Re: arch/x86/include/asm/pgtable_32.h:68:5: warning: 'PTRS_PER_PMD' is not defined, evaluates to 0

[Philip Li]

On Mon, Aug 28, 2023 at 11:56:09PM +0800, kernel test robot wrote:
> Hi Masahiro,
> 
> FYI, the error/warning still remains.

Sorry for the wrong report, kindly ignore this.

> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   2dde18cd1d8fac735875f2e4987f11817cc0bc2c
> commit: 80b6093b55e31c2c40ff082fb32523d4e852954f kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds
> date:   9 months ago
> config: i386-allnoconfig (https://download.01.org/0day-ci/archive/20230828/202308282335.fH9YoGYl-lkp@xxxxxxxxx/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230828/202308282335.fH9YoGYl-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/202308282335.fH9YoGYl-lkp@xxxxxxxxx/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from arch/x86/kernel/head_32.S:29:
> >> arch/x86/include/asm/pgtable_32.h:68:5: warning: 'PTRS_PER_PMD' is not defined, evaluates to 0 [-Wundef]
>    #if PTRS_PER_PMD > 1
>        ^
>    1 warning generated.
> 
> 
> vim +/PTRS_PER_PMD +68 arch/x86/include/asm/pgtable_32.h
> 
> ^1da177e4c3f41 include/asm-i386/pgtable.h        Linus Torvalds  2005-04-16  58  
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  59  /*
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  60   * This is used to calculate the .brk reservation for initial pagetables.
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  61   * Enough space is reserved to allocate pagetables sufficient to cover all
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  62   * of LOWMEM_PAGES, which is an upper bound on the size of the direct map of
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  63   * lowmem.
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  64   *
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  65   * With PAE paging (PTRS_PER_PMD > 1), we allocate PTRS_PER_PGD == 4 pages for
> ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  66   * the PMD's in addition to the pages required for the last level pagetables.
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  67   */
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08 @68  #if PTRS_PER_PMD > 1
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  69  #define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  70  #else
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  71  #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  72  #endif
> 1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  73  
> 
> :::::: The code at line 68 was first introduced by commit
> :::::: 1e620f9b23e598ab936ece12233e98e97930b692 x86/boot/32: Convert the 32-bit pgtable setup code from assembly to C
> 
> :::::: TO: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> :::::: CC: Ingo Molnar <mingo@xxxxxxxxxx>
> 
> -- 
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