linux-kernel - [PATCH v5 4/6] arm64/mm: Create the final page table directly in swapper_pg

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Date:   Mon, 17 Sep 2018 12:43:31 +0800
From:   Jun Yao <yaojun8558363@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will.deacon@....com, james.morse@....com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 4/6] arm64/mm: Create the final page table directly in swapper_pg_dir.

As the initial page table is created in the init_pg_dir, we can set
up the final page table directly in the swapper_pg_dir. And it only
contains the top level page table, so we can reduce it to a page
size.

Signed-off-by: Jun Yao <yaojun8558363@...il.com>
---
 arch/arm64/kernel/vmlinux.lds.S |  2 +-
 arch/arm64/mm/mmu.c             | 29 ++---------------------------
 2 files changed, 3 insertions(+), 28 deletions(-)

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 612ffc0bbe11..a634def77442 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -237,7 +237,7 @@ SECTIONS
 	. += RESERVED_TTBR0_SIZE;
 #endif
 	swapper_pg_dir = .;
-	. += SWAPPER_DIR_SIZE;
+	. += PAGE_SIZE;
 	swapper_pg_end = .;
 
 	__pecoff_data_size = ABSOLUTE(. - __initdata_begin);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index af80dca335ce..71532bcd76c1 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -629,35 +629,10 @@ 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);
+	map_kernel(swapper_pg_dir);
+	map_mem(swapper_pg_dir);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 	init_mm.pgd = swapper_pg_dir;
-
-	pgd_clear_fixmap();
-	memblock_free(pgd_phys, PAGE_SIZE);
-
-	/*
-	 * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
-	 * allocated with it.
-	 */
-	memblock_free(__pa_symbol(swapper_pg_dir) + PAGE_SIZE,
-		      __pa_symbol(swapper_pg_end) - __pa_symbol(swapper_pg_dir)
-		      - PAGE_SIZE);
 }
 
 /*
-- 
2.17.1