linux-kernel - Re: [PATCH V2] mm/debug_vm_pgtable: Replace pte_mkhuge() with arch_make_huge

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Date:   Thu, 2 Mar 2023 13:42:21 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc:     mike.kravetz@...cle.com, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Mike Rapoport (IBM)" <rppt@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>
Subject: Re: [PATCH V2] mm/debug_vm_pgtable: Replace pte_mkhuge() with
 arch_make_huge_pte()

On 02.03.23 12:48, Anshuman Khandual wrote:
> Since the following commit arch_make_huge_pte() should be used directly in
> generic memory subsystem as a platform provided page table helper, instead
> of pte_mkhuge(). Change hugetlb_basic_tests() to call arch_make_huge_pte()
> directly, and update its relevant documentation entry as required.
> 
> 'commit 16785bd77431 ("mm: merge pte_mkhuge() call into arch_make_huge_pte()")'
> 
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: "Mike Rapoport (IBM)" <rppt@...nel.org>
> Cc: linux-doc@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-mm@...ck.org
> Reported-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Link: https://lore.kernel.org/all/1ea45095-0926-a56a-a273-816709e9075e@csgroup.eu/
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This applies on latest mainline.
> 
> Changes in V2:
> 
> - Send PMD_SHIFT and VM_ACCESS_FLAGS as arguments for arch_make_huge_pte()
>   
> Changes in V1:
> 
> https://lore.kernel.org/all/20230302031833.360679-1-anshuman.khandual@arm.com/
> 
>   Documentation/mm/arch_pgtable_helpers.rst | 2 +-
>   mm/debug_vm_pgtable.c                     | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst
> index 30d9a09f01f4..af3891f895b0 100644
> --- a/Documentation/mm/arch_pgtable_helpers.rst
> +++ b/Documentation/mm/arch_pgtable_helpers.rst
> @@ -214,7 +214,7 @@ HugeTLB Page Table Helpers
>   +---------------------------+--------------------------------------------------+
>   | pte_huge                  | Tests a HugeTLB                                  |
>   +---------------------------+--------------------------------------------------+
> -| pte_mkhuge                | Creates a HugeTLB                                |
> +| arch_make_huge_pte        | Creates a HugeTLB                                |
>   +---------------------------+--------------------------------------------------+
>   | huge_pte_dirty            | Tests a dirty HugeTLB                            |
>   +---------------------------+--------------------------------------------------+
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index af59cc7bd307..7887cc2b75bf 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -934,7 +934,7 @@ static void __init hugetlb_basic_tests(struct pgtable_debug_args *args)
>   #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
>   	pte = pfn_pte(args->fixed_pmd_pfn, args->page_prot);
>   
> -	WARN_ON(!pte_huge(pte_mkhuge(pte)));
> +	WARN_ON(!pte_huge(arch_make_huge_pte(pte, PMD_SHIFT, VM_ACCESS_FLAGS)));
>   #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
>   }
>   #else  /* !CONFIG_HUGETLB_PAGE */


IMHO, it's a bit weird that we are starting to call these things 
"arch_*". PTE operations like these are already mostly arch-specific 
helpers with custom implementations (and some generic ones in 
asm-generic as a fallback).

So this one certainly sticks out now ... anyhow, change itself LGTM ...

-- 
Thanks,

David / dhildenb