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AJvYcCVg3gtOYJr5iA0gBEvk6dKdRUxHlJ+zt1jpCLb6t61mDhvaFVRVogDNWaW5UsaZVh/zEa2mB+d5Pho=@vger.kernel.org X-Gm-Message-State: AOJu0YwbdQo2bJ1E+RfufYhaep6iyzzdPQ622avsqo/F/6TCm/yayk9U 0oeP5/4jFj2XFCiOWLAKOZLKoxZW1DnJ3FGHKzcQvYk21HiD9pj0Y7FNgeF53Nx2QWed3Jju4qQ DAbJ1FiXkjEN/Uic5249Y+soTRvoNkY4KZYGILdaO4A== X-Gm-Gg: ASbGncvKIZBpnO6iTVI3udQQh6rGGbnuh/J61OFuGOxxw7E2pbkf7dM8V+KPV5HDBc3 p5w4msL8C0LEE30+4S4X7IXJIseuVEy5YDlLkk+9PRFSJjx2ZaokpTUqNDrzr966itu6HeV12mO YsTit94oTSqxplA6NgjtFOEtY/ZVYd7m8HA3vtu4cN X-Google-Smtp-Source: AGHT+IH9AiO07plJSRhLB6tkJdXaDFzPn2pHd+a7L3X+gKjm+z/Fz4czzaEUCOxKugIFDOgFxL19MklfYzAdFZ2DkVY= X-Received: by 2002:a05:622a:5811:b0:494:9d34:fca5 with SMTP id d75a77b69052e-49f3394f70emr7714631cf.13.1748023701929; Fri, 23 May 2025 11:08:21 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250515182322.117840-1-pasha.tatashin@soleen.com> In-Reply-To: From: Pasha Tatashin Date: Fri, 23 May 2025 14:07:45 -0400 X-Gm-Features: AX0GCFt9InSi-jbnPqjcDUibRJENQKP67YavT0G51MPVz1pVL-VvRvyfzD-NRvg Message-ID: Subject: Re: [RFC v2 00/16] Live Update Orchestrator To: Mike Rapoport Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.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, zhangguopeng@kylinos.cn, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, May 20, 2025 at 3:25=E2=80=AFAM Mike Rapoport wro= te: > > Hi Pasha, > > On Thu, May 15, 2025 at 06:23:04PM +0000, Pasha Tatashin wrote: > > This v2 series introduces the LUO, a kernel subsystem designed to > > facilitate live kernel updates with minimal downtime, > > particularly in cloud delplyoments aiming to update without fully > > disrupting running virtual machines. > > > > This series builds upon KHO framework [1] by adding programmatic > > control over KHO's lifecycle and leveraging KHO for persisting LUO's > > own metadata across the kexec boundary. The git branch for this series > > can be found at: > > https://github.com/googleprodkernel/linux-liveupdate/tree/luo/rfc-v2 > > > > What is Live Update? > > Live Update is a specialized reboot process where selected kernel > > resources (memory, file descriptors, and eventually devices) are kept > > operational or their state preserved across a kernel transition (e.g., > > via kexec). For certain resources, DMA and interrupt activity might > > continue with minimal interruption during the kernel reboot. > > > > LUO v2 Overview: > > LUO v2 provides a framework for coordinating live updates. It features: > > State Machine: Manages the live update process through states: > > NORMAL, PREPARED, FROZEN, UPDATED. > > > > KHO Integration: > > > > LUO programmatically drives KHO's finalization and abort sequences. > > KHO's debugfs interface is now optional configured via > > CONFIG_KEXEC_HANDOVER_DEBUG. > > > > LUO preserves its own metadata via KHO's kho_add_subtree and > > kho_preserve_phys() mechanisms. > > I've only had time to skip through the patches, one thing that came to mi= nd > was that since LUO is quite tightly coupled with KHO maybe we'll put them > together in, say, kernel/liveupdate? Thank you Mike, yes, a good idea, I also thought that it would make sense for them to be in the same place, but initially I thought perhaps KHO should be moved to misc/liveupdate/, but since it is already landing in kernel/kexec_*, and it works with a bunch of core kernel subsystems it makes sense to move LUO and KHO together under kernel/liveupdate/ Pasha