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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 96011C433E0 for ; Mon, 8 Jun 2020 11:01:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4B4D32078B for ; Mon, 8 Jun 2020 11:01:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4B4D32078B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EC36F6B0003; Mon, 8 Jun 2020 07:01:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E73A96B0005; Mon, 8 Jun 2020 07:01:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D62EF6B0006; Mon, 8 Jun 2020 07:01:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id B96286B0003 for ; Mon, 8 Jun 2020 07:01:55 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 7B24A18059547 for ; Mon, 8 Jun 2020 11:01:55 +0000 (UTC) X-FDA: 76905754590.01.nail26_510b86326db9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 4C37D18188E47 for ; Mon, 8 Jun 2020 11:01:55 +0000 (UTC) X-HE-Tag: nail26_510b86326db9 X-Filterd-Recvd-Size: 3435 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Mon, 8 Jun 2020 11:01:54 +0000 (UTC) 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 0778A1FB; Mon, 8 Jun 2020 04:01:54 -0700 (PDT) Received: from [10.163.79.100] (unknown [10.163.79.100]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 53A293F73D; Mon, 8 Jun 2020 04:01:52 -0700 (PDT) Subject: Re: [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate To: "Aneesh Kumar K.V" , linux-mm@kvack.org Cc: akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au References: <20200608062739.378902-1-aneesh.kumar@linux.ibm.com> From: Anshuman Khandual Message-ID: <2497c7b7-b5cf-8df4-dc82-efefe2fb6f5a@arm.com> Date: Mon, 8 Jun 2020 16:31:51 +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: <20200608062739.378902-1-aneesh.kumar@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4C37D18188E47 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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: Hi Aneesh, On 06/08/2020 11:57 AM, Aneesh Kumar K.V wrote: > Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but > no THP support enabled based on platforms. For ex: with 4K > PAGE_SIZE ppc64 supports THP only with radix translation. Good catch, never hit this before. > > This results in below crash when running with hash translation and > 4K PAGE_SIZE. > > kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140! > cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860] > pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0 > lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0 > ... > [c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable) > [c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0 > [c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc > [c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148 > [c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78 > > Check for THP support correctly Makes sense, is this the only configuration which hit the problem ? > > Cc: anshuman.khandual@arm.com > Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers") > Signed-off-by: Aneesh Kumar K.V > --- > mm/debug_vm_pgtable.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 188c18908964..e60151c5e997 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -61,6 +61,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) > { > pmd_t pmd = pfn_pmd(pfn, prot); > > + if (!has_transparent_hugepage()) > + return; > + We should also add this check to pud_basic_tests() as well. > WARN_ON(!pmd_same(pmd, pmd)); > WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd)))); > WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd)))); > The subject line here should mention about correct THP support detection which fixes the problem. Probably something like this or similar ("Fix kernel crash with correct THP support check"). - Anshuman