The patch titled
Subject: arch, mm: set high_memory in free_area_init()
has been added to the -mm mm-unstable branch. Its filename is
arch-mm-set-high_memory-in-free_area_init.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arch-mm-set-high_memory-in-free_area_init.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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and is updated there every 2-3 working days
------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@xxxxxxxxxx>
Subject: arch, mm: set high_memory in free_area_init()
Date: Thu, 13 Mar 2025 15:50:00 +0200
high_memory defines upper bound on the directly mapped memory. This bound
is defined by the beginning of ZONE_HIGHMEM when a system has high memory
and by the end of memory otherwise.
All this is known to generic memory management initialization code that
can set high_memory while initializing core mm structures.
Add a generic calculation of high_memory to free_area_init() and remove
per-architecture calculation except for the architectures that set and use
high_memory earlier than that.
Link: https://lkml.kernel.org/r/20250313135003.836600-11-rppt@xxxxxxxxxx
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> [x86]
Tested-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Andreas Larsson <andreas@xxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Borislav Betkov <bp@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Guo Ren (csky) <guoren@xxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Cc: Madhavan Srinivasan <maddy@xxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Max Filippov <jcmvbkbc@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Michal Simek <monstr@xxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Richard Weinberger <richard@xxxxxx>
Cc: Russel King <linux@xxxxxxxxxxxxxxx>
Cc: Stafford Horne <shorne@xxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Thomas Gleinxer <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/alpha/mm/init.c | 1 -
arch/arc/mm/init.c | 2 --
arch/arm64/mm/init.c | 2 --
arch/csky/mm/init.c | 1 -
arch/hexagon/mm/init.c | 6 ------
arch/loongarch/kernel/numa.c | 1 -
arch/loongarch/mm/init.c | 2 --
arch/microblaze/mm/init.c | 2 --
arch/mips/mm/init.c | 2 --
arch/nios2/mm/init.c | 6 ------
arch/openrisc/mm/init.c | 2 --
arch/parisc/mm/init.c | 1 -
arch/riscv/mm/init.c | 1 -
arch/s390/mm/init.c | 2 --
arch/sh/mm/init.c | 7 -------
arch/sparc/mm/init_32.c | 1 -
arch/sparc/mm/init_64.c | 2 --
arch/um/kernel/um_arch.c | 1 -
arch/x86/kernel/setup.c | 2 --
arch/x86/mm/init_32.c | 3 ---
arch/x86/mm/numa_32.c | 3 ---
arch/xtensa/mm/init.c | 2 --
mm/memory.c | 8 --------
mm/mm_init.c | 30 ++++++++++++++++++++++++++++++
mm/nommu.c | 2 --
25 files changed, 30 insertions(+), 62 deletions(-)
--- a/arch/alpha/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/alpha/mm/init.c
@@ -276,7 +276,6 @@ srm_paging_stop (void)
void __init
mem_init(void)
{
- high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
memblock_free_all();
}
--- a/arch/arc/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/arc/mm/init.c
@@ -150,8 +150,6 @@ void __init setup_arch_memory(void)
*/
max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn;
- high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
-
arch_pfn_offset = min(min_low_pfn, min_high_pfn);
kmap_init();
#endif /* CONFIG_HIGHMEM */
--- a/arch/arm64/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/arm64/mm/init.c
@@ -309,8 +309,6 @@ void __init arm64_memblock_init(void)
}
early_init_fdt_scan_reserved_mem();
-
- high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
}
void __init bootmem_init(void)
--- a/arch/csky/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/csky/mm/init.c
@@ -47,7 +47,6 @@ void __init mem_init(void)
#ifdef CONFIG_HIGHMEM
unsigned long tmp;
#endif
- high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
memblock_free_all();
--- a/arch/hexagon/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/hexagon/mm/init.c
@@ -100,12 +100,6 @@ static void __init paging_init(void)
* initial kernel segment table's physical address.
*/
init_mm.context.ptbase = __pa(init_mm.pgd);
-
- /*
- * Start of high memory area. Will probably need something more
- * fancy if we... get more fancy.
- */
- high_memory = (void *)((bootmem_lastpg + 1) << PAGE_SHIFT);
}
#ifndef DMA_RESERVE
--- a/arch/loongarch/kernel/numa.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/loongarch/kernel/numa.c
@@ -389,7 +389,6 @@ void __init paging_init(void)
void __init mem_init(void)
{
- high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
memblock_free_all();
}
--- a/arch/loongarch/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/loongarch/mm/init.c
@@ -78,8 +78,6 @@ void __init paging_init(void)
void __init mem_init(void)
{
- high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
-
memblock_free_all();
}
#endif /* !CONFIG_NUMA */
--- a/arch/microblaze/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/microblaze/mm/init.c
@@ -120,8 +120,6 @@ void __init setup_memory(void)
void __init mem_init(void)
{
- high_memory = (void *)__va(memory_start + lowmem_size - 1);
-
/* this will put all memory onto the freelists */
memblock_free_all();
#ifdef CONFIG_HIGHMEM
--- a/arch/mips/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/mips/mm/init.c
@@ -417,7 +417,6 @@ void __init paging_init(void)
max_zone_pfns[ZONE_HIGHMEM] = max_low_pfn;
}
#endif
- high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);
free_area_init(max_zone_pfns);
}
@@ -469,7 +468,6 @@ void __init mem_init(void)
#else /* CONFIG_NUMA */
void __init mem_init(void)
{
- high_memory = (void *) __va(get_num_physpages() << PAGE_SHIFT);
setup_zero_pages(); /* This comes from node 0 */
memblock_free_all();
}
--- a/arch/nios2/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/nios2/mm/init.c
@@ -62,12 +62,6 @@ void __init paging_init(void)
void __init mem_init(void)
{
- unsigned long end_mem = memory_end; /* this must not include
- kernel stack at top */
-
- end_mem &= PAGE_MASK;
- high_memory = __va(end_mem);
-
/* this will put all memory onto the freelists */
memblock_free_all();
}
--- a/arch/openrisc/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/openrisc/mm/init.c
@@ -193,8 +193,6 @@ void __init mem_init(void)
{
BUG_ON(!mem_map);
- high_memory = (void *)__va(max_low_pfn * PAGE_SIZE);
-
/* clear the zero-page */
memset((void *)empty_zero_page, 0, PAGE_SIZE);
--- a/arch/parisc/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/parisc/mm/init.c
@@ -562,7 +562,6 @@ void __init mem_init(void)
BUILD_BUG_ON(TMPALIAS_MAP_START >= 0x80000000);
#endif
- high_memory = __va((max_pfn << PAGE_SHIFT));
memblock_free_all();
#ifdef CONFIG_PA11
--- a/arch/riscv/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/riscv/mm/init.c
@@ -295,7 +295,6 @@ static void __init setup_bootmem(void)
phys_ram_end = memblock_end_of_DRAM();
min_low_pfn = PFN_UP(phys_ram_base);
max_low_pfn = max_pfn = PFN_DOWN(phys_ram_end);
- high_memory = (void *)(__va(PFN_PHYS(max_low_pfn)));
dma32_phys_limit = min(4UL * SZ_1G, (unsigned long)PFN_PHYS(max_low_pfn));
--- a/arch/s390/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/s390/mm/init.c
@@ -159,8 +159,6 @@ void __init mem_init(void)
cpumask_set_cpu(0, &init_mm.context.cpu_attach_mask);
cpumask_set_cpu(0, mm_cpumask(&init_mm));
- high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
-
pv_init();
kfence_split_mapping();
--- a/arch/sh/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/sh/mm/init.c
@@ -330,13 +330,6 @@ unsigned int mem_init_done = 0;
void __init mem_init(void)
{
- pg_data_t *pgdat;
-
- high_memory = NULL;
- for_each_online_pgdat(pgdat)
- high_memory = max_t(void *, high_memory,
- __va(pgdat_end_pfn(pgdat) << PAGE_SHIFT));
-
memblock_free_all();
/* Set this up early, so we can take care of the zero page */
--- a/arch/sparc/mm/init_32.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/sparc/mm/init_32.c
@@ -275,7 +275,6 @@ void __init mem_init(void)
taint_real_pages();
- high_memory = __va(max_low_pfn << PAGE_SHIFT);
memblock_free_all();
for (i = 0; sp_banks[i].num_bytes != 0; i++) {
--- a/arch/sparc/mm/init_64.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/sparc/mm/init_64.c
@@ -2505,8 +2505,6 @@ static void __init register_page_bootmem
}
void __init mem_init(void)
{
- high_memory = __va(last_valid_pfn << PAGE_SHIFT);
-
memblock_free_all();
/*
--- a/arch/um/kernel/um_arch.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/um/kernel/um_arch.c
@@ -385,7 +385,6 @@ int __init linux_main(int argc, char **a
high_physmem = uml_physmem + physmem_size;
end_iomem = high_physmem + iomem_size;
- high_memory = (void *) end_iomem;
start_vm = VMALLOC_START;
--- a/arch/x86/kernel/setup.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/x86/kernel/setup.c
@@ -972,8 +972,6 @@ void __init setup_arch(char **cmdline_p)
max_low_pfn = e820__end_of_low_ram_pfn();
else
max_low_pfn = max_pfn;
-
- high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
#endif
/* Find and reserve MPTABLE area */
--- a/arch/x86/mm/init_32.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/x86/mm/init_32.c
@@ -643,9 +643,6 @@ void __init initmem_init(void)
highstart_pfn = max_low_pfn;
printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
pages_to_mb(highend_pfn - highstart_pfn));
- high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
-#else
- high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
#endif
memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
--- a/arch/x86/mm/numa_32.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/x86/mm/numa_32.c
@@ -41,9 +41,6 @@ void __init initmem_init(void)
highstart_pfn = max_low_pfn;
printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
pages_to_mb(highend_pfn - highstart_pfn));
- high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
-#else
- high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
#endif
printk(KERN_NOTICE "%ldMB LOWMEM available.\n",
pages_to_mb(max_low_pfn));
--- a/arch/xtensa/mm/init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/arch/xtensa/mm/init.c
@@ -164,8 +164,6 @@ void __init mem_init(void)
{
free_highpages();
- high_memory = (void *)__va(max_low_pfn << PAGE_SHIFT);
-
memblock_free_all();
}
--- a/mm/memory.c~arch-mm-set-high_memory-in-free_area_init
+++ a/mm/memory.c
@@ -114,14 +114,6 @@ static __always_inline bool vmf_orig_pte
}
/*
- * A number of key systems in x86 including ioremap() rely on the assumption
- * that high_memory defines the upper bound on direct map memory, then end
- * of ZONE_NORMAL.
- */
-void *high_memory;
-EXPORT_SYMBOL(high_memory);
-
-/*
* Randomize the address space (stacks, mmaps, brk, etc.).
*
* ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
--- a/mm/mm_init.c~arch-mm-set-high_memory-in-free_area_init
+++ a/mm/mm_init.c
@@ -45,6 +45,13 @@ struct page *mem_map;
EXPORT_SYMBOL(mem_map);
#endif
+/*
+ * high_memory defines the upper bound on direct map memory, then end
+ * of ZONE_NORMAL.
+ */
+void *high_memory;
+EXPORT_SYMBOL(high_memory);
+
#ifdef CONFIG_DEBUG_MEMORY_INIT
int __meminitdata mminit_loglevel;
@@ -1778,6 +1785,27 @@ static bool arch_has_descending_max_zone
return IS_ENABLED(CONFIG_ARC) && !IS_ENABLED(CONFIG_ARC_HAS_PAE40);
}
+static void set_high_memory(void)
+{
+ phys_addr_t highmem = memblock_end_of_DRAM();
+
+ /*
+ * Some architectures (e.g. ARM) set high_memory very early and
+ * use it in arch setup code.
+ * If an architecture already set high_memory don't overwrite it
+ */
+ if (high_memory)
+ return;
+
+#ifdef CONFIG_HIGHMEM
+ if (arch_has_descending_max_zone_pfns() ||
+ highmem > PFN_PHYS(arch_zone_lowest_possible_pfn[ZONE_HIGHMEM]))
+ highmem = PFN_PHYS(arch_zone_lowest_possible_pfn[ZONE_HIGHMEM]);
+#endif
+
+ high_memory = phys_to_virt(highmem - 1) + 1;
+}
+
/**
* free_area_init - Initialise all pg_data_t and zone data
* @max_zone_pfn: an array of max PFNs for each zone
@@ -1900,6 +1928,8 @@ void __init free_area_init(unsigned long
/* disable hash distribution for systems with a single node */
fixup_hashdist();
+
+ set_high_memory();
}
/**
--- a/mm/nommu.c~arch-mm-set-high_memory-in-free_area_init
+++ a/mm/nommu.c
@@ -42,8 +42,6 @@
#include <asm/mmu_context.h>
#include "internal.h"
-void *high_memory;
-EXPORT_SYMBOL(high_memory);
unsigned long highest_memmap_pfn;
int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
int heap_stack_gap = 0;
_
Patches currently in -mm which might be from rppt@xxxxxxxxxx are
arm-mem_init-use-memblock_phys_free-to-free-dma-memory-on-sa1111.patch
csky-move-setup_initrd-to-setupc.patch
hexagon-move-initialization-of-init_mmcontext-init-to-paging_init.patch
mips-consolidate-mem_init-for-numa-machines.patch
mips-make-setup_zero_pages-use-memblock.patch
nios2-move-pr_debug-about-memory-start-and-end-to-setup_arch.patch
s390-make-setup_zero_pages-use-memblock.patch
xtensa-split-out-printing-of-virtual-memory-layout-to-a-function.patch
arch-mm-set-max_mapnr-when-allocating-memory-map-for-flatmem.patch
arch-mm-set-high_memory-in-free_area_init.patch
arch-mm-streamline-highmem-freeing.patch
arch-mm-introduce-arch_mm_preinit.patch
arch-mm-make-releasing-of-memory-to-page-allocator-more-explicit.patch
