[PATCH v3 3/5] arm64/mm: Create initial page tables in init_pg_dir

[Jun Yao]

Create initial page tables in init_pg_dir and then create final
page tables in swapper_pg_dir directly.

Signed-off-by: Jun Yao <yaojun8558363@xxxxxxxxx>
---
 arch/arm64/include/asm/pgtable.h |  2 ++
 arch/arm64/kernel/head.S         |  4 ++--
 arch/arm64/kernel/setup.c        |  1 +
 arch/arm64/mm/mmu.c              | 24 ++++--------------------
 4 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7c4c8f318ba9..3b408f21fe2e 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -718,6 +718,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
 }
 #endif
 
+extern pgd_t init_pg_dir[PTRS_PER_PGD] __section(.init.data);
+extern pgd_t init_pg_end[] __section(.init.data);
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 extern pgd_t swapper_pg_end[];
 extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index a1c7a4d3b9f3..a8e9432ffa8a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -380,7 +380,7 @@ __create_page_tables:
 	/*
 	 * Map the kernel image (starting with PHYS_OFFSET).
 	 */
-	adrp	x0, swapper_pg_dir
+	adrp	x0, init_pg_dir
 	mov_q	x5, KIMAGE_VADDR + TEXT_OFFSET	// compile time __va(_text)
 	add	x5, x5, x23			// add KASLR displacement
 	mov	x4, PTRS_PER_PGD
@@ -837,7 +837,7 @@ __primary_switch:
 	mrs	x20, sctlr_el1			// preserve old SCTLR_EL1 value
 #endif
 
-	adrp	x26, swapper_pg_dir
+	adrp	x26, init_pg_dir
 	bl	__enable_mmu
 #ifdef CONFIG_RELOCATABLE
 	bl	__relocate_kernel
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 30ad2f085d1f..b065c08d4008 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -249,6 +249,7 @@ void __init setup_arch(char **cmdline_p)
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
 	init_mm.brk	   = (unsigned long) _end;
+	init_mm.pgd	   = init_pg_dir;
 
 	*cmdline_p = boot_command_line;
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9f1ec1..a7ab0010ff80 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -628,26 +628,10 @@ static void __init map_kernel(pgd_t *pgdp)
  */
 void __init paging_init(void)
 {
-	phys_addr_t pgd_phys = early_pgtable_alloc();
-	pgd_t *pgdp = pgd_set_fixmap(pgd_phys);
-
-	map_kernel(pgdp);
-	map_mem(pgdp);
-
-	/*
-	 * We want to reuse the original swapper_pg_dir so we don't have to
-	 * communicate the new address to non-coherent secondaries in
-	 * secondary_entry, and so cpu_switch_mm can generate the address with
-	 * adrp+add rather than a load from some global variable.
-	 *
-	 * To do this we need to go via a temporary pgd.
-	 */
-	cpu_replace_ttbr1(__va(pgd_phys));
-	memcpy(swapper_pg_dir, pgdp, PGD_SIZE);
-	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
-
-	pgd_clear_fixmap();
-	memblock_free(pgd_phys, PAGE_SIZE);
+	map_kernel(swapper_pg_dir);
+	map_mem(swapper_pg_dir);
+	cpu_replace_ttbr1(swapper_pg_dir);
+	init_mm.pgd = swapper_pg_dir;
 
 	/*
 	 * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
-- 
2.17.1