linux.git/include/linux/memblock.h, branch v7.2-rc1

kho: fix deferred initialization of scratch areas

2026-05-31T23:31:37+00:00

Currently, if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled,
kho_release_scratch() will initialize the struct pages and set migratetype
of KHO scratch. Unless the whole scratch fits below first_deferred_pfn,
some of that will be overwritten either by deferred_init_pages() or
memmap_init_reserved_range().

To fix it, make memmap_init_range(), deferred_init_memmap_chunk() and
__init_page_from_nid() recognize KHO scratch regions and set
migratetype of pageblocks in those regions to MIGRATE_CMA.

Co-developed-by: Mike Rapoport (Microsoft) 
Signed-off-by: Michal Clapinski 
Reviewed-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Link: https://patch.msgid.link/20260423122538.140993-2-mclapinski@google.com
Signed-off-by: Mike Rapoport (Microsoft)

Merge tag 'memblock-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock

2026-04-18T18:29:14+00:00

Pull memblock updates from Mike Rapoport:

 - improve debuggability of reserve_mem kernel parameter handling with
   print outs in case of a failure and debugfs info showing what was
   actually reserved

 - Make memblock_free_late() and free_reserved_area() use the same core
   logic for freeing the memory to buddy and ensure it takes care of
   updating memblock arrays when ARCH_KEEP_MEMBLOCK is enabled.

* tag 'memblock-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock:
  x86/alternative: delay freeing of smp_locks section
  memblock: warn when freeing reserved memory before memory map is initialized
  memblock, treewide: make memblock_free() handle late freeing
  memblock: make free_reserved_area() update memblock if ARCH_KEEP_MEMBLOCK=y
  memblock: extract page freeing from free_reserved_area() into a helper
  memblock: make free_reserved_area() more robust
  mm: move free_reserved_area() to mm/memblock.c
  powerpc: opal-core: pair alloc_pages_exact() with free_pages_exact()
  powerpc: fadump: pair alloc_pages_exact() with free_pages_exact()
  memblock: reserve_mem: fix end caclulation in reserve_mem_release_by_name()
  memblock: move reserve_bootmem_range() to memblock.c and make it static
  memblock: Add reserve_mem debugfs info
  memblock: Print out errors on reserve_mem parser

memblock: Permit existing reserved regions to be marked RSRV_KERN

2026-04-09T15:14:36+00:00

Permit existing memblock reservations to be marked as RSRV_KERN. This
will be used by the EFI code on x86 to distinguish between reservations
of boot services data regions that have actual significance to the
kernel and regions that are reserved temporarily to work around buggy
firmware.

Acked-by: Mike Rapoport (Microsoft) 
Signed-off-by: Ard Biesheuvel

memblock, treewide: make memblock_free() handle late freeing

2026-04-01T08:20:15+00:00

It shouldn't be responsibility of memblock users to detect if they free
memory allocated from memblock late and should use memblock_free_late().

Make memblock_free() and memblock_phys_free() take care of late memory
freeing and drop memblock_free_late().

Link: https://patch.msgid.link/20260323074836.3653702-9-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft)

mm/mm_init: replace simple_strtoul with kstrtobool in set_hashdist

2026-01-21T03:24:47+00:00

Use bool for 'hashdist' and replace simple_strtoul() with kstrtobool() for
parsing the 'hashdist=' boot parameter.  Unlike simple_strtoul(), which
returns an unsigned long, kstrtobool() converts the string directly to
bool and avoids implicit casting.

Check the return value of kstrtobool() and reject invalid values.  This
adds error handling while preserving behavior for existing values, and
removes use of the deprecated simple_strtoul() helper.  The current code
silently sets 'hashdist = 0' if parsing fails, instead of leaving the
default value (HASHDIST_DEFAULT) unchanged.

Additionally, kstrtobool() accepts common boolean strings such as "on" and
"off".

Link: https://lkml.kernel.org/r/20251217110214.50807-1-thorsten.blum@linux.dev
Signed-off-by: Thorsten Blum 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: Mike Rapoport (Microsoft) 
Signed-off-by: Andrew Morton

memblock: drop for_each_free_mem_pfn_range_in_zone_from()

2025-09-14T05:49:03+00:00

for_each_free_mem_pfn_range_in_zone_from() and its "backend" implementation
__next_mem_pfn_range_in_zone() were only used by deferred initialization of
the memory map.

Remove them as they are not used anymore.

Reviewed-by: Wei Yang 
Reviewed-by: David Hildenbrand 
Signed-off-by: Mike Rapoport (Microsoft)

memblock: fix kernel-doc for MEMBLOCK_RSRV_NOINIT

2025-08-26T07:47:03+00:00

The kernel-doc description of MEMBLOCK_RSRV_NOINIT and
memblock_reserved_mark_noinit() do not accurately describe their
functionality.

Expand their kernel doc to make it clear that the user of
MEMBLOCK_RSRV_NOINIT is responsible to properly initialize the struct pages
for such regions and add more details about effects of using this flag.

Reviewed-by: David Hildenbrand 
Link: https://lore.kernel.org/r/f8140a17-c4ec-489b-b314-d45abe48bf36@redhat.com
Link: https://lore.kernel.org/r/20250826071947.1949725-1-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft)

x86: Handle KCOV __init vs inline mismatches

2025-07-24T23:55:11+00:00

GCC appears to have kind of fragile inlining heuristics, in the
sense that it can change whether or not it inlines something based on
optimizations. It looks like the kcov instrumentation being added (or in
this case, removed) from a function changes the optimization results,
and some functions marked "inline" are _not_ inlined. In that case,
we end up with __init code calling a function not marked __init, and we
get the build warnings I'm trying to eliminate in the coming patch that
adds __no_sanitize_coverage to __init functions:

WARNING: modpost: vmlinux: section mismatch in reference: xbc_exit+0x8 (section: .text.unlikely) -> _xbc_exit (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: real_mode_size_needed+0x15 (section: .text.unlikely) -> real_mode_blob_end (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: __set_percpu_decrypted+0x16 (section: .text.unlikely) -> early_set_memory_decrypted (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: memblock_alloc_from+0x26 (section: .text.unlikely) -> memblock_alloc_try_nid (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_set_root_pointer+0xc (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_get_root_pointer+0x8 (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: efi_config_table_is_usable+0x16 (section: .text.unlikely) -> xen_efi_config_table_is_usable (section: .init.text)

This problem is somewhat fragile (though using either __always_inline
or __init will deterministically solve it), but we've tripped over
this before with GCC and the solution has usually been to just use
__always_inline and move on.

For x86 this means forcing several functions to be inline with
__always_inline.

Link: https://lore.kernel.org/r/20250724055029.3623499-2-kees@kernel.org
Signed-off-by: Kees Cook

memblock: introduce memmap_init_kho_scratch()

2025-05-13T06:50:39+00:00

With deferred initialization of struct page it will be necessary to
initialize memory map for KHO scratch regions early.

Add memmap_init_kho_scratch() method that will allow such initialization
in upcoming patches.

Link: https://lkml.kernel.org/r/20250509074635.3187114-4-changyuanl@google.com
Signed-off-by: Mike Rapoport (Microsoft) 
Signed-off-by: Changyuan Lyu 
Cc: Alexander Graf 
Cc: Andy Lutomirski 
Cc: Anthony Yznaga 
Cc: Arnd Bergmann 
Cc: Ashish Kalra 
Cc: Ben Herrenschmidt 
Cc: Borislav Betkov 
Cc: Catalin Marinas 
Cc: Dave Hansen 
Cc: David Woodhouse 
Cc: Eric Biederman 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: James Gowans 
Cc: Jason Gunthorpe 
Cc: Jonathan Corbet 
Cc: Krzysztof Kozlowski 
Cc: Marc Rutland 
Cc: Paolo Bonzini 
Cc: Pasha Tatashin 
Cc: Peter Zijlstra 
Cc: Pratyush Yadav 
Cc: Rob Herring 
Cc: Saravana Kannan 
Cc: Stanislav Kinsburskii 
Cc: Steven Rostedt 
Cc: Thomas Gleinxer 
Cc: Thomas Lendacky 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

memblock: add support for scratch memory

2025-05-13T06:50:39+00:00

With KHO (Kexec HandOver), we need a way to ensure that the new kernel
does not allocate memory on top of any memory regions that the previous
kernel was handing over.  But to know where those are, we need to include
them in the memblock.reserved array which may not be big enough to hold
all ranges that need to be persisted across kexec.  To resize the array,
we need to allocate memory.  That brings us into a catch 22 situation.

The solution to that is limit memblock allocations to the scratch regions:
safe regions to operate in the case when there is memory that should
remain intact across kexec.

KHO provides several "scratch regions" as part of its metadata.  These
scratch regions are contiguous memory blocks that known not to contain any
memory that should be persisted across kexec.  These regions should be
large enough to accommodate all memblock allocations done by the kexeced
kernel.

We introduce a new memblock_set_scratch_only() function that allows KHO to
indicate that any memblock allocation must happen from the scratch
regions.

Later, we may want to perform another KHO kexec.  For that, we reuse the
same scratch regions.  To ensure that no eventually handed over data gets
allocated inside a scratch region, we flip the semantics of the scratch
region with memblock_clear_scratch_only(): After that call, no allocations
may happen from scratch memblock regions.  We will lift that restriction
in the next patch.

Link: https://lkml.kernel.org/r/20250509074635.3187114-3-changyuanl@google.com
Signed-off-by: Alexander Graf 
Co-developed-by: Mike Rapoport (Microsoft) 
Signed-off-by: Mike Rapoport (Microsoft) 
Signed-off-by: Changyuan Lyu 
Cc: Andy Lutomirski 
Cc: Anthony Yznaga 
Cc: Arnd Bergmann 
Cc: Ashish Kalra 
Cc: Ben Herrenschmidt 
Cc: Borislav Betkov 
Cc: Catalin Marinas 
Cc: Dave Hansen 
Cc: David Woodhouse 
Cc: Eric Biederman 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: James Gowans 
Cc: Jason Gunthorpe 
Cc: Jonathan Corbet 
Cc: Krzysztof Kozlowski 
Cc: Marc Rutland 
Cc: Paolo Bonzini 
Cc: Pasha Tatashin 
Cc: Peter Zijlstra 
Cc: Pratyush Yadav 
Cc: Rob Herring 
Cc: Saravana Kannan 
Cc: Stanislav Kinsburskii 
Cc: Steven Rostedt 
Cc: Thomas Gleinxer 
Cc: Thomas Lendacky 
Cc: Will Deacon 
Signed-off-by: Andrew Morton