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kho: make preserved pages compatible with deferred struct page init

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When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct page
initialization is deferred to parallel kthreads that run later
in the boot process.

During KHO restoration, kho_preserved_memory_reserve() writes metadata
for each preserved memory region. However, if the struct page has not
been initialized, this write targets uninitialized memory, potentially
leading to errors like:
BUG: unable to handle page fault for address: ...

Fix this by introducing kho_get_preserved_page(),  which ensures
all struct pages in a preserved region are initialized by calling
init_deferred_page() which is a no-op when the struct page is already
initialized.

Signed-off-by: Evangelos Petrongonas <epetron@amazon.de>
Co-developed-by: Michal Clapinski <mclapinski@google.com>
Signed-off-by: Michal Clapinski <mclapinski@google.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260423122538.140993-3-mclapinski@google.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This commit is contained in:
Evangelos Petrongonas
2026-04-23 14:25:37 +02:00
committed by Mike Rapoport (Microsoft)
parent bf480c6133
commit c6073743d0
2 changed files with 26 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/liveupdate/Kconfig
View File

@@ -1,12 +1,10 @@
# SPDX-License-Identifier: GPL-2.0-only
menu "Live Update and Kexec HandOver"
depends on !DEFERRED_STRUCT_PAGE_INIT
config KEXEC_HANDOVER
bool "kexec handover"
depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
depends on !DEFERRED_STRUCT_PAGE_INIT
select MEMBLOCK_KHO_SCRATCH
select KEXEC_FILE
select LIBFDT

27
kernel/liveupdate/kexec_handover.c
View File

@@ -459,6 +459,31 @@ struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages)
}
EXPORT_SYMBOL_GPL(kho_restore_pages);
/*
* With CONFIG_DEFERRED_STRUCT_PAGE_INIT, struct pages in higher memory regions
* may not be initialized yet at the time KHO deserializes preserved memory.
* KHO uses the struct page to store metadata and a later initialization would
* overwrite it.
* Ensure all the struct pages in the preservation are
* initialized. kho_preserved_memory_reserve() marks the reservation as noinit
* to make sure they don't get re-initialized later.
*/
static struct page *__init kho_get_preserved_page(phys_addr_t phys,
unsigned int order)
{
unsigned long pfn = PHYS_PFN(phys);
int nid;
if (!IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT))
return pfn_to_page(pfn);
nid = early_pfn_to_nid(pfn);
for (unsigned long i = 0; i < (1UL << order); i++)
init_deferred_page(pfn + i, nid);
return pfn_to_page(pfn);
}
static int __init kho_preserved_memory_reserve(phys_addr_t phys,
unsigned int order)
{
@@ -467,7 +492,7 @@ static int __init kho_preserved_memory_reserve(phys_addr_t phys,
u64 sz;
sz = 1 << (order + PAGE_SHIFT);
page = phys_to_page(phys);
page = kho_get_preserved_page(phys, order);
/* Reserve the memory preserved in KHO in memblock */
memblock_reserve(phys, sz);