5gglZdEL2QfxuiaNFhcU/EkXh0g1VQ4HU6l/skiJznmydFTWY8m5Mm/LtY+oYUzvQ+v6wdZYccDUHw8gSvKjIpuAr9XUjHMtT+e/WRArbv/6L0e00p4ljEBqv7uK9zWuXGt54lYuwTfVZSXW4kS9K5HVJWDq7v10AHTy2J1fZYTJs+ycvdm1ObWsTzxQMFHRupKrjYQ16kfNlyEYnUKdYZ+DCntS3TE8M4OKAFaP3LG1YQm7oLMRBGSg+lm2lt8OeN+veCTtBDWlCcfX0LKbg2zdvmWUUlIcx+pFbuFLDKAZV+M9Lr5bbuWlqpb258AKgqwANt/frXR0r8Z7bcWmr0+crQaDuW0SHcQNI+FB3BLh1DlY+VqdejykghDUtyB63aF48eB8mlf32dGXQOwEaCYFJlxWsqv4lcKx12YnFzWAS6dZ3USh4Z+/J89CsSYglhncUqRcYW+YOBY5F8c1EXLOH72/rgW98Zm298NTX7nH1JoGnMs59Xb40nBRFEaIJt3Q7qkPEH/1T7m57tnQb9xpa6jYmFNsbDuB2nIZLVw8jUUHpoCfcF+S4+jwh4LIEx0qEhgEtJlvr8ZSPZiSXcvD87sIgSK0QNE2/9ahTSnMuuFlx1yreFgXRB55YThakygyKZb6s2cjnUr8vVVjthxUZy2q14KkTy5jOaOxyk0pdFx/Az7jv7NLQmgrxwJU6W7Knzbhu5Dgr/S52CWmQHxljOVfmQJXOfg5FRgGJePbeGgLwXizrZduuh2SW6sCUABYgBXuZH6KgTmvtiB9RAHNFkfivQioacTqCY4vtqf08o2mi8Mf/B76KM4Y24MGOD2Zp8KIwskib+xRJmm4HTMxuuTzbFGWzNrU75APtzCdMK80H4MflJNIBBjx4BAs+5mp1YKAUbvis2zKn5pwu8BRBGrUpvBQZx824yM3mhnJCq3i/RlK6WC2Tt Ckex8HNw nXIXMD0TK7aXXcWMoJq2Ydf080uZvwRYh5ex+2kZK+gxoPAG96jLMB7i0Y1K0PA4/uEGSjypJWl/+hxNQzwtn0BH11ry3FAk4FwpumIdCFZEZP4ybSBnU9zIVJabqQP8RTukapnK1ighklSd5rLIYLbvJToNCrs+pLTtzOYNHhejVWuFluSjZ9UqMCwG9TkYV4ynKxshVuBNXM5RD9VuBxuA+URb9Axo3x1aXOMT52svR6RRdx448c+W88y8q4PBcMJAuSLRKU8s7/liZjfTTfBWd2t/PgNeXottsu1UFAqlEc0782nMFggOCjg+FOSKpfiHGQyBGuldn9C4h7YAlmXKVIlXylIOk2F+qNEWptOFsFg5UXlJ0z0LzlqZzKcbKeGW3/SRbEgfon1BiZgAKDBipCOMRS7cZpqo1u7EytXBeCQKcuQ7xQB4KjG971eFoye6NJuA8Dh3hKmCTwQEV9ia59+yspx1BEDMa 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 Sun, Nov 23, 2025 at 07:15:44AM -0500, Pasha Tatashin wrote: > On Sun, Nov 23, 2025 at 6:12 AM Mike Rapoport wrote: > > > > 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) > > Thank you > > > > > 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? > > Sure, or I can remove all of them from Kconfig, whatever you prefer :-) Quick grepping shows that the vast majority of Kconfigs does not have copyright, let's just drop it. > > > 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 :) > > Device preservation through file descriptors: memfd, iommufd, vfiofd > are all dependencies for preserving devices. > > That Kconfig description is correct and essential because the core > complexity of the LUO is the preservation of device state and I/O > across a kernel transition, which is a harder problem than just > preserving memory or files, for that we could have used a file system > instead of inventing something new with logic of can_preserve() etc. > > Device preservation requires exactly what is stated in the description > for this config: > "Ability to handover a device from current to the next kernel depends > on specific support within device drivers and related kernel > subsystems." The only subsystem that is getting upstreamed with this > series is MEMFD, it is a hard pre-requirement for iommufd > preservation; the other subsystems: VFIO, PCI, IOMMU are WIP. Ok. -- Sincerely yours, Mike.