[PATCH 3/3] arm64: mmu: pgd_pgtable_alloc: drop barrier

[Peng Fan]

The barriers are added for empty_zero_page, however the
empty zero page has been moved to bss area by
commit 5227cfa71f9e ("arm64: mm: place empty_zero_page in bss"),
and it alreay added "dsb     ishst" in head.S to make sure
the empty zero page visible to PTW.

pgd_pgtable_alloc is only called by __create_pgd_mapping, and
there are implicit barriers in __create_pgd_mapping, so we
could remove the barrier pgd_pgtable_alloc

Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
---

Note: this patch tested on qemu-system-aarch64, not real hardware.

 arch/arm64/mm/mmu.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f61fa7c8fd2e..04e3d4d070ce 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -371,8 +371,6 @@ static phys_addr_t pgd_pgtable_alloc(void)
 	if (!ptr || !pgtable_page_ctor(virt_to_page(ptr)))
 		BUG();
 
-	/* Ensure the zeroed page is visible to the page table walker */
-	dsb(ishst);
 	return __pa(ptr);
 }
 
-- 
2.16.4