FAILED: patch "[PATCH] kho: make sure scratch size is always aligned by" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] kho: make sure scratch size is always aligned by" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 0e39380a7316122e1b00012b3f3cd3e318b3e7d3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026072031-lapping-tubby-5b19@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0e39380a7316122e1b00012b3f3cd3e318b3e7d3 Mon Sep 17 00:00:00 2001
From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
Date: Tue, 19 May 2026 18:05:49 +0200
Subject: [PATCH] kho: make sure scratch size is always aligned by
 CMA_MIN_ALIGNMENT_BYTES

When using scratch_scale, the scratch sizes are rounded up to
CMA_MIN_ALIGNMENT_BYTES since they will be released as MIGRATE_CMA. This
is not done when using fixed scratch sizes via command line. This can
result in user specifying a size which is not aligned, and thus kernel
releasing a pageblock that is only partially scratch.

Do the rounding up for both cases in scratch_size_update().

Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
Cc: stable@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Link: https://patch.msgid.link/20260519160554.2713361-1-pratyush@kernel.org
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index eb8abd04e7ff..4834a809985a 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -618,20 +618,30 @@ early_param("kho_scratch", kho_parse_scratch_size);
 
 static void __init scratch_size_update(void)
 {
-	phys_addr_t size;
+	/*
+	 * If fixed sizes are not provided via command line, calculate them
+	 * now.
+	 */
+	if (scratch_scale) {
+		phys_addr_t size;
 
-	if (!scratch_scale)
-		return;
+		size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
+						   NUMA_NO_NODE);
+		size = size * scratch_scale / 100;
+		scratch_size_lowmem = size;
 
-	size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
-					   NUMA_NO_NODE);
-	size = size * scratch_scale / 100;
-	scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+		size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+						   NUMA_NO_NODE);
+		size = size * scratch_scale / 100 - scratch_size_lowmem;
+		scratch_size_global = size;
+	}
 
-	size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
-					   NUMA_NO_NODE);
-	size = size * scratch_scale / 100 - scratch_size_lowmem;
-	scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+	/*
+	 * Scratch areas are released as MIGRATE_CMA. Round them up to the right
+	 * size.
+	 */
+	scratch_size_lowmem = round_up(scratch_size_lowmem, CMA_MIN_ALIGNMENT_BYTES);
+	scratch_size_global = round_up(scratch_size_global, CMA_MIN_ALIGNMENT_BYTES);
 }
 
 static phys_addr_t __init scratch_size_node(int nid)

[PATCH 6.18.y 1/2] kho: add interfaces to unpreserve folios, page ranges, and vmalloc

[Sasha Levin]

From: Pasha Tatashin <pasha.tatashin@soleen.com>

[ Upstream commit 36f8f7ef7fd2f238922e9d217e86c69838319d8c ]

Allow users of KHO to cancel the previous preservation by adding the
necessary interfaces to unpreserve folio, pages, and vmallocs.

Link: https://lkml.kernel.org/r/20251101142325.1326536-4-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Simon Horman <horms@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 0e39380a7316 ("kho: make sure scratch size is always aligned by CMA_MIN_ALIGNMENT_BYTES")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/kexec_handover.h |  18 ++++++
 kernel/kexec_handover.c        | 104 ++++++++++++++++++++++++++++-----
 2 files changed, 109 insertions(+), 13 deletions(-)

diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 25042c1d8d54af..e1af332a262fba 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -52,8 +52,11 @@ 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);
+int kho_unpreserve_vmalloc(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);
 void *kho_restore_vmalloc(const struct kho_vmalloc *preservation);
@@ -83,17 +86,32 @@ 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)
 {
 	return -EOPNOTSUPP;
 }
 
+static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline struct folio *kho_restore_folio(phys_addr_t phys)
 {
 	return NULL;
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index c13b99f7c9891e..37e6048118e8b7 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)
 	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 (WARN_ON_ONCE(!physxa))
+		return;
 
-		physxa = xa_load(&track->orders, order);
-		if (WARN_ON_ONCE(!physxa))
-			return;
+	bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+	if (WARN_ON_ONCE(!bits))
+		return;
+
+	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 (WARN_ON_ONCE(!bits))
-			return;
+	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;
 	}
@@ -739,6 +746,30 @@ 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.
@@ -783,6 +814,33 @@ 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 *);
 };
@@ -944,6 +1002,26 @@ int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
 }
 EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
 
+/**
+ * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()
+ * @preservation: preservation metadata returned by kho_preserve_vmalloc()
+ *
+ * Instructs KHO to unpreserve the area in vmalloc address space that was
+ * previously preserved with kho_preserve_vmalloc().
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
+{
+	if (kho_out.finalized)
+		return -EBUSY;
+
+	kho_vmalloc_free_chunks(preservation);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);
+
 /**
  * kho_restore_vmalloc - recreates and populates an area in vmalloc address
  * space from the preserved memory.
-- 
2.53.0

[PATCH 6.18.y 2/2] kho: make sure scratch size is always aligned by CMA_MIN_ALIGNMENT_BYTES

[Sasha Levin]

From: "Pratyush Yadav (Google)" <pratyush@kernel.org>

[ Upstream commit 0e39380a7316122e1b00012b3f3cd3e318b3e7d3 ]

When using scratch_scale, the scratch sizes are rounded up to
CMA_MIN_ALIGNMENT_BYTES since they will be released as MIGRATE_CMA. This
is not done when using fixed scratch sizes via command line. This can
result in user specifying a size which is not aligned, and thus kernel
releasing a pageblock that is only partially scratch.

Do the rounding up for both cases in scratch_size_update().

Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
Cc: stable@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Link: https://patch.msgid.link/20260519160554.2713361-1-pratyush@kernel.org
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/kexec_handover.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 37e6048118e8b7..bd10660db469a2 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -569,20 +569,30 @@ early_param("kho_scratch", kho_parse_scratch_size);
 
 static void __init scratch_size_update(void)
 {
-	phys_addr_t size;
+	/*
+	 * If fixed sizes are not provided via command line, calculate them
+	 * now.
+	 */
+	if (scratch_scale) {
+		phys_addr_t size;
 
-	if (!scratch_scale)
-		return;
+		size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
+						   NUMA_NO_NODE);
+		size = size * scratch_scale / 100;
+		scratch_size_lowmem = size;
 
-	size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
-					   NUMA_NO_NODE);
-	size = size * scratch_scale / 100;
-	scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+		size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+						   NUMA_NO_NODE);
+		size = size * scratch_scale / 100 - scratch_size_lowmem;
+		scratch_size_global = size;
+	}
 
-	size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
-					   NUMA_NO_NODE);
-	size = size * scratch_scale / 100 - scratch_size_lowmem;
-	scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+	/*
+	 * Scratch areas are released as MIGRATE_CMA. Round them up to the right
+	 * size.
+	 */
+	scratch_size_lowmem = round_up(scratch_size_lowmem, CMA_MIN_ALIGNMENT_BYTES);
+	scratch_size_global = round_up(scratch_size_global, CMA_MIN_ALIGNMENT_BYTES);
 }
 
 static phys_addr_t __init scratch_size_node(int nid)
-- 
2.53.0

Re: [PATCH 6.18.y 1/2] kho: add interfaces to unpreserve folios, page ranges, and vmalloc

[Greg KH]

On Sat, Jul 25, 2026 at 06:54:32AM -0400, Sasha Levin wrote:
> From: Pasha Tatashin <pasha.tatashin@soleen.com>
> 
> [ Upstream commit 36f8f7ef7fd2f238922e9d217e86c69838319d8c ]
> 
> Allow users of KHO to cancel the previous preservation by adding the
> necessary interfaces to unpreserve folio, pages, and vmallocs.
> 
> Link: https://lkml.kernel.org/r/20251101142325.1326536-4-pasha.tatashin@soleen.com
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Cc: Alexander Graf <graf@amazon.com>
> Cc: Changyuan Lyu <changyuanl@google.com>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Jason Gunthorpe <jgg@nvidia.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Miguel Ojeda <ojeda@kernel.org>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Simon Horman <horms@kernel.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Stable-dep-of: 0e39380a7316 ("kho: make sure scratch size is always aligned by CMA_MIN_ALIGNMENT_BYTES")
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  include/linux/kexec_handover.h |  18 ++++++
>  kernel/kexec_handover.c        | 104 ++++++++++++++++++++++++++++-----
>  2 files changed, 109 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> index 25042c1d8d54af..e1af332a262fba 100644
> --- a/include/linux/kexec_handover.h
> +++ b/include/linux/kexec_handover.h
> @@ -52,8 +52,11 @@ 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);
> +int kho_unpreserve_vmalloc(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);
>  void *kho_restore_vmalloc(const struct kho_vmalloc *preservation);
> @@ -83,17 +86,32 @@ 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)
>  {
>  	return -EOPNOTSUPP;
>  }
>  
> +static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  static inline struct folio *kho_restore_folio(phys_addr_t phys)
>  {
>  	return NULL;
> diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
> index c13b99f7c9891e..37e6048118e8b7 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)
>  	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 (WARN_ON_ONCE(!physxa))
> +		return;
>  
> -		physxa = xa_load(&track->orders, order);
> -		if (WARN_ON_ONCE(!physxa))
> -			return;
> +	bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
> +	if (WARN_ON_ONCE(!bits))
> +		return;
> +
> +	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 (WARN_ON_ONCE(!bits))
> -			return;
> +	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;
>  	}
> @@ -739,6 +746,30 @@ 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.
> @@ -783,6 +814,33 @@ 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 *);
>  };
> @@ -944,6 +1002,26 @@ int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
>  }
>  EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
>  
> +/**
> + * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()
> + * @preservation: preservation metadata returned by kho_preserve_vmalloc()
> + *
> + * Instructs KHO to unpreserve the area in vmalloc address space that was
> + * previously preserved with kho_preserve_vmalloc().
> + *
> + * Return: 0 on success, error code on failure
> + */
> +int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> +{
> +	if (kho_out.finalized)
> +		return -EBUSY;
> +
> +	kho_vmalloc_free_chunks(preservation);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);
> +
>  /**
>   * kho_restore_vmalloc - recreates and populates an area in vmalloc address
>   * space from the preserved memory.
> -- 
> 2.53.0
> 
> 

Oops, nope, dropped this and patch 2/2 as this causes a build error :(

Re: [PATCH 6.18.y 1/2] kho: add interfaces to unpreserve folios, page ranges, and vmalloc

[Greg KH]

On Thu, Jul 30, 2026 at 02:33:30PM +0200, Greg KH wrote:
> On Sat, Jul 25, 2026 at 06:54:32AM -0400, Sasha Levin wrote:
> > From: Pasha Tatashin <pasha.tatashin@soleen.com>
> > 
> > [ Upstream commit 36f8f7ef7fd2f238922e9d217e86c69838319d8c ]
> > 
> > Allow users of KHO to cancel the previous preservation by adding the
> > necessary interfaces to unpreserve folio, pages, and vmallocs.
> > 
> > Link: https://lkml.kernel.org/r/20251101142325.1326536-4-pasha.tatashin@soleen.com
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
> > Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > Cc: Alexander Graf <graf@amazon.com>
> > Cc: Changyuan Lyu <changyuanl@google.com>
> > Cc: Christian Brauner <brauner@kernel.org>
> > Cc: Jason Gunthorpe <jgg@nvidia.com>
> > Cc: Jason Gunthorpe <jgg@ziepe.ca>
> > Cc: Jonathan Corbet <corbet@lwn.net>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Miguel Ojeda <ojeda@kernel.org>
> > Cc: Randy Dunlap <rdunlap@infradead.org>
> > Cc: Simon Horman <horms@kernel.org>
> > Cc: Tejun Heo <tj@kernel.org>
> > Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > Stable-dep-of: 0e39380a7316 ("kho: make sure scratch size is always aligned by CMA_MIN_ALIGNMENT_BYTES")
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> >  include/linux/kexec_handover.h |  18 ++++++
> >  kernel/kexec_handover.c        | 104 ++++++++++++++++++++++++++++-----
> >  2 files changed, 109 insertions(+), 13 deletions(-)
> > 
> > diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> > index 25042c1d8d54af..e1af332a262fba 100644
> > --- a/include/linux/kexec_handover.h
> > +++ b/include/linux/kexec_handover.h
> > @@ -52,8 +52,11 @@ 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);
> > +int kho_unpreserve_vmalloc(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);
> >  void *kho_restore_vmalloc(const struct kho_vmalloc *preservation);
> > @@ -83,17 +86,32 @@ 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)
> >  {
> >  	return -EOPNOTSUPP;
> >  }
> >  
> > +static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> > +{
> > +	return -EOPNOTSUPP;
> > +}
> > +
> >  static inline struct folio *kho_restore_folio(phys_addr_t phys)
> >  {
> >  	return NULL;
> > diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
> > index c13b99f7c9891e..37e6048118e8b7 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)
> >  	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 (WARN_ON_ONCE(!physxa))
> > +		return;
> >  
> > -		physxa = xa_load(&track->orders, order);
> > -		if (WARN_ON_ONCE(!physxa))
> > -			return;
> > +	bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
> > +	if (WARN_ON_ONCE(!bits))
> > +		return;
> > +
> > +	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 (WARN_ON_ONCE(!bits))
> > -			return;
> > +	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;
> >  	}
> > @@ -739,6 +746,30 @@ 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.
> > @@ -783,6 +814,33 @@ 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 *);
> >  };
> > @@ -944,6 +1002,26 @@ int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
> >  }
> >  EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
> >  
> > +/**
> > + * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()
> > + * @preservation: preservation metadata returned by kho_preserve_vmalloc()
> > + *
> > + * Instructs KHO to unpreserve the area in vmalloc address space that was
> > + * previously preserved with kho_preserve_vmalloc().
> > + *
> > + * Return: 0 on success, error code on failure
> > + */
> > +int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> > +{
> > +	if (kho_out.finalized)
> > +		return -EBUSY;
> > +
> > +	kho_vmalloc_free_chunks(preservation);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);
> > +
> >  /**
> >   * kho_restore_vmalloc - recreates and populates an area in vmalloc address
> >   * space from the preserved memory.
> > -- 
> > 2.53.0
> > 
> > 
> 
> Oops, nope, dropped this and patch 2/2 as this causes a build error :(
> 
> 

Actually patch 2/2 works just fine on it's own, so I've kept that.