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Received: from [50.53.25.54] (helo=[192.168.254.17]) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUaUZ-000000060m1-18Zj; Thu, 26 Jun 2025 00:29:27 +0000 Message-ID: Date: Wed, 25 Jun 2025 17:29:15 -0700 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 17/32] liveupdate: luo_sysfs: add sysfs state monitoring To: Pasha Tatashin , pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, rppt@kernel.org, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, 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, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20250625231838.1897085-1-pasha.tatashin@soleen.com> <20250625231838.1897085-18-pasha.tatashin@soleen.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: <20250625231838.1897085-18-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 6/25/25 4:18 PM, Pasha Tatashin wrote: > diff --git a/Documentation/ABI/testing/sysfs-kernel-liveupdate b/Documentation/ABI/testing/sysfs-kernel-liveupdate > new file mode 100644 > index 000000000000..4cd4a4fe2f93 > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-kernel-liveupdate > @@ -0,0 +1,51 @@ > +What: /sys/kernel/liveupdate/ > +Date: May 2025 > +KernelVersion: 6.16.0 > +Contact: pasha.tatashin@soleen.com > +Description: Directory containing interfaces to query the live > + update orchestrator. Live update is the ability to reboot the > + host kernel (e.g., via kexec, without a full power cycle) while > + keeping specifically designated devices operational ("alive") > + across the transition. After the new kernel boots, these devices > + can be re-attached to their original workloads (e.g., virtual > + machines) with their state preserved. This is particularly > + useful, for example, for quick hypervisor updates without > + terminating running virtual machines. > + > + > +What: /sys/kernel/liveupdate/state > +Date: May 2025 > +KernelVersion: 6.16.0 > +Contact: pasha.tatashin@soleen.com > +Description: Read-only file that displays the current state of the live > + update orchestrator as a string. Possible values are: > + > + "normal": No live update operation is in progress. This is > + the default operational state. Just an opinion, but the ':'s after each possible value aren't needed and just add noise. You could just drop the ':'s -- or you could make a table here, like Documentation/ABI/testing/sysfs-hypervisor-xen does, by adding =========== ================================================ > + "prepared": The live update preparation phase has completed > + successfully (e.g., triggered via the > + /dev/liveupdate event). Kernel subsystems have > + been notified via the %LIVEUPDATE_PREPARE > + event/callback and should have initiated state > + saving. User workloads (e.g., VMs) are generally > + still running, but some operations (like device > + unbinding or new DMA mappings) might be > + restricted. The system is ready for the reboot > + trigger. > + > + "frozen": The final reboot notification has been sent > + (e.g., triggered via the 'reboot()' syscall), > + corresponding to the %LIVEUPDATE_REBOOT kernel > + event. Subsystems have had their final chance to > + save state. User workloads must be suspended. > + The system is about to execute the reboot into > + the new kernel (imminent kexec). This state > + corresponds to the "blackout window". > + > + "updated": The system has successfully rebooted into the > + new kernel via live update. Restoration of > + preserved resources can now occur (typically via > + ioctl commands). The system is awaiting the > + final 'finish' signal after user space completes > + restoration tasks. and =========== ================================================ Or just disagree or ignore. :) -- ~Randy