arm64: mm: ensure that the zero page is visible to the page table walker

commit 32d6397 upstream. In paging_init, we allocate the zero page, memset it to zero and then point TTBR0 to it in order to avoid speculative fetches through the identity mapping. In order to guarantee that the freshly zeroed page is indeed visible to the page table walker, we need to execute a dsb instruction prior to writing the TTBR. Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
Freescale · Jan 29, 2016 · c05b439 · c05b439
1 parent c87aa8c
commit c05b439
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
@@ -374,6 +374,9 @@ void __init paging_init(void)
 
 	empty_zero_page = virt_to_page(zero_page);
 
+	/* Ensure the zero page is visible to the page table walker */
+	dsb(ishst);
+
 	/*
 	 * TTBR0 is only used for the identity mapping at this stage. Make it
 	 * point to zero page to avoid speculatively fetching new entries.