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b=gVqLXxCoHubWmmYGMBSppHz6v+K6gOlZuSYxfANkq1RKW8ckeEAIrlml2vKMxAe5L 3C8zjm11dqTah0Vkmy2M8q3igXZkmU+HXuX48hcaI8METAODITZD7cxnwl2IMKPiXP otr7qxYH6DGeVFsBC2ronbizF4drLwhTO4cKnQUZC7lBlo0I2qlELAAZm/qaFIqsjG HfRaIi6Y5JnNl3ZWxHIr/R7/kiqKBhKBd1W+81GC9ZMcqhlXX4EWL9wpc7TXvC/n65 fdY1qa4EgfHtTIYbz0kzbq1HE98C977U9Rl1R9Gg51/HhI1YNVY1YoDlShCZkuqVyr rOJgoCOWRfH0g== Date: Tue, 18 Nov 2025 17:06:20 +0200 From: Mike Rapoport To: Jason Gunthorpe Cc: Pasha Tatashin , 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, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org Subject: Re: [PATCH v6 02/20] liveupdate: luo_core: integrate with KHO Message-ID: References: <20251115233409.768044-1-pasha.tatashin@soleen.com> <20251115233409.768044-3-pasha.tatashin@soleen.com> <20251118140300.GK10864@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251118140300.GK10864@nvidia.com> X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 446501C001C X-Stat-Signature: zufgktez5wweqnqcz57xpocbezsq5hwj X-HE-Tag: 1763478406-488901 X-HE-Meta: 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 pCW47xTO IDlFIj8TndoKUGb+nKXTR/K4kiuOcbxqvIHQ+Tm51Swe35XN2i23+KoWOI/zweGJ3ZpIPHPlP7eeLdL6j/crzTqRiV3HwunwzW3xR8UEIh4F9oUPvGPnTPp5PTN546WxZxM4HvXWGxReHrjdszduJPAlbDoPnP3KI5lz3BCWBVqI/+OE4ownofb1KOtkwqU3AdVyPQPzB6y1ugf3RCtuv9AgjC8DzqVwxS4WkVHjvIdFLkSO4vAEF3x6htxzuC0soPlbx1fk886ytjwndC6yv1+eUh0OYyYIIK4ym73JhA9Psq7gax7ITFtJ2hUhgLx/1/cDMuBx97Xs3zMfKESCyOCV/I6V6IXC905IdYZ2tVkHx17drIR8lqt9TWQ== 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 Tue, Nov 18, 2025 at 10:03:00AM -0400, Jason Gunthorpe wrote: > On Tue, Nov 18, 2025 at 01:21:34PM +0200, Mike Rapoport wrote: > > On Mon, Nov 17, 2025 at 11:22:54PM -0500, Pasha Tatashin wrote: > > > > You can avoid that complexity if you register the device with a different > > > > fops, but that's technicality. > > > > > > > > Your point about treating the incoming FDT as an underlying resource that > > > > failed to initialize makes sense, but nevertheless userspace needs a > > > > reliable way to detect it and parsing dmesg is not something we should rely > > > > on. > > > > > > I see two solutions: > > > > > > 1. LUO fails to retrieve the preserved data, the user gets informed by > > > not finding /dev/liveupdate, and studying the dmesg for what has > > > happened (in reality in fleets version mismatches should not be > > > happening, those should be detected in quals). > > > 2. Create a zombie device to return some errno on open, and still > > > study dmesg to understand what really happened. > > > > User should not study dmesg. We need another solution. > > What's wrong with e.g. ioctl()? > > It seems very dangerous to even boot at all if the next kernel doesn't > understand the serialization information.. > > IMHO I think we should not even be thinking about this, it is up to > the predecessor environment to prevent it from happening. The ideas to > use ELF metadata/etc to allow a pre-flight validation are the right > solution. > > If we get into the next kernel and it receives information it cannot > process it should just BUG_ON and die, or some broad equivalent. > It is a catastrophic orchestration error, and we don't need some fine > grain recovery or userspace visibility. Crash dump the system and > reboot it. I was under impression Pasha wanted to get up to the userspace no matter what. panic() in liveupdate_early_init() makes perfect sense to me. Parsing dmesg does not. > IOW, I would not invest time in this. > > Jason -- Sincerely yours, Mike.