From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752367AbdBEQRQ (ORCPT ); Sun, 5 Feb 2017 11:17:16 -0500 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:56684 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751883AbdBEQOd (ORCPT ); Sun, 5 Feb 2017 11:14:33 -0500 X-ME-Sender: X-Sasl-enc: Snl+K3SNVQwgE3p1mpY+RrOB3tIehqCikxSRmGOsxz8j 1486311273 From: Zi Yan To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kirill.shutemov@linux.intel.com Cc: akpm@linux-foundation.org, minchan@kernel.org, vbabka@suse.cz, mgorman@techsingularity.net, n-horiguchi@ah.jp.nec.com, khandual@linux.vnet.ibm.com, zi.yan@cs.rutgers.edu Subject: [PATCH v3 04/14] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1 Date: Sun, 5 Feb 2017 11:12:42 -0500 Message-Id: <20170205161252.85004-5-zi.yan@sent.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170205161252.85004-1-zi.yan@sent.com> References: <20170205161252.85004-1-zi.yan@sent.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Naoya Horiguchi pmd_present() checks _PAGE_PSE along with _PAGE_PRESENT to avoid false negative return when it races with thp spilt (during which _PAGE_PRESENT is temporary cleared.) I don't think that dropping _PAGE_PSE check in pmd_present() works well because it can hurt optimization of tlb handling in thp split. In the current kernel, bits 1-4 are not used in non-present format since commit 00839ee3b299 ("x86/mm: Move swap offset/type up in PTE to work around erratum"). So let's move _PAGE_SWP_SOFT_DIRTY to bit 1. Bit 7 is used as reserved (always clear), so please don't use it for other purpose. Signed-off-by: Naoya Horiguchi ChangeLog v3: - Move _PAGE_SWP_SOFT_DIRTY to bit 1, it was placed at bit 6. Because some CPUs might accidentally set bit 5 or 6. Signed-off-by: Zi Yan --- arch/x86/include/asm/pgtable_types.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index 8b4de22d6429..3695abd58ef6 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -97,15 +97,15 @@ /* * Tracking soft dirty bit when a page goes to a swap is tricky. * We need a bit which can be stored in pte _and_ not conflict - * with swap entry format. On x86 bits 6 and 7 are *not* involved - * into swap entry computation, but bit 6 is used for nonlinear - * file mapping, so we borrow bit 7 for soft dirty tracking. + * with swap entry format. On x86 bits 1-4 are *not* involved + * into swap entry computation, but bit 7 is used for thp migration, + * so we borrow bit 1 for soft dirty tracking. * * Please note that this bit must be treated as swap dirty page - * mark if and only if the PTE has present bit clear! + * mark if and only if the PTE/PMD has present bit clear! */ #ifdef CONFIG_MEM_SOFT_DIRTY -#define _PAGE_SWP_SOFT_DIRTY _PAGE_PSE +#define _PAGE_SWP_SOFT_DIRTY _PAGE_RW #else #define _PAGE_SWP_SOFT_DIRTY (_AT(pteval_t, 0)) #endif -- 2.11.0