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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 B8D9AC43460 for ; Mon, 17 May 2021 14:12:20 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 108D861456 for ; Mon, 17 May 2021 14:12:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 108D861456 Authentication-Results: mail.kernel.org; dmarc=fail (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 boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4FkLg6523Zz30Bc for ; Tue, 18 May 2021 00:12:18 +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=) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4FkLfk3rDnz2yYS for ; Tue, 18 May 2021 00:11:56 +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 6355812FC; Mon, 17 May 2021 07:11:53 -0700 (PDT) Received: from [192.168.0.130] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 24DD03F73B; Mon, 17 May 2021 07:11:51 -0700 (PDT) Subject: Re: Fwd: [Bug 213069] New: kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:147! Oops: Exception in kernel mode, sig: 5 [#1] To: "Aneesh Kumar K.V" , Christophe Leroy , "linuxppc-dev@lists.ozlabs.org" References: <4deb5cd5-c713-b020-9143-c74a031e3fd5@csgroup.eu> <7ebc28ad-61e3-ef43-d670-9b80a61268c4@csgroup.eu> <6fcdf4f2-9bed-4b0f-8ed8-74cb25484ea6@arm.com> <87tun1qxh8.fsf@linux.ibm.com> From: Anshuman Khandual Message-ID: Date: Mon, 17 May 2021 19:42:38 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <87tun1qxh8.fsf@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: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 5/17/21 7:22 PM, Aneesh Kumar K.V wrote: > Anshuman Khandual writes: > >> On 5/17/21 11:25 AM, Aneesh Kumar K.V wrote: >>> On 5/17/21 11:17 AM, Christophe Leroy wrote: >>>> +aneesh >>>> +linuxppc-dev list >>>> >>>> Le 17/05/2021 à 07:44, Anshuman Khandual a écrit : >>>>> Hello Christophe, >>>>> >>>>> DEBUG_VM_PGTABLE has now been re-enabled on powerpc recently ? was not >>>>> aware about this. From the error log, it failed explicitly on 4K page >>>>> size hash config. >>>>> >>>>> static inline pmd_t hash__pmd_mkhuge(pmd_t pmd) >>>>> { >>>>>          BUG();        ------> Failed >>>>>          return pmd; >>>>> } >>>>> >>>>> static inline pmd_t __pmd_mkhuge(pmd_t pmd) >>>>> { >>>>>          if (radix_enabled()) >>>>>                  return radix__pmd_mkhuge(pmd); >>>>>          return hash__pmd_mkhuge(pmd); >>>>> } >>>>> >>>>> pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot) >>>>> { >>>>>          unsigned long pmdv; >>>>> >>>>>          pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK; >>>>> >>>>>          return __pmd_mkhuge(pmd_set_protbits(__pmd(pmdv), pgprot)); >>>>> } >>>>> >>>>> It seems like on powerpc, where pfn_pmd() makes a huge page but which >>>>> is not supported on 4K hash config thus triggering the BUG(). But all >>>>> pfn_pmd() call sites inside the debug_vm_pgtable() test are protected >>>>> with CONFIG_TRANSPARENT_HUGEPAGE. IIUC unlike powerpc, pfn_pmd() does >>>>> not directly make a huge page on other platforms. >>>>> >>>>> Looking at arch/powerpc/include/asm/book3s/64/hash-4k.h, all relevant >>>>> THP helpers has BUG() or 0 which indicates THP might not be supported >>>>> on 4K page size hash config ? >>>>> >>>>> But looking at arch/powerpc/platforms/Kconfig.cputype, it seems like >>>>> HAVE_ARCH_TRANSPARENT_HUGEPAGE is invariably selected on PPC_BOOK3S_64 >>>>> platforms which I assume includes 4K page size hash config as well. >>>>> >>>>> Is THP some how getting enabled on this 4K page size hash config where >>>>> it should not be (thus triggering the BUG) ? OR am I missing something >>>>> here. >>>>> >>>> >>> >>> We should put those  pfn_pmd()  and pfn_pud() after >>> >>>     if (!has_transparent_hugepage()) >>>         return; >> >> The following patch has been lightly tested on arm64 and x86 platforms. >> Could you please verify if this solves the problem on powerpc 4K hash >> config ? Thank you. > > Tested the patch with the below additional change. > > modified mm/debug_vm_pgtable.c > @@ -186,12 +186,13 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, > unsigned long pfn, unsigned long vaddr, > pgprot_t prot, pgtable_t pgtable) > { > - pmd_t pmd = pfn_pmd(pfn, prot); > + pmd_t pmd; > > if (!has_transparent_hugepage()) > return; > > pr_debug("Validating PMD advanced\n"); > + pmd = pfn_pmd(pfn, prot); > /* Align the address wrt HPAGE_PMD_SIZE */ > vaddr = (vaddr & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE; > > @@ -334,12 +335,13 @@ static void __init pud_advanced_tests(struct mm_struct *mm, > unsigned long pfn, unsigned long vaddr, > pgprot_t prot) > { > - pud_t pud = pfn_pud(pfn, prot); > + pud_t pud; > > if (!has_transparent_hugepage()) > return; > > pr_debug("Validating PUD advanced\n"); > + pud = pfn_pud(pfn, prot); > /* Align the address wrt HPAGE_PUD_SIZE */ > vaddr = (vaddr & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE; > Right. But this change is already on the linux-next (20210514) via another commit ae7920ce9e9bb ("mm/debug_vm_pgtable: remove redundant pfn_{pmd/pte}() and fix one comment mistake") which got queued recently. Anyways, now that we have verified the fix, will send it out against linux-next soon.