linux-kernel - Re: [PATCH v4 02/15] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc

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Message-ID: <1e4e1d6c-671a-4c62-a8ca-597689395cf7@ghiti.fr>
Date: Mon, 6 Jan 2025 12:20:09 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Qi Zheng <zhengqi.arch@...edance.com>, peterz@...radead.org,
 agordeev@...ux.ibm.com, kevin.brodsky@....com, palmer@...belt.com,
 tglx@...utronix.de, david@...hat.com, jannh@...gle.com, hughd@...gle.com,
 yuzhao@...gle.com, willy@...radead.org, muchun.song@...ux.dev,
 vbabka@...nel.org, lorenzo.stoakes@...cle.com, akpm@...ux-foundation.org,
 rientjes@...gle.com, vishal.moola@...il.com, arnd@...db.de, will@...nel.org,
 aneesh.kumar@...nel.org, npiggin@...il.com, dave.hansen@...ux.intel.com,
 rppt@...nel.org, ryan.roberts@....com
Cc: linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
 linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org, linux-arch@...r.kernel.org,
 linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org,
 linux-mips@...r.kernel.org, linux-openrisc@...r.kernel.org,
 linux-sh@...r.kernel.org, linux-um@...ts.infradead.org,
 Palmer Dabbelt <palmer@...osinc.com>
Subject: Re: [PATCH v4 02/15] riscv: mm: Skip pgtable level check in
 {pud,p4d}_alloc_one

Hi Qi,

On 30/12/2024 10:07, Qi Zheng wrote:
> From: Kevin Brodsky <kevin.brodsky@....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@....com>
> Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Acked-by: Palmer Dabbelt <palmer@...osinc.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)


You can add:

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex