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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id bg3-20020a05600c3c8300b004077219aed5sm3232262wmb.6.2023.11.16.03.01.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Nov 2023 03:01:49 -0800 (PST) Message-ID: <930b5f6a-27d9-43da-bf9f-1478c8de1af8@redhat.com> Date: Thu, 16 Nov 2023 12:01:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/14] mm: Batch-copy PTE ranges during fork() To: Ryan Roberts , 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: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 6796320021 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4fgcea36aocxmo3i3ew1aa9spum44mir X-HE-Tag: 1700132514-159099 X-HE-Meta: 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 7OwnwEfe 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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 16.11.23 11:36, Ryan Roberts wrote: > 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? Good question. Mimicing what the current code already does should be sufficient. uffd-wp should have the PTE R/O. You can set the contpte bit independent of any SW bit (uffd-wp, softdirty, ...) I guess, no need to worry about that. -- Cheers, David / dhildenb