[PATCH v2 12/13] arch, mm: introduce arch_mm_preinit

From: Mike Rapoport <rppt@kernel.org>
Date: 2025-03-13 13:53:04
Also in: linux-alpha, linux-arch, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, loongarch, sparclinux
Subsystem: arm port, arm64 port (aarch64 architecture), linux for powerpc (32-bit and 64-bit), memblock and memory management initialization, memory management, memory management - core, mips, risc-v architecture, s390 architecture, sparc + ultrasparc (sparc/sparc64), synopsys arc architecture, the rest, user-mode linux (uml), x86 architecture (32-bit and 64-bit), x86 mm · Maintainers: Russell King, Catalin Marinas, Will Deacon, Madhavan Srinivasan, Michael Ellerman, Mike Rapoport, Andrew Morton, David Hildenbrand, Thomas Bogendoerfer, Paul Walmsley, Palmer Dabbelt, Albert Ou, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, "David S. Miller", Andreas Larsson, Vineet Gupta, Linus Torvalds, Richard Weinberger, Anton Ivanov, Johannes Berg, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Currently, implementation of mem_init() in every architecture consists of
one or more of the following:

* initializations that must run before page allocator is active, for
  instance swiotlb_init()
* a call to memblock_free_all() to release all the memory to the buddy
  allocator
* initializations that must run after page allocator is ready and there is
  no arch-specific hook other than mem_init() for that, like for example
  register_page_bootmem_info() in x86 and sparc64 or simple setting of
  mem_init_done = 1 in several architectures
* a bunch of semi-related stuff that apparently had no better place to
  live, for example a ton of BUILD_BUG_ON()s in parisc.

Introduce arch_mm_preinit() that will be the first thing called from
mm_core_init(). On architectures that have initializations that must happen
before the page allocator is ready, move those into arch_mm_preinit() along
with the code that does not depend on ordering with page allocator setup.

On several architectures this results in reduction of mem_init() to a
single call to memblock_free_all() that allows its consolidation next.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>	# x86
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/arc/mm/init.c      | 13 ++++++-------
 arch/arm/mm/init.c      | 21 ++++++++++++---------
 arch/arm64/mm/init.c    | 21 ++++++++++++---------
 arch/mips/mm/init.c     | 11 +++++++----
 arch/powerpc/mm/mem.c   |  9 ++++++---
 arch/riscv/mm/init.c    |  8 ++++++--
 arch/s390/mm/init.c     |  5 ++++-
 arch/sparc/mm/init_32.c |  5 ++++-
 arch/um/kernel/mem.c    |  7 +++++--
 arch/x86/mm/init_32.c   |  6 +++++-
 arch/x86/mm/init_64.c   |  5 ++++-
 include/linux/mm.h      |  1 +
 mm/mm_init.c            |  5 +++++
 13 files changed, 77 insertions(+), 40 deletions(-)

diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 11ce638731c9..90715b4a0bfa 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c

@@ -157,11 +157,16 @@ void __init setup_arch_memory(void)
 	free_area_init(max_zone_pfn);
 }
 
-static void __init highmem_init(void)
+void __init arch_mm_preinit(void)
 {
 #ifdef CONFIG_HIGHMEM
 	memblock_phys_free(high_mem_start, high_mem_sz);
 #endif
+
+	BUILD_BUG_ON((PTRS_PER_PGD * sizeof(pgd_t)) > PAGE_SIZE);
+	BUILD_BUG_ON((PTRS_PER_PUD * sizeof(pud_t)) > PAGE_SIZE);
+	BUILD_BUG_ON((PTRS_PER_PMD * sizeof(pmd_t)) > PAGE_SIZE);
+	BUILD_BUG_ON((PTRS_PER_PTE * sizeof(pte_t)) > PAGE_SIZE);
 }
 
 /*

@@ -172,13 +177,7 @@ static void __init highmem_init(void)
  */
 void __init mem_init(void)
 {
-	highmem_init();
 	memblock_free_all();
-
-	BUILD_BUG_ON((PTRS_PER_PGD * sizeof(pgd_t)) > PAGE_SIZE);
-	BUILD_BUG_ON((PTRS_PER_PUD * sizeof(pud_t)) > PAGE_SIZE);
-	BUILD_BUG_ON((PTRS_PER_PMD * sizeof(pmd_t)) > PAGE_SIZE);
-	BUILD_BUG_ON((PTRS_PER_PTE * sizeof(pte_t)) > PAGE_SIZE);
 }
 
 #ifdef CONFIG_HIGHMEM

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 7bb5ce02b9b5..7222100b0631 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c

@@ -237,12 +237,7 @@ static inline void poison_init_mem(void *s, size_t count)
 		*p++ = 0xe7fddef0;
 }
 
-/*
- * mem_init() marks the free areas in the mem_map and tells us how much
- * memory is free.  This is done after various parts of the system have
- * claimed their memory after the kernel image.
- */
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 #ifdef CONFIG_ARM_LPAE
 	swiotlb_init(max_pfn > arm_dma_pfn_limit, SWIOTLB_VERBOSE);

@@ -253,9 +248,6 @@ void __init mem_init(void)
 	memblock_phys_free(PHYS_OFFSET, __pa(swapper_pg_dir) - PHYS_OFFSET);
 #endif
 
-	/* this will put all unused low memory onto the freelists */
-	memblock_free_all();
-
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can
 	 * be detected at build time already.

@@ -271,6 +263,17 @@ void __init mem_init(void)
 #endif
 }
 
+/*
+ * mem_init() marks the free areas in the mem_map and tells us how much
+ * memory is free.  This is done after various parts of the system have
+ * claimed their memory after the kernel image.
+ */
+void __init mem_init(void)
+{
+	/* this will put all unused low memory onto the freelists */
+	memblock_free_all();
+}
+
 #ifdef CONFIG_STRICT_KERNEL_RWX
 struct section_perm {
 	const char *name;

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index a48fcccd67fa..8eff6a6eb11e 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -362,12 +362,7 @@ void __init bootmem_init(void)
 	memblock_dump_all();
 }
 
-/*
- * mem_init() marks the free areas in the mem_map and tells us how much memory
- * is free.  This is done after various parts of the system have claimed their
- * memory after the kernel image.
- */
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	unsigned int flags = SWIOTLB_VERBOSE;
 	bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);

@@ -391,9 +386,6 @@ void __init mem_init(void)
 	swiotlb_init(swiotlb, flags);
 	swiotlb_update_mem_attributes();
 
-	/* this will put all unused low memory onto the freelists */
-	memblock_free_all();
-
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can be
 	 * detected at build time already.

@@ -419,6 +411,17 @@ void __init mem_init(void)
 	}
 }
 
+/*
+ * mem_init() marks the free areas in the mem_map and tells us how much memory
+ * is free.  This is done after various parts of the system have claimed their
+ * memory after the kernel image.
+ */
+void __init mem_init(void)
+{
+	/* this will put all unused low memory onto the freelists */
+	memblock_free_all();
+}
+
 void free_initmem(void)
 {
 	void *lm_init_begin = lm_alias(__init_begin);

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 075177e817ac..eec38e7735dd 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c

@@ -425,7 +425,7 @@ void __init paging_init(void)
 static struct kcore_list kcore_kseg0;
 #endif
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	/*
 	 * When PFN_PTE_SHIFT is greater than PAGE_SHIFT we won't have enough PTE

@@ -435,7 +435,6 @@ void __init mem_init(void)
 
 	maar_init();
 	setup_zero_pages();	/* Setup zeroed pages.  */
-	memblock_free_all();
 
 #ifdef CONFIG_64BIT
 	if ((unsigned long) &_text > (unsigned long) CKSEG0)

@@ -446,13 +445,17 @@ void __init mem_init(void)
 #endif
 }
 #else  /* CONFIG_NUMA */
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	setup_zero_pages();	/* This comes from node 0 */
-	memblock_free_all();
 }
 #endif /* !CONFIG_NUMA */
 
+void __init mem_init(void)
+{
+	memblock_free_all();
+}
+
 void free_init_pages(const char *what, unsigned long begin, unsigned long end)
 {
 	unsigned long pfn;

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 1bc94bca9944..68efdaf14e58 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c

@@ -273,7 +273,7 @@ void __init paging_init(void)
 	mark_nonram_nosave();
 }
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	/*
 	 * book3s is limited to 16 page sizes due to encoding this in

@@ -295,8 +295,6 @@ void __init mem_init(void)
 
 	kasan_late_init();
 
-	memblock_free_all();
-
 #if defined(CONFIG_PPC_E500) && !defined(CONFIG_SMP)
 	/*
 	 * If smp is enabled, next_tlbcam_idx is initialized in the cpu up

@@ -329,6 +327,11 @@ void __init mem_init(void)
 #endif /* CONFIG_PPC32 */
 }
 
+void __init mem_init(void)
+{
+	memblock_free_all();
+}
+
 void free_initmem(void)
 {
 	ppc_md.progress = ppc_printk_progress;

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index ac6d41e86243..9efadabf6be1 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c

@@ -171,7 +171,7 @@ static void __init print_vm_layout(void)
 static void print_vm_layout(void) { }
 #endif /* CONFIG_DEBUG_VM */
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	bool swiotlb = max_pfn > PFN_DOWN(dma32_phys_limit);
 #ifdef CONFIG_FLATMEM

@@ -192,11 +192,15 @@ void __init mem_init(void)
 	}
 
 	swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
-	memblock_free_all();
 
 	print_vm_layout();
 }
 
+void __init mem_init(void)
+{
+	memblock_free_all();
+}
+
 /* Limit the memory size via mem. */
 static phys_addr_t memory_limit;
 #ifdef CONFIG_XIP_KERNEL

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 0c485884d373..c496dfa48bdc 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c

@@ -154,7 +154,7 @@ static void pv_init(void)
 	swiotlb_update_mem_attributes();
 }
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	cpumask_set_cpu(0, &init_mm.context.cpu_attach_mask);
 	cpumask_set_cpu(0, mm_cpumask(&init_mm));

@@ -163,7 +163,10 @@ void __init mem_init(void)
 	kfence_split_mapping();
 
 	setup_zero_pages();	/* Setup zeroed pages. */
+}
 
+void __init mem_init(void)
+{
 	/* this will put all low memory onto the freelists */
 	memblock_free_all();
 }

diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
index 043e9b6fadd0..e16c32c5728f 100644
--- a/arch/sparc/mm/init_32.c
+++ b/arch/sparc/mm/init_32.c

@@ -232,7 +232,7 @@ static void __init taint_real_pages(void)
 	}
 }
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	int i;

@@ -262,7 +262,10 @@ void __init mem_init(void)
 	memset(sparc_valid_addr_bitmap, 0, i << 2);
 
 	taint_real_pages();
+}
 
+void __init mem_init(void)
+{
 	memblock_free_all();
 }

diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index befed230aac2..cce387438e60 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c

@@ -54,7 +54,7 @@ int kmalloc_ok = 0;
 /* Used during early boot */
 static unsigned long brk_end;
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	/* clear the zero-page */
 	memset(empty_zero_page, 0, PAGE_SIZE);

@@ -66,10 +66,13 @@ void __init mem_init(void)
 	map_memory(brk_end, __pa(brk_end), uml_reserved - brk_end, 1, 1, 0);
 	memblock_free((void *)brk_end, uml_reserved - brk_end);
 	uml_reserved = brk_end;
+	max_pfn = max_low_pfn;
+}
 
+void __init mem_init(void)
+{
 	/* this will put all low memory onto the freelists */
 	memblock_free_all();
-	max_pfn = max_low_pfn;
 	kmalloc_ok = 1;
 }

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 9ee8ec2bc5d1..16664c5464b5 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c

@@ -691,13 +691,17 @@ static void __init test_wp_bit(void)
 	panic("Linux doesn't support CPUs with broken WP.");
 }
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	pci_iommu_alloc();
 
 #ifdef CONFIG_FLATMEM
 	BUG_ON(!mem_map);
 #endif
+}
+
+void __init mem_init(void)
+{
 	/* this will put all low memory onto the freelists */
 	memblock_free_all();

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 01ea7c6df303..f8981e29633c 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c

@@ -1348,10 +1348,13 @@ static void __init preallocate_vmalloc_pages(void)
 	panic("Failed to pre-allocate %s pages for vmalloc area\n", lvl);
 }
 
-void __init mem_init(void)
+void __init arch_mm_preinit(void)
 {
 	pci_iommu_alloc();
+}
 
+void __init mem_init(void)
+{
 	/* clear_bss() already clear the empty_zero_page */
 
 	/* this will put all memory onto the freelists */

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6fccd3b3248c..ae9cfb9612ea 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -42,6 +42,7 @@ struct folio_batch;
 
 extern int sysctl_page_lock_unfairness;
 
+void arch_mm_preinit(void);
 void mm_core_init(void);
 void init_mm_internals(void);

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 61ac0cea711a..57f762c16c02 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c

@@ -2675,11 +2675,16 @@ static void __init mem_init_print_info(void)
 		);
 }
 
+void __init __weak arch_mm_preinit(void)
+{
+}
+
 /*
  * Set up kernel memory allocators
  */
 void __init mm_core_init(void)
 {
+	arch_mm_preinit();
 	/* Initializations relying on SMP setup */
 	BUILD_BUG_ON(MAX_ZONELISTS > 2);
 	build_all_zonelists(NULL);

-- 
2.47.2

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