Allow users of KHO to cancel the previous preservation by adding the
necessary interfaces to unpreserve folio and pages.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
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-googOn 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 <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> 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.
On Tue, Oct 21 2025, 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 <pasha.tatashin@soleen.com>
> ---
> include/linux/kexec_handover.h | 12 +++++
> kernel/kexec_handover.c | 85 ++++++++++++++++++++++++++++------
> 2 files changed, 84 insertions(+), 13 deletions(-)
>
[...]
>
> +/**
> + * 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.
s/contigious/contiguous. Also drop the extra space after it.
> + * 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
Stray closing parenthesis here. Perhaps a rewording to: "This must be
called with the same @page and @nr_pages as the corresponding
kho_preserve_pages() call. Unpreserving arbitrary..."
Other than this,
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
> + * 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 *);
> };
--
Regards,
Pratyush Yadav
On Wed, Oct 22, 2025 at 7:10 AM Pratyush Yadav <pratyush@kernel.org> wrote: > > On Tue, Oct 21 2025, 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 <pasha.tatashin@soleen.com> > > --- > > include/linux/kexec_handover.h | 12 +++++ > > kernel/kexec_handover.c | 85 ++++++++++++++++++++++++++++------ > > 2 files changed, 84 insertions(+), 13 deletions(-) > > > [...] > > > > +/** > > + * 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. > > s/contigious/contiguous. Also drop the extra space after it. > > > + * 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 > > Stray closing parenthesis here. Perhaps a rewording to: "This must be > called with the same @page and @nr_pages as the corresponding > kho_preserve_pages() call. Unpreserving arbitrary..." Done. > > Other than this, > > Reviewed-by: Pratyush Yadav <pratyush@kernel.org> Thank you.
© 2016 - 2026 Red Hat, Inc.