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AJvYcCVGy2GeiddFgKP41J0GYCv+RcTszNC8upzu5kefVgo1B5Uj5JaOuy6KZy17VhkA6gW7++de/3lJZA==@kvack.org X-Gm-Message-State: AOJu0YxyVnfkJ9GXGPFvoGxJG/MraIe4eCu0SVx5VsH8aY7/w13IiLBW DFq2kW8nyZfq/QqDHqvPUZsoLUi3djZSBHmOEiCiRyEaAw+cQIrKVRFgRFfTiGh6VYmAXtexY+o My403LCofTLxF3tM/y/ADFLq458VKMerx32xXE9R8qQ== X-Gm-Gg: AY/fxX7U1YvU+71gQ6fr1iHxewQJFxVRzzWt8cqV69t5WD4G73skKyHkvbmVr/mRHCr 3PR0UlWUGe4NQ9nlNTHVjuQ5WhzVIAiuntOqYDg62g9iMmrDEzXJ3neOzP4PRZ3PMjjQ/7fx9IV Tk2/eIh5PI5czMg4b/xQN2iiXbLwlkhXd5GXBlWHc4TCy6+x/xuMVerE1CWV5AmCIsppb41gLkK htFjNkGenEwkB4NAdbJgZYCMID4m2ibOd1kyBn8IJPcWTOAAzUMjsmHpPYGU9f6xRZOnXSIkwjc QtXnHLDu2ARK3G2qG5pID0kPpw== X-Google-Smtp-Source: AGHT+IHQMNdZxKpFplxLNEZDOJPbPyGwfr/HlkFZY36RmkmAFCMov8zhCujR2fQsSGMcUi5+FxSA2oJ6tr2W+Ngwqlc= X-Received: by 2002:a05:6402:1d53:b0:64b:654f:8738 with SMTP id 4fb4d7f45d1cf-64b8e94bf4emr28321463a12.14.1767107056147; Tue, 30 Dec 2025 07:04:16 -0800 (PST) MIME-Version: 1.0 References: <20251230-kho-v1-1-4d795a24da9e@debian.org> In-Reply-To: <20251230-kho-v1-1-4d795a24da9e@debian.org> From: Pasha Tatashin Date: Tue, 30 Dec 2025 10:03:38 -0500 X-Gm-Features: AQt7F2rG1eJ6wegbNUrAZYGhxgtB9GBYd5uKgFVrn4Rx6w8K7hySaB_w8u97UO4 Message-ID: Subject: Re: [PATCH RFC] kexec: add option to print previous kernel release after kexec To: Breno Leitao Cc: Alexander Graf , Mike Rapoport , Pratyush Yadav , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, usamaarif642@gmail.com, rmikey@meta.com, clm@fb.com, riel@surriel.com, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C7A63C0019 X-Rspamd-Server: rspam03 X-Stat-Signature: u4it7x5wky88egjg5jh3xmee49515aw4 X-Rspam-User: X-HE-Tag: 1767107057-504242 X-HE-Meta: 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 XyXedBKY /iLI4iP5JNHiQe88EOtF8L32wLwCLIjLZZubCJh+olD53Lq/jRTgc35Ttx/aqwDMPmb4CE/kWlBtFzC+8101aBqZe8oUZ2HA9c5tClPpd+NPhMEwIOrzafK6pIKJjACEIIjT1cdlRbj2AtLot0y0Jb591iw/tBd986In3qAAHk5zBXiTyKsrL//bHTnqe3VWO1dR2T+5/r4Tn4wZL3nNy4OBh+D8xWWIxrXBOQs9iV8rCIF7EePt5SEeVtDTnIWor02SptREqA82Ojb8DH2m+ZKZ3H717lquw61jqIpROCbw7jd0= 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, Dec 30, 2025 at 9:13=E2=80=AFAM Breno Leitao wr= ote: > > Introduce a new Kconfig option, CONFIG_KEXEC_SHOW_PREVIOUS_RELEASE, I don't think we need a config for this. Let's just show the previous kernel version unconditionally when KHO is enabled. > which enables the storage and display of the previous kernel's release > version across kexec boots when using Kexec Handover (KHO). > > Motivation > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > Kernel bugs that depend on the version of the previously running kernel > are not uncommon, especially in scenarios where a buggy kernel kexecs > into a new one and the issue only manifests in the subsequent kernel. > > Recent examples include: > > * eb2266312507 ("x86/boot: Fix page table access in 5-level to 4-level p= aging transition") > * 77d48d39e991 ("efistub/tpm: Use ACPI reclaim memory for event log to a= void corruption") > * 64b45dd46e15 ("x86/efi: skip memattr table on kexec boot") > > As kexec-based reboots become more widespread among Linux users, these > issues are becoming increasingly prominent. > > When such crashes occur, correlating them to the previous kernel version > is challenging, especially at scale, where the problem may only appear in > specific cases and it is hard to correlate. > > With the introduction of Kexec Handover (KHO), we now have a reliable > mechanism to pass information between kernels. This presents an > opportunity to address the problem by carrying the previous kernel's > release version to the next kernel and printing it at boot time. LUO added the number of times a machine has been live updated to help debugging problems that are related to live update, perhaps, in addition to the previous kernel version, we should also add a number of times the machine has been kexec'd. It is useful when a bug manifests only after a number of kexec's which is also sometimes a case. Pasha