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=-13.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 DDC9DC433DF for ; Fri, 21 Aug 2020 08:22:49 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 531FC20639 for ; Fri, 21 Aug 2020 08:22:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 531FC20639 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BXvdy714ZzDql6 for ; Fri, 21 Aug 2020 18:22:46 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=anshuman.khandual@arm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=arm.com Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4BXvbt4fxNzDqd7 for ; Fri, 21 Aug 2020 18:20:56 +1000 (AEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 051C230E; Fri, 21 Aug 2020 01:20:55 -0700 (PDT) Received: from [10.163.67.49] (unknown [10.163.67.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 46EDE3F66B; Fri, 21 Aug 2020 01:20:53 -0700 (PDT) Subject: Re: [PATCH v2 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry To: "Aneesh Kumar K.V" , Christophe Leroy , linux-mm@kvack.org, akpm@linux-foundation.org References: <20200819130107.478414-1-aneesh.kumar@linux.ibm.com> <20200819130107.478414-8-aneesh.kumar@linux.ibm.com> <3d966519-0a6b-3ccb-fd21-b7f06c8e4df7@linux.ibm.com> From: Anshuman Khandual Message-ID: <5a7f6dd1-eb13-d942-6fab-80265cd421fc@arm.com> Date: Fri, 21 Aug 2020 13:50:22 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <3d966519-0a6b-3ccb-fd21-b7f06c8e4df7@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 08/21/2020 12:44 PM, Aneesh Kumar K.V wrote: > On 8/20/20 8:02 PM, Christophe Leroy wrote: >> >> >> Le 19/08/2020 à 15:01, Aneesh Kumar K.V a écrit : >>> set_pte_at() should not be used to set a pte entry at locations that >>> already holds a valid pte entry. Architectures like ppc64 don't do TLB >>> invalidate in set_pte_at() and hence expect it to be used to set locations >>> that are not a valid PTE. >>> >>> Signed-off-by: Aneesh Kumar K.V >>> --- >>>   mm/debug_vm_pgtable.c | 35 +++++++++++++++-------------------- >>>   1 file changed, 15 insertions(+), 20 deletions(-) >>> >>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >>> index 76f4c713e5a3..9c7e2c9cfc76 100644 >>> --- a/mm/debug_vm_pgtable.c >>> +++ b/mm/debug_vm_pgtable.c >>> @@ -74,15 +74,18 @@ static void __init pte_advanced_tests(struct mm_struct *mm, >>>   { >>>       pte_t pte = pfn_pte(pfn, prot); >>> +    /* >>> +     * Architectures optimize set_pte_at by avoiding TLB flush. >>> +     * This requires set_pte_at to be not used to update an >>> +     * existing pte entry. Clear pte before we do set_pte_at >>> +     */ >>> + >>>       pr_debug("Validating PTE advanced\n"); >>>       pte = pfn_pte(pfn, prot); >>>       set_pte_at(mm, vaddr, ptep, pte); >>>       ptep_set_wrprotect(mm, vaddr, ptep); >>>       pte = ptep_get(ptep); >>>       WARN_ON(pte_write(pte)); >>> - >>> -    pte = pfn_pte(pfn, prot); >>> -    set_pte_at(mm, vaddr, ptep, pte); >>>       ptep_get_and_clear(mm, vaddr, ptep); >>>       pte = ptep_get(ptep); >>>       WARN_ON(!pte_none(pte)); >>> @@ -96,13 +99,11 @@ static void __init pte_advanced_tests(struct mm_struct *mm, >>>       ptep_set_access_flags(vma, vaddr, ptep, pte, 1); >>>       pte = ptep_get(ptep); >>>       WARN_ON(!(pte_write(pte) && pte_dirty(pte))); >>> - >>> -    pte = pfn_pte(pfn, prot); >>> -    set_pte_at(mm, vaddr, ptep, pte); >>>       ptep_get_and_clear_full(mm, vaddr, ptep, 1); >>>       pte = ptep_get(ptep); >>>       WARN_ON(!pte_none(pte)); >>> +    pte = pfn_pte(pfn, prot); >>>       pte = pte_mkyoung(pte); >>>       set_pte_at(mm, vaddr, ptep, pte); >>>       ptep_test_and_clear_young(vma, vaddr, ptep); >>> @@ -164,9 +165,6 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, >>>       pmdp_set_wrprotect(mm, vaddr, pmdp); >>>       pmd = READ_ONCE(*pmdp); >>>       WARN_ON(pmd_write(pmd)); >>> - >>> -    pmd = pmd_mkhuge(pfn_pmd(pfn, prot)); >>> -    set_pmd_at(mm, vaddr, pmdp, pmd); >>>       pmdp_huge_get_and_clear(mm, vaddr, pmdp); >>>       pmd = READ_ONCE(*pmdp); >>>       WARN_ON(!pmd_none(pmd)); >>> @@ -180,13 +178,11 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, >>>       pmdp_set_access_flags(vma, vaddr, pmdp, pmd, 1); >>>       pmd = READ_ONCE(*pmdp); >>>       WARN_ON(!(pmd_write(pmd) && pmd_dirty(pmd))); >>> - >>> -    pmd = pmd_mkhuge(pfn_pmd(pfn, prot)); >>> -    set_pmd_at(mm, vaddr, pmdp, pmd); >>>       pmdp_huge_get_and_clear_full(vma, vaddr, pmdp, 1); >>>       pmd = READ_ONCE(*pmdp); >>>       WARN_ON(!pmd_none(pmd)); >>> +    pmd = pmd_mkhuge(pfn_pmd(pfn, prot)); >>>       pmd = pmd_mkyoung(pmd); >>>       set_pmd_at(mm, vaddr, pmdp, pmd); >>>       pmdp_test_and_clear_young(vma, vaddr, pmdp); >>> @@ -283,18 +279,10 @@ static void __init pud_advanced_tests(struct mm_struct *mm, >>>       WARN_ON(pud_write(pud)); >>>   #ifndef __PAGETABLE_PMD_FOLDED >> >> Same as below, once set_put_at() is gone, I don't think this #ifndef __PAGETABLE_PMD_FOLDED is still need, should be possible to replace by 'if (mm_pmd_folded())' > > I would skip that change in this series because I still haven't worked out what it means to have FOLDED PMD with CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD. > > > We should probably push that as a cleanup later and somebody who can test that config can do that? Currently i can't boot ppc64 with DBUG_VM_PGTABLE enabled on ppc64 because it is all buggy w.r.t rules. Agreed. I think its OK not address these changes/improvements in this particular series which is trying to modify the test to make it run on ppc64 platform. I will probably look into that later.