[PATCH 10/13] arch, mm: set high_memory in free_area_init()

Mike Rapoport
2025-03-06T18:53:56Z

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.

Remove per-architecture calculation of high_memory and add a generic
version to free_area_init().

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
arch/alpha/mm/init.c | 1 -
arch/arc/mm/init.c | 2 --
arch/arm/mm/mmu.c | 2 --
arch/arm/mm/nommu.c | 1 -
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/m68k/mm/init.c | 2 --
arch/m68k/mm/mcfmmu.c | 1 -
arch/m68k/mm/motorola.c | 2 --
arch/m68k/sun3/config.c | 1 -
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/powerpc/kernel/setup-common.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 | 23 +++++++++++++++++++++++
mm/nommu.c | 2 --
32 files changed, 23 insertions(+), 72 deletions(-)

diff --git a/arch/alpha/mm/init.c b/arch/alpha/mm/init.c
index ec0eeae9c653..3ab2d2f3c917 100644
--- a/arch/alpha/mm/init.c
+++ b/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();
}

diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 7ef883d58dc1..05025122e965 100644
--- a/arch/arc/mm/init.c
+++ b/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 */
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index f02f872ea8a9..e492d58a0386 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1250,8 +1250,6 @@ void __init adjust_lowmem_bounds(void)

arm_lowmem_limit = lowmem_limit;

- high_memory = __va(arm_lowmem_limit - 1) + 1;
-
if (!memblock_limit)
memblock_limit = arm_lowmem_limit;

diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index 1a8f6914ee59..65903ed5e80d 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -146,7 +146,6 @@ void __init adjust_lowmem_bounds(void)
phys_addr_t end;
adjust_lowmem_bounds_mpu();
end = memblock_end_of_DRAM();
- high_memory = __va(end - 1) + 1;
memblock_set_current_limit(end);
}

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9c0b8d9558fc..a48fcccd67fa 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -314,8 +314,6 @@ 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)
diff --git a/arch/csky/mm/init.c b/arch/csky/mm/init.c
index ba6694d6170a..a22801aa503a 100644
--- a/arch/csky/mm/init.c
+++ b/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();

diff --git a/arch/hexagon/mm/init.c b/arch/hexagon/mm/init.c
index 508bb6a8dcc9..d412c2314509 100644
--- a/arch/hexagon/mm/init.c
+++ b/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
diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
index 84fe7f854820..8eb489725b1a 100644
--- a/arch/loongarch/kernel/numa.c
+++ b/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();
}

diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
index 00449df50db1..6affa3609188 100644
--- a/arch/loongarch/mm/init.c
+++ b/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 */
diff --git a/arch/m68k/mm/init.c b/arch/m68k/mm/init.c
index 8b11d0d545aa..e03ac556c59e 100644
--- a/arch/m68k/mm/init.c
+++ b/arch/m68k/mm/init.c
@@ -66,8 +66,6 @@ void __init paging_init(void)
unsigned long end_mem = memory_end & PAGE_MASK;
unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0, };

- high_memory = (void *) end_mem;
-
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
max_zone_pfn[ZONE_DMA] = end_mem >> PAGE_SHIFT;
free_area_init(max_zone_pfn);
diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
index 19a75029036c..1750cf9f0369 100644
--- a/arch/m68k/mm/mcfmmu.c
+++ b/arch/m68k/mm/mcfmmu.c
@@ -168,7 +168,6 @@ void __init cf_bootmem_alloc(void)
memstart = PAGE_ALIGN(_ramstart);
min_low_pfn = PFN_DOWN(_rambase);
max_pfn = max_low_pfn = PFN_DOWN(_ramend);
- high_memory = (void *)_ramend;

/* Reserve kernel text/data/bss */
memblock_reserve(_rambase, memstart - _rambase);
diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
index 73651e093c4d..312efcd4b353 100644
--- a/arch/m68k/mm/motorola.c
+++ b/arch/m68k/mm/motorola.c
@@ -472,8 +472,6 @@ void __init paging_init(void)
module_fixup(NULL, __start_fixup, __stop_fixup);
flush_icache();

- high_memory = phys_to_virt(max_addr) + 1;
-
min_low_pfn = availmem >> PAGE_SHIFT;
max_pfn = max_low_pfn = (max_addr >> PAGE_SHIFT) + 1;

diff --git a/arch/m68k/sun3/config.c b/arch/m68k/sun3/config.c
index cd8af809e0ca..925818278e34 100644
--- a/arch/m68k/sun3/config.c
+++ b/arch/m68k/sun3/config.c
@@ -115,7 +115,6 @@ static void __init sun3_bootmem_alloc(unsigned long memory_start,

max_pfn = num_pages = __pa(memory_end) >> PAGE_SHIFT;

- high_memory = (void *)memory_end;
availmem = memory_start;

m68k_setup_node(0);
diff --git a/arch/microblaze/mm/init.c b/arch/microblaze/mm/init.c
index 857cd2b44bcf..7e2e342e84c5 100644
--- a/arch/microblaze/mm/init.c
+++ b/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
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 338b3c9fc5bc..99cefb58fba3 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -419,7 +419,6 @@ 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);
}
@@ -471,7 +470,6 @@ 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();
}
diff --git a/arch/nios2/mm/init.c b/arch/nios2/mm/init.c
index 3cafa87ead9e..4ba8dfa0d238 100644
--- a/arch/nios2/mm/init.c
+++ b/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();
}
diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
index 9093c336e158..72c5952607ac 100644
--- a/arch/openrisc/mm/init.c
+++ b/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);

diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 2cdfc0b1195c..4fbe354dc9b4 100644
--- a/arch/parisc/mm/init.c
+++ b/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
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 68d47c53876c..de34c40ccb21 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -957,7 +957,6 @@ void __init setup_arch(char **cmdline_p)

/* Parse memory topology */
mem_topology_setup();
- high_memory = (void *)__va(max_low_pfn * PAGE_SIZE);

/*
* Release secondary cpus out of their spinloops at 0x60 now that
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 157c9ca51541..ac6d41e86243 100644
--- a/arch/riscv/mm/init.c
+++ b/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));

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 7e64243693c9..08ebc9a9344a 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -161,8 +161,6 @@ 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();

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 72aea5cd1b85..6d459ffba4bc 100644
--- a/arch/sh/mm/init.c
+++ b/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 */
diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
index 6b58da14edc6..81a468a9c223 100644
--- a/arch/sparc/mm/init_32.c
+++ b/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++) {
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 05882bca5b73..34d46adb9571 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2505,8 +2505,6 @@ static void __init register_page_bootmem_info(void)
}
void __init mem_init(void)
{
- high_memory = __va(last_valid_pfn << PAGE_SHIFT);
-
memblock_free_all();

/*
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 6414cbf00572..f24a3ce37ab7 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -385,7 +385,6 @@ int __init linux_main(int argc, char **argv, char **envp)

high_physmem = uml_physmem + physmem_size;
end_iomem = high_physmem + iomem_size;
- high_memory = (void *) end_iomem;

start_vm = VMALLOC_START;

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index cebee310e200..5c9ec876915e 100644
--- a/arch/x86/kernel/setup.c
+++ b/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 */
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 6d2f8cb9451e..801b659ead0c 100644
--- a/arch/x86/mm/init_32.c
+++ b/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);
diff --git a/arch/x86/mm/numa_32.c b/arch/x86/mm/numa_32.c
index 65fda406e6f2..442ef3facff0 100644
--- a/arch/x86/mm/numa_32.c
+++ b/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));
diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index 9f1b0d5fccc7..9b662477b3d4 100644
--- a/arch/xtensa/mm/init.c
+++ b/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();
}

diff --git a/mm/memory.c b/mm/memory.c
index 126fdd3001e3..2351f3f6b9ed 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -113,14 +113,6 @@ static __always_inline bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
return pte_marker_uffd_wp(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.).
*
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 50a93714e1c6..5e5f6ba73757 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -44,6 +44,13 @@ 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;

@@ -1756,6 +1763,20 @@ static bool arch_has_descending_max_zone_pfns(void)
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();
+
+#ifdef CONFIG_HIGHMEM
+ unsigned long pfn = arch_zone_lowest_possible_pfn[ZONE_HIGHMEM];
+
+ if (arch_has_descending_max_zone_pfns() || highmem > PFN_PHYS(pfn))
+ highmem = PFN_PHYS(pfn);
+#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
@@ -1875,6 +1896,8 @@ void __init free_area_init(unsigned long *max_zone_pfn)

/* disable hash distribution for systems with a single node */
fixup_hashdist();
+
+ set_high_memory();
}

/**
diff --git a/mm/nommu.c b/mm/nommu.c
index f0209dd26dfa..b9783638fbd4 100644
--- a/mm/nommu.c
+++ b/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;
--
2.47.2