* Ingo Molnar <mingo@xxxxxxxxxx> wrote: > Separating out the assembler-compatible defines from the types > headers appears to be a bigger patch, since it's all mixed in with C > syntax: > > <=-----------------------------------=============================== > typedef struct { pud_t pud; } pmd_t; > > #define PMD_SHIFT PUD_SHIFT > #define PTRS_PER_PMD 1 > #define PMD_SIZE (1UL << PMD_SHIFT) > #define PMD_MASK (~(PMD_SIZE-1)) > > /* > * The "pud_xxx()" functions here are trivial for a folded two-level > * setup: the pmd is never bad, and a pmd always exists (as it's folded > * into the pud entry) > */ > static inline int pud_none(pud_t pud) { return 0; } > static inline int pud_bad(pud_t pud) { return 0; } > static inline int pud_present(pud_t pud) { return 1; } > ================================================================> > > In any case I've removed the commit for the time being until this all > is cleared up. So there's a simple solution: define it on i386 too, via the patch below. It appears the double-definition doesn't create any warnings, on GCC at least. But if it's an issue, we could do something like this in <asm-generic/pgtable-nopmd.h>: #if defined(PTRS_PER_PMD) && (PTRS_PER_PMD != 1) # error "mm: Wait a minute, that's a super confusing pagetable setup ..." #endif ? Thanks, Ingo =========================> From: Ingo Molnar <mingo@xxxxxxxxxx> Date: Thu, 6 Mar 2025 22:53:49 +0100 Subject: [PATCH] x86/mm: Define PTRS_PER_PMD for assembly code too Andy reported the following build warning from head_32.S: In file included from arch/x86/kernel/head_32.S:29: arch/x86/include/asm/pgtable_32.h:59:5: error: "PTRS_PER_PMD" is not defined, evaluates to 0 [-Werror=undef] 59 | #if PTRS_PER_PMD > 1 The reason is that on 2-level i386 paging the folded in PMD's PTRS_PER_PMD constant is not defined in assembly headers, only in generic MM C headers. Instead of trying to fish out the definition from the generic headers, just define it - it even has a comment for it already... Reported-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/include/asm/pgtable-2level_types.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/pgtable-2level_types.h b/arch/x86/include/asm/pgtable-2level_types.h index 7f6ccff0ba72..4a12c276b181 100644 --- a/arch/x86/include/asm/pgtable-2level_types.h +++ b/arch/x86/include/asm/pgtable-2level_types.h @@ -23,17 +23,17 @@ typedef union { #define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED /* - * traditional i386 two-level paging structure: + * Traditional i386 two-level paging structure: */ #define PGDIR_SHIFT 22 #define PTRS_PER_PGD 1024 - /* - * the i386 is two-level, so we don't really have any - * PMD directory physically. + * The i386 is two-level, so we don't really have any + * PMD directory physically: */ +#define PTRS_PER_PMD 1 #define PTRS_PER_PTE 1024
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