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b=hN2KP4pNFL2p90V8j3d/hLfQeX2QZzb9dkQfAat0qfzSTf5GYlqtJ1PzjKS3P2zkJ RrjjMqw+iYfqFbInhZ3OrlHp5yEbrrPc+3VPUCVPVwd4Y77RXJWajAGWelPr76iq/X j1acplbF3c8IQ5DGD30RFStFv7VTdoX+KHqeGgwbXJYgXaEen+icaidGQPc/upEpxg QzHtvAqKv5xIeq01p4QdTNiIBlicUcI9sypwrt2z3DX8n04rS9oYy77b8b1NTVwBW+ H3n7kH9vKsu9goozvQPdw88H+cmY5p22CzQdSDTZ+7JEX2eFYcQr2pCjOPcyuiyy/J iaAlGW95UJnlA== Date: Mon, 2 Nov 2026 10:36:09 +0200 From: Mike Rapoport To: Greg Thelen Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Andrew Morton , Evangelos Petrongonas , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kho: check fdt_phys in is_kho_boot() Message-ID: References: <20261023054518.3258350-1-gthelen@google.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023054518.3258350-1-gthelen@google.com> X-Rspamd-Queue-Id: 54C2B1A0002 X-Stat-Signature: fss5giduwp31orss57gb5inidpsy34gk X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793608577-619160 X-HE-Meta: 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 Wb4h6mkE CTSRktRnRjlzhNRoOlyEeWOL04NBfF/sQc8WrqvBEUK/rTDTbc2uJ7OTuvGqf1AnjnIHBNBczvUQvcj6bONwJzqILBZmiSE6uV+bGimKHW0VF4TgzMm1z/LdO4+Q3JzuMX0PVectSCDkcKXd9+k/3yIey6TSS1AM8Er3db9MWQHmU8Jj0K+13wQOVOM1/GF94SuH45q3kI7yS/h2JMp2QEhyaUvR4zgjbessJ58wBXcoq4e89RnZASabr0thoGVCTSymR8wuOMhR1XCJzsXwsdn9IGaK7WhKb8v6k7U/Sr96bDJPwp/HVtz5DrDU4za8y0BGv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi, On Thu, Oct 22, 2026 at 10:45:18PM -0700, Greg Thelen wrote: > During arm64 setup_arch(), efi_init() -> reserve_regions() calls > is_kho_boot() before arm64_memblock_init() initializes memstart_addr. > At this point memstart_addr still holds its initial sentinel value (-1). > > When booting via kexec with KHO enabled, kho_populate() sets > kho_in.fdt_phys from the /chosen FDT node. Calling is_kho_boot() -> > kho_get_fdt() invokes phys_to_virt(kho_in.fdt_phys), which evaluates > PHYS_OFFSET and triggers VM_BUG_ON(memstart_addr & 1) on arm64 kernels > built with CONFIG_DEBUG_VM=y: Can't see the forest for the trees ;-) Can you please translate the gist of the issue from LLMish to English? > kernel BUG at ./arch/arm64/include/asm/memory.h:377! > Internal error: Oops - BUG: 00000000f2000800 [#1] SMP > Call trace: > is_kho_boot+0x2c/0x38 (P) > efi_init+0x94/0xf8 > setup_arch+0xf0/0x240 > start_kernel+0x84/0x490 > __primary_switched+0x88/0x98 > > Check kho_in.fdt_phys directly in is_kho_boot() instead of calling > kho_get_fdt() so that early boot callers do not invoke phys_to_virt() > before the linear map offset is initialized. > > Fixes: d6d511639185 ("kexec: introduce is_kho_boot()") > Assisted-by: Gemini:gemini-3.8-flash > Signed-off-by: Greg Thelen > --- > kernel/liveupdate/kexec_handover.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index 7c4d86daf86d..d81baa38497f 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -1630,7 +1630,7 @@ EXPORT_SYMBOL_GPL(kho_restore_free); > */ > bool is_kho_boot(void) > { > - return !!kho_get_fdt(); > + return !!kho_in.fdt_phys; > } > EXPORT_SYMBOL_GPL(is_kho_boot); > > -- > 2.56.0.257.gf7497c7d27-goog > -- Sincerely yours, Mike.