linux-kernel - Re: [PATCH v3 2/2] MIPS: io: add a barrier after register read in readX()

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Date:   Thu, 5 Apr 2018 21:34:31 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     linux-mips@...ux-mips.org, arnd@...db.de, timur@...eaurora.org,
        sulrich@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] MIPS: io: add a barrier after register read in
 readX()

On 4/3/2018 8:55 AM, Sinan Kaya wrote:
> While a barrier is present in writeX() function before the register write,
> a similar barrier is missing in the readX() function after the register
> read. This could allow memory accesses following readX() to observe
> stale data.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> Reported-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/mips/include/asm/io.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
> index fd00ddaf..6ac502f 100644
> --- a/arch/mips/include/asm/io.h
> +++ b/arch/mips/include/asm/io.h
> @@ -377,6 +377,7 @@ static inline type pfx##read##bwlq(const volatile void __iomem *mem)	\
>  		BUG();							\
>  	}								\
>  									\
> +	rmb();								\
>  	return pfx##ioswab##bwlq(__mem, __val);				\
>  }
>  
> 

Can we get these merged to 4.17? 

There was a consensus to fix the architectures having API violation issues.
https://www.mail-archive.com/netdev@vger.kernel.org/msg225971.html


-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.