Currently, clients of KHO must manually allocate memory (e.g., via
alloc_pages), calculate the page order, and explicitly call
kho_preserve_folio(). Similarly, cleanup requires separate calls to
unpreserve and free the memory.
Introduce a high-level API to streamline this common pattern:
- kho_alloc_preserve(size): Allocates physically contiguous, zeroed
memory and immediately marks it for preservation.
- kho_unpreserve_free(ptr): Unpreserves and frees the memory
in the current kernel.
- kho_restore_free(ptr): Restores the struct page state of
preserved memory in the new kernel and immediately frees it to the
page allocator.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
include/linux/kexec_handover.h | 22 +++++---
kernel/liveupdate/kexec_handover.c | 87 ++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+), 7 deletions(-)
diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 80ece4232617..38a9487a1a00 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -2,8 +2,9 @@
#ifndef LINUX_KEXEC_HANDOVER_H
#define LINUX_KEXEC_HANDOVER_H
-#include <linux/types.h>
+#include <linux/err.h>
#include <linux/errno.h>
+#include <linux/types.h>
struct kho_scratch {
phys_addr_t addr;
@@ -48,6 +49,9 @@ 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);
+void *kho_alloc_preserve(size_t size);
+void kho_unpreserve_free(void *mem);
+void kho_restore_free(void *mem);
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);
@@ -101,6 +105,14 @@ static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
return -EOPNOTSUPP;
}
+void *kho_alloc_preserve(size_t size)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
+void kho_unpreserve_free(void *mem) { }
+void kho_restore_free(void *mem) { }
+
static inline struct folio *kho_restore_folio(phys_addr_t phys)
{
return NULL;
@@ -122,18 +134,14 @@ static inline int kho_add_subtree(const char *name, void *fdt)
return -EOPNOTSUPP;
}
-static inline void kho_remove_subtree(void *fdt)
-{
-}
+static inline void kho_remove_subtree(void *fdt) { }
static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
{
return -EOPNOTSUPP;
}
-static inline void kho_memory_init(void)
-{
-}
+static inline void kho_memory_init(void) { }
static inline void kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
phys_addr_t scratch_phys, u64 scratch_len)
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index bc7f046a1313..5c5c9c46fe92 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -4,6 +4,7 @@
* Copyright (C) 2023 Alexander Graf <graf@amazon.com>
* Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
* Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ * Copyright (C) 2025 Pasha Tatashin <pasha.tatashin@soleen.com>
*/
#define pr_fmt(fmt) "KHO: " fmt
@@ -1117,6 +1118,92 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
}
EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
+/**
+ * kho_alloc_preserve - Allocate, zero, and preserve memory.
+ * @size: The number of bytes to allocate.
+ *
+ * Allocates a physically contiguous block of zeroed pages that is large
+ * enough to hold @size bytes. The allocated memory is then registered with
+ * KHO for preservation across a kexec.
+ *
+ * Note: The actual allocated size will be rounded up to the nearest
+ * power-of-two page boundary.
+ *
+ * @return A virtual pointer to the allocated and preserved memory on success,
+ * or an ERR_PTR() encoded error on failure.
+ */
+void *kho_alloc_preserve(size_t size)
+{
+ struct folio *folio;
+ int order, ret;
+
+ if (!size)
+ return ERR_PTR(-EINVAL);
+
+ order = get_order(size);
+ if (order > MAX_PAGE_ORDER)
+ return ERR_PTR(-E2BIG);
+
+ folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, order);
+ if (!folio)
+ return ERR_PTR(-ENOMEM);
+
+ ret = kho_preserve_folio(folio);
+ if (ret) {
+ folio_put(folio);
+ return ERR_PTR(ret);
+ }
+
+ return folio_address(folio);
+}
+EXPORT_SYMBOL_GPL(kho_alloc_preserve);
+
+/**
+ * kho_unpreserve_free - Unpreserve and free memory.
+ * @mem: Pointer to the memory allocated by kho_alloc_preserve().
+ *
+ * Unregisters the memory from KHO preservation and frees the underlying
+ * pages back to the system. This function should be called to clean up
+ * memory allocated with kho_alloc_preserve().
+ */
+void kho_unpreserve_free(void *mem)
+{
+ struct folio *folio;
+
+ if (!mem)
+ return;
+
+ folio = virt_to_folio(mem);
+ WARN_ON_ONCE(kho_unpreserve_folio(folio));
+ folio_put(folio);
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_free);
+
+/**
+ * kho_restore_free - Restore and free memory after kexec.
+ * @mem: Pointer to the memory (in the new kernel's address space)
+ * that was allocated by the old kernel.
+ *
+ * This function is intended to be called in the new kernel (post-kexec)
+ * to take ownership of and free a memory region that was preserved by the
+ * old kernel using kho_alloc_preserve().
+ *
+ * It first restores the pages from KHO (using their physical address)
+ * and then frees the pages back to the new kernel's page allocator.
+ */
+void kho_restore_free(void *mem)
+{
+ struct folio *folio;
+
+ if (!mem)
+ return;
+
+ folio = kho_restore_folio(__pa(mem));
+ if (!WARN_ON(!folio))
+ folio_put(folio);
+}
+EXPORT_SYMBOL_GPL(kho_restore_free);
+
static void __kho_abort(void)
{
if (kho_out.preserved_mem_map) {
--
2.52.0.rc1.455.g30608eb744-googFrom: Lance Yang <lance.yang@linux.dev>
On Fri, 14 Nov 2025 13:59:52 -0500, Pasha Tatashin wrote:
> Currently, clients of KHO must manually allocate memory (e.g., via
> alloc_pages), calculate the page order, and explicitly call
> kho_preserve_folio(). Similarly, cleanup requires separate calls to
> unpreserve and free the memory.
>
> Introduce a high-level API to streamline this common pattern:
>
> - kho_alloc_preserve(size): Allocates physically contiguous, zeroed
> memory and immediately marks it for preservation.
> - kho_unpreserve_free(ptr): Unpreserves and frees the memory
> in the current kernel.
> - kho_restore_free(ptr): Restores the struct page state of
> preserved memory in the new kernel and immediately frees it to the
> page allocator.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> include/linux/kexec_handover.h | 22 +++++---
> kernel/liveupdate/kexec_handover.c | 87 ++++++++++++++++++++++++++++++
> 2 files changed, 102 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> index 80ece4232617..38a9487a1a00 100644
> --- a/include/linux/kexec_handover.h
> +++ b/include/linux/kexec_handover.h
> @@ -2,8 +2,9 @@
> #ifndef LINUX_KEXEC_HANDOVER_H
> #define LINUX_KEXEC_HANDOVER_H
>
> -#include <linux/types.h>
> +#include <linux/err.h>
> #include <linux/errno.h>
> +#include <linux/types.h>
>
> struct kho_scratch {
> phys_addr_t addr;
> @@ -48,6 +49,9 @@ 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);
> +void *kho_alloc_preserve(size_t size);
> +void kho_unpreserve_free(void *mem);
> +void kho_restore_free(void *mem);
> 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);
> @@ -101,6 +105,14 @@ static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> return -EOPNOTSUPP;
> }
>
> +void *kho_alloc_preserve(size_t size)
> +{
> + return ERR_PTR(-EOPNOTSUPP);
> +}
> +
> +void kho_unpreserve_free(void *mem) { }
> +void kho_restore_free(void *mem) { }
The compile is unhapply here when CONFIG_KEXEC_HANDOVER is not set ...
```
ld: arch/x86/realmode/rm/video-mode.o: in function `kho_alloc_preserve':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
ld: arch/x86/realmode/rm/video-mode.o: in function `kho_unpreserve_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
ld: arch/x86/realmode/rm/video-mode.o: in function `kho_restore_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
ld: arch/x86/realmode/rm/regs.o: in function `kho_alloc_preserve':
/home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
ld: arch/x86/realmode/rm/regs.o: in function `kho_unpreserve_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
ld: arch/x86/realmode/rm/regs.o: in function `kho_restore_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
ld: arch/x86/realmode/rm/video-vga.o: in function `kho_alloc_preserve':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
ld: arch/x86/realmode/rm/video-vga.o: in function `kho_unpreserve_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
ld: arch/x86/realmode/rm/video-vga.o: in function `kho_restore_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_alloc_preserve':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_unpreserve_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_restore_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
ld: arch/x86/realmode/rm/video-bios.o: in function `kho_alloc_preserve':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
ld: arch/x86/realmode/rm/video-bios.o: in function `kho_unpreserve_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
ld: arch/x86/realmode/rm/video-bios.o: in function `kho_restore_free':
/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
make[5]: *** [arch/x86/realmode/rm/Makefile:49: arch/x86/realmode/rm/realmode.elf] Error 1
make[4]: *** [arch/x86/realmode/Makefile:22: arch/x86/realmode/rm/realmode.bin] Error 2
make[3]: *** [scripts/Makefile.build:556: arch/x86/realmode] Error 2
```
Perhaps these stubs should be declared as static inline? That should make
the compiler happy and resolve the linking errors :)
----8<----
diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 6dd0dcdf0ec1..5f7b9de97e8d 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -96,13 +96,13 @@ static inline int kho_preserve_vmalloc(void *ptr,
static inline void kho_unpreserve_vmalloc(struct kho_vmalloc *preservation) { }
-void *kho_alloc_preserve(size_t size)
+static inline void *kho_alloc_preserve(size_t size)
{
return ERR_PTR(-EOPNOTSUPP);
}
-void kho_unpreserve_free(void *mem) { }
-void kho_restore_free(void *mem) { }
+static inline void kho_unpreserve_free(void *mem) { }
+static inline void kho_restore_free(void *mem) { }
static inline struct folio *kho_restore_folio(phys_addr_t phys)
{
---
[...]
Cheers,
Lance
On Sun, Nov 16, 2025 at 1:49 AM Lance Yang <ioworker0@gmail.com> wrote:
>
> From: Lance Yang <lance.yang@linux.dev>
>
>
> On Fri, 14 Nov 2025 13:59:52 -0500, Pasha Tatashin wrote:
> > Currently, clients of KHO must manually allocate memory (e.g., via
> > alloc_pages), calculate the page order, and explicitly call
> > kho_preserve_folio(). Similarly, cleanup requires separate calls to
> > unpreserve and free the memory.
> >
> > Introduce a high-level API to streamline this common pattern:
> >
> > - kho_alloc_preserve(size): Allocates physically contiguous, zeroed
> > memory and immediately marks it for preservation.
> > - kho_unpreserve_free(ptr): Unpreserves and frees the memory
> > in the current kernel.
> > - kho_restore_free(ptr): Restores the struct page state of
> > preserved memory in the new kernel and immediately frees it to the
> > page allocator.
> >
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> > include/linux/kexec_handover.h | 22 +++++---
> > kernel/liveupdate/kexec_handover.c | 87 ++++++++++++++++++++++++++++++
> > 2 files changed, 102 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> > index 80ece4232617..38a9487a1a00 100644
> > --- a/include/linux/kexec_handover.h
> > +++ b/include/linux/kexec_handover.h
> > @@ -2,8 +2,9 @@
> > #ifndef LINUX_KEXEC_HANDOVER_H
> > #define LINUX_KEXEC_HANDOVER_H
> >
> > -#include <linux/types.h>
> > +#include <linux/err.h>
> > #include <linux/errno.h>
> > +#include <linux/types.h>
> >
> > struct kho_scratch {
> > phys_addr_t addr;
> > @@ -48,6 +49,9 @@ 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);
> > +void *kho_alloc_preserve(size_t size);
> > +void kho_unpreserve_free(void *mem);
> > +void kho_restore_free(void *mem);
> > 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);
> > @@ -101,6 +105,14 @@ static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> > return -EOPNOTSUPP;
> > }
> >
> > +void *kho_alloc_preserve(size_t size)
> > +{
> > + return ERR_PTR(-EOPNOTSUPP);
> > +}
> > +
> > +void kho_unpreserve_free(void *mem) { }
> > +void kho_restore_free(void *mem) { }
>
> The compile is unhapply here when CONFIG_KEXEC_HANDOVER is not set ...
Thank you, Andrew already applied a fix:
https://lore.kernel.org/all/CA+CK2bBgXDhrHwTVgxrw7YTQ-0=LgW0t66CwPCgG=C85ftz4zw@mail.gmail.com/T/#u
>
> ```
> ld: arch/x86/realmode/rm/video-mode.o: in function `kho_alloc_preserve':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
> ld: arch/x86/realmode/rm/video-mode.o: in function `kho_unpreserve_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
> ld: arch/x86/realmode/rm/video-mode.o: in function `kho_restore_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
> ld: arch/x86/realmode/rm/regs.o: in function `kho_alloc_preserve':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
> ld: arch/x86/realmode/rm/regs.o: in function `kho_unpreserve_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
> ld: arch/x86/realmode/rm/regs.o: in function `kho_restore_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/arch/x86/realmode/rm/regs.c:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
> ld: arch/x86/realmode/rm/video-vga.o: in function `kho_alloc_preserve':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
> ld: arch/x86/realmode/rm/video-vga.o: in function `kho_unpreserve_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
> ld: arch/x86/realmode/rm/video-vga.o: in function `kho_restore_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
> ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_alloc_preserve':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
> ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_unpreserve_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
> ld: arch/x86/realmode/rm/video-vesa.o: in function `kho_restore_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
> ld: arch/x86/realmode/rm/video-bios.o: in function `kho_alloc_preserve':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: multiple definition of `kho_alloc_preserve'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:102: first defined here
> ld: arch/x86/realmode/rm/video-bios.o: in function `kho_unpreserve_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: multiple definition of `kho_unpreserve_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:104: first defined here
> ld: arch/x86/realmode/rm/video-bios.o: in function `kho_restore_free':
> /home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: multiple definition of `kho_restore_free'; arch/x86/realmode/rm/wakemain.o:/home/runner/work/mm-test-robot/mm-test-robot/linux/./include/linux/kexec_handover.h:105: first defined here
> make[5]: *** [arch/x86/realmode/rm/Makefile:49: arch/x86/realmode/rm/realmode.elf] Error 1
> make[4]: *** [arch/x86/realmode/Makefile:22: arch/x86/realmode/rm/realmode.bin] Error 2
> make[3]: *** [scripts/Makefile.build:556: arch/x86/realmode] Error 2
> ```
>
> Perhaps these stubs should be declared as static inline? That should make
> the compiler happy and resolve the linking errors :)
>
> ----8<----
> diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> index 6dd0dcdf0ec1..5f7b9de97e8d 100644
> --- a/include/linux/kexec_handover.h
> +++ b/include/linux/kexec_handover.h
> @@ -96,13 +96,13 @@ static inline int kho_preserve_vmalloc(void *ptr,
>
> static inline void kho_unpreserve_vmalloc(struct kho_vmalloc *preservation) { }
>
> -void *kho_alloc_preserve(size_t size)
> +static inline void *kho_alloc_preserve(size_t size)
> {
> return ERR_PTR(-EOPNOTSUPP);
> }
>
> -void kho_unpreserve_free(void *mem) { }
> -void kho_restore_free(void *mem) { }
> +static inline void kho_unpreserve_free(void *mem) { }
> +static inline void kho_restore_free(void *mem) { }
>
> static inline struct folio *kho_restore_folio(phys_addr_t phys)
> {
> ---
>
> [...]
>
> Cheers,
> Lance
On Fri, Nov 14 2025, Pasha Tatashin wrote: > Currently, clients of KHO must manually allocate memory (e.g., via > alloc_pages), calculate the page order, and explicitly call > kho_preserve_folio(). Similarly, cleanup requires separate calls to > unpreserve and free the memory. > > Introduce a high-level API to streamline this common pattern: > > - kho_alloc_preserve(size): Allocates physically contiguous, zeroed > memory and immediately marks it for preservation. > - kho_unpreserve_free(ptr): Unpreserves and frees the memory > in the current kernel. > - kho_restore_free(ptr): Restores the struct page state of > preserved memory in the new kernel and immediately frees it to the > page allocator. > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> > Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Reviewed-by: Pratyush Yadav <pratyush@kernel.org> [...] -- Regards, Pratyush Yadav
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