On 16/11/2023 11:01, David Hildenbrand wrote: > 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@xxxxxxxxx/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@xxxxxxxxx/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 <lkp@xxxxxxxxx> >>>>> | Closes: >>>>> https://lore.kernel.org/oe-kbuild-all/202311160516.kHhfmjvl-lkp@xxxxxxxxx/ >>>>> >>>>> 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. > OK thanks. I'll rework for this approach in v3.
