Le 10/02/2020 à 06:35, Anshuman Khandual a écrit :

On 02/10/2020 10:22 AM, Andrew Morton wrote:

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On Thu, 6 Feb 2020 13:49:35 +0530 Anshuman Khandual [off-list ref] wrote:

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On 02/06/2020 04:40 AM, kbuild test robot wrote:

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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 <redacted>

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':

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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) })
                                    ^

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mm/debug_vm_pgtable.c:141:8: note: in expansion of macro '__pud'

      pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
            ^~~~~

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include/asm-generic/pgtable-nop4d-hack.h:47:22: warning: missing braces around initializer [-Wmissing-braces]

     #define __pud(x)    ((pud_t) { __pgd(x) })
                          ^

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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 ?

Christophe

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