netdev - Re: Memory corruption with r8169 across several device revisions and kernels

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Date:   Wed, 24 Jan 2018 06:31:41 +0100
From:   Andreas Hartmann <andihartmann@...19freenet.de>
To:     Oliver Freyermuth <o.freyermuth@...glemail.com>,
        David Miller <davem@...emloft.net>
Cc:     romieu@...zoreil.com, netdev@...r.kernel.org
Subject: Re: Memory corruption with r8169 across several device revisions and
 kernels

On 01/23/2018 at 04:47 PM Oliver Freyermuth wrote:
> Am 23.01.2018 um 16:28 schrieb David Miller:
>> Looking at how these DMA counters are handled, there appears to be a
>> requirement that the memory buffer is 64-byte aligned.
>>
>> [...]
>>
>> Therefore the driver needs to allocate "size + (64 - 1)" bytes and do
>> the 64-byte alignment of the CPU pointer and the DMA address by hand.
> 
> This is also what I wondered about as a non-expert in hardware drivers; 
> alignment should surely be enforced here. 
> 
> However, for the memory corruption I observed, I used an x86_64 system
> (which I believe always has PAGE_SIZE aligned buffers). 
> So there should be another bug, unless I am mistaken about x86_64. 
> 
> I checked the deprecated r8168 driver by Realtek (I am not sure if this one is also affected by the issue, though)

I'm using since years this driver because r8169 is broken (it is slow
and it misses packages - which is extremely bad for real time
applications like asterisk, if they appear 50s later ...).

r8168-8.045.08 is an actual version which is provided by realtek on
their homepage and which even compiles fine w/ 4.14.x.


Regards,
Andreas