linux-kernel - Re: [PATCH v1 3/8] riscv: hugetlb: Convert set_huge_pte

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Message-ID: <7bbceed4-c5f6-42d4-5d94-060032b73385@ghiti.fr>
Date:   Fri, 22 Sep 2023 09:54:21 +0200
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Ryan Roberts <ryan.roberts@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        SeongJae Park <sj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Peter Xu <peterx@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v1 3/8] riscv: hugetlb: Convert set_huge_pte_at() to take
 vma

Hi Ryan,

On 21/09/2023 18:20, Ryan Roberts wrote:
> In order to fix a bug, arm64 needs access to the vma inside it's
> implementation of set_huge_pte_at(). Provide for this by converting the
> mm parameter to be a vma. Any implementations that require the mm can
> access it via vma->vm_mm.
>
> This commit makes the required riscv modifications. Separate commits
> update the other arches and core code, before the actual bug is fixed in
> arm64.
>
> No behavioral changes intended.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>   arch/riscv/include/asm/hugetlb.h | 2 +-
>   arch/riscv/mm/hugetlbpage.c      | 3 ++-
>   2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/hugetlb.h b/arch/riscv/include/asm/hugetlb.h
> index 34e24f078cc1..be1ac8582bc2 100644
> --- a/arch/riscv/include/asm/hugetlb.h
> +++ b/arch/riscv/include/asm/hugetlb.h
> @@ -17,7 +17,7 @@ void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>   		    pte_t *ptep, unsigned long sz);
>   
>   #define __HAVE_ARCH_HUGE_SET_HUGE_PTE_AT
> -void set_huge_pte_at(struct mm_struct *mm,
> +void set_huge_pte_at(struct vm_area_struct *vma,
>   		     unsigned long addr, pte_t *ptep, pte_t pte);
>   
>   #define __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
> diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
> index 96225a8533ad..7cdbf0960772 100644
> --- a/arch/riscv/mm/hugetlbpage.c
> +++ b/arch/riscv/mm/hugetlbpage.c
> @@ -177,11 +177,12 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>   	return entry;
>   }
>   
> -void set_huge_pte_at(struct mm_struct *mm,
> +void set_huge_pte_at(struct vm_area_struct *vma,
>   		     unsigned long addr,
>   		     pte_t *ptep,
>   		     pte_t pte)
>   {
> +	struct mm_struct *mm = vma->vm_mm;
>   	int i, pte_num;
>   
>   	if (!pte_napot(pte)) {


You can add:

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

I realize that we may have the same issue with our contig pte 
implementation (called napot in riscv) as we don't handle swap/migration 
entries at all. So I guess we need something similar, and I'll implement 
it (unless you want to do it of course, but I guess it's easier for me 
to test). One (maybe stupid) question though: wouldn't it be possible to 
extract the contig pte size from the value of ptep instead of using a vma?

Thanks,

Alex