linux-kernel - Re: [PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to __tlb_remove

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Message-ID: <4a0b5edb-6fc7-4df4-93d9-ca834e6a760b@arm.com>
Date: Tue, 7 Jan 2025 12:58:08 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: agordeev@...ux.ibm.com, palmer@...belt.com, tglx@...utronix.de,
 david@...hat.com, jannh@...gle.com, hughd@...gle.com, yuzhao@...gle.com,
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 dave.hansen@...ux.intel.com, rppt@...nel.org, ryan.roberts@....com,
 linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
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Subject: Re: [PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to
 __tlb_remove_table()

On 07/01/2025 11:51, Qi Zheng wrote:
> [...]
>
> Author: Qi Zheng <zhengqi.arch@...edance.com>
> Date:   Fri Dec 13 17:13:48 2024 +0800
>
>     mm: pgtable: completely move pagetable_dtor() to generic
> tlb_remove_table()
>
>     For the generic tlb_remove_table(), it is implemented in the
> following two
>     forms:
>
>     1) CONFIG_MMU_GATHER_TABLE_FREE is enabled
>
>     tlb_remove_table
>     --> generic __tlb_remove_table()
>
>     2) CONFIG_MMU_GATHER_TABLE_FREE is disabled
>
>     tlb_remove_table
>     --> tlb_remove_page
>
>     For case 1), the pagetable_dtor() has already been moved to generic
>     __tlb_remove_table().
>
>     For case 2), now only arm will call
> tlb_remove_table()/tlb_remove_ptdesc()
>     when CONFIG_MMU_GATHER_TABLE_FREE is disabled. Let's move
> pagetable_dtor()
>     completely to generic tlb_remove_table(), so that the
> architectures can
>     follow more easily.
>
>     Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
>
> diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
> index b8eebdb598631..ea4fbe7b17f6f 100644
> --- a/arch/arm/include/asm/tlb.h
> +++ b/arch/arm/include/asm/tlb.h
> @@ -34,10 +34,6 @@ __pte_free_tlb(struct mmu_gather *tlb, pgtable_t
> pte, unsigned long addr)
>  {
>         struct ptdesc *ptdesc = page_ptdesc(pte);
>
> -#ifndef CONFIG_MMU_GATHER_TABLE_FREE
> -       pagetable_dtor(ptdesc);
> -#endif

I guess this hunk will disappear since this call isn't present to start
with.

> -
>  #ifndef CONFIG_ARM_LPAE
>         /*
>          * With the classic ARM MMU, a pte page has two corresponding pmd
> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index 69de47c7ef3c5..53ae7748f555b 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -220,14 +220,20 @@ static inline void __tlb_remove_table(void *table)
>
>  extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
>
> -#else /* !CONFIG_MMU_GATHER_HAVE_TABLE_FREE */
> +#else /* !CONFIG_MMU_GATHER_TABLE_FREE */

Good catch!

>
> +static inline void tlb_remove_page(struct mmu_gather *tlb, struct
> page *page);

Nit: might be better to move the declaration up, e.g. above #ifdef
CONFIG_MMU_GATHER_TABLE_FREE.

>  /*
>   * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have
> page based
>   * page directories and we can use the normal page batching to free
> them.
>   */
> -#define tlb_remove_table(tlb, page) tlb_remove_page((tlb), (page))
> +static inline void tlb_remove_table(struct mmu_gather *tlb, void *table)
> +{
> +       struct page *page = (struct page *)table;
>
> +       pagetable_dtor(page_ptdesc(page));
> +       tlb_remove_page(tlb, page);
> +}
>  #endif /* CONFIG_MMU_GATHER_TABLE_FREE */
>
>  #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE

Looks good to me otherwise.

- Kevin