From patchwork Sun Sep 18 07:59:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yu Zhao X-Patchwork-Id: 12979341 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0B34C6FA86 for ; Sun, 18 Sep 2022 08:01:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3EBDB80009; Sun, 18 Sep 2022 04:01:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 375CA80007; Sun, 18 Sep 2022 04:01:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 215BF80009; Sun, 18 Sep 2022 04:01:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 10D5D80007 for ; Sun, 18 Sep 2022 04:01:04 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D9B43C0902 for ; Sun, 18 Sep 2022 08:01:03 +0000 (UTC) X-FDA: 79924460406.23.67FB22D Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) by imf07.hostedemail.com (Postfix) with ESMTP id 8B5224000F for ; Sun, 18 Sep 2022 08:01:03 +0000 (UTC) Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-345482ec6adso228669487b3.18 for ; Sun, 18 Sep 2022 01:01:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=content-transfer-encoding:cc:to:from:subject:references :mime-version:message-id:in-reply-to:date:from:to:cc:subject:date; bh=uIpsnmF4pNNpvR9FKSQcBNh3dSBTINaFrnzbo+6oRAg=; b=M5OlAAGs2fywmBJkqUW8xQU8ESvfwt9KXOemBgMx/g9hQaZfzZ3rO2rdtAm4cpUQal Vnrw+b1IUemxH+Ljuc+qbvwiBT2pGjXZCyH2Gh3j04sniGZIdX50sbtO+q5T2sOuQ4n2 aYuDiQn9J/bDJ9e2hBNeErl7HcHdtnsAbUK9mcTEH51Q6roLy3MUuKMOpl16upXIT/SX o8opMqf/LtvsyqcC1HYfcpAoQjUKLceb0a2xIslpw/AmUrjT1UDWfeRLZPfV6PvidVyx 4SSREpkn/esT+X4LMKRidEhVI2rZxPgfDFh8vlCOpJ9QJICJsOLCoQtJBQlmjnXuVjcx ggMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:from:subject:references :mime-version:message-id:in-reply-to:date:x-gm-message-state:from:to :cc:subject:date; bh=uIpsnmF4pNNpvR9FKSQcBNh3dSBTINaFrnzbo+6oRAg=; b=qoJ/wFg0GOKxQlMPQVvFuqkIfnYUAYu/TDxJHvAzrOfBY15mPZnUHDAFIxlnnTUfIA MTUTRlgYDMHBnGwQvvwMgRNgaTQshV0gHkM9znHREE2Bec9UCgbdfEXUYRl1Q+R8DE4l waZmtrP9y9YoDXtDk5EKZ/GYVzai8CDYm7m7d4qKpLe5REOWg8aUrMr6agKm9Mz0ROjJ 8oIAh0k3zRoWcKYt4avtgOWzvX8qDyEABx5NF9eywWaQ3hLPpM0bmEAb931g+GxBiPUz czgMnqnnwJPzJXWv/786dOA5Hxr+yAXLa110tgTvpHgqOZe2cqMh5dAqTCIAZjUQQ/X5 BU6Q== X-Gm-Message-State: ACrzQf0I0na9/sH6bAkp0hyUKmVhLhOQpeBs0qIDwJOYkj88ou3p4IeY N8yZUtTbmMI7qLbVFY+CrD95JUcOO30= X-Google-Smtp-Source: AMsMyM7r1OVVUX7lLJyqN55p0VnSmQAzgbkGpq4C8t658Vtuup4oMaaDN5OfPJBh3x8L6K/+LeaSKp4wk1A= X-Received: from yuzhao.bld.corp.google.com ([2620:15c:183:200:c05a:2e99:29cd:d157]) (user=yuzhao job=sendgmr) by 2002:a25:2d46:0:b0:6a8:72b2:a4db with SMTP id s6-20020a252d46000000b006a872b2a4dbmr10415982ybe.468.1663488062637; Sun, 18 Sep 2022 01:01:02 -0700 (PDT) Date: Sun, 18 Sep 2022 01:59:58 -0600 In-Reply-To: <20220918080010.2920238-1-yuzhao@google.com> Message-Id: <20220918080010.2920238-2-yuzhao@google.com> Mime-Version: 1.0 References: <20220918080010.2920238-1-yuzhao@google.com> X-Mailer: git-send-email 2.37.3.968.ga6b4b080e4-goog Subject: [PATCH mm-unstable v15 01/14] mm: x86, arm64: add arch_has_hw_pte_young() From: Yu Zhao To: Andrew Morton Cc: Andi Kleen , Aneesh Kumar , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , Linus Torvalds , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Peter Zijlstra , Tejun Heo , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, page-reclaim@google.com, Yu Zhao , Barry Song , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , " =?utf-8?q?Holger_Hoffst=C3=A4tte?= " , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663488063; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=uIpsnmF4pNNpvR9FKSQcBNh3dSBTINaFrnzbo+6oRAg=; b=YPWNNIKdXZu3YhgqiQr9EH/wPBw/lCC5JvssqxUju/8MRYNh6CLqrFtiVoXpdWqOaYdRfm tRlu24g4Z2TAroRKMODiYyHPDK04Z7hsyPkD8rd/jdsyRodJT+qPvtdrdPNahx+VZTayxV OiwFrjVHeFKBIWxlbTn0m6/EZHxfjTg= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=M5OlAAGs; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of 3PtAmYwYKCJkRNSA3H9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--yuzhao.bounces.google.com designates 209.85.128.202 as permitted sender) smtp.mailfrom=3PtAmYwYKCJkRNSA3H9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--yuzhao.bounces.google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663488063; a=rsa-sha256; cv=none; b=SbYxalUu/Ia5TG6PQgOEkW6fHxZ/8nKY/8I6igTxsgPW9loJ63MvC+miL4poqp/VaE84U4 OTItJD2YJjLCP5znRuoxtHFi0fxteiNnerlz0ToyyUvrsGZvtFeAYs439l6hLy5gRC/BIm 1VXQb+mGIwwHxDw9TZNId3DQdbduEBU= X-Stat-Signature: 9jn7pmj6iqtaxf55utkzco7np5xecdat X-Rspamd-Queue-Id: 8B5224000F Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=M5OlAAGs; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of 3PtAmYwYKCJkRNSA3H9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--yuzhao.bounces.google.com designates 209.85.128.202 as permitted sender) smtp.mailfrom=3PtAmYwYKCJkRNSA3H9HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--yuzhao.bounces.google.com X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1663488063-549913 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Some architectures automatically set the accessed bit in PTEs, e.g., x86 and arm64 v8.2. On architectures that do not have this capability, clearing the accessed bit in a PTE usually triggers a page fault following the TLB miss of this PTE (to emulate the accessed bit). Being aware of this capability can help make better decisions, e.g., whether to spread the work out over a period of time to reduce bursty page faults when trying to clear the accessed bit in many PTEs. Note that theoretically this capability can be unreliable, e.g., hotplugged CPUs might be different from builtin ones. Therefore it should not be used in architecture-independent code that involves correctness, e.g., to determine whether TLB flushes are required (in combination with the accessed bit). Signed-off-by: Yu Zhao Reviewed-by: Barry Song Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Acked-by: Will Deacon Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain --- arch/arm64/include/asm/pgtable.h | 15 ++------------- arch/x86/include/asm/pgtable.h | 6 +++--- include/linux/pgtable.h | 13 +++++++++++++ mm/memory.c | 14 +------------- 4 files changed, 19 insertions(+), 29 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index b5df82aa99e6..71a1af42f0e8 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1082,24 +1082,13 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, * page after fork() + CoW for pfn mappings. We don't always have a * hardware-managed access flag on arm64. */ -static inline bool arch_faults_on_old_pte(void) -{ - /* The register read below requires a stable CPU to make any sense */ - cant_migrate(); - - return !cpu_has_hw_af(); -} -#define arch_faults_on_old_pte arch_faults_on_old_pte +#define arch_has_hw_pte_young cpu_has_hw_af /* * Experimentally, it's cheap to set the access flag in hardware and we * benefit from prefaulting mappings as 'old' to start with. */ -static inline bool arch_wants_old_prefaulted_pte(void) -{ - return !arch_faults_on_old_pte(); -} -#define arch_wants_old_prefaulted_pte arch_wants_old_prefaulted_pte +#define arch_wants_old_prefaulted_pte cpu_has_hw_af static inline bool pud_sect_supported(void) { diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 44e2d6f1dbaa..dc5f7d8ef68a 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1431,10 +1431,10 @@ static inline bool arch_has_pfn_modify_check(void) return boot_cpu_has_bug(X86_BUG_L1TF); } -#define arch_faults_on_old_pte arch_faults_on_old_pte -static inline bool arch_faults_on_old_pte(void) +#define arch_has_hw_pte_young arch_has_hw_pte_young +static inline bool arch_has_hw_pte_young(void) { - return false; + return true; } #ifdef CONFIG_PAGE_TABLE_CHECK diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index d13b4f7cc5be..375e8e7e64f4 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -260,6 +260,19 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif +#ifndef arch_has_hw_pte_young +/* + * Return whether the accessed bit is supported on the local CPU. + * + * This stub assumes accessing through an old PTE triggers a page fault. + * Architectures that automatically set the access bit should overwrite it. + */ +static inline bool arch_has_hw_pte_young(void) +{ + return false; +} +#endif + #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long address, diff --git a/mm/memory.c b/mm/memory.c index e38f9245470c..3a9b00c765c2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -126,18 +126,6 @@ int randomize_va_space __read_mostly = 2; #endif -#ifndef arch_faults_on_old_pte -static inline bool arch_faults_on_old_pte(void) -{ - /* - * Those arches which don't have hw access flag feature need to - * implement their own helper. By default, "true" means pagefault - * will be hit on old pte. - */ - return true; -} -#endif - #ifndef arch_wants_old_prefaulted_pte static inline bool arch_wants_old_prefaulted_pte(void) { @@ -2871,7 +2859,7 @@ static inline bool __wp_page_copy_user(struct page *dst, struct page *src, * On architectures with software "accessed" bits, we would * take a double page fault, so mark it accessed here. */ - if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { + if (!arch_has_hw_pte_young() && !pte_young(vmf->orig_pte)) { pte_t entry; vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);