Re: [PATCH v3 02/17] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc_one

Palmer Dabbelt
2024-12-27T16:40:14Z

On Mon, 23 Dec 2024 01:40:48 PST (-0800), zhengqi.arch@bytedance.com wrote:
> From: Kevin Brodsky <kevin.brodsky@arm.com>
>
> {pmd,pud,p4d}_alloc_one() is never called if the corresponding page
> table level is folded, as {pmd,pud,p4d}_alloc() already does the
> required check. We can therefore remove the runtime page table level
> checks in {pud,p4d}_alloc_one. The PUD helper becomes equivalent to
> the generic version, so we remove it altogether.
>
> This is consistent with the way arm64 and x86 handle this situation
> (runtime check in p4d_free() only).
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> ---
> arch/riscv/include/asm/pgalloc.h | 22 ++++------------------
> 1 file changed, 4 insertions(+), 18 deletions(-)
>
> diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
> index f52264304f772..8ad0bbe838a24 100644
> --- a/arch/riscv/include/asm/pgalloc.h
> +++ b/arch/riscv/include/asm/pgalloc.h
> @@ -12,7 +12,6 @@
> #include <asm/tlb.h>
>
> #ifdef CONFIG_MMU
> -#define __HAVE_ARCH_PUD_ALLOC_ONE
> #define __HAVE_ARCH_PUD_FREE
> #include <asm-generic/pgalloc.h>
>
> @@ -88,15 +87,6 @@ static inline void pgd_populate_safe(struct mm_struct *mm, pgd_t *pgd,
> }
> }
>
> -#define pud_alloc_one pud_alloc_one
> -static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
> -{
> - if (pgtable_l4_enabled)
> - return __pud_alloc_one(mm, addr);
> -
> - return NULL;
> -}
> -
> #define pud_free pud_free
> static inline void pud_free(struct mm_struct *mm, pud_t *pud)
> {
> @@ -118,15 +108,11 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
> #define p4d_alloc_one p4d_alloc_one
> static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
> {
> - if (pgtable_l5_enabled) {
> - gfp_t gfp = GFP_PGTABLE_USER;
> -
> - if (mm == &init_mm)
> - gfp = GFP_PGTABLE_KERNEL;
> - return (p4d_t *)get_zeroed_page(gfp);
> - }
> + gfp_t gfp = GFP_PGTABLE_USER;
>
> - return NULL;
> + if (mm == &init_mm)
> + gfp = GFP_PGTABLE_KERNEL;
> + return (p4d_t *)get_zeroed_page(gfp);
> }
>
> static inline void __p4d_free(struct mm_struct *mm, p4d_t *p4d)

Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

Are you trying to keep these together, or do you want me to try and pick
up the RISC-V bits on their own?