From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:33139 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967342AbcA1Kwv (ORCPT ); Thu, 28 Jan 2016 05:52:51 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: Will Deacon , Greg Kroah-Hartman Subject: [patch added to 3.12-stable] arm64: mm: ensure that the zero page is visible to the page table walker Date: Thu, 28 Jan 2016 11:52:19 +0100 Message-Id: <1453978346-20237-28-git-send-email-jslaby@suse.cz> In-Reply-To: <1453978346-20237-1-git-send-email-jslaby@suse.cz> References: <1453978346-20237-1-git-send-email-jslaby@suse.cz> Sender: stable-owner@vger.kernel.org List-ID: From: Will Deacon This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== commit 32d6397805d00573ce1fa55f408ce2bca15b0ad3 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 Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/mmu.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index f8dc7e8fce6f..84ddb372fbc6 100644 --- 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(); + /* * TTBR0 is only used for the identity mapping at this stage. Make it * point to zero page to avoid speculatively fetching new entries. -- 2.7.0