On 02/10/2020 04:36 PM, Russell King - ARM Linux admin wrote: > On Mon, Feb 10, 2020 at 11:46:23AM +0100, Christophe Leroy wrote: >> >> >> Le 10/02/2020 à 11:02, Russell King - ARM Linux admin a écrit : >>> On Mon, Feb 10, 2020 at 07:38:38AM +0100, Christophe Leroy wrote: >>>> >>>> >>>> Le 10/02/2020 à 06:35, Anshuman Khandual a écrit : >>>>> >>>>> >>>>> On 02/10/2020 10:22 AM, Andrew Morton wrote: >>>>>> On Thu, 6 Feb 2020 13:49:35 +0530 Anshuman Khandual <anshuman.khandual@xxxxxxx> wrote: >>>>>> >>>>>>> >>>>>>> On 02/06/2020 04:40 AM, kbuild test robot wrote: >>>>>>>> Hi Anshuman, >>>>>>>> >>>>>>>> Thank you for the patch! Yet something to improve: >>>>>>>> >>>>>>>> [auto build test ERROR on powerpc/next] >>>>>>>> [also build test ERROR on s390/features linus/master arc/for-next v5.5] >>>>>>>> [cannot apply to mmotm/master tip/x86/core arm64/for-next/core next-20200205] >>>>>>>> [if your patch is applied to the wrong git tree, please drop us a note to help >>>>>>>> improve the system. BTW, we also suggest to use '--base' option to specify the >>>>>>>> base tree in git format-patch, please see https://stackoverflow.com/a/37406982] >>>>>>>> >>>>>>>> url: https://github.com/0day-ci/linux/commits/Anshuman-Khandual/mm-debug-Add-tests-validating-architecture-page-table-helpers/20200205-215507 >>>>>>>> base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next >>>>>>>> config: ia64-allmodconfig (attached as .config) >>>>>>>> compiler: ia64-linux-gcc (GCC) 7.5.0 >>>>>>>> reproduce: >>>>>>>> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross >>>>>>>> chmod +x ~/bin/make.cross >>>>>>>> # save the attached .config to linux build tree >>>>>>>> GCC_VERSION=7.5.0 make.cross ARCH=ia64 >>>>>>>> >>>>>>>> If you fix the issue, kindly add following tag >>>>>>>> Reported-by: kbuild test robot <lkp@xxxxxxxxx> >>>>>>>> >>>>>>>> All error/warnings (new ones prefixed by >>): >>>>>>>> >>>>>>>> In file included from include/asm-generic/pgtable-nopud.h:8:0, >>>>>>>> from arch/ia64/include/asm/pgtable.h:586, >>>>>>>> from include/linux/mm.h:99, >>>>>>>> from include/linux/highmem.h:8, >>>>>>>> from mm/debug_vm_pgtable.c:14: >>>>>>>> mm/debug_vm_pgtable.c: In function 'pud_clear_tests': >>>>>>>>>> include/asm-generic/pgtable-nop4d-hack.h:47:32: error: implicit declaration of function '__pgd'; did you mean '__p4d'? [-Werror=implicit-function-declaration] >>>>>>>> #define __pud(x) ((pud_t) { __pgd(x) }) >>>>>>>> ^ >>>>>>>>>> mm/debug_vm_pgtable.c:141:8: note: in expansion of macro '__pud' >>>>>>>> pud = __pud(pud_val(pud) | RANDOM_ORVALUE); >>>>>>>> ^~~~~ >>>>>>>>>> include/asm-generic/pgtable-nop4d-hack.h:47:22: warning: missing braces around initializer [-Wmissing-braces] >>>>>>>> #define __pud(x) ((pud_t) { __pgd(x) }) >>>>>>>> ^ >>>>>>>>>> mm/debug_vm_pgtable.c:141:8: note: in expansion of macro '__pud' >>>>>>>> pud = __pud(pud_val(pud) | RANDOM_ORVALUE); >>>>>>>> ^~~~~ >>>>>>>> cc1: some warnings being treated as errors >>>>>>> >>>>>>> This build failure is expected now given that we have allowed DEBUG_VM_PGTABLE >>>>>>> with EXPERT without platform requiring ARCH_HAS_DEBUG_VM_PGTABLE. This problem >>>>>>> i.e build failure caused without a platform __pgd(), is known to exist both on >>>>>>> ia64 and arm (32bit) platforms. Please refer https://lkml.org/lkml/2019/9/24/314 >>>>>>> for details where this was discussed earlier. >>>>>>> >>>>>> >>>>>> I'd prefer not to merge a patch which is known to cause build >>>>>> regressions. Is there some temporary thing we can do to prevent these >>>>>> errors until arch maintainers(?) get around to implementing the >>>>>> long-term fixes? >>>>> >>>>> We could explicitly disable CONFIG_DEBUG_VM_PGTABLE on ia64 and arm platforms >>>>> which will ensure that others can still use the EXPERT path. >>>>> >>>>> config DEBUG_VM_PGTABLE >>>>> bool "Debug arch page table for semantics compliance" >>>>> depends on MMU >>>>> depends on !(IA64 || ARM) >>>>> depends on ARCH_HAS_DEBUG_VM_PGTABLE || EXPERT >>>>> default n if !ARCH_HAS_DEBUG_VM_PGTABLE >>>>> default y if DEBUG_VM >>>>> >>>> >>>> On both ia32 and arm, the fix is trivial. >>>> >>>> Can we include the fix within this patch, just the same way as the >>>> mm_p4d_folded() fix for x86 ? >>> >>> Why should arm include a macro for something that nothing (apart from >>> this checker) requires? If the checker requires it but the rest of >>> the kernel does not, it suggests that the checker isn't actually >>> correct, and the results can't be relied upon. >>> >> >> As far as I can see, the problem is that arm opencodes part of the API >> instead of including asm-generic/pgtable-nopmd.h >> >> Here, the ARM has 2 levels, ie only PGD and PTE. But instead of defining >> __pgd and __pte and getting everything else from asm-generic, it defines a >> __pmd then redefines the folded levels like the pud, etc ... >> >> That's exactly what the checker aims at detecting: architectures than do not >> properly use the standard linux page table structures. > > There are good reasons for the way ARM does stuff. The generic crap was > written without regard for the circumstances that ARM has, and thus is > entirely unsuitable for 32-bit ARM. Since we dont have an agreement here, lets just settle with disabling the test for now on platforms where the build fails. CONFIG_EXPERT is enabling this test for better adaptability and coverage, hence how about re framing the config like this ? This at the least conveys the fact that EXPERT only works when platform is neither IA64 or ARM. config DEBUG_VM_PGTABLE bool "Debug arch page table for semantics compliance" depends on MMU depends on ARCH_HAS_DEBUG_VM_PGTABLE || (EXPERT && !(IA64 || ARM)) default n if !ARCH_HAS_DEBUG_VM_PGTABLE default y if DEBUG_VM
