[PATCH V2] riscv: Fixup race condition on PG_dcache_clean in flush_icache_pte

[Conor Dooley]

Hey Guo Ren,

On Thu, Jan 26, 2023 at 10:53:06PM -0500, guoren at kernel.org wrote:
> From: Guo Ren <guoren at linux.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 at linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren at kernel.org>
> ---
> Changelog:
> V2:
>  - Optimize commit log

Probably would have benefited from providing the analysis that the arm64
commit did, for riscv, rather than referring to theirs.
But that's not really important and the diff itself seems sound, so:
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>

Thanks,
Conor.

>  - 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
> 
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