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Date:   Fri, 28 Apr 2023 14:40:08 +0200
From:   Andrew Jones <ajones@ventanamicro.com>
To:     Alexandre Ghiti <alexghiti@rivosinc.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Qinglin Pan <panqinglin2020@iscas.ac.cn>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -fixes 1/2] riscv: Fix huge_ptep_set_wrprotect when PTE
 is a NAPOT
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References: <20230428120120.21620-1-alexghiti@rivosinc.com>
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On Fri, Apr 28, 2023 at 02:01:19PM +0200, Alexandre Ghiti wrote:
> We need to avoid inconsistencies across the PTEs that form a NAPOT
> region, so when we write protect such a region, we should clear and flush
> all the PTEs to make sure that any of those PTEs is not cached which would
> result in such inconsistencies (arm64 does the same).
> 
> Fixes: f2aeb0118ddd ("riscv: mm: support Svnapot in hugetlb page")
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
>  arch/riscv/mm/hugetlbpage.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
> index a163a3e0f0d4..238d00bdac14 100644
> --- a/arch/riscv/mm/hugetlbpage.c
> +++ b/arch/riscv/mm/hugetlbpage.c
> @@ -218,6 +218,7 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm,
>  {
>  	pte_t pte = ptep_get(ptep);
>  	unsigned long order;
> +	pte_t orig_pte;
>  	int i, pte_num;
>  
>  	if (!pte_napot(pte)) {
> @@ -228,9 +229,12 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm,
>  	order = napot_cont_order(pte);
>  	pte_num = napot_pte_num(order);
>  	ptep = huge_pte_offset(mm, addr, napot_cont_size(order));
> +	orig_pte = get_clear_contig_flush(mm, addr, ptep, pte_num);
> +
> +	orig_pte = pte_wrprotect(orig_pte);
>  
>  	for (i = 0; i < pte_num; i++, addr += PAGE_SIZE, ptep++)
> -		ptep_set_wrprotect(mm, addr, ptep);
> +		set_pte_at(mm, addr, ptep, orig_pte);
>  }
>  
>  pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
> -- 
> 2.37.2
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>