[PATCH v3 04/29] arm: make initialization of zero page independent of the memory map
From: Mike Rapoport <rppt@kernel.org>
Date: 2026-01-11 08:22:24
Also in:
linux-alpha, linux-cxl, linux-doc, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, loongarch, sparclinux
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
From: Klara Modin <redacted> Unlike most architectures, arm keeps a struct page pointer to the empty_zero_page and to initialize it requires conversion of a virtual address to page which makes it necessary to have memory map initialized before creating the empty_zero_page. Make empty_zero_page a stataic array in BSS to decouple it's initialization from the initialization of the memory map. This also aligns arm with vast majorty of architectures. Signed-off-by: Klara Modin <redacted> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org> --- arch/arm/include/asm/pgtable.h | 4 ++-- arch/arm/mm/mmu.c | 10 +--------- arch/arm/mm/nommu.c | 10 +--------- 3 files changed, 4 insertions(+), 20 deletions(-)
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 86378eec7757..6fa9acd6a7f5 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h@@ -15,8 +15,8 @@ * ZERO_PAGE is a global shared page that is always zero: used * for zero-mapped memory areas etc.. */ -extern struct page *empty_zero_page; -#define ZERO_PAGE(vaddr) (empty_zero_page) +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>
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 8bac96e205ac..518def8314e7 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c@@ -45,7 +45,7 @@ extern unsigned long __atags_pointer; * empty_zero_page is a special page that is used for * zero-initialized data and COW. */ -struct page *empty_zero_page; +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); /*
@@ -1754,8 +1754,6 @@ static void __init early_fixmap_shutdown(void) */ void __init paging_init(const struct machine_desc *mdesc) { - void *zero_page; - #ifdef CONFIG_XIP_KERNEL /* Store the kernel RW RAM region start/end in these variables */ kernel_sec_start = CONFIG_PHYS_OFFSET & SECTION_MASK;
@@ -1781,13 +1779,7 @@ void __init paging_init(const struct machine_desc *mdesc) top_pmd = pmd_off_k(0xffff0000); - /* allocate the zero page. */ - zero_page = early_alloc(PAGE_SIZE); - bootmem_init(); - - empty_zero_page = virt_to_page(zero_page); - __flush_dcache_folio(NULL, page_folio(empty_zero_page)); } void __init early_mm_init(const struct machine_desc *mdesc)
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index d638cc87807e..7e42d8accec6 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c@@ -31,7 +31,7 @@ unsigned long vectors_base; * empty_zero_page is a special page that is used for * zero-initialized data and COW. */ -struct page *empty_zero_page; +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); #ifdef CONFIG_ARM_MPU
@@ -156,18 +156,10 @@ void __init adjust_lowmem_bounds(void) */ void __init paging_init(const struct machine_desc *mdesc) { - void *zero_page; - early_trap_init((void *)vectors_base); mpu_setup(); - /* allocate the zero page. */ - zero_page = (void *)memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE); - bootmem_init(); - - empty_zero_page = virt_to_page(zero_page); - flush_dcache_page(empty_zero_page); } /*
--
2.51.0