On Tue, Oct 21, 2025 at 08:57:16PM -0400, Pasha Tatashin wrote: > Allow users of KHO to cancel the previous preservation by adding the > necessary interfaces to unpreserve folio and pages. > > Signed-off-by: Pasha Tatashin <[email protected]>
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> > --- > 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 > -- Sincerely yours, Mike.
