linux-kernel - Re: [PATCH] riscv: fix pfn_to_virt err in do_page

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Message-ID: <20200917152518.GA8930@infradead.org>
Date:   Thu, 17 Sep 2020 16:25:18 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     liush <liush@...winnertech.com>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, akpm@...ux-foundation.org,
        peterx@...hat.com, walken@...gle.com, daniel.m.jordan@...cle.com,
        vbabka@...e.cz, rppt@...nel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: fix pfn_to_virt err in do_page_fault().

On Thu, Sep 17, 2020 at 03:25:49PM +0800, liush wrote:
> The argument to pfn_to_virt() should be pfn not the value of CSR_SATP.
> 
> Signed-off-by: liush <liush@...winnertech.com>
> ---
>  arch/riscv/mm/fault.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 716d64e..9b4e088 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -212,7 +212,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  		 * of a task switch.
>  		 */
>  		index = pgd_index(addr);
> -		pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
> +		pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP) & SATP_PPN) + index;

This adds a crazy long line.  One nice way to clean this up would be to
add a local pfn variable, as it would also make the code more readable.