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[34.86.47.53]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-552ea335f07sm2446030e0c.15.2025.10.06.20.31.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Oct 2025 20:31:10 -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: [PATCH v5 4/7] kho: add interfaces to unpreserve folios and page ranes Date: Tue, 7 Oct 2025 03:30:57 +0000 Message-ID: <20251007033100.836886-5-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.51.0.618.g983fd99d29-goog In-Reply-To: <20251007033100.836886-1-pasha.tatashin@soleen.com> References: <20251007033100.836886-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 37FB840011 X-Stat-Signature: rd9wodrafia45ks41xo3sonjpisf7z87 X-Rspam-User: X-HE-Tag: 1759807872-845507 X-HE-Meta: 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 mGxFr2Gb OahYH1+zNJ/rlxSvaG6b9JYetIYYjUdd5R6fG2cnPM94K3IpJJTa1nVc2SQrRsMcSLeVYPLOKLfRRA4cWGDtp4TqWRAdbry9VN6hmGL6jZH4o2v6wB7pHEH3PfjWQHNhbzD13I3WyOq5qH6uLVlGNXNvRRbncfxD+v77ziO0OcjTct2nIXmJkPUumSrgV8wbA7ztRVcRZN3toRG8An9ET6lIpVCSTHt8HuwabUbdErYSwBhZuB769gDnSEJI+oAyRJFHS0rgyRFye1DskNEYE6SW2RypUrdu1kxOgtSMoEJ9ZYxVBlrdanenKQVmT+tt/rjgVJ9HZya9wM1HpRLJuDF66SDbRCqFW0jaFZM64+spdLtM= 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 846fb4aa6948..77fd7dd991d2 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -153,26 +153,33 @@ static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz) return 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; } @@ -734,6 +741,30 @@ 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. @@ -773,6 +804,34 @@ 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 *); }; -- 2.51.0.618.g983fd99d29-goog