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[34.86.47.53]) by smtp.gmail.com with ESMTPSA id 00721157ae682-785cd6edd87sm14099197b3.51.2025.10.24.09.10.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Oct 2025 09:10:07 -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 v8 4/8] kho: add interfaces to unpreserve folios and page ranges Date: Fri, 24 Oct 2025 12:09:58 -0400 Message-ID: <20251024161002.747372-5-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.51.1.821.gb6fe4d2222-goog In-Reply-To: <20251024161002.747372-1-pasha.tatashin@soleen.com> References: <20251024161002.747372-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: ADFA8A000F X-Stat-Signature: uxha645mgx8e7q1egiojcknyu4gf3ioj X-Rspam-User: X-HE-Tag: 1761322209-583662 X-HE-Meta: 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 bvf3E7iR D8fYfnDHqfJBmjZI39t+HEI6vxPej69HdA9NxP0/FqRcHTGdTcqRNAyzD07I/tUz5YdXJWhGtHo8/B745/M7j6FwtSd4bj0ensI6ZEz3RBLkVKAtiv3GEFMMsM43Vmm0qKUjG3Vf2Xcenxhc3h0WQkR7aDd9nJQa2SR0dhV7qmguNtOXpmwTW9G8681JibkBlIx3dr1MVkpFjqD5KzyFU/oKXo4yDzQkP1dhYKIrjVANxdcqjS7ovH9SmoHN3Zl+jKl4D9jVCb1Pc9LGPmrsDoUn2eBoN2nQjocBR9NAxRklUSklJ2NZPa2KZpJmKAU0xxgyzG8QG7Nzkq/kwYMxrpTiDTDM5iwa8QlVxXm8IanDn2H5B/LTSfTGBE6IR2oSpRv9q 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 Reviewed-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) --- include/linux/kexec_handover.h | 12 +++++ kernel/kexec_handover.c | 84 ++++++++++++++++++++++++++++------ 2 files changed, 83 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 82137eba1474..994ee0b70757 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; } @@ -745,6 +752,30 @@ 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. @@ -789,6 +820,33 @@ 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 contiguous pages starting from @page. + * This must be called with the same @page and @nr_pages as the corresponding + * kho_preserve_pages() call. 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 *); }; -- 2.51.1.821.gb6fe4d2222-goog