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b=HhlJuTsS9etJriQhma1EQG8iRFbEildqNTcjp8UrZmjCy1Y5uyZVhxDqZ2UN7jX45 /UmEPju6KkW9SBS0sH5Ao29HbZ3Z10Qj2m51ct1m2ZQdSxr52E1SOmc/9PSmIZ5wDb yRgDcOXTgeBylHjxFIR/piJvlU9UmKKSX6aYLaeKITrReJxEZvEgDvnzqphs8kRwS0 J7NCjjOaJ6NbSIM4WTO4+qJMk8FkR0qvpthCeYfRt3PDxuOPZj/PgdnKVEsnwEj/7z pMUB8xnDnnAlObV5tuwZEQrEkq71yXpl+HpnF+51DEptXpjFV4NruVV3/cD2WR1Cbl 43c1uP2lb/vHg== Date: Sun, 16 Aug 2026 12:03:08 +0300 From: Mike Rapoport To: Maxi Saparov Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Evangelos Petrongonas , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, sdimitropoulos@coreweave.com, Maxi Saparov , stable@vger.kernel.org Subject: Re: [PATCH v2] kho: do not reserve scratch memory in the kdump kernel Message-ID: References: <20260803193938.8778-1-maxi.saparov@gmail.com> <20260811161857.3096-1-maxi.saparov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260811161857.3096-1-maxi.saparov@gmail.com> X-Rspam-User: X-Stat-Signature: 8639p6j1rnth5tizpjrgf3bh3rpsejf4 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7ADAD140008 X-HE-Tag: 1786870997-888352 X-HE-Meta: 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 waKDLUAZ gANS6DZfDCgZ3NHv60GhNhOxKV8dLTHVqDrNOdqiYP9MfNAAMMPZcn+SQh6obnOU1Fab5nf3J4yl76PjkIUJLnR7MFjue49Ob0JmbMw6F7LTTLlEnb0cdd2kt9YZBqw7MU9PXNiJqXSaqz8UwGhIBh+XVEcZyrPtKBBXrgKnXqaENgbC5rxdcY30Ve0/mevKEmSKr9jtKmijiuG4w1nA/Ej98/O4qdcwupSzOr1ushBIIu3yducpQSrUWFfUCuVQGMD1nKTx/H0VbMNnlArwwS6Q1CiRLAC7J/fYeCDdQ9aW0Epasf9OelUomk9ZxQAoOHNhjvdA6hRNqThgzvr/r6ZmveT6BmYEVA3DSdkGHOPgUP5zD/7a8MS4I5ZpZRk5e/0needIBCMCOiIvAgTK8/wAfZFj/rlkYhZln4SMG42sx597htE2gnw9+Jg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, Please don't send vN+1 as a reply to vN next time. On Tue, Aug 11, 2026 at 12:18:57PM -0400, Maxi Saparov wrote: > From: Maxi Saparov > > If a kernel with CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y (or kho=on) > does not receive a handover FDT, it reserves KHO scratch memory in > kho_reserve_scratch(). > > The kdump kernel always takes this path. Since commit a6715d7ec472 > ("kho: skip KHO for crash kernel"), the kernel does not add KHO > metadata to the crash kimage. As a result, the kdump kernel never > receives a handover FDT and always reserves scratch memory. > > The kdump kernel boots in the small crashkernel= memory reservation. > On our x86 hosts, the kernel and initramfs make approximately 176 MB > of early reservations. The scratch areas then use approximately > 650 MB more of the crashkernel memory. When a large early allocation > fails, the kdump kernel panics: > > bio: can't create integrity buf pool > > A kdump kernel has nothing to hand over: its only task is to dump the > memory of the old kernel and reboot. Fix is to disable KHO at the top of > kho_memory_init() so that the kdump kernel does not reserve scratch > memory. > > Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers") > Cc: stable@vger.kernel.org > Signed-off-by: Maxi Saparov I queued this patch for v7.4, it'll appear in the liveupdate tree after the merge window. > --- > v2: Move the kdump check to the top of kho_memory_init() as an early return. > v1: https://lore.kernel.org/all/20260803193938.8778-1-maxi.saparov@gmail.com/ > > kernel/liveupdate/kexec_handover.c | 7 +++++++ > 1 file changed, 7 insertions(+) -- Sincerely yours, Mike.