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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15327C54FB9 for ; Thu, 16 Nov 2023 10:36:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9E7446B0457; Thu, 16 Nov 2023 05:36:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9972E6B0459; Thu, 16 Nov 2023 05:36:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 837F66B045A; Thu, 16 Nov 2023 05:36:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 70D0C6B0457 for ; Thu, 16 Nov 2023 05:36:54 -0500 (EST) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 455641CB95D for ; 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imf09.hostedemail.com; dkim=none; spf=pass (imf09.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700131011; a=rsa-sha256; cv=none; b=47ydavjFrQ5V0vLywqakqlwQVzVga2yua+0V8jrhUbEgQomPVzNl+mHt+RRBd87Qsz7M5c DWFuq7A4tCfLlQKJAs22817wB4fQ/jLZeyWL1iv7XurTbQRPKXMSaPmltsazIHsEDElqRs Jiq2iJYOybBzPE6eA+Xxni1NzHmVnD0= 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 47AA51595; Thu, 16 Nov 2023 02:37:36 -0800 (PST) Received: from [10.1.35.163] (XHFQ2J9959.cambridge.arm.com [10.1.35.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1F8C23F6C4; Thu, 16 Nov 2023 02:36:47 -0800 (PST) Message-ID: Date: Thu, 16 Nov 2023 10:36:45 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/14] mm: Batch-copy PTE ranges during fork() Content-Language: en-GB To: David Hildenbrand , kernel test robot , Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Anshuman Khandual , Matthew Wilcox , Yu Zhao , Mark Rutland , Kefeng Wang , John Hubbard , Zi Yan Cc: oe-kbuild-all@lists.linux.dev, Linux Memory Management List , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231115163018.1303287-2-ryan.roberts@arm.com> <202311160516.kHhfmjvl-lkp@intel.com> <4e8d329c-eda6-4ff8-bb56-8924bb4583b2@redhat.com> From: Ryan Roberts In-Reply-To: <4e8d329c-eda6-4ff8-bb56-8924bb4583b2@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7811E140004 X-Rspam-User: X-Stat-Signature: uzhg3hphtykwbzec7afy8678osoddpiq X-Rspamd-Server: rspam01 X-HE-Tag: 1700131011-930600 X-HE-Meta: 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 GPii1HsP 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 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: List-Subscribe: List-Unsubscribe: On 16/11/2023 10:12, David Hildenbrand wrote: > On 16.11.23 11:07, Ryan Roberts wrote: >> Hi All, >> >> Hoping for some guidance below! >> >> >> On 15/11/2023 21:26, kernel test robot wrote: >>> Hi Ryan, >>> >>> kernel test robot noticed the following build errors: >>> >>> [auto build test ERROR on akpm-mm/mm-everything] >>> [also build test ERROR on linus/master v6.7-rc1 next-20231115] >>> [cannot apply to arm64/for-next/core efi/next] >>> [If your patch is applied to the wrong git tree, kindly drop us a note. >>> And when submitting patch, we suggest to use '--base' as documented in >>> https://git-scm.com/docs/git-format-patch#_base_tree_information] >>> >>> url:    >>> https://github.com/intel-lab-lkp/linux/commits/Ryan-Roberts/mm-Batch-copy-PTE-ranges-during-fork/20231116-010123 >>> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git >>> mm-everything >>> patch link:    >>> https://lore.kernel.org/r/20231115163018.1303287-2-ryan.roberts%40arm.com >>> patch subject: [PATCH v2 01/14] mm: Batch-copy PTE ranges during fork() >>> config: arm-randconfig-002-20231116 >>> (https://download.01.org/0day-ci/archive/20231116/202311160516.kHhfmjvl-lkp@intel.com/config) >>> compiler: arm-linux-gnueabi-gcc (GCC) 13.2.0 >>> reproduce (this is a W=1 build): >>> (https://download.01.org/0day-ci/archive/20231116/202311160516.kHhfmjvl-lkp@intel.com/reproduce) >>> >>> If you fix the issue in a separate patch/commit (i.e. not just a new version of >>> the same patch/commit), kindly add following tags >>> | Reported-by: kernel test robot >>> | Closes: >>> https://lore.kernel.org/oe-kbuild-all/202311160516.kHhfmjvl-lkp@intel.com/ >>> >>> All errors (new ones prefixed by >>): >>> >>>     mm/memory.c: In function 'folio_nr_pages_cont_mapped': >>>>> mm/memory.c:969:16: error: implicit declaration of function 'pte_pgprot'; >>>>> did you mean 'ptep_get'? [-Werror=implicit-function-declaration] >>>       969 |         prot = pte_pgprot(pte_mkold(pte_mkclean(ptent))); >>>           |                ^~~~~~~~~~ >>>           |                ptep_get >>>     cc1: some warnings being treated as errors >> >> It turns out that pte_pgprot() is not universal; its only implemented by >> architectures that select CONFIG_HAVE_IOREMAP_PROT (currently arc, arm64, >> loongarch, mips, powerpc, s390, sh, x86). >> >> I'm using it in core-mm to help calculate the number of "contiguously mapped" >> pages within a folio (note that's not the same as arm64's notion of >> contpte-mapped. I just want to know that there are N physically contiguous pages >> mapped virtually contiguously with the same permissions). And I'm using >> pte_pgprot() to extract the permissions for each pte to compare. It's important >> that we compare the permissions because just because the pages belongs to the >> same folio doesn't imply they are mapped with the same permissions; think >> mprotect()ing a sub-range. >> >> I don't have a great idea for how to fix this - does anyone have any thoughts? > > KIS :) fork() operates on individual VMAs if I am not daydreaming. > > Just check for the obvious pte_write()/dirty/ and you'll be fine. Yes, that seems much simpler! I think we might have to be careful about the uffd wp bit too? I think that's it - are there any other exotic bits that might need to be considered? > > If your code tries to optimize "between VMAs", you really shouldn't be doing > that at this point. No I'm not doing that; It's one VMA at a time. > > If someone did an mprotect(), there are separate VMAs, and you shouldn't be > looking at the PTEs belonging to a different VMA. > Yep understood, thanks.