[PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Mike Rapoport]

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

Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
ZERO_PAGE() to 4.

Every architecture defines empty_zero_page that way or another, but for the
most of them it is always a page aligned page in BSS and most definitions
of ZERO_PAGE do virt_to_page(empty_zero_page).

Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
core MM and drop these definitions in architectures that do not implement
colored zero page (MIPS and s390).

ZERO_PAGE() remains a macro because turning it to a wrapper for a static
inline causes severe pain in header dependencies.

For the most part the change is mechanical, with these being noteworthy:

* alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
  parameters. Switching to a generic empty_zero_page removes the aliasing
  and keeps ZERO_PGE for boot parameters only
* arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
  ZERO_PAGE() is kept intact.
* m68k/parisc/sparc64/um: allocated empty_zero_page from memblock,
  although they do not support zero page coloring and having it in BSS
  will work fine.
* sh: used empty_zero_page for boot parameters at the very early boot.
  Rename the parameters page to boot_params_page and let sh use the generic
  empty_zero_page.
* hexagon: had an amusing comment about empty_zero_page

	/* A handy thing to have if one has the RAM. Declared in head.S */

  that unfortunately had to go :)

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/alpha/include/asm/pgtable.h          |  6 ------
 arch/arc/include/asm/pgtable.h            |  3 ---
 arch/arc/mm/init.c                        |  2 --
 arch/arm/include/asm/pgtable.h            |  9 ---------
 arch/arm/mm/mmu.c                         |  7 -------
 arch/arm/mm/nommu.c                       |  7 -------
 arch/arm64/include/asm/pgtable.h          |  1 -
 arch/arm64/mm/mmu.c                       |  7 -------
 arch/csky/include/asm/pgtable.h           |  3 ---
 arch/csky/mm/init.c                       |  3 ---
 arch/hexagon/include/asm/pgtable.h        |  6 ------
 arch/hexagon/kernel/head.S                |  5 -----
 arch/hexagon/kernel/hexagon_ksyms.c       |  1 -
 arch/loongarch/include/asm/pgtable.h      |  9 ---------
 arch/loongarch/mm/init.c                  |  3 ---
 arch/m68k/include/asm/pgtable_mm.h        |  9 ---------
 arch/m68k/include/asm/pgtable_no.h        |  7 -------
 arch/m68k/mm/init.c                       |  9 ---------
 arch/m68k/mm/mcfmmu.c                     |  2 --
 arch/m68k/mm/motorola.c                   |  6 ------
 arch/m68k/mm/sun3mmu.c                    |  2 --
 arch/microblaze/include/asm/pgtable.h     | 10 ----------
 arch/microblaze/kernel/head.S             |  4 ----
 arch/microblaze/kernel/microblaze_ksyms.c |  2 --
 arch/nios2/include/asm/pgtable.h          |  7 -------
 arch/nios2/kernel/head.S                  | 10 ----------
 arch/nios2/kernel/nios2_ksyms.c           |  1 -
 arch/openrisc/include/asm/pgtable.h       |  4 ----
 arch/openrisc/kernel/head.S               |  3 ---
 arch/openrisc/kernel/or32_ksyms.c         |  1 -
 arch/openrisc/mm/init.c                   |  3 ---
 arch/parisc/include/asm/pgtable.h         | 11 -----------
 arch/parisc/mm/init.c                     |  6 ------
 arch/powerpc/include/asm/pgtable.h        |  6 ------
 arch/powerpc/mm/mem.c                     |  3 ---
 arch/riscv/include/asm/pgtable.h          |  7 -------
 arch/riscv/mm/init.c                      |  4 ----
 arch/sh/include/asm/pgtable.h             |  8 --------
 arch/sh/include/asm/setup.h               |  3 ++-
 arch/sh/kernel/head_32.S                  |  4 ++--
 arch/sh/kernel/sh_ksyms_32.c              |  1 -
 arch/sh/mm/init.c                         |  1 -
 arch/sparc/include/asm/pgtable_32.h       |  8 --------
 arch/sparc/include/asm/pgtable_64.h       |  3 ---
 arch/sparc/include/asm/setup.h            |  2 --
 arch/sparc/kernel/head_32.S               |  7 -------
 arch/sparc/mm/init_32.c                   |  4 ----
 arch/sparc/mm/init_64.c                   | 15 ---------------
 arch/um/include/asm/pgtable.h             |  9 ---------
 arch/um/include/shared/kern_util.h        |  1 -
 arch/um/kernel/mem.c                      | 16 ----------------
 arch/um/kernel/um_arch.c                  |  1 -
 arch/x86/include/asm/pgtable.h            |  8 --------
 arch/x86/kernel/head_32.S                 |  4 ----
 arch/x86/kernel/head_64.S                 |  7 -------
 arch/xtensa/include/asm/pgtable.h         |  4 ----
 arch/xtensa/kernel/head.S                 |  3 ---
 arch/xtensa/kernel/xtensa_ksyms.c         |  2 --
 include/linux/pgtable.h                   |  8 ++++++++
 mm/mm_init.c                              |  9 +++++++++
 60 files changed, 21 insertions(+), 296 deletions(-)

diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h
index 90e7a9539102..12a3c5f8ece8 100644
--- a/arch/alpha/include/asm/pgtable.h
+++ b/arch/alpha/include/asm/pgtable.h
@@ -125,12 +125,6 @@ struct vm_area_struct;
  */
 #define pgprot_noncached(prot)	(prot)
 
-/*
- * ZERO_PAGE is a global shared page that is always zero:  used
- * for zero-mapped memory areas etc..
- */
-#define ZERO_PAGE(vaddr)	(virt_to_page(ZERO_PGE))
-
 /*
  * On certain platforms whose physical address space can overlap KSEG,
  * namely EV6 and above, we must re-twiddle the physaddr to restore the
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index bd580e2b62d7..0fdaea81b5fa 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -21,9 +21,6 @@
 
 #ifndef __ASSEMBLER__
 
-extern char empty_zero_page[PAGE_SIZE];
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-
 extern pgd_t swapper_pg_dir[] __aligned(PAGE_SIZE);
 
 /* to cope with aliasing VIPT cache */
diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index a5e92f46e5d1..d6b5c27a0098 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -19,8 +19,6 @@
 #include <asm/arcregs.h>
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __aligned(PAGE_SIZE);
-char empty_zero_page[PAGE_SIZE] __aligned(PAGE_SIZE);
-EXPORT_SYMBOL(empty_zero_page);
 
 static const unsigned long low_mem_start = CONFIG_LINUX_RAM_BASE;
 static unsigned long low_mem_sz;
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 6fa9acd6a7f5..982795cf4563 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -10,15 +10,6 @@
 #include <linux/const.h>
 #include <asm/proc-fns.h>
 
-#ifndef __ASSEMBLY__
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-#endif
-
 #include <asm-generic/pgtable-nopud.h>
 
 #ifndef CONFIG_MMU
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 518def8314e7..23b87b5ef7f1 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -41,13 +41,6 @@
 
 extern unsigned long __atags_pointer;
 
-/*
- * empty_zero_page is a special page that is used for
- * zero-initialized data and COW.
- */
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 /*
  * The pmd table for the upper-most set of pages.
  */
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index 7e42d8accec6..040ea43cce32 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -27,13 +27,6 @@
 
 unsigned long vectors_base;
 
-/*
- * empty_zero_page is a special page that is used for
- * zero-initialized data and COW.
- */
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 #ifdef CONFIG_ARM_MPU
 struct mpu_rgn_info mpu_rgn_info;
 #endif
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a17eb8a76788..516147f06fe8 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -110,7 +110,6 @@ static inline void arch_leave_lazy_mmu_mode(void)
  * ZERO_PAGE is a global shared page that is always zero: used
  * for zero-mapped memory areas etc..
  */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
 #define ZERO_PAGE(vaddr)	phys_to_page(__pa_symbol(empty_zero_page))
 
 #define pte_ERROR(e)	\
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a6a00accf4f9..0f6a171faf1f 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -64,13 +64,6 @@ static bool rodata_is_rw __ro_after_init = true;
  */
 long __section(".mmuoff.data.write") __early_cpu_boot_status;
 
-/*
- * Empty_zero_page is a special page that is used for zero-initialized data
- * and COW.
- */
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 static DEFINE_SPINLOCK(swapper_pgdir_lock);
 static DEFINE_MUTEX(fixmap_lock);
 
diff --git a/arch/csky/include/asm/pgtable.h b/arch/csky/include/asm/pgtable.h
index d606afbabce1..bafcd5823531 100644
--- a/arch/csky/include/asm/pgtable.h
+++ b/arch/csky/include/asm/pgtable.h
@@ -76,9 +76,6 @@
 #define MAX_SWAPFILES_CHECK() \
 		BUILD_BUG_ON(MAX_SWAPFILES_SHIFT != 5)
 
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-
 extern void load_pgd(unsigned long pg_dir);
 extern pte_t invalid_pte_table[PTRS_PER_PTE];
 
diff --git a/arch/csky/mm/init.c b/arch/csky/mm/init.c
index 573da66b2543..fa16015ea1c0 100644
--- a/arch/csky/mm/init.c
+++ b/arch/csky/mm/init.c
@@ -38,9 +38,6 @@ pte_t invalid_pte_table[PTRS_PER_PTE] __page_aligned_bss;
 pte_t kernel_pte_tables[PTRS_KERN_TABLE] __page_aligned_bss;
 
 EXPORT_SYMBOL(invalid_pte_table);
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
-						__page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
 
 void free_initmem(void)
 {
diff --git a/arch/hexagon/include/asm/pgtable.h b/arch/hexagon/include/asm/pgtable.h
index fbf24d1d1ca6..27b269e2870d 100644
--- a/arch/hexagon/include/asm/pgtable.h
+++ b/arch/hexagon/include/asm/pgtable.h
@@ -14,9 +14,6 @@
 #include <asm/page.h>
 #include <asm-generic/pgtable-nopmd.h>
 
-/* A handy thing to have if one has the RAM. Declared in head.S */
-extern unsigned long empty_zero_page;
-
 /*
  * The PTE model described here is that of the Hexagon Virtual Machine,
  * which autonomously walks 2-level page tables.  At a lower level, we
@@ -348,9 +345,6 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
 	return (unsigned long)__va(pmd_val(pmd) & PAGE_MASK);
 }
 
-/* ZERO_PAGE - returns the globally shared zero page */
-#define ZERO_PAGE(vaddr) (virt_to_page(&empty_zero_page))
-
 /*
  * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
  * are !pte_none() && !pte_present().
diff --git a/arch/hexagon/kernel/head.S b/arch/hexagon/kernel/head.S
index 0b016308cc79..908ffece9132 100644
--- a/arch/hexagon/kernel/head.S
+++ b/arch/hexagon/kernel/head.S
@@ -216,8 +216,3 @@ __head_s_vaddr_target:
 .p2align PAGE_SHIFT
 ENTRY(external_cmdline_buffer)
         .fill _PAGE_SIZE,1,0
-
-.data
-.p2align PAGE_SHIFT
-ENTRY(empty_zero_page)
-        .fill _PAGE_SIZE,1,0
diff --git a/arch/hexagon/kernel/hexagon_ksyms.c b/arch/hexagon/kernel/hexagon_ksyms.c
index 36a80e31d187..81bc6f81e200 100644
--- a/arch/hexagon/kernel/hexagon_ksyms.c
+++ b/arch/hexagon/kernel/hexagon_ksyms.c
@@ -17,7 +17,6 @@ EXPORT_SYMBOL(raw_copy_to_user);
 EXPORT_SYMBOL(__vmgetie);
 EXPORT_SYMBOL(__vmsetie);
 EXPORT_SYMBOL(__vmyield);
-EXPORT_SYMBOL(empty_zero_page);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memset);
 
diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index c33b3bcb733e..a244de27a03e 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -74,15 +74,6 @@
 struct mm_struct;
 struct vm_area_struct;
 
-/*
- * ZERO_PAGE is a global shared page that is always zero; used
- * for zero-mapped memory areas etc..
- */
-
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-
-#define ZERO_PAGE(vaddr)	virt_to_page(empty_zero_page)
-
 #ifdef CONFIG_32BIT
 
 #define VMALLOC_START	(vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE))
diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
index c331bf69d2ec..00f3822b6e47 100644
--- a/arch/loongarch/mm/init.c
+++ b/arch/loongarch/mm/init.c
@@ -36,9 +36,6 @@
 #include <asm/pgalloc.h>
 #include <asm/tlb.h>
 
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 void copy_user_highpage(struct page *to, struct page *from,
 	unsigned long vaddr, struct vm_area_struct *vma)
 {
diff --git a/arch/m68k/include/asm/pgtable_mm.h b/arch/m68k/include/asm/pgtable_mm.h
index bba64a9c49ac..7501ff030c63 100644
--- a/arch/m68k/include/asm/pgtable_mm.h
+++ b/arch/m68k/include/asm/pgtable_mm.h
@@ -110,15 +110,6 @@ extern unsigned long m68k_vmalloc_end;
 #define VMALLOC_END KMAP_START
 #endif
 
-/* zero page used for uninitialized stuff */
-extern void *empty_zero_page;
-
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-
 extern void kernel_set_cachemode(void *addr, unsigned long size, int cmode);
 
 /*
diff --git a/arch/m68k/include/asm/pgtable_no.h b/arch/m68k/include/asm/pgtable_no.h
index 1a86c15b9008..11751807a3f3 100644
--- a/arch/m68k/include/asm/pgtable_no.h
+++ b/arch/m68k/include/asm/pgtable_no.h
@@ -30,13 +30,6 @@
 
 #define swapper_pg_dir ((pgd_t *) 0)
 
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern void *empty_zero_page;
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-
 /*
  * All 32bit addresses are effectively valid for vmalloc...
  * Sort of meaningless for non-VM targets.
diff --git a/arch/m68k/mm/init.c b/arch/m68k/mm/init.c
index 53b71f786c27..3b88c0dd1616 100644
--- a/arch/m68k/mm/init.c
+++ b/arch/m68k/mm/init.c
@@ -33,13 +33,6 @@
 #include <asm/sections.h>
 #include <asm/tlb.h>
 
-/*
- * ZERO_PAGE is a special page that is used for zero-initialized
- * data and COW.
- */
-void *empty_zero_page;
-EXPORT_SYMBOL(empty_zero_page);
-
 void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
 {
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(memblock_end_of_DRAM());
@@ -71,8 +64,6 @@ void __init paging_init(void)
 	unsigned long end_mem = memory_end & PAGE_MASK;
 
 	high_memory = (void *) end_mem;
-
-	empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
 }
 
 #endif /* CONFIG_MMU */
diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
index 3418fd864237..4924f2ff8ef8 100644
--- a/arch/m68k/mm/mcfmmu.c
+++ b/arch/m68k/mm/mcfmmu.c
@@ -41,8 +41,6 @@ void __init paging_init(void)
 	unsigned long next_pgtable;
 	int i;
 
-	empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
-
 	pg_dir = swapper_pg_dir;
 	memset(swapper_pg_dir, 0, sizeof(swapper_pg_dir));
 
diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
index 127a3fa69f4c..b30aa69a73a6 100644
--- a/arch/m68k/mm/motorola.c
+++ b/arch/m68k/mm/motorola.c
@@ -498,12 +498,6 @@ void __init paging_init(void)
 
 	early_memtest(min_addr, max_addr);
 
-	/*
-	 * initialize the bad page table and bad page to point
-	 * to a couple of allocated pages
-	 */
-	empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
-
 	/*
 	 * Set up SFC/DFC registers
 	 */
diff --git a/arch/m68k/mm/sun3mmu.c b/arch/m68k/mm/sun3mmu.c
index c801677f7df8..f139cc15753a 100644
--- a/arch/m68k/mm/sun3mmu.c
+++ b/arch/m68k/mm/sun3mmu.c
@@ -43,8 +43,6 @@ void __init paging_init(void)
 	unsigned long bootmem_end;
 	unsigned long size;
 
-	empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
-
 	address = PAGE_OFFSET;
 	pg_dir = swapper_pg_dir;
 	memset (swapper_pg_dir, 0, sizeof (swapper_pg_dir));
diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
index 4eb76de6be4a..ea72291de553 100644
--- a/arch/microblaze/include/asm/pgtable.h
+++ b/arch/microblaze/include/asm/pgtable.h
@@ -207,16 +207,6 @@ extern pte_t *va_to_pte(unsigned long address);
  * Also, write permissions imply read permissions.
  */
 
-#ifndef __ASSEMBLER__
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[1024];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
-#endif /* __ASSEMBLER__ */
-
 #define pte_none(pte)		((pte_val(pte) & ~_PTE_NONE_MASK) == 0)
 #define pte_present(pte)	(pte_val(pte) & _PAGE_PRESENT)
 #define pte_clear(mm, addr, ptep) \
diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S
index ec2fcb545e64..808019c3b7ac 100644
--- a/arch/microblaze/kernel/head.S
+++ b/arch/microblaze/kernel/head.S
@@ -39,10 +39,6 @@
 #include <asm/processor.h>
 
 .section .data
-.global empty_zero_page
-.align 12
-empty_zero_page:
-	.space	PAGE_SIZE
 .global swapper_pg_dir
 swapper_pg_dir:
 	.space	PAGE_SIZE
diff --git a/arch/microblaze/kernel/microblaze_ksyms.c b/arch/microblaze/kernel/microblaze_ksyms.c
index a8553f54152b..ad7596d7ba07 100644
--- a/arch/microblaze/kernel/microblaze_ksyms.c
+++ b/arch/microblaze/kernel/microblaze_ksyms.c
@@ -33,8 +33,6 @@ EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memmove);
 #endif
 
-EXPORT_SYMBOL(empty_zero_page);
-
 EXPORT_SYMBOL(mbc);
 
 extern void __divsi3(void);
diff --git a/arch/nios2/include/asm/pgtable.h b/arch/nios2/include/asm/pgtable.h
index 844dce55569f..d389aa9ca57c 100644
--- a/arch/nios2/include/asm/pgtable.h
+++ b/arch/nios2/include/asm/pgtable.h
@@ -65,13 +65,6 @@ struct mm_struct;
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
-
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 extern pte_t invalid_pte_table[PAGE_SIZE/sizeof(pte_t)];
 
diff --git a/arch/nios2/kernel/head.S b/arch/nios2/kernel/head.S
index 372ce4a33018..613212e1a63a 100644
--- a/arch/nios2/kernel/head.S
+++ b/arch/nios2/kernel/head.S
@@ -23,16 +23,6 @@
 #include <asm/asm-offsets.h>
 #include <asm/asm-macros.h>
 
-/*
- * ZERO_PAGE is a special page that is used for zero-initialized
- * data and COW.
- */
-.data
-.global empty_zero_page
-.align 12
-empty_zero_page:
-	.space	PAGE_SIZE
-
 /*
  * This global variable is used as an extension to the nios'
  * STATUS register to emulate a user/supervisor mode.
diff --git a/arch/nios2/kernel/nios2_ksyms.c b/arch/nios2/kernel/nios2_ksyms.c
index 54f7b23df1bf..c40aa39e8658 100644
--- a/arch/nios2/kernel/nios2_ksyms.c
+++ b/arch/nios2/kernel/nios2_ksyms.c
@@ -20,7 +20,6 @@ EXPORT_SYMBOL(memmove);
 
 /* memory management */
 
-EXPORT_SYMBOL(empty_zero_page);
 EXPORT_SYMBOL(flush_icache_range);
 
 /*
diff --git a/arch/openrisc/include/asm/pgtable.h b/arch/openrisc/include/asm/pgtable.h
index b218050e2f6d..6b89996d0b62 100644
--- a/arch/openrisc/include/asm/pgtable.h
+++ b/arch/openrisc/include/asm/pgtable.h
@@ -179,10 +179,6 @@ extern void paging_init(void);
 	__pgprot(_PAGE_ALL | _PAGE_SRE | _PAGE_SWE \
 		 | _PAGE_SHARED | _PAGE_DIRTY | _PAGE_EXEC | _PAGE_CI)
 
-/* zero page used for uninitialized stuff */
-extern unsigned long empty_zero_page[2048];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 #define pte_none(x)	(!pte_val(x))
 #define pte_present(x)	(pte_val(x) & _PAGE_PRESENT)
 #define pte_clear(mm, addr, xp)	do { pte_val(*(xp)) = 0; } while (0)
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index bd760066f1cd..45890393947d 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -1563,9 +1563,6 @@ _string_nl:
  */
 	.section .data,"aw"
 	.align	8192
-	.global  empty_zero_page
-empty_zero_page:
-	.space  8192
 
 	.global  swapper_pg_dir
 swapper_pg_dir:
diff --git a/arch/openrisc/kernel/or32_ksyms.c b/arch/openrisc/kernel/or32_ksyms.c
index 212e5f85004c..84a937a64e2a 100644
--- a/arch/openrisc/kernel/or32_ksyms.c
+++ b/arch/openrisc/kernel/or32_ksyms.c
@@ -40,7 +40,6 @@ DECLARE_EXPORT(__ashldi3);
 DECLARE_EXPORT(__lshrdi3);
 DECLARE_EXPORT(__ucmpdi2);
 
-EXPORT_SYMBOL(empty_zero_page);
 EXPORT_SYMBOL(__copy_tofrom_user);
 EXPORT_SYMBOL(__clear_user);
 EXPORT_SYMBOL(memset);
diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
index 78fb0734cdbc..89d8c6df8855 100644
--- a/arch/openrisc/mm/init.c
+++ b/arch/openrisc/mm/init.c
@@ -188,9 +188,6 @@ void __init mem_init(void)
 {
 	BUG_ON(!mem_map);
 
-	/* clear the zero-page */
-	memset((void *)empty_zero_page, 0, PAGE_SIZE);
-
 	printk("mem_init_done ...........................................\n");
 	mem_init_done = 1;
 	return;
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 2c139a4dbf4b..cbdc01a26ea0 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -262,17 +262,6 @@ extern pgd_t swapper_pg_dir[]; /* declared in init_task.c */
 
 extern pte_t pg0[];
 
-/* zero page used for uninitialized stuff */
-
-extern unsigned long *empty_zero_page;
-
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 #define pte_none(x)     (pte_val(x) == 0)
 #define pte_present(x)	(pte_val(x) & _PAGE_PRESENT)
 #define pte_user(x)	(pte_val(x) & _PAGE_USER)
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 6a39e031e5ff..be3380c9bcda 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -604,9 +604,6 @@ void __init mem_init(void)
 #endif
 }
 
-unsigned long *empty_zero_page __ro_after_init;
-EXPORT_SYMBOL(empty_zero_page);
-
 /*
  * pagetable_init() sets up the page tables
  *
@@ -639,9 +636,6 @@ static void __init pagetable_init(void)
 			  initrd_end - initrd_start, PAGE_KERNEL, 0);
 	}
 #endif
-
-	empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
-
 }
 
 static void __init gateway_init(void)
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index dcd3a88caaf6..b27d94c06d0e 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -76,12 +76,6 @@ static inline const void *pmd_page_vaddr(pmd_t pmd)
 }
 #define pmd_page_vaddr pmd_page_vaddr
 #endif
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
 
 extern pgd_t swapper_pg_dir[];
 
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 3789a51bdaae..85508392a6b6 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -34,9 +34,6 @@
 
 unsigned long long memory_limit __initdata;
 
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 pgprot_t __phys_mem_access_prot(unsigned long pfn, unsigned long size,
 				pgprot_t vma_prot)
 {
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 9ecbf0366719..a6b496f4944f 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -1258,13 +1258,6 @@ extern u64 satp_mode;
 void paging_init(void);
 void misc_mem_init(void);
 
-/*
- * ZERO_PAGE is a global shared page that is always zero,
- * used for zero-mapped memory areas, etc.
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 /*
  * Use set_p*_safe(), and elide TLB flushing, when confident that *no*
  * TLB flush will be required as a result of the "set". For example, use
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 848efeb9e163..95ac79c62067 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -69,10 +69,6 @@ unsigned long vmemmap_start_pfn __ro_after_init;
 EXPORT_SYMBOL(vmemmap_start_pfn);
 #endif
 
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
-							__page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 extern char _start[];
 void *_dtb_early_va __initdata;
 uintptr_t _dtb_early_pa __initdata;
diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 10fa8f2bb8d1..d5ce0950a323 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -20,14 +20,6 @@
 #ifndef __ASSEMBLER__
 #include <asm/addrspace.h>
 #include <asm/fixmap.h>
-
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 #endif /* !__ASSEMBLER__ */
 
 /*
diff --git a/arch/sh/include/asm/setup.h b/arch/sh/include/asm/setup.h
index 84bb23a771f3..63c9efc06348 100644
--- a/arch/sh/include/asm/setup.h
+++ b/arch/sh/include/asm/setup.h
@@ -7,7 +7,8 @@
 /*
  * This is set up by the setup-routine at boot-time
  */
-#define PARAM	((unsigned char *)empty_zero_page)
+extern unsigned char *boot_params_page;
+#define PARAM boot_params_page
 
 #define MOUNT_ROOT_RDONLY (*(unsigned long *) (PARAM+0x000))
 #define RAMDISK_FLAGS (*(unsigned long *) (PARAM+0x004))
diff --git a/arch/sh/kernel/head_32.S b/arch/sh/kernel/head_32.S
index b603b7968b38..0b91bb85d40a 100644
--- a/arch/sh/kernel/head_32.S
+++ b/arch/sh/kernel/head_32.S
@@ -26,7 +26,7 @@
 #endif
 
 	.section	.empty_zero_page, "aw"
-ENTRY(empty_zero_page)
+ENTRY(boot_params_page)
 	.long	1		/* MOUNT_ROOT_RDONLY */
 	.long	0		/* RAMDISK_FLAGS */
 	.long	0x0200		/* ORIG_ROOT_DEV */
@@ -39,7 +39,7 @@ ENTRY(empty_zero_page)
 	.long	0x53453f00 + 29	/* "SE?" = 29 bit */
 #endif
 1:
-	.skip	PAGE_SIZE - empty_zero_page - 1b
+	.skip	PAGE_SIZE - boot_params_page - 1b
 
 	__HEAD
 
diff --git a/arch/sh/kernel/sh_ksyms_32.c b/arch/sh/kernel/sh_ksyms_32.c
index 5858936cb431..041191002e2e 100644
--- a/arch/sh/kernel/sh_ksyms_32.c
+++ b/arch/sh/kernel/sh_ksyms_32.c
@@ -20,7 +20,6 @@ EXPORT_SYMBOL(csum_partial);
 EXPORT_SYMBOL(csum_partial_copy_generic);
 EXPORT_SYMBOL(copy_page);
 EXPORT_SYMBOL(__clear_user);
-EXPORT_SYMBOL(empty_zero_page);
 #ifdef CONFIG_FLATMEM
 /* need in pfn_valid macro */
 EXPORT_SYMBOL(min_low_pfn);
diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 464a3a63e2fa..4e40d5e96be9 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -332,7 +332,6 @@ void __init mem_init(void)
 	cpu_cache_init();
 
 	/* clear the zero-page */
-	memset(empty_zero_page, 0, PAGE_SIZE);
 	__flush_wback_region(empty_zero_page, PAGE_SIZE);
 
 	vsyscall_init();
diff --git a/arch/sparc/include/asm/pgtable_32.h b/arch/sparc/include/asm/pgtable_32.h
index a9f802d1dd64..f89b1250661d 100644
--- a/arch/sparc/include/asm/pgtable_32.h
+++ b/arch/sparc/include/asm/pgtable_32.h
@@ -71,14 +71,6 @@ extern unsigned long ptr_in_current_pgd;
 extern unsigned long phys_base;
 extern unsigned long pfn_base;
 
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 /*
  * In general all page table modifications should use the V8 atomic
  * swap instruction.  This insures the mmu and the cpu are in sync
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 615f460c50af..74ede706fb32 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -210,9 +210,6 @@ extern unsigned long _PAGE_CACHE;
 extern unsigned long pg_iobits;
 extern unsigned long _PAGE_ALL_SZ_BITS;
 
-extern struct page *mem_map_zero;
-#define ZERO_PAGE(vaddr)	(mem_map_zero)
-
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,
diff --git a/arch/sparc/include/asm/setup.h b/arch/sparc/include/asm/setup.h
index 72205684e51e..21bed5514028 100644
--- a/arch/sparc/include/asm/setup.h
+++ b/arch/sparc/include/asm/setup.h
@@ -17,8 +17,6 @@ extern char reboot_command[];
  */
 extern unsigned char boot_cpu_id;
 
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-
 extern int serial_console;
 static inline int con_is_present(void)
 {
diff --git a/arch/sparc/kernel/head_32.S b/arch/sparc/kernel/head_32.S
index 38345460d542..8c320fa25a67 100644
--- a/arch/sparc/kernel/head_32.S
+++ b/arch/sparc/kernel/head_32.S
@@ -57,13 +57,6 @@ sun4e_notsup:
 
 	.align PAGE_SIZE
 
-/* This was the only reasonable way I could think of to properly align
- * these page-table data structures.
- */
-	.globl empty_zero_page
-empty_zero_page:	.skip PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
-
 	.global root_flags
 	.global ram_flags
 	.global root_dev
diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
index fdc93dd12c3e..e0e66f91ceeb 100644
--- a/arch/sparc/mm/init_32.c
+++ b/arch/sparc/mm/init_32.c
@@ -246,10 +246,6 @@ void __init arch_mm_preinit(void)
 		prom_halt();
 	}
 
-
-	/* Saves us work later. */
-	memset((void *)empty_zero_page, 0, PAGE_SIZE);
-
 	i = last_valid_pfn >> ((20 - PAGE_SHIFT) + 5);
 	i += 1;
 	sparc_valid_addr_bitmap = (unsigned long *)
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index c2d19c9a9244..2bd99944176d 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64;
 extern unsigned int sparc_ramdisk_image;
 extern unsigned int sparc_ramdisk_size;
 
-struct page *mem_map_zero __read_mostly;
-EXPORT_SYMBOL(mem_map_zero);
-
 unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
 
 unsigned long sparc64_kern_pri_context __read_mostly;
@@ -2506,18 +2503,6 @@ void __init mem_init(void)
 	 */
 	register_page_bootmem_info();
 
-	/*
-	 * Set up the zero page, mark it reserved, so that page count
-	 * is not manipulated when freeing the page from user ptes.
-	 */
-	mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
-	if (mem_map_zero == NULL) {
-		prom_printf("paging_init: Cannot alloc zero page.\n");
-		prom_halt();
-	}
-	mark_page_reserved(mem_map_zero);
-
-
 	if (tlb_type == cheetah || tlb_type == cheetah_plus)
 		cheetah_ecache_flush_init();
 }
diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index 3b42b0f45bf6..19e0608fb649 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -34,9 +34,6 @@
 
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 
-/* zero page used for uninitialized stuff */
-extern unsigned long *empty_zero_page;
-
 /* Just any arbitrary offset to the start of the vmalloc VM area: the
  * current 8MB value just means that there will be a 8MB "hole" after the
  * physical memory until the kernel virtual memory starts.  That means that
@@ -74,12 +71,6 @@ extern unsigned long *empty_zero_page;
  * get..
  */
 
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-#define ZERO_PAGE(vaddr) virt_to_page(empty_zero_page)
-
 #define pte_clear(mm, addr, xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEEDSYNC))
 
 #define pmd_none(x)	(!((unsigned long)pmd_val(x) & ~_PAGE_NEEDSYNC))
diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h
index 38321188c04c..9812efd14ec0 100644
--- a/arch/um/include/shared/kern_util.h
+++ b/arch/um/include/shared/kern_util.h
@@ -38,7 +38,6 @@ extern void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs
 extern void uml_pm_wake(void);
 
 extern int start_uml(void);
-extern void paging_init(void);
 
 extern void uml_cleanup(void);
 extern void do_uml_exitcalls(void);
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 89c8c8b94a79..1eef0e42ef5d 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -44,10 +44,6 @@ __section(".kasan_init") __used
 = kasan_init;
 #endif
 
-/* allocated in paging_init, zeroed in mem_init, and unchanged thereafter */
-unsigned long *empty_zero_page = NULL;
-EXPORT_SYMBOL(empty_zero_page);
-
 /*
  * Initialized during boot, and readonly for initializing page tables
  * afterwards
@@ -65,9 +61,6 @@ void __init arch_mm_preinit(void)
 	/* Safe to call after jump_label_init(). Enables KASAN. */
 	kasan_init_generic();
 
-	/* clear the zero-page */
-	memset(empty_zero_page, 0, PAGE_SIZE);
-
 	/* Map in the area just after the brk now that kmalloc is about
 	 * to be turned on.
 	 */
@@ -89,15 +82,6 @@ void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
 	max_zone_pfns[ZONE_NORMAL] = high_physmem >> PAGE_SHIFT;
 }
 
-void __init paging_init(void)
-{
-	empty_zero_page = (unsigned long *) memblock_alloc_low(PAGE_SIZE,
-							       PAGE_SIZE);
-	if (!empty_zero_page)
-		panic("%s: Failed to allocate %lu bytes align=%lx\n",
-		      __func__, PAGE_SIZE, PAGE_SIZE);
-}
-
 /*
  * This can't do anything because nothing in the kernel image can be freed
  * since it's not in kernel physical memory.
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index e2b24e1ecfa6..2141f5f1f5a2 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -413,7 +413,6 @@ void __init setup_arch(char **cmdline_p)
 	uml_dtb_init();
 	read_initrd();
 
-	paging_init();
 	strscpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
 	*cmdline_p = command_line;
 	setup_hostinfo(host_info, sizeof host_info);
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1662c5a8f445..54289f4587a4 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -47,14 +47,6 @@ void ptdump_walk_user_pgd_level_checkwx(void);
 #define debug_checkwx_user()	do { } while (0)
 #endif
 
-/*
- * ZERO_PAGE is a global shared page that is always zero: used
- * for zero-mapped memory areas etc..
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
-	__visible;
-#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page))
-
 extern spinlock_t pgd_lock;
 extern struct list_head pgd_list;
 
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 80ef5d386b03..5171cb746444 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -441,10 +441,6 @@ initial_pg_fixmap:
 swapper_pg_dir:
 	.fill 1024,4,0
 	.fill PTI_USER_PGD_FILL,4,0
-.globl empty_zero_page
-empty_zero_page:
-	.fill 4096,1,0
-EXPORT_SYMBOL(empty_zero_page)
 
 /*
  * This starts the data section.
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 21816b48537c..cbf7647a25d8 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -712,10 +712,3 @@ SYM_PIC_ALIAS(phys_base);
 EXPORT_SYMBOL(phys_base)
 
 #include "../xen/xen-head.S"
-
-	__PAGE_ALIGNED_BSS
-SYM_DATA_START_PAGE_ALIGNED(empty_zero_page)
-	.skip PAGE_SIZE
-SYM_DATA_END(empty_zero_page)
-EXPORT_SYMBOL(empty_zero_page)
-
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index 50a136213b2b..61f07d981a94 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -209,10 +209,6 @@
 #define pgd_ERROR(e) \
 	printk("%s:%d: bad pgd entry %08lx.\n", __FILE__, __LINE__, pgd_val(e))
 
-extern unsigned long empty_zero_page[1024];
-
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
 #ifdef CONFIG_MMU
 extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
 extern void paging_init(void);
diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S
index 8484294bc623..4b0c5c5e685a 100644
--- a/arch/xtensa/kernel/head.S
+++ b/arch/xtensa/kernel/head.S
@@ -381,6 +381,3 @@ ENTRY(swapper_pg_dir)
 	.fill	PAGE_SIZE, 1, 0
 END(swapper_pg_dir)
 #endif
-ENTRY(empty_zero_page)
-	.fill	PAGE_SIZE, 1, 0
-END(empty_zero_page)
diff --git a/arch/xtensa/kernel/xtensa_ksyms.c b/arch/xtensa/kernel/xtensa_ksyms.c
index 62d81e76e18e..ced335b4df5f 100644
--- a/arch/xtensa/kernel/xtensa_ksyms.c
+++ b/arch/xtensa/kernel/xtensa_ksyms.c
@@ -15,8 +15,6 @@
 #include <linux/module.h>
 #include <asm/pgtable.h>
 
-EXPORT_SYMBOL(empty_zero_page);
-
 unsigned int __sync_fetch_and_and_4(volatile void *p, unsigned int v)
 {
 	BUG();
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 4f063438a4fc..3687ea2ddedb 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -2188,6 +2188,14 @@ static inline const char *pgtable_level_to_str(enum pgtable_level level)
 	}
 }
 
+#ifndef __HAVE_COLOR_ZERO_PAGE
+extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
+#endif
+
+#ifndef ZERO_PAGE
+#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page))
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 1a29a719af58..8ea5b76f317f 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -53,6 +53,15 @@ EXPORT_SYMBOL(mem_map);
 void *high_memory;
 EXPORT_SYMBOL(high_memory);
 
+#ifndef __HAVE_COLOR_ZERO_PAGE
+/*
+ * ZERO_PAGE is a global shared page that is always zero: used
+ * for zero-mapped memory areas etc..
+ */
+unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
+EXPORT_SYMBOL(empty_zero_page);
+#endif
+
 #ifdef CONFIG_DEBUG_MEMORY_INIT
 int __meminitdata mminit_loglevel;
 

base-commit: 10de4550639e9df9242e32e9affc90ed75a27c7d
-- 
2.51.0

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Christophe Leroy (CS GROUP)]

Le 24/01/2026 à 10:56, Mike Rapoport a écrit :
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
> ZERO_PAGE() to 4.
> 
> Every architecture defines empty_zero_page that way or another, but for the
> most of them it is always a page aligned page in BSS and most definitions
> of ZERO_PAGE do virt_to_page(empty_zero_page).
> 
> Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
> core MM and drop these definitions in architectures that do not implement
> colored zero page (MIPS and s390).
> 
> ZERO_PAGE() remains a macro because turning it to a wrapper for a static
> inline causes severe pain in header dependencies.
> 
> For the most part the change is mechanical, with these being noteworthy:
> 
> * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
>    parameters. Switching to a generic empty_zero_page removes the aliasing
>    and keeps ZERO_PGE for boot parameters only
> * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
>    ZERO_PAGE() is kept intact.
> * m68k/parisc/sparc64/um: allocated empty_zero_page from memblock,
>    although they do not support zero page coloring and having it in BSS
>    will work fine.
> * sh: used empty_zero_page for boot parameters at the very early boot.
>    Rename the parameters page to boot_params_page and let sh use the generic
>    empty_zero_page.
> * hexagon: had an amusing comment about empty_zero_page
> 
> 	/* A handy thing to have if one has the RAM. Declared in head.S */
> 
>    that unfortunately had to go :)
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>   arch/alpha/include/asm/pgtable.h          |  6 ------
>   arch/arc/include/asm/pgtable.h            |  3 ---
>   arch/arc/mm/init.c                        |  2 --
>   arch/arm/include/asm/pgtable.h            |  9 ---------
>   arch/arm/mm/mmu.c                         |  7 -------
>   arch/arm/mm/nommu.c                       |  7 -------
>   arch/arm64/include/asm/pgtable.h          |  1 -
>   arch/arm64/mm/mmu.c                       |  7 -------
>   arch/csky/include/asm/pgtable.h           |  3 ---
>   arch/csky/mm/init.c                       |  3 ---
>   arch/hexagon/include/asm/pgtable.h        |  6 ------
>   arch/hexagon/kernel/head.S                |  5 -----
>   arch/hexagon/kernel/hexagon_ksyms.c       |  1 -
>   arch/loongarch/include/asm/pgtable.h      |  9 ---------
>   arch/loongarch/mm/init.c                  |  3 ---
>   arch/m68k/include/asm/pgtable_mm.h        |  9 ---------
>   arch/m68k/include/asm/pgtable_no.h        |  7 -------
>   arch/m68k/mm/init.c                       |  9 ---------
>   arch/m68k/mm/mcfmmu.c                     |  2 --
>   arch/m68k/mm/motorola.c                   |  6 ------
>   arch/m68k/mm/sun3mmu.c                    |  2 --
>   arch/microblaze/include/asm/pgtable.h     | 10 ----------
>   arch/microblaze/kernel/head.S             |  4 ----
>   arch/microblaze/kernel/microblaze_ksyms.c |  2 --
>   arch/nios2/include/asm/pgtable.h          |  7 -------
>   arch/nios2/kernel/head.S                  | 10 ----------
>   arch/nios2/kernel/nios2_ksyms.c           |  1 -
>   arch/openrisc/include/asm/pgtable.h       |  4 ----
>   arch/openrisc/kernel/head.S               |  3 ---
>   arch/openrisc/kernel/or32_ksyms.c         |  1 -
>   arch/openrisc/mm/init.c                   |  3 ---
>   arch/parisc/include/asm/pgtable.h         | 11 -----------
>   arch/parisc/mm/init.c                     |  6 ------
>   arch/powerpc/include/asm/pgtable.h        |  6 ------
>   arch/powerpc/mm/mem.c                     |  3 ---

For powerpc:

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>

>   arch/riscv/include/asm/pgtable.h          |  7 -------
>   arch/riscv/mm/init.c                      |  4 ----
>   arch/sh/include/asm/pgtable.h             |  8 --------
>   arch/sh/include/asm/setup.h               |  3 ++-
>   arch/sh/kernel/head_32.S                  |  4 ++--
>   arch/sh/kernel/sh_ksyms_32.c              |  1 -
>   arch/sh/mm/init.c                         |  1 -
>   arch/sparc/include/asm/pgtable_32.h       |  8 --------
>   arch/sparc/include/asm/pgtable_64.h       |  3 ---
>   arch/sparc/include/asm/setup.h            |  2 --
>   arch/sparc/kernel/head_32.S               |  7 -------
>   arch/sparc/mm/init_32.c                   |  4 ----
>   arch/sparc/mm/init_64.c                   | 15 ---------------
>   arch/um/include/asm/pgtable.h             |  9 ---------
>   arch/um/include/shared/kern_util.h        |  1 -
>   arch/um/kernel/mem.c                      | 16 ----------------
>   arch/um/kernel/um_arch.c                  |  1 -
>   arch/x86/include/asm/pgtable.h            |  8 --------
>   arch/x86/kernel/head_32.S                 |  4 ----
>   arch/x86/kernel/head_64.S                 |  7 -------
>   arch/xtensa/include/asm/pgtable.h         |  4 ----
>   arch/xtensa/kernel/head.S                 |  3 ---
>   arch/xtensa/kernel/xtensa_ksyms.c         |  2 --
>   include/linux/pgtable.h                   |  8 ++++++++
>   mm/mm_init.c                              |  9 +++++++++
>   60 files changed, 21 insertions(+), 296 deletions(-)
> 

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Andreas Larsson]

On 2026-01-24 10:56, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
> ZERO_PAGE() to 4.
> 
> Every architecture defines empty_zero_page that way or another, but for the
> most of them it is always a page aligned page in BSS and most definitions
> of ZERO_PAGE do virt_to_page(empty_zero_page).
> 
> Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
> core MM and drop these definitions in architectures that do not implement
> colored zero page (MIPS and s390).
> 
> ZERO_PAGE() remains a macro because turning it to a wrapper for a static
> inline causes severe pain in header dependencies.
> 
> For the most part the change is mechanical, with these being noteworthy:
> 
> * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
>   parameters. Switching to a generic empty_zero_page removes the aliasing
>   and keeps ZERO_PGE for boot parameters only
> * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
>   ZERO_PAGE() is kept intact.
> * m68k/parisc/sparc64/um: allocated empty_zero_page from memblock,
>   although they do not support zero page coloring and having it in BSS
>   will work fine.
> * sh: used empty_zero_page for boot parameters at the very early boot.
>   Rename the parameters page to boot_params_page and let sh use the generic
>   empty_zero_page.
> * hexagon: had an amusing comment about empty_zero_page
> 
> 	/* A handy thing to have if one has the RAM. Declared in head.S */
> 
>   that unfortunately had to go :)
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---

Running this in an LDOM on an UltraSparc T4 sparc64, the entire LDOM
hangs after a while during boot.


> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index c2d19c9a9244..2bd99944176d 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64;
>  extern unsigned int sparc_ramdisk_image;
>  extern unsigned int sparc_ramdisk_size;
>  
> -struct page *mem_map_zero __read_mostly;
> -EXPORT_SYMBOL(mem_map_zero);
> -
>  unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
>  
>  unsigned long sparc64_kern_pri_context __read_mostly;
> @@ -2506,18 +2503,6 @@ void __init mem_init(void)
>  	 */
>  	register_page_bootmem_info();
>  
> -	/*
> -	 * Set up the zero page, mark it reserved, so that page count
> -	 * is not manipulated when freeing the page from user ptes.
> -	 */
> -	mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
> -	if (mem_map_zero == NULL) {
> -		prom_printf("paging_init: Cannot alloc zero page.\n");
> -		prom_halt();
> -	}
> -	mark_page_reserved(mem_map_zero);
> -
> -
>  	if (tlb_type == cheetah || tlb_type == cheetah_plus)
>  		cheetah_ecache_flush_init();
>  }

This just removes the mark_page_reserved(mem_map_zero) without 
replacing it with something corresponding to that. Perhaps part
of the problem?

Cheers,
Andreas

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Mike Rapoport]

Hi,

On Tue, Jan 27, 2026 at 05:02:39PM +0100, Andreas Larsson wrote:
> On 2026-01-24 10:56, Mike Rapoport wrote:
>
> > Every architecture defines empty_zero_page that way or another, but for the
> > most of them it is always a page aligned page in BSS and most definitions
> > of ZERO_PAGE do virt_to_page(empty_zero_page).
> 
> Running this in an LDOM on an UltraSparc T4 sparc64, the entire LDOM
> hangs after a while during boot.
> 
> > diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> > index c2d19c9a9244..2bd99944176d 100644
> > --- a/arch/sparc/mm/init_64.c
> > +++ b/arch/sparc/mm/init_64.c
> > @@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64;
> >  extern unsigned int sparc_ramdisk_image;
> >  extern unsigned int sparc_ramdisk_size;
> >  
> > -struct page *mem_map_zero __read_mostly;
> > -EXPORT_SYMBOL(mem_map_zero);
> > -
> >  unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
> >  
> >  unsigned long sparc64_kern_pri_context __read_mostly;
> > @@ -2506,18 +2503,6 @@ void __init mem_init(void)
> >  	 */
> >  	register_page_bootmem_info();
> >  
> > -	/*
> > -	 * Set up the zero page, mark it reserved, so that page count
> > -	 * is not manipulated when freeing the page from user ptes.
> > -	 */
> > -	mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
> > -	if (mem_map_zero == NULL) {
> > -		prom_printf("paging_init: Cannot alloc zero page.\n");
> > -		prom_halt();
> > -	}
> > -	mark_page_reserved(mem_map_zero);
> > -
> > -
> >  	if (tlb_type == cheetah || tlb_type == cheetah_plus)
> >  		cheetah_ecache_flush_init();
> >  }
> 
> This just removes the mark_page_reserved(mem_map_zero) without 
> replacing it with something corresponding to that. Perhaps part
> of the problem?

I don't think so, empty_zero_page is in BSS now an it's reserved as a part
of the kernel image.

I suspect that virt_to_page() does not work BSS symbols on sparc64. Can you
please try with this patch:

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 74ede706fb32..0578c5172d4e 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -22,6 +22,7 @@
 #include <asm/adi.h>
 #include <asm/page.h>
 #include <asm/processor.h>
+#include <asm/vaddrs.h>
 
 /* The kernel image occupies 0x4000000 to 0x6000000 (4MB --> 96MB).
  * The page copy blockops can use 0x6000000 to 0x8000000.
@@ -210,6 +211,11 @@ extern unsigned long _PAGE_CACHE;
 extern unsigned long pg_iobits;
 extern unsigned long _PAGE_ALL_SZ_BITS;
 
+extern unsigned long kern_base;
+#define ZERO_PAGE(vaddr)						   \
+	(virt_to_page(empty_zero_page + ((unsigned long)__va(kern_base)) - \
+		      ((unsigned long)KERNBASE)))
+
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 2bd99944176d..d2d724ba4f83 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -170,6 +170,8 @@ static void __init read_obp_memory(const char *property,
 
 /* Kernel physical address base and size in bytes.  */
 unsigned long kern_base __read_mostly;
+EXPORT_SYMBOL(kern_base);
+
 unsigned long kern_size __read_mostly;
 
 /* Initial ramdisk setup */
 
> Cheers,
> Andreas

-- 
Sincerely yours,
Mike.

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Andreas Larsson]

On 2026-01-27 19:11, Mike Rapoport wrote:
> On Tue, Jan 27, 2026 at 05:02:39PM +0100, Andreas Larsson wrote:
>> On 2026-01-24 10:56, Mike Rapoport wrote:
>>
>>> Every architecture defines empty_zero_page that way or another, but for the
>>> most of them it is always a page aligned page in BSS and most definitions
>>> of ZERO_PAGE do virt_to_page(empty_zero_page).
>>
>> Running this in an LDOM on an UltraSparc T4 sparc64, the entire LDOM
>> hangs after a while during boot.
>>
>>> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
>>> index c2d19c9a9244..2bd99944176d 100644
>>> --- a/arch/sparc/mm/init_64.c
>>> +++ b/arch/sparc/mm/init_64.c
>>> @@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64;
>>>  extern unsigned int sparc_ramdisk_image;
>>>  extern unsigned int sparc_ramdisk_size;
>>>  
>>> -struct page *mem_map_zero __read_mostly;
>>> -EXPORT_SYMBOL(mem_map_zero);
>>> -
>>>  unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
>>>  
>>>  unsigned long sparc64_kern_pri_context __read_mostly;
>>> @@ -2506,18 +2503,6 @@ void __init mem_init(void)
>>>  	 */
>>>  	register_page_bootmem_info();
>>>  
>>> -	/*
>>> -	 * Set up the zero page, mark it reserved, so that page count
>>> -	 * is not manipulated when freeing the page from user ptes.
>>> -	 */
>>> -	mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
>>> -	if (mem_map_zero == NULL) {
>>> -		prom_printf("paging_init: Cannot alloc zero page.\n");
>>> -		prom_halt();
>>> -	}
>>> -	mark_page_reserved(mem_map_zero);
>>> -
>>> -
>>>  	if (tlb_type == cheetah || tlb_type == cheetah_plus)
>>>  		cheetah_ecache_flush_init();
>>>  }
>>
>> This just removes the mark_page_reserved(mem_map_zero) without 
>> replacing it with something corresponding to that. Perhaps part
>> of the problem?
> 
> I don't think so, empty_zero_page is in BSS now an it's reserved as a part
> of the kernel image.
> 
> I suspect that virt_to_page() does not work BSS symbols on sparc64. Can you
> please try with this patch:
> 
> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> index 74ede706fb32..0578c5172d4e 100644
> --- a/arch/sparc/include/asm/pgtable_64.h
> +++ b/arch/sparc/include/asm/pgtable_64.h
> @@ -22,6 +22,7 @@
>  #include <asm/adi.h>
>  #include <asm/page.h>
>  #include <asm/processor.h>
> +#include <asm/vaddrs.h>
>  
>  /* The kernel image occupies 0x4000000 to 0x6000000 (4MB --> 96MB).
>   * The page copy blockops can use 0x6000000 to 0x8000000.
> @@ -210,6 +211,11 @@ extern unsigned long _PAGE_CACHE;
>  extern unsigned long pg_iobits;
>  extern unsigned long _PAGE_ALL_SZ_BITS;
>  
> +extern unsigned long kern_base;
> +#define ZERO_PAGE(vaddr)						   \
> +	(virt_to_page(empty_zero_page + ((unsigned long)__va(kern_base)) - \
> +		      ((unsigned long)KERNBASE)))
> +
>  /* PFNs are real physical page numbers.  However, mem_map only begins to record
>   * per-page information starting at pfn_base.  This is to handle systems where
>   * the first physical page in the machine is at some huge physical address,
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index 2bd99944176d..d2d724ba4f83 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -170,6 +170,8 @@ static void __init read_obp_memory(const char *property,
>  
>  /* Kernel physical address base and size in bytes.  */
>  unsigned long kern_base __read_mostly;
> +EXPORT_SYMBOL(kern_base);
> +
>  unsigned long kern_size __read_mostly;
>  
>  /* Initial ramdisk setup */
Hi,

Unfortunately, that does not help. The LDOM goes down in the same fashion.

In QEMU, with or without this extra patch, I get this:

[    3.310674] BUG: Bad page map in process mount  pte:ffffc800016436b0
[    3.310778] pgd:027dc000 p4d:027dc000 pud:027d8000 pmd:0269a000
[    3.311686] addr:000001000020a000 vm_flags:00100077 anon_vma:fffff80002688548 mapping:0000000000000000 index:8000105
[    3.312449] file:(null) fault:0x0 mmap:0x0 mmap_prepare: 0x0 read_folio:0x0
[    3.313622] CPU: 0 UID: 0 PID: 46 Comm: mount Not tainted 6.19.0-rc5-00269-g28acabacf9b0 #22 VOLUNTARY 
[    3.314056] Call Trace:
[    3.314182] [<00000000005e822c>] print_bad_page_map+0x10c/0x260
[    3.314375] [<00000000005e9f30>] vm_normal_page+0x70/0x80
[    3.314400] [<00000000005ea5a8>] unmap_page_range+0x4e8/0x13c0
[    3.314421] [<00000000005eb54c>] unmap_vmas+0x2c/0x120
[    3.314440] [<00000000005f781c>] exit_mmap+0xdc/0x440
[    3.314457] [<000000000047193c>] mmput+0x3c/0x100
[    3.314477] [<0000000000479e94>] do_exit+0x1f4/0xa00
[    3.314494] [<000000000047a83c>] do_group_exit+0x1c/0xa0
[    3.314511] [<0000000000489b28>] get_signal+0x8a8/0x8e0
[    3.314529] [<000000000043be24>] do_notify_resume+0xa4/0x5a0
[    3.314549] [<0000000000404b48>] __handle_signal+0xc/0x30
[    3.314687] Disabling lock debugging due to kernel taint

Cheers,
Andreas

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[David Hildenbrand (arm)]

On 1/24/26 10:56, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
> ZERO_PAGE() to 4.
> 
> Every architecture defines empty_zero_page that way or another, but for the
> most of them it is always a page aligned page in BSS and most definitions
> of ZERO_PAGE do virt_to_page(empty_zero_page).
> 
> Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
> core MM and drop these definitions in architectures that do not implement
> colored zero page (MIPS and s390).
> 
> ZERO_PAGE() remains a macro because turning it to a wrapper for a static
> inline causes severe pain in header dependencies.

That's just what I wanted to ask after looking at it :)

> 
> For the most part the change is mechanical, with these being noteworthy:
> 
> * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
>    parameters. Switching to a generic empty_zero_page removes the aliasing
>    and keeps ZERO_PGE for boot parameters only
> * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
>    ZERO_PAGE() is kept intact.
> * m68k/parisc/sparc64/um: allocated empty_zero_page from memblock,
>    although they do not support zero page coloring and having it in BSS
>    will work fine.
> * sh: used empty_zero_page for boot parameters at the very early boot.
>    Rename the parameters page to boot_params_page and let sh use the generic
>    empty_zero_page.
> * hexagon: had an amusing comment about empty_zero_page
> 
> 	/* A handy thing to have if one has the RAM. Declared in head.S */
> 
>    that unfortunately had to go :)
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

[...]

>   
> +#ifndef __HAVE_COLOR_ZERO_PAGE
> +extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
> +#endif
> +
> +#ifndef ZERO_PAGE
> +#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page))

Took me a second ...

> +#endif
> +
>   #endif /* !__ASSEMBLY__ */
>   
>   #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 1a29a719af58..8ea5b76f317f 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -53,6 +53,15 @@ EXPORT_SYMBOL(mem_map);
>   void *high_memory;
>   EXPORT_SYMBOL(high_memory);
>   
> +#ifndef __HAVE_COLOR_ZERO_PAGE
> +/*
> + * ZERO_PAGE is a global shared page that is always zero: used
> + * for zero-mapped memory areas etc..
> + */

I am not so sure of how much value that comment here is.

... and in particular, why it is not next to ZERO_PAGE in pgtable.h? ;)

> +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;

Is there a good (or historic) reason why this is not simply

uint8_t empty_zero_page[PAGE_SIZE] __page_aligned_bss;

Almost looks to simple, right? So there must be some problem with it :)

> +EXPORT_SYMBOL(empty_zero_page);
> +#endif

Nothing else jumped at me, nice cleanup ... if you get sparc to work :P

-- 
Cheers,

David

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Helge Deller]

On 1/24/26 10:56, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
> ZERO_PAGE() to 4.
> 
...
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
...

>   arch/parisc/include/asm/pgtable.h         | 11 -----------
>   arch/parisc/mm/init.c                     |  6 ------

I reviewed and tested the patch on parisc, so:

Acked-by: Helge Deller <deller@gmx.de>   # parisc
Tested-by: Helge Deller <deller@gmx.de>  # parisc

Thanks!
Helge

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Mike Rapoport]

On Tue, Feb 03, 2026 at 11:17:08AM +0100, Andreas Larsson wrote:
> On 2026-01-27 19:11, Mike Rapoport wrote:
> > On Tue, Jan 27, 2026 at 05:02:39PM +0100, Andreas Larsson wrote:
> >> On 2026-01-24 10:56, Mike Rapoport wrote:
> >>
> >>> Every architecture defines empty_zero_page that way or another, but for the
> >>> most of them it is always a page aligned page in BSS and most definitions
> >>> of ZERO_PAGE do virt_to_page(empty_zero_page).
> >>
> >> Running this in an LDOM on an UltraSparc T4 sparc64, the entire LDOM
> >> hangs after a while during boot.
> >>
> >>> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> >>> index c2d19c9a9244..2bd99944176d 100644
> >>> --- a/arch/sparc/mm/init_64.c
> >>> +++ b/arch/sparc/mm/init_64.c
> >>> @@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64;
> >>>  extern unsigned int sparc_ramdisk_image;
> >>>  extern unsigned int sparc_ramdisk_size;
> >>>  
> >>> -struct page *mem_map_zero __read_mostly;
> >>> -EXPORT_SYMBOL(mem_map_zero);
> >>> -
> >>>  unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
> >>>  
> >>>  unsigned long sparc64_kern_pri_context __read_mostly;
> >>> @@ -2506,18 +2503,6 @@ void __init mem_init(void)
> >>>  	 */
> >>>  	register_page_bootmem_info();
> >>>  
> >>> -	/*
> >>> -	 * Set up the zero page, mark it reserved, so that page count
> >>> -	 * is not manipulated when freeing the page from user ptes.
> >>> -	 */
> >>> -	mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
> >>> -	if (mem_map_zero == NULL) {
> >>> -		prom_printf("paging_init: Cannot alloc zero page.\n");
> >>> -		prom_halt();
> >>> -	}
> >>> -	mark_page_reserved(mem_map_zero);
> >>> -
> >>> -
> >>>  	if (tlb_type == cheetah || tlb_type == cheetah_plus)
> >>>  		cheetah_ecache_flush_init();
> >>>  }
> >>
> >> This just removes the mark_page_reserved(mem_map_zero) without 
> >> replacing it with something corresponding to that. Perhaps part
> >> of the problem?
> > 
> > I don't think so, empty_zero_page is in BSS now an it's reserved as a part
> > of the kernel image.
> > 
> > I suspect that virt_to_page() does not work BSS symbols on sparc64. Can you
> > please try with this patch:
> > 
> > diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> > index 74ede706fb32..0578c5172d4e 100644
> > --- a/arch/sparc/include/asm/pgtable_64.h
> > +++ b/arch/sparc/include/asm/pgtable_64.h
> > @@ -22,6 +22,7 @@
> >  #include <asm/adi.h>
> >  #include <asm/page.h>
> >  #include <asm/processor.h>
> > +#include <asm/vaddrs.h>
> >  
> >  /* The kernel image occupies 0x4000000 to 0x6000000 (4MB --> 96MB).
> >   * The page copy blockops can use 0x6000000 to 0x8000000.
> > @@ -210,6 +211,11 @@ extern unsigned long _PAGE_CACHE;
> >  extern unsigned long pg_iobits;
> >  extern unsigned long _PAGE_ALL_SZ_BITS;
> >  
> > +extern unsigned long kern_base;
> > +#define ZERO_PAGE(vaddr)						   \
> > +	(virt_to_page(empty_zero_page + ((unsigned long)__va(kern_base)) - \
> > +		      ((unsigned long)KERNBASE)))
> > +
> >  /* PFNs are real physical page numbers.  However, mem_map only begins to record
> >   * per-page information starting at pfn_base.  This is to handle systems where
> >   * the first physical page in the machine is at some huge physical address,
> > diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> > index 2bd99944176d..d2d724ba4f83 100644
> > --- a/arch/sparc/mm/init_64.c
> > +++ b/arch/sparc/mm/init_64.c
> > @@ -170,6 +170,8 @@ static void __init read_obp_memory(const char *property,
> >  
> >  /* Kernel physical address base and size in bytes.  */
> >  unsigned long kern_base __read_mostly;
> > +EXPORT_SYMBOL(kern_base);
> > +
> >  unsigned long kern_size __read_mostly;
> >  
> >  /* Initial ramdisk setup */
> Hi,
> 
> Unfortunately, that does not help. The LDOM goes down in the same fashion.

Apparently something is wrong with my pointer arithmetics :/

Can you try this one instead?

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 74ede706fb32..615f460c50af 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -210,6 +210,9 @@ extern unsigned long _PAGE_CACHE;
 extern unsigned long pg_iobits;
 extern unsigned long _PAGE_ALL_SZ_BITS;
 
+extern struct page *mem_map_zero;
+#define ZERO_PAGE(vaddr)	(mem_map_zero)
+
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 2bd99944176d..aa1f9f071fb2 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -177,6 +177,9 @@ extern unsigned long sparc_ramdisk_image64;
 extern unsigned int sparc_ramdisk_image;
 extern unsigned int sparc_ramdisk_size;
 
+struct page *mem_map_zero __read_mostly;
+EXPORT_SYMBOL(mem_map_zero);
+
 unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
 
 unsigned long sparc64_kern_pri_context __read_mostly;
@@ -2495,6 +2498,9 @@ static void __init register_page_bootmem_info(void)
 }
 void __init mem_init(void)
 {
+	phys_addr_t zero_page_pa = kern_base +
+		((unsigned long)&empty_zero_page[0] - KERNBASE);
+
 	/*
 	 * Must be done after boot memory is put on freelist, because here we
 	 * might set fields in deferred struct pages that have not yet been
@@ -2503,6 +2509,12 @@ void __init mem_init(void)
 	 */
 	register_page_bootmem_info();
 
+	/*
+	 * Set up the zero page, mark it reserved, so that page count
+	 * is not manipulated when freeing the page from user ptes.
+	 */
+	mem_map_zero = pfn_to_page(PHYS_PFN(zero_page_pa));
+
 	if (tlb_type == cheetah || tlb_type == cheetah_plus)
 		cheetah_ecache_flush_init();
 }

-- 
Sincerely yours,
Mike.

Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

[Andreas Larsson]

On 2026-02-07 11:36, Mike Rapoport wrote:
>> Unfortunately, that does not help. The LDOM goes down in the same fashion.
> 
> Apparently something is wrong with my pointer arithmetics :/
> 
> Can you try this one instead?
> 
> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> index 74ede706fb32..615f460c50af 100644
> --- a/arch/sparc/include/asm/pgtable_64.h
> +++ b/arch/sparc/include/asm/pgtable_64.h
> @@ -210,6 +210,9 @@ extern unsigned long _PAGE_CACHE;
>  extern unsigned long pg_iobits;
>  extern unsigned long _PAGE_ALL_SZ_BITS;
>  
> +extern struct page *mem_map_zero;
> +#define ZERO_PAGE(vaddr)	(mem_map_zero)
> +
>  /* PFNs are real physical page numbers.  However, mem_map only begins to record
>   * per-page information starting at pfn_base.  This is to handle systems where
>   * the first physical page in the machine is at some huge physical address,
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index 2bd99944176d..aa1f9f071fb2 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -177,6 +177,9 @@ extern unsigned long sparc_ramdisk_image64;
>  extern unsigned int sparc_ramdisk_image;
>  extern unsigned int sparc_ramdisk_size;
>  
> +struct page *mem_map_zero __read_mostly;
> +EXPORT_SYMBOL(mem_map_zero);
> +
>  unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly;
>  
>  unsigned long sparc64_kern_pri_context __read_mostly;
> @@ -2495,6 +2498,9 @@ static void __init register_page_bootmem_info(void)
>  }
>  void __init mem_init(void)
>  {
> +	phys_addr_t zero_page_pa = kern_base +
> +		((unsigned long)&empty_zero_page[0] - KERNBASE);
> +
>  	/*
>  	 * Must be done after boot memory is put on freelist, because here we
>  	 * might set fields in deferred struct pages that have not yet been
> @@ -2503,6 +2509,12 @@ void __init mem_init(void)
>  	 */
>  	register_page_bootmem_info();
>  
> +	/*
> +	 * Set up the zero page, mark it reserved, so that page count
> +	 * is not manipulated when freeing the page from user ptes.
> +	 */
> +	mem_map_zero = pfn_to_page(PHYS_PFN(zero_page_pa));
> +
>  	if (tlb_type == cheetah || tlb_type == cheetah_plus)
>  		cheetah_ecache_flush_init();
>  }
> 

With that one, things work fine.

Cheers,
Andreas