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b=GhB7IVkwG/XveGj1F09VZwJYfZ6BTg7yXMg4IEJIePaigtf7knr23e4MQvTMxS+XR 3XGbUKDlpl5+VcPlQFcjc3V9gDkHfwLhvQtn1622KVxhrL30oJc5/p1DDSVoy5b+oK gBhlEsuMf2+/UQWGOlx0kq6hZGbVeB28j90YZPDymuuRHHHrT0mJOWLA4U3nnby16v xCMZ/fk+eOp/cSZbaK58BPKykl50BWitcslIvDcc3KdijKzNQ8tUR6m4ERC7oTDGHh 8D5Dnc+dFsby36GI2D0phtpjip1EDcbHqJ8Lu/KtkMuKJMuTGQxieNcRvQdi2kptia B2purnqkBT7Ig== Date: Tue, 20 Jan 2026 20:58:02 +0200 From: Mike Rapoport To: Pratyush Yadav Cc: Breno Leitao , Alexander Graf , Pasha Tatashin , 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 Subject: Re: [PATCH v3 1/2] kho: history: track previous kernel version Message-ID: References: <20260108-kho-v3-0-b1d6b7a89342@debian.org> <20260108-kho-v3-1-b1d6b7a89342@debian.org> <2vxzy0m0gfyo.fsf@kernel.org> <2vxzms28e1ib.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2vxzms28e1ib.fsf@kernel.org> X-Rspamd-Queue-Id: E1390180010 X-Stat-Signature: hz7zgzjwika573fspg7qh43bw9i7po8o X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1768935490-134749 X-HE-Meta: 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 /oJceSNn SHwj991SHoGU8bSRpbMef0gbRn2pfWGRdxU04i8xOW7mHRZBT5T7h296xbjH5vXxGItH3YUvFwSzQtZXsrtrlhDDJNFxmdw2KfB4GY0RmJm8Y0fC7eE8klpg+0K8vc/iIj3uwJLLELqZJj9mGwmU467FGPPPQ8J6yArasmpbj9uUnhUbsnhuOJqQvYGRgW8tinNj1I2M5H//FNg2QCp97qbSVlWwbVHnc1u936w8eroo0l1PdGirB3RZ6GIfe+ePgbluy 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: Hi, On Tue, Jan 20, 2026 at 03:40:12PM +0000, Pratyush Yadav wrote: > On Fri, Jan 16 2026, Breno Leitao wrote: > > > > On cold boot, kexec-count starts at 0 and increments with each kexec. > > The count helps identify issues that only manifest after multiple > > consecutive kexec reboots. > > Very well written changelog! @Breno, the submission would be perfect if you'd start a new thread rather than reply to v1 ;-) > > +/* > > + * The "history" subtree stores optional metadata about the kexec chain. > > + * It is registered as a separate FDT via kho_add_subtree(), keeping it > > + * independent from the core KHO ABI. This allows the history format to > > + * evolve without affecting other KHO consumers. > > + * > > + * The history FDT structure: > > I don't have a strong preference here, but you don't _have_ to use FDT. > For example, with memfd, we moved from FDT to plain C structs during the > evolution of the patchset. Main reason is that FDT programming is a bit > annoying. C structs make many things much easier. For example, you can > always assume a certain property always exists and is of a given size, > and you don't have to validate every single property you read. > > Anyway, I don't mind either way. Yeah, I agree that a plain C structure with an array of chars and u64 will make things simpler. > > + * > > + * / { > > + * compatible = "kho-history-v1"; > > + * previous-release = "6.x.y-..."; > > + * kexec-count = ; > > + * }; > > + */ > > +#define KHO_HISTORY_NODE_NAME "history" > > Do we want to call it history? Perhaps "kexec-metadata" instead? So we > could use it for other misc information if needed later. > > Mike/Pasha, any thoughts? I like kexec-metadata. -- Sincerely yours, Mike.