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[34.86.47.53]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4e8aaf3432dsm84169501cf.2.2025.10.21.17.57.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Oct 2025 17:57:24 -0700 (PDT) From: Pasha Tatashin To: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Subject: [PATCHv7 4/7] kho: add interfaces to unpreserve folios and page ranges Date: Tue, 21 Oct 2025 20:57:16 -0400 Message-ID: <20251022005719.3670224-5-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.51.0.915.g61a8936c21-goog In-Reply-To: <20251022005719.3670224-1-pasha.tatashin@soleen.com> References: <20251022005719.3670224-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 5skfq6t8n8s5i835sknhpq4uc65i8z7t X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CBDBB120005 X-HE-Tag: 1761094645-324511 X-HE-Meta: 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 9i3AFtyT bPgS2jl9Jb2pDspPURMUSA9odQKf+/hsZ7fnlBpYbX+OcB3iQWUd7I2dGGTdNKq2/yLFbwXjTPf0i/IBVvCv5T9nAny8JM6J6g7zPMTBAYGt9JTdtViOf+MVXVBB0vbWN2R1sJkGKqcdjpK8FIMRhmcAd7p7DFaqN7bbtHhd1/8tJymAsuO4Mc1pzegarKs67PzJdyUaR10xZTy/69E3Dv/PZG13zStTcchHz2NI8V6uFiKOI45KJz+dRO8wUtFfj6gmzTTWS8Z9yQ63Khyk67/rpz15HyoyVYjQjUtxBXI6EVHYFMIIhkP4HcKr35RMHix0syzKpgU5IAJ6pjoTDRWokYGV+oHUir7tv4I7U83Uoxu8= 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: Allow users of KHO to cancel the previous preservation by adding the necessary interfaces to unpreserve folio and pages. Signed-off-by: Pasha Tatashin --- include/linux/kexec_handover.h | 12 +++++ kernel/kexec_handover.c | 85 ++++++++++++++++++++++++++++------ 2 files changed, 84 insertions(+), 13 deletions(-) diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h index 2faf290803ce..4ba145713838 100644 --- a/include/linux/kexec_handover.h +++ b/include/linux/kexec_handover.h @@ -43,7 +43,9 @@ bool kho_is_enabled(void); bool is_kho_boot(void); int kho_preserve_folio(struct folio *folio); +int kho_unpreserve_folio(struct folio *folio); int kho_preserve_pages(struct page *page, unsigned int nr_pages); +int kho_unpreserve_pages(struct page *page, unsigned int nr_pages); int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation); struct folio *kho_restore_folio(phys_addr_t phys); struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages); @@ -76,11 +78,21 @@ static inline int kho_preserve_folio(struct folio *folio) return -EOPNOTSUPP; } +static inline int kho_unpreserve_folio(struct folio *folio) +{ + return -EOPNOTSUPP; +} + static inline int kho_preserve_pages(struct page *page, unsigned int nr_pages) { return -EOPNOTSUPP; } +static inline int kho_unpreserve_pages(struct page *page, unsigned int nr_pages) +{ + return -EOPNOTSUPP; +} + static inline int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation) { diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c index 0a4234269fe5..8412897385ad 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -157,26 +157,33 @@ static void *xa_load_or_alloc(struct xarray *xa, unsigned long index) return no_free_ptr(elm); } -static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn, - unsigned long end_pfn) +static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn, + unsigned int order) { struct kho_mem_phys_bits *bits; struct kho_mem_phys *physxa; + const unsigned long pfn_high = pfn >> order; - while (pfn < end_pfn) { - const unsigned int order = - min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); - const unsigned long pfn_high = pfn >> order; + physxa = xa_load(&track->orders, order); + if (!physxa) + return; + + bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS); + if (!bits) + return; - physxa = xa_load(&track->orders, order); - if (!physxa) - continue; + clear_bit(pfn_high % PRESERVE_BITS, bits->preserve); +} + +static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn, + unsigned long end_pfn) +{ + unsigned int order; - bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS); - if (!bits) - continue; + while (pfn < end_pfn) { + order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); - clear_bit(pfn_high % PRESERVE_BITS, bits->preserve); + __kho_unpreserve_order(track, pfn, order); pfn += 1 << order; } @@ -749,6 +756,30 @@ int kho_preserve_folio(struct folio *folio) } EXPORT_SYMBOL_GPL(kho_preserve_folio); +/** + * kho_unpreserve_folio - unpreserve a folio. + * @folio: folio to unpreserve. + * + * Instructs KHO to unpreserve a folio that was preserved by + * kho_preserve_folio() before. The provided @folio (pfn and order) + * must exactly match a previously preserved folio. + * + * Return: 0 on success, error code on failure + */ +int kho_unpreserve_folio(struct folio *folio) +{ + const unsigned long pfn = folio_pfn(folio); + const unsigned int order = folio_order(folio); + struct kho_mem_track *track = &kho_out.track; + + if (kho_out.finalized) + return -EBUSY; + + __kho_unpreserve_order(track, pfn, order); + return 0; +} +EXPORT_SYMBOL_GPL(kho_unpreserve_folio); + /** * kho_preserve_pages - preserve contiguous pages across kexec * @page: first page in the list. @@ -793,6 +824,34 @@ int kho_preserve_pages(struct page *page, unsigned int nr_pages) } EXPORT_SYMBOL_GPL(kho_preserve_pages); +/** + * kho_unpreserve_pages - unpreserve contiguous pages. + * @page: first page in the list. + * @nr_pages: number of pages. + * + * Instructs KHO to unpreserve @nr_pages contigious pages starting from @page. + * This call must exactly match a granularity at which memory was originally + * preserved by kho_preserve_pages, call with the same @page and + * @nr_pages). Unpreserving arbitrary sub-ranges of larger preserved blocks is + * not supported. + * + * Return: 0 on success, error code on failure + */ +int kho_unpreserve_pages(struct page *page, unsigned int nr_pages) +{ + struct kho_mem_track *track = &kho_out.track; + const unsigned long start_pfn = page_to_pfn(page); + const unsigned long end_pfn = start_pfn + nr_pages; + + if (kho_out.finalized) + return -EBUSY; + + __kho_unpreserve(track, start_pfn, end_pfn); + + return 0; +} +EXPORT_SYMBOL_GPL(kho_unpreserve_pages); + struct kho_vmalloc_hdr { DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *); }; -- 2.51.0.915.g61a8936c21-goog