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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6F00DC433DB for ; Wed, 3 Mar 2021 21:24:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB14864EF6 for ; Wed, 3 Mar 2021 21:24:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB14864EF6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 67D756B0007; Wed, 3 Mar 2021 16:24:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 62DE86B0008; Wed, 3 Mar 2021 16:24:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A7576B000A; Wed, 3 Mar 2021 16:24:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0052.hostedemail.com [216.40.44.52]) by kanga.kvack.org (Postfix) with ESMTP id 2DB466B0007 for ; Wed, 3 Mar 2021 16:24:22 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DF292180AD5C9 for ; Wed, 3 Mar 2021 21:24:21 +0000 (UTC) X-FDA: 77879841522.16.EE95760 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf17.hostedemail.com (Postfix) with ESMTP id 568D040B8CE6 for ; Wed, 3 Mar 2021 21:24:19 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 7C11464ECF; Wed, 3 Mar 2021 21:24:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614806652; bh=SvDkyFYVfStCWghVCxzZppYFC8pvCQWOR+Jyt6ehiU8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F3rj6IXEb6fHjyfgV6MYWIZut/FnM46xza/gLI9u5IDTdM4DgbipZtTBm2Vw7SqhZ HUO/gMJwfdc5mTH7EKTNt6JIVINRFXPXxNwKyGBi29zue98pxpPopeLBjU6iLBaCeG CtDrGTxtIS613mZkEy4X+aSWa6nx3vhSL/AXc5UcrSGJYm6bBhUMIsQWQFHblyW1vU Z0ECDhsExjNlMAfmNwU092WdgG5YBGxj+SFen0TMro779wZC+g5ohCkxe9vzCMShQb 2/A3IlK2HqY38IcfVjFFO1dexbVVMpoYPyuEzUY4I2k/uFiaku7EGfuikMI5WQEPwP Z8WhcZ4FUZ8Ow== Date: Wed, 3 Mar 2021 21:24:07 +0000 From: Will Deacon To: Catalin Marinas Cc: David Hildenbrand , Anshuman Khandual , Mark Rutland , linux-kernel@vger.kernel.org, Mike Rapoport , linux-mm@kvack.org, =?iso-8859-1?B?Suly9G1l?= Glisse , James Morse , Dan Williams , Robin Murphy , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH V2 1/2] arm64/mm: Fix pfn_valid() for ZONE_DEVICE based memory Message-ID: <20210303212406.GB20055@willie-the-truck> References: <20210202123524.GB16868@willie-the-truck> <20210202125152.GC16868@willie-the-truck> <4d8f5156-8628-5531-1485-322ad92aa15c@redhat.com> <0e649f28-4d54-319d-f876-8a93870cda7f@arm.com> <20210205185552.GA23216@willie-the-truck> <20210211115354.GB29894@willie-the-truck> <23e5eb93-a39c-c68e-eac1-c5ccf9036079@arm.com> <20210303190428.GB24035@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303190428.GB24035@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 568D040B8CE6 X-Stat-Signature: u1qrzh74mn3cbmbyjtkj65zafpe86nck Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614806659-900456 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: On Wed, Mar 03, 2021 at 07:04:33PM +0000, Catalin Marinas wrote: > On Thu, Feb 11, 2021 at 01:35:56PM +0100, David Hildenbrand wrote: > > On 11.02.21 13:10, Anshuman Khandual wrote: > > > On 2/11/21 5:23 PM, Will Deacon wrote: > > > > ... and dropped. These patches appear to be responsible for a boot > > > > regression reported by CKI: > > > > > > Ahh, boot regression ? These patches only change the behaviour > > > for non boot memory only. > > > > > > > https://lore.kernel.org/r/cki.8D1CB60FEC.K6NJMEFQPV@redhat.com > > > > > > Will look into the logs and see if there is something pointing to > > > the problem. > > > > It's strange. One thing I can imagine is a mis-detection of early sections. > > However, I don't see that happening: > > > > In sparse_init_nid(), we: > > 1. Initialize the memmap > > 2. Set SECTION_IS_EARLY | SECTION_HAS_MEM_MAP via > > sparse_init_one_section() > > > > Only hotplugged sections (DIMMs, dax/kmem) set SECTION_HAS_MEM_MAP without > > SECTION_IS_EARLY - which is correct, because these are not early. > > > > So once we know that we have valid_section() -- SECTION_HAS_MEM_MAP is set > > -- early_section() should be correct. > > > > Even if someone would be doing a pfn_valid() after > > memblocks_present()->memory_present() but before > > sparse_init_nid(), we should be fine (!valid_section() -> return 0). > > I couldn't figure out how this could fail with Anshuman's patches. > Will's suspicion is that some invalid/null pointer gets dereferenced > before being initialised but the only case I see is somewhere in > pfn_section_valid() (ms->usage) if valid_section() && !early_section(). > > Assuming that we do get a valid_section(ms) && !early_section(ms), is > there a case where ms->usage is not initialised? I guess races with > section_deactivate() are not possible this early. > > Another situation could be that pfn_valid() returns true when no memory > is mapped for that pfn. The case I wondered about was __pfn_to_section() with a bogus pfn, since with patch 2/2 we call that *before* checking that pfn_to_section_nr() is sane. Will