[PATCH -fixes 2/2] riscv: Fix set_huge_pte_at() for NAPOT mappings when a swap entry is set

[Conor Dooley]

On Thu, Sep 28, 2023 at 05:18:46PM +0200, Alexandre Ghiti wrote:
> We used to determine the number of page table entries to set for a NAPOT
> hugepage by using the pte value which actually fails when the pte to set is
> a swap entry.
> 
> So take advantage of a recent fix for arm64 reported in [1] which
> introduces the size of the mapping as an argument of set_huge_pte_at(): we
> can then use this size to compute the number of page table entries to set
> for a NAPOT region.
> 
> Fixes: 82a1a1f3bfb6 ("riscv: mm: support Svnapot in hugetlb page")
> Reported-by: Ryan Roberts <ryan.roberts at arm.com>
> Closes: https://lore.kernel.org/linux-arm-kernel/20230922115804.2043771-1-ryan.roberts@arm.com/ [1]
> Signed-off-by: Alexandre Ghiti <alexghiti at rivosinc.com>

Breaks the build. Your $subject marks this for -fixes, but this will not
build there, as it relies on content that's not yet in that branch.
AFAICT, you're going to have to resend this with akpm on CC, as the
dependency is in his tree...

Thanks,
Conor.

> ---
>  arch/riscv/mm/hugetlbpage.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
> index e4a2ace92dbe..b52f0210481f 100644
> --- a/arch/riscv/mm/hugetlbpage.c
> +++ b/arch/riscv/mm/hugetlbpage.c
> @@ -183,15 +183,22 @@ void set_huge_pte_at(struct mm_struct *mm,
>  		     pte_t pte,
>  		     unsigned long sz)
>  {
> +	unsigned long hugepage_shift;
>  	int i, pte_num;
>  
> -	if (!pte_napot(pte)) {
> -		set_pte_at(mm, addr, ptep, pte);
> -		return;
> -	}
> +	if (sz >= PGDIR_SIZE)
> +		hugepage_shift = PGDIR_SHIFT;
> +	else if (sz >= P4D_SIZE)
> +		hugepage_shift = P4D_SHIFT;
> +	else if (sz >= PUD_SIZE)
> +		hugepage_shift = PUD_SHIFT;
> +	else if (sz >= PMD_SIZE)
> +		hugepage_shift = PMD_SHIFT;
> +	else
> +		hugepage_shift = PAGE_SHIFT;
>  
> -	pte_num = napot_pte_num(napot_cont_order(pte));
> -	for (i = 0; i < pte_num; i++, ptep++, addr += PAGE_SIZE)
> +	pte_num = sz >> hugepage_shift;
> +	for (i = 0; i < pte_num; i++, ptep++, addr += (1 << hugepage_shift))
>  		set_pte_at(mm, addr, ptep, pte);
>  }
>  
> -- 
> 2.39.2
> 
> 
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