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=-11.5 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 374A4C433DF for ; Fri, 14 Aug 2020 08:32:43 +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 8BD852074D for ; Fri, 14 Aug 2020 08:32:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8BD852074D 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 4BScBc2VQbzDqmJ for ; Fri, 14 Aug 2020 18:32:40 +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 4BSc8C3V4kzDqMF for ; Fri, 14 Aug 2020 18:30:33 +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 E79171063; Fri, 14 Aug 2020 01:30:29 -0700 (PDT) Received: from [10.163.65.227] (unknown [10.163.65.227]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 668623F22E; Fri, 14 Aug 2020 01:30:26 -0700 (PDT) From: Anshuman Khandual Subject: Re: [PATCH 16/16] debug_vm_pgtable/ppc64: Add a variant of pfn_pte/pmd To: "Aneesh Kumar K.V" , linux-mm@kvack.org, akpm@linux-foundation.org References: <20200812063358.369514-1-aneesh.kumar@linux.ibm.com> <20200812063358.369514-16-aneesh.kumar@linux.ibm.com> Message-ID: <44586359-f3bd-096c-ef5d-38d520eae072@arm.com> Date: Fri, 14 Aug 2020 13:59:55 +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: 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 08/13/2020 12:07 PM, Aneesh Kumar K.V wrote: > On 8/13/20 11:00 AM, Anshuman Khandual wrote: >> >> On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote: >>> The tests do expect _PAGE_PTE bit set by different page table accessors. >>> This is not true for the kernel. Within the kernel, _PAGE_PTE bits are >>> usually set by set_pte_at(). To make the below tests work correctly add test >>> specific pfn_pte/pmd helpers that set _PAGE_PTE bit. >>> >>> pte_t pte = pfn_pte(pfn, prot); >>> WARN_ON(!pte_devmap(pte_mkdevmap(pte))); >>> WARN_ON(!pte_savedwrite(pte_mk_savedwrite(pte_clear_savedwrite(pte)))); >>> >>> Signed-off-by: Aneesh Kumar K.V >>> --- >>>   mm/debug_vm_pgtable.c | 65 +++++++++++++++++++++++++++---------------- >>>   1 file changed, 41 insertions(+), 24 deletions(-) >>> >>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >>> index eea62d5e503b..153c925b5273 100644 >>> --- a/mm/debug_vm_pgtable.c >>> +++ b/mm/debug_vm_pgtable.c >>> @@ -31,6 +31,23 @@ >>>   #include >>>   #include >>>   +#ifdef CONFIG_PPC_BOOK3S_64 >>> +static inline pte_t debug_vm_pfn_pte(unsigned long pfn, pgprot_t pgprot) >>> +{ >>> +    pte_t pte = pfn_pte(pfn, pgprot); >>> +    return __pte(pte_val(pte) | _PAGE_PTE); >>> + >>> +} >>> +static inline pmd_t debug_vm_pfn_pmd(unsigned long pfn, pgprot_t pgprot) >>> +{ >>> +    pmd_t pmd = pfn_pmd(pfn, pgprot); >>> +    return __pmd(pmd_val(pmd) | _PAGE_PTE); >>> +} >>> +#else >>> +#define debug_vm_pfn_pte(pfn, pgprot) pfn_pte(pfn, pgprot) >>> +#define debug_vm_pfn_pmd(pfn, pgprot) pfn_pmd(pfn, pgprot) >>> +#endif >> >> Again, no platform specific constructs please. This defeats the whole purpose of >> this test. If __PAGE_PTE is required for the helpers, then pfn_pmd/pte() could >> be modified to accommodate that. We dont see similar issues on other platforms, >> hence could you please explain why ppc64 is different here. >> > > It is not platform specific. set_pte_at is the one that set the _PAGE_PTE bit. We don't call that in the test.  The test seems to make the assumption that pfn_pte returns a proper pte which is not true. '#ifdef CONFIG_PPC_BOOK3S_64' definitely makes it platform specific. Here is how set_pte_at() updates an entry on other platforms without changing the pte value. _PAGE_PTE bit update during set_pte_at() on ppc64 seems to be a deviation. 1. set_pte_at() on arm64 directly update the entry after TLB, cache maintenance 2. set_pte_at() on s390 directly updates the entry for !CONFIG_PGSTE 3. set_pte_at() on arc directly updates the entry via set_pte() 4. set_pte_at() on x86 directly update the entry via native_set_pte() set_pte_at() does take a pte created with pfn_pte(). As an example do_anonymous_page() does the same. ...... entry = mk_pte(page, vma->vm_page_prot); /* Call pfn_pte() */ entry = pte_sw_mkyoung(entry); if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry)); ..... set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); .....