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AJvYcCWPl9FioRcv40+FBtOG4UN0hqIgItHNL/IUKi+aeRcEiFbvm8GsJCN0BZIIroQdolljDSKG1+W/Zw==@kvack.org X-Gm-Message-State: AOJu0YwFAjrdq1DQAx/rZ5SN13iNF+f0TiOqqTTqVnfhWagLUe8iPaYM iNARVY3pdXHijIgfQ2wYZgqHeD0CU8M56TUkmgg2+FE15o03rtTsUtlkq/jND5a6UWZd2yVoK6J KTiC8qT4GHvhh6Kwsf2fKPy/Ufum/02N7TXHaga/cog== X-Gm-Gg: ASbGncs1PBq4uWI7CUElU+hJu7wr2dx0SU31kKhJZYLKBLnpw2nGGhAy5MtaG2hjVx5 E/kgW+RkkiKZ2sSv9h6EiXOrY4GJ/uM1WvjYYD9q6sGHT/6d7SA6kF7N8cZwfnk0K5l17tnavj0 fFqssRuH5HYZXcZY+RdYNlqb93Mry17wCNofjmb9pTlRMOMf+cA/bzEY2t05nXaHgAVxdHEAkib iPFxWvx7iXDv0Hf5YjWccfTeh9OqcZsQOwd047uC9Ni0/Ct8HS3RH1icIQY0f6nk9Y/8vQRt0Jv RFk= X-Google-Smtp-Source: AGHT+IFl4FaDFqzlx6bWBXZq0K6NpC2OdnYDHICZqNqSZXVeIXY6NixyhYod+1/BeWpybcUus0n1F+KTrSDNCoyB1KE= X-Received: by 2002:a05:6402:5c8:b0:641:5bb9:fdfb with SMTP id 4fb4d7f45d1cf-64350e9d8acmr13722597a12.33.1763480833517; Tue, 18 Nov 2025 07:47:13 -0800 (PST) MIME-Version: 1.0 References: <20251118140300.GK10864@nvidia.com> <20251118153631.GB90703@nvidia.com> In-Reply-To: <20251118153631.GB90703@nvidia.com> From: Pasha Tatashin Date: Tue, 18 Nov 2025 10:46:35 -0500 X-Gm-Features: AWmQ_blpsIaa7po7XSkrfRCPIMZ4WBj-h08xugNazGwsDJ_E9pCQg-N3cDPVz28 Message-ID: Subject: Re: [PATCH v6 02/20] liveupdate: luo_core: integrate with KHO To: Jason Gunthorpe Cc: Mike Rapoport , 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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 501D416000B X-Stat-Signature: jnokn5nqjkrqw41ykdspoijqrk89nkai X-Rspam-User: X-HE-Tag: 1763480835-734703 X-HE-Meta: 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 5lJYkl8w 3qVLW99IipkYNKz/ChLi7HjmQf/0mIhNk6F5KU6zVKTFELjkjnCkslicgxJlWOICqDmvPVSRO4FeZ1I8OwsrcPH3L7jluw5+j5Ezy+pHwZ8vTLrkqxDHOu2bL/f7pBTJKpkIBwPRpXFzIgVJjly8TdQBga37No5VI7HJ2SY+F6hVua3xIq91Jgw6QKKCtPnlR7n2mr3o26o5bILvPglI2qH3M73U4Wl4trgTR9SezJdlOHwwFzYX8m3fn10+QZc5c4Odg3fj8MwF+34M= 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: > > This won't leak data, as /dev/liveupdate is completely disabled, so > > nothing preserved in memory will be recoverable. > > This seems reasonable, but it is still dangerous. > > At the minimum the KHO startup either needs to succeed, panic, or fail > to online most of the memory (ie run from the safe region only) Allowing degrade booting using only scratch memory sounds like a very good compromise. This allows the live-update boot to stay alive as a sort of "crash kernel," particularly since kdump functionality is not available here. However, it would require some work in KHO to enable such a feature. > The above approach works better for things like VFIO or memfd where > you can boot significantly safely. Not sure about iommu though, if > iommu doesn't deserialize properly then it probably corrupts all > memory too. Yes, DMA may corrupt memory if KHO is broken, *but* we are discussing broken LUO recovering, the KHO preserved memory should still stay as preserved but unretriable, so DMA activity should only happen to those regions... Pasha > > Jason