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Tue, 06 Jan 2026 03:04:30 -0800 (PST) Date: Tue, 6 Jan 2026 03:04:28 -0800 From: Breno Leitao To: Pratyush Yadav Cc: Alexander Graf , Mike Rapoport , 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 v2 2/2] kexec: history: track kexec boot counter Message-ID: References: <20260102-kho-v2-0-1747b1a3a1d6@debian.org> <20260102-kho-v2-2-1747b1a3a1d6@debian.org> <86o6nb7oi1.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86o6nb7oi1.fsf@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 37DE7C0015 X-Stat-Signature: uf381nttaozftkbrbi8izhcxn5biok3u X-HE-Tag: 1767697472-475247 X-HE-Meta: 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 iKo97DGH qAoj7kBjwHswN/wgicNJpGzdN0KCLyAaDlxeXOXgJQqHAcXTRLNrsrJQlQdYe5iTPDKL1NqK5sodXkcjH5TjcWiGyYXxo7Efw1LuziJu9JPalufVvr1UmwIQkzYMbnpwN4EvJApbg1xDrtWqj0gdD/m1nKbxjm2FLs268pevd5h/gTMQrNuwvh+zEOnvs3KvaMbyhi32HmB4S/94u+h0cl6F2bCzTnkYkNoYZiQvhgR35O8XVl+CRR+SSdU57X3yufIKoG2KrAqUkOaJOuqfBGVIqd0cl5DuWAdS8plVJrXp3RCgfK3hVmfxnOwIqtOIMr8CJuei1xR3YpLZFXWsu/KRPV+ALhJ4O7SvS8nb8ceKDBQ7ucsF4JfCh65xn7ck4O+UuqBwFN3VL8BRfG/hOU0zwS9d6TGx1ec7u 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 Fri, Jan 02, 2026 at 09:23:18PM +0100, Pratyush Yadav wrote: > On Fri, Jan 02 2026, Breno Leitao wrote: > > > Track and display the number of kexec boots since the last cold reboot > > Nit: this does not track kexec boots, it tracks KHO boots. None of this > can work on normal kexec boots. Can you please update the wording to > make that clear? > > > when CONFIG_KEXEC_HISTORY is enabled. > > > > This extends the previous kernel release tracking feature by adding > > a counter that increments with each kexec boot. The counter provides > > visibility into the kexec chain depth, which is useful for understanding > > boot history in production environments. > > > > Add a new property, "kexec-count" in KHO FDT alongside the existing > > "previous-release" property. The counter is: > > > > - Initialized to 0 when kho_in is instantiated. > > - Incremented by 1 on each subsequent kexec. > > - Printed alongside the previous kernel release version. > > > > The counter is stored as a 32-bit unsigned integer in FDT format and is > > only active when CONFIG_KEXEC_HISTORY is enabled. > > We have such a counter for LUO as well from the properly > "liveupdate-number". If you're using LUO, why can't you use that counter > directly? > > If you're not using LUO, I'm curious, what's your use case? Right now > KHO only supports reserve-mem outside of LUO. Is that what you plan to > use? > > Also, do we want to keep both counters independently? Or do we have one > and drop the other? Pasha, what do you think? In fact, I do not have plan to use LUO right now. My goal is to pass the kexec release from kernel to another, and for that I am using KHO to pass this information. That said, I am planning to use KHO as the infrastructure to pass the kernel version from one kernel to another. Given that I don't think this "feature" should depend on LUO, maybe the counters should be independent (?!) Thanks --breno