linux-kernel - Re: [PATCH v2 2/3] RISC-V: mm: Enable huge page support to kernel_page

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Date:   Mon, 9 Jan 2023 15:45:25 +0100
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Sia Jee Heng <jeeheng.sia@...rfivetech.com>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, leyfoon.tan@...rfivetech.com,
        mason.huo@...rfivetech.com
Subject: Re: [PATCH v2 2/3] RISC-V: mm: Enable huge page support to
 kernel_page_present() function

On Mon, Jan 09, 2023 at 02:24:06PM +0800, Sia Jee Heng wrote:
> Currently kernel_page_present() function doesn't support huge page
> detection causes the function to mistakenly return false to the
> hibernation core.
> 
> Add huge page detection to the function to solve the problem.
> 
> Signed-off-by: Sia Jee Heng <jeeheng.sia@...rfivetech.com>
> Reviewed-by: Ley Foon Tan <leyfoon.tan@...rfivetech.com>
> Reviewed-by: Mason Huo <mason.huo@...rfivetech.com>
> ---
>  arch/riscv/mm/pageattr.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
> index 86c56616e5de..73fdec8c0a72 100644
> --- a/arch/riscv/mm/pageattr.c
> +++ b/arch/riscv/mm/pageattr.c
> @@ -221,14 +221,20 @@ bool kernel_page_present(struct page *page)
>  	p4d = p4d_offset(pgd, addr);
>  	if (!p4d_present(*p4d))
>  		return false;
> +	if (p4d_leaf(*pud))
                      ^ p4d

I guess you got lucky with the stack garbage in your testing.

> +		return true;
>  
>  	pud = pud_offset(p4d, addr);
>  	if (!pud_present(*pud))
>  		return false;
> +	if (pud_leaf(*pud))
> +		return true;
>  
>  	pmd = pmd_offset(pud, addr);
>  	if (!pmd_present(*pmd))
>  		return false;
> +	if (pmd_leaf(*pmd))
> +		return true;
>  
>  	pte = pte_offset_kernel(pmd, addr);
>  	return pte_present(*pte);
> -- 
> 2.34.1
>

Thanks,
drew