linux-kernel - Re: [PATCH V2] riscv: Fixup race condition on PG_dcache_clean in flush_icache

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Date:   Fri, 27 Jan 2023 12:34:51 +0100
From:   Andrew Jones <ajones@...tanamicro.com>
To:     guoren@...nel.org
Cc:     arnd@...db.de, palmer@...osinc.com, conor.dooley@...rochip.com,
        apatel@...tanamicro.com, atishp@...shpatra.org,
        mark.rutland@....com, bjorn@...nel.org, tongtiangen@...wei.com,
        andrew@...ive.com, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V2] riscv: Fixup race condition on PG_dcache_clean in
 flush_icache_pte

On Thu, Jan 26, 2023 at 10:53:06PM -0500, guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> In commit 588a513d3425 ("arm64: Fix race condition on PG_dcache_clean
> in __sync_icache_dcache()"), we found RISC-V has the same issue as the
> previous arm64. The previous implementation didn't guarantee the correct
> sequence of operations, which means flush_icache_all() hasn't been
> called when the PG_dcache_clean was set. That would cause a risk of page
> synchronization.
> 
> Fixes: 08f051eda33b ("RISC-V: Flush I$ when making a dirty page executable")
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> ---
> Changelog:
> V2:
>  - Optimize commit log
>  - Rebase on riscv for-next (20230127)
> 
> V1:
> https://lore.kernel.org/linux-riscv/20221023133205.3493564-2-guoren@kernel.org/
> ---
>  arch/riscv/mm/cacheflush.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> index 3cc07ed45aeb..fcd6145fbead 100644
> --- a/arch/riscv/mm/cacheflush.c
> +++ b/arch/riscv/mm/cacheflush.c
> @@ -90,8 +90,10 @@ void flush_icache_pte(pte_t pte)
>  	if (PageHuge(page))
>  		page = compound_head(page);
>  
> -	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
> +	if (!test_bit(PG_dcache_clean, &page->flags)) {
>  		flush_icache_all();
> +		set_bit(PG_dcache_clean, &page->flags);
> +	}
>  }
>  #endif /* CONFIG_MMU */
>  
> -- 
> 2.36.1
>

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

Thanks,
drew