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

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Message-ID: <b748fdcb-e09f-9fe3-dc74-30b6a7d40cbe@codeaurora.org>
Date:   Fri, 6 Apr 2018 14:15:57 -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 4/5/2018 9:34 PM, Sinan Kaya wrote:
> 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
> 
> 

Any news on the MIPS front? Is this something that Arnd can merge? or does it have
to go through the MIPS tree.

It feels like the MIPS is dead since nobody replied to me in the last few weeks on
a very important topic.

-- 
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.