From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39639C4361B for ; Wed, 9 Dec 2020 16:41:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1B5623BCD for ; Wed, 9 Dec 2020 16:41:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732047AbgLIQks (ORCPT ); Wed, 9 Dec 2020 11:40:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:44384 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731923AbgLIQkl (ORCPT ); Wed, 9 Dec 2020 11:40:41 -0500 From: Will Deacon Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Will Deacon , Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , "Kirill A . Shutemov" , Linus Torvalds , Vinayak Menon , kernel-team@android.com Subject: [PATCH 2/2] arm64: mm: Implement arch_wants_old_faultaround_pte() Date: Wed, 9 Dec 2020 16:39:50 +0000 Message-Id: <20201209163950.8494-3-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201209163950.8494-1-will@kernel.org> References: <20201209163950.8494-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On CPUs with hardware AF/DBM, initialising prefaulted PTEs as 'old' improves vmscan behaviour and does not appear to introduce any overhead. Implement arch_wants_old_faultaround_pte() to return 'true' if we detect hardware access flag support at runtime. This can be extended in future based on MIDR matching if necessary. Cc: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/include/asm/cpufeature.h | 12 ++++++++++++ arch/arm64/include/asm/pgtable.h | 8 +++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index da250e4741bd..3424f5881390 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -764,6 +764,18 @@ static inline bool cpu_has_hw_af(void) ID_AA64MMFR1_HADBS_SHIFT); } +static inline bool system_has_hw_af(void) +{ + u64 mmfr1; + + if (!IS_ENABLED(CONFIG_ARM64_HW_AFDBM)) + return false; + + mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1); + return cpuid_feature_extract_unsigned_field(mmfr1, + ID_AA64MMFR1_HADBS_SHIFT); +} + #ifdef CONFIG_ARM64_AMU_EXTN /* Check whether the cpu supports the Activity Monitors Unit (AMU) */ extern bool cpu_has_amu_feat(int cpu); diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 5628289b9d5e..d5c2a7625e9a 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -974,7 +974,13 @@ static inline bool arch_faults_on_old_pte(void) return !cpu_has_hw_af(); } -#define arch_faults_on_old_pte arch_faults_on_old_pte +#define arch_faults_on_old_pte arch_faults_on_old_pte + +/* + * Experimentally, it's cheap to set the access flag in hardware and we + * benefit from prefaulting mappings as 'old' to start with. + */ +#define arch_wants_old_faultaround_pte system_has_hw_af #endif /* !__ASSEMBLY__ */ -- 2.29.2.576.ga3fc446d84-goog