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

From: Philip Li
Date: Sun Nov 12 2023 - 07:13:54 EST


On Sun, Nov 12, 2023 at 06:48:47PM +0800, kernel test robot wrote:
> Hi Masahiro,
>
> FYI, the error/warning still remains.

Kindly ignore this report, as the commit is not the cause of the warning itself.
Sorry for the false positive.

>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 1b907d0507354b74a4f2c286380cd6059af79248
> commit: 80b6093b55e31c2c40ff082fb32523d4e852954f kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds
> date: 11 months ago
> config: i386-allnoconfig (https://download.01.org/0day-ci/archive/20231112/202311121854.UxxoSqkX-lkp@xxxxxxxxx/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231112/202311121854.UxxoSqkX-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/202311121854.UxxoSqkX-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]
> 68 | #if PTRS_PER_PMD > 1
> | ^~~~~~~~~~~~
>
>
> 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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