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AJvYcCXEiqR/DV1Bg+eCpLVmqTMN7AZbB5ybUKzYNnxQhfk4o4RcJb5ME0wkJZ+qMFSMDd8YRYux9X7RIA==@kvack.org X-Gm-Message-State: AOJu0YzUOT1NS8WkFovzcGM4ZJtG2/bg/6jLIdN34hq+lPE1KMk2uN3v IGBV+DjHmkBwm0HShuWB/QIVFkmnQrCnyZdqloGA4qFoqscTqMj/ONW5TZ7OVhnstecZt6dEaoP ccmMm75Tp4h+4fcmkUvOStw== X-Received: from wmby16.prod.google.com ([2002:a05:600c:c050:b0:480:6b05:6b9a]) (user=mclapinski job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:458e:b0:485:3ae8:2231 with SMTP id 5b1f17b1804b1-4854b11a321mr35639475e9.30.1773233755110; Wed, 11 Mar 2026 05:55:55 -0700 (PDT) Date: Wed, 11 Mar 2026 13:55:39 +0100 In-Reply-To: <20260311125539.4123672-1-mclapinski@google.com> Mime-Version: 1.0 References: <20260311125539.4123672-1-mclapinski@google.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260311125539.4123672-3-mclapinski@google.com> Subject: [PATCH v6 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 , Samiullah Khawaja , 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-Stat-Signature: jmpu3qbpsgpkbc4qsk9rt1muaogxhx8n X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: D07AC1C000C X-HE-Tag: 1773233756-339066 X-HE-Meta: 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 Ss730rr1 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 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, kho_preserved_memory_reserve() 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 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 09cb6660ade7..1f9707d11e5f 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -471,6 +471,31 @@ struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages) } EXPORT_SYMBOL_GPL(kho_restore_pages); +/* + * 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. kho_preserved_memory_reserve() 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 int __init kho_preserved_memory_reserve(phys_addr_t phys, unsigned int order) { @@ -479,7 +504,7 @@ static int __init kho_preserved_memory_reserve(phys_addr_t phys, u64 sz; sz = 1 << (order + PAGE_SHIFT); - page = phys_to_page(phys); + page = kho_get_preserved_page(phys, order); /* Reserve the memory preserved in KHO in memblock */ memblock_reserve(phys, sz); -- 2.53.0.473.g4a7958ca14-goog