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AJvYcCWNmycUUtlLONr2VQSdD3HdMchbmcsbnguSE3PVBGKcwEJE4CNu/EULcOFF0LBTO/xeiwZLUf8omg==@kvack.org X-Gm-Message-State: AOJu0YwUHO+i3BLI4cWeWp0aFC3pdVP7PlbbX0f5eArPgdY4oSdDesRs o45xljuZbB8SYH0RamBoyU4CM4RCynyxJGvkD+ItcNsWNllkB7zQkwOvV9ZM2N9p49E/LrjRJ7T 8rH2oiuLgn/uhpNGQWKcSoA== X-Received: from wmpu13.prod.google.com ([2002:a05:600c:4d0d:b0:483:a1ee:5eb8]) (user=mclapinski job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:8b03:b0:477:54cd:200e with SMTP id 5b1f17b1804b1-483a95eb622mr2764805e9.1.1771606335280; Fri, 20 Feb 2026 08:52:15 -0800 (PST) Date: Fri, 20 Feb 2026 17:52:03 +0100 In-Reply-To: <20260220165203.3213375-1-mclapinski@google.com> Mime-Version: 1.0 References: <20260220165203.3213375-1-mclapinski@google.com> X-Mailer: git-send-email 2.53.0.345.g96ddfc5eaa-goog Message-ID: <20260220165203.3213375-3-mclapinski@google.com> Subject: [PATCH v4 2/2] kho: make preserved pages compatible with deferred struct page init From: Michal Clapinski To: Evangelos Petrongonas , Pasha Tatashin , Mike Rapoport , Pratyush Yadav , Alexander Graf , kexec@lists.infradead.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Michal Clapinski Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: CB7EE80007 X-Rspamd-Server: rspam02 X-Stat-Signature: 7owkdipmz849rzxcb5p8cmnyxudg694x X-HE-Tag: 1771606336-360610 X-HE-Meta: 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 rpe7R94f 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 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: From: Evangelos Petrongonas When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct page initialization is deferred to parallel kthreads that run later in the boot process. During KHO restoration, deserialize_bitmap() writes metadata for each preserved memory region. However, if the struct page has not been initialized, this write targets uninitialized memory, potentially leading to errors like: BUG: unable to handle page fault for address: ... Fix this by introducing kho_get_preserved_page(), which ensures all struct pages in a preserved region are initialized by calling init_deferred_page() which is a no-op when deferred init is disabled or when the struct page is already initialized. Signed-off-by: Evangelos Petrongonas Co-developed-by: Michal Clapinski Signed-off-by: Michal Clapinski Reviewed-by: Pratyush Yadav (Google) Reviewed-by: Pasha Tatashin Reviewed-by: Mike Rapoport (Microsoft) --- I think we can't initialize those struct pages in kho_restore_page. I encountered this stack: page_zone(start_page) __pageblock_pfn_to_page set_zone_contiguous page_alloc_init_late So, at the end of page_alloc_init_late struct pages are expected to be already initialized. set_zone_contiguous() looks at the first and last struct page of each pageblock in each populated zone to figure out if the zone is contiguous. If a kho page lands on a pageblock boundary, this will lead to access of an uninitialized struct page. There is also page_ext_init that invokes pfn_to_nid, which calls page_to_nid for each section-aligned page. There might be other places that do something similar. Therefore, it's a good idea to initialize all struct pages by the end of deferred struct page init. That's why I'm resending Evangelos's patch. I also tried to implement Pratyush's idea, i.e. iterate over zones, then get node from zone. I didn't notice any performance difference even with 8GB of kho. --- kernel/liveupdate/Kconfig | 2 -- kernel/liveupdate/kexec_handover.c | 27 ++++++++++++++++++++++++++- 2 files changed, 26 insertions(+), 3 deletions(-) diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig index 1a8513f16ef7..c13af38ba23a 100644 --- a/kernel/liveupdate/Kconfig +++ b/kernel/liveupdate/Kconfig @@ -1,12 +1,10 @@ # SPDX-License-Identifier: GPL-2.0-only menu "Live Update and Kexec HandOver" - depends on !DEFERRED_STRUCT_PAGE_INIT config KEXEC_HANDOVER bool "kexec handover" depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE - depends on !DEFERRED_STRUCT_PAGE_INIT select MEMBLOCK_KHO_SCRATCH select KEXEC_FILE select LIBFDT diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index de167bfa2c8d..fe9c88fd2541 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -457,6 +457,31 @@ static int kho_mem_serialize(struct kho_out *kho_out) return err; } +/* + * With CONFIG_DEFERRED_STRUCT_PAGE_INIT, struct pages in higher memory regions + * may not be initialized yet at the time KHO deserializes preserved memory. + * KHO uses the struct page to store metadata and a later initialization would + * overwrite it. + * Ensure all the struct pages in the preservation are + * initialized. deserialize_bitmap() marks the reservation as noinit to make + * sure they don't get re-initialized later. + */ +static struct page *__init kho_get_preserved_page(phys_addr_t phys, + unsigned int order) +{ + unsigned long pfn = PHYS_PFN(phys); + int nid; + + if (!IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT)) + return pfn_to_page(pfn); + + nid = early_pfn_to_nid(pfn); + for (unsigned long i = 0; i < (1UL << order); i++) + init_deferred_page(pfn + i, nid); + + return pfn_to_page(pfn); +} + static void __init deserialize_bitmap(unsigned int order, struct khoser_mem_bitmap_ptr *elm) { @@ -467,7 +492,7 @@ static void __init deserialize_bitmap(unsigned int order, int sz = 1 << (order + PAGE_SHIFT); phys_addr_t phys = elm->phys_start + (bit << (order + PAGE_SHIFT)); - struct page *page = phys_to_page(phys); + struct page *page = kho_get_preserved_page(phys, order); union kho_page_info info; memblock_reserve(phys, sz); -- 2.53.0.345.g96ddfc5eaa-goog