From: Lance Yang <ioworker0@gmail.com>
To: pasha.tatashin@soleen.com
Cc: akpm@linux-foundation.org, arnd@arndb.de, bhe@redhat.com,
coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com,
graf@amazon.com, jasonmiu@google.com, kees@kernel.org,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, rppt@kernel.org,
Lance Yang <lance.yang@linux.dev>
Subject: Re: [PATCH v2 03/13] kho: Introduce high-level memory allocation API
Date: Sun, 16 Nov 2025 14:49:18 +0800 [thread overview]
Message-ID: <20251116064918.35549-1-ioworker0@gmail.com> (raw)
In-Reply-To: <20251114190002.3311679-4-pasha.tatashin@soleen.com>
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 ...
```
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
next prev parent reply other threads:[~2025-11-16 6:49 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-14 18:59 [PATCH v2 00/13] kho: simplify state machine and enable dynamic updates Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 01/13] kho: Fix misleading log message in kho_populate() Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 02/13] kho: Convert __kho_abort() to return void Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 03/13] kho: Introduce high-level memory allocation API Pasha Tatashin
2025-11-14 19:33 ` Pratyush Yadav
2025-11-16 6:49 ` Lance Yang [this message]
2025-11-16 14:57 ` Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 04/13] kho: Preserve FDT folio only once during initialization Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 05/13] kho: Verify deserialization status and fix FDT alignment access Pasha Tatashin
2025-11-14 19:33 ` Pratyush Yadav
2025-11-14 18:59 ` [PATCH v2 06/13] kho: Always expose output FDT in debugfs Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 07/13] kho: Simplify serialization and remove __kho_abort Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 08/13] kho: Remove global preserved_mem_map and store state in FDT Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 09/13] kho: Remove abort functionality and support state refresh Pasha Tatashin
2025-11-14 18:59 ` [PATCH v2 10/13] kho: Update FDT dynamically for subtree addition/removal Pasha Tatashin
2025-11-15 9:40 ` Mike Rapoport
2025-11-15 14:51 ` Pasha Tatashin
2025-11-16 5:46 ` Mike Rapoport
2025-11-14 19:00 ` [PATCH v2 11/13] kho: Allow kexec load before KHO finalization Pasha Tatashin
2025-11-14 19:00 ` [PATCH v2 12/13] kho: Allow memory preservation state updates after finalization Pasha Tatashin
2025-11-14 19:35 ` Pratyush Yadav
2025-11-14 19:00 ` [PATCH v2 13/13] kho: Add Kconfig option to enable KHO by default Pasha Tatashin
2025-11-14 19:35 ` Pratyush Yadav
2025-11-14 21:44 ` [PATCH v2 00/13] kho: simplify state machine and enable dynamic updates Andrew Morton
2025-11-14 22:00 ` Pasha Tatashin
2025-11-14 22:06 ` Pasha Tatashin
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