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[34.86.47.53]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4db0c0fbe63sm64561521cf.23.2025.09.28.18.03.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 Sep 2025 18:03:36 -0700 (PDT) From: Pasha Tatashin To: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, pasha.tatashin@soleen.com, rppt@kernel.org, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org, steven.sistare@oracle.com Subject: [PATCH v4 04/30] kho: add interfaces to unpreserve folios and page ranes Date: Mon, 29 Sep 2025 01:02:55 +0000 Message-ID: <20250929010321.3462457-5-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.51.0.536.g15c5d4f767-goog In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com> References: <20250929010321.3462457-1-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Allow users of KHO to cancel the previous preservation by adding the necessary interfaces to unpreserve folio and pages. Co-developed-by: Changyuan Lyu 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); =20 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 *foli= o) return -EOPNOTSUPP; } =20 +static inline int kho_unpreserve_folio(struct folio *folio) +{ + return -EOPNOTSUPP; +} + static inline int kho_preserve_pages(struct page *page, unsigned int nr_pa= ges) { return -EOPNOTSUPP; } =20 +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 e0dc0ed565ef..26e035eb1314 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -153,26 +153,33 @@ static void *xa_load_or_alloc(struct xarray *xa, unsi= gned long index, size_t sz) return elm; } =20 -static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pf= n, - unsigned long end_pfn) +static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned l= ong pfn, + unsigned int order) { struct kho_mem_phys_bits *bits; struct kho_mem_phys *physxa; + const unsigned long pfn_high =3D pfn >> order; =20 - while (pfn < end_pfn) { - const unsigned int order =3D - min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); - const unsigned long pfn_high =3D pfn >> order; + physxa =3D xa_load(&track->orders, order); + if (!physxa) + return; + + bits =3D xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS); + if (!bits) + return; =20 - physxa =3D 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 pf= n, + unsigned long end_pfn) +{ + unsigned int order; =20 - bits =3D xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS); - if (!bits) - continue; + while (pfn < end_pfn) { + order =3D min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); =20 - clear_bit(pfn_high % PRESERVE_BITS, bits->preserve); + __kho_unpreserve_order(track, pfn, order); =20 pfn +=3D 1 << order; } @@ -734,6 +741,30 @@ int kho_preserve_folio(struct folio *folio) } EXPORT_SYMBOL_GPL(kho_preserve_folio); =20 +/** + * 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 =3D folio_pfn(folio); + const unsigned int order =3D folio_order(folio); + struct kho_mem_track *track =3D &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); =20 +/** + * 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 original= ly + * preserved by kho_preserve_pages, call with the same @page and + * @nr_pages). Unpreserving arbitrary sub-ranges of larger preserved block= s 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 =3D &kho_out.track; + const unsigned long start_pfn =3D page_to_pfn(page); + const unsigned long end_pfn =3D 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 *); }; --=20 2.51.0.536.g15c5d4f767-goog