Re: [PATCH v1 3/8] riscv: hugetlb: Convert set_huge_pte_at() to take vma

Alexandre Ghiti
2023-09-22T07:54:42Z

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@arm.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@rivosinc.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