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b=N9e8bCrVuBEncQY6DY/pq7L587pcxnuZNkUiX7jAH7g7gNTO0y0pXZPeInuYaf0m9 812ZhsV0+TyJogWbd9NPmIeqMpvofs98qURaj9WiG48AwIN7WvvmvCmSzSWgXie0KA CCAy5b26YL9gzrOmAo6bPMUaYRtYNsuJiVy5YWpxZpJRA+eh0vBVaHHKkn+5dTKB9q XCga1hD5U5zBXosGvPjHHU92N6xxbsFtWsf+67cUv/sWP/Ntbxl5dUA7cPwVE3XsMH a77CArbgngll92iBlUHc4ILjqjWsepe7/hqHpU9yHYBS6tEI+xdWwAPg1YhKoLEg35 nTP6Pz7wt0lBQ== From: Pratyush Yadav To: Fadouse Cc: Evangelos Petrongonas , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Alexander Graf , Andrew Morton , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Subject: Re: [PATCH] kho: add support for deferred struct page init In-Reply-To: <7024cefd-bf27-430b-b8fa-04e1457e0eb8@proton.me> (fadouse@proton.me's message of "Wed, 24 Dec 2025 07:34:04 +0000") References: <7024cefd-bf27-430b-b8fa-04e1457e0eb8@proton.me> Date: Mon, 29 Dec 2025 22:09:21 +0100 Message-ID: <86zf718072.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Stat-Signature: n7f1nkxgoi3bqdbs7gcpx6k44tmd3koo X-Rspam-User: X-Rspamd-Queue-Id: 81ACCA0003 X-HE-Tag: 1767042568-418864 X-HE-Meta: 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 W0wt+Z12 5QkTl+dwsyWg0/sEMyDXklUqI586nAYzM9JsLGFh4Nuve6vG6x6W4Mx7VWGCMnkiUiOIpWPckMCP1GaqMXxXBmPJhaM88Vln52Z3Yn1dJQXlww98rLI79S9Sdp1f1KtKFIzvnDv2a+bVrlT3xXYycYafDJm1QpQJnPmO9wFTb5GjmqDJXr9WVm5aozDbicyw1p7ipi6Ba5HiBfA7bZGIEBqEtEdaM8LtItvlt 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 Wed, Dec 24 2025, Fadouse wrote: > Hi Evangelos, Mike, Pasha, Pratyush, > > I independently hit a crash in the LUO/memfd restore path with > CONFIG_DEFERRED_STRUCT_PAGE_INIT=3Dy, on a local build based on dd9b004b7= ff3 > (x86_64 QEMU, 6.19.0-rc1 timeframe). How? config KEXEC_HANDOVER depends on !DEFERRED_STRUCT_PAGE_INIT. So you shouldn't even be able to enable KHO or LUO with CONFIG_DEFERRED_STRUCT_PAGE_INIT=3Dy. Are you sure it is enabled? > > In my reproducer, stage1 preserves a memfd via LUO and kexecs into stage2; > stage2 calls LIVEUPDATE_SESSION_FINISH without retrieving files. I observ= ed > a reliable crash in adjust_managed_page_count() from kho_restore_page(). > > Minimal excerpt: > > stage2: start > stage2: retrieved session fd=3D4 > BUG: unable to handle page fault for address: 0000000000001410 > RIP: adjust_managed_page_count+0x29/0x40 > Call Trace: > =C2=A0 kho_restore_page+0x18a/0x1c0 > =C2=A0 kho_restore_folio+0xe/0x60 > =C2=A0 memfd_luo_finish+0xe6/0x160 > =C2=A0 luo_file_finish+0x188/0x240 > =C2=A0 luo_session_finish+0x2c/0x80 > =C2=A0 luo_session_ioctl+0xf5/0x170 > =C2=A0 __x64_sys_ioctl+0x91/0xe0 > > Applying the patch in <20251216084913.86342-1-epetron@amazon.de> makes the > issue no longer reproduce for me. > > I can share full logs and the small two-stage initramfs reproducer if nee= ded. > > Thanks, > YanXin Li > > Tested-by: YanXin Li > [...] --=20 Regards, Pratyush Yadav