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Fri, 01 May 2026 10:31:26 -0700 (PDT) From: Cris Jacob Maamor To: Mike Rapoport , Pasha Tatashin , Pratyush Yadav Cc: Alexander Graf , Andrew Morton , Greg Kroah-Hartman , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/5] kexec: handover: add helper to check preserved page ranges Date: Sat, 2 May 2026 01:30:49 +0800 Message-ID: <20260501173053.73116-2-crisjacobmaamor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260501173053.73116-1-crisjacobmaamor@gmail.com> References: <20260501094637.38650-1-crisjacobmaamor@gmail.com> <20260501173053.73116-1-crisjacobmaamor@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Restore code should not use phys_to_virt() on physical addresses from restored metadata until it verifies that the range was preserved by KHO. Add kho_is_preserved() so callers can check a preserved page range without restoring, freeing, or taking ownership of the pages. Signed-off-by: Cris Jacob Maamor --- include/linux/kexec_handover.h | 6 +++++ kernel/liveupdate/kexec_handover.c | 35 ++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h index 8968c56d2d73..fb09943ab232 100644 --- a/include/linux/kexec_handover.h +++ b/include/linux/kexec_handover.h @@ -19,6 +19,7 @@ struct page; #ifdef CONFIG_KEXEC_HANDOVER bool kho_is_enabled(void); bool is_kho_boot(void); +bool kho_is_preserved(phys_addr_t phys, unsigned long nr_pages); int kho_preserve_folio(struct folio *folio); void kho_unpreserve_folio(struct folio *folio); @@ -51,6 +52,11 @@ static inline bool is_kho_boot(void) return false; } +static inline bool kho_is_preserved(phys_addr_t phys, unsigned long nr_pages) +{ + return false; +} + static inline int kho_preserve_folio(struct folio *folio) { return -EOPNOTSUPP; diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 94762de1fe5f..fe9f11190705 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -10,6 +10,7 @@ #define pr_fmt(fmt) "KHO: " fmt +#include #include #include #include @@ -429,6 +430,40 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio) return page; } +/** + * kho_is_preserved - Verify that a physical page range belongs to KHO. + * @phys: physical address of the first page in the range. + * @nr_pages: number of pages that the caller expects to access. + * + * Use this before phys_to_virt() when a physical address comes from restored + * metadata. It checks that @phys starts a KHO-preserved allocation large + * enough to cover @nr_pages. + * + * This only checks the KHO marker. It does not restore, free, or take + * ownership of the pages. + * + * Return: true if @phys starts a preserved KHO allocation large enough to cover + * @nr_pages, false otherwise. + */ +bool kho_is_preserved(phys_addr_t phys, unsigned long nr_pages) +{ + struct page *page; + union kho_page_info info; + + if (!nr_pages || !IS_ALIGNED(phys, PAGE_SIZE)) + return false; + + page = pfn_to_online_page(PHYS_PFN(phys)); + if (!page) + return false; + + info.page_private = page->private; + if (info.magic != KHO_PAGE_MAGIC || info.order >= BITS_PER_LONG) + return false; + + return nr_pages <= BIT(info.order); +} + /** * kho_restore_folio - recreates the folio from the preserved memory. * @phys: physical address of the folio. -- 2.53.0