From: David Miller <davem@davemloft.net>
To: okaya@codeaurora.org
Cc: linux-rdma@vger.kernel.org, timur@codeaurora.org,
cov@codeaurora.org, yishaih@mellanox.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] net: ethernet: mellanox: correct page conversion
Date: Mon, 18 Apr 2016 11:59:02 -0400 (EDT) [thread overview]
Message-ID: <20160418.115902.1053705461620271779.davem@davemloft.net> (raw)
In-Reply-To: <87c17d3f979cf0167cd37077f39d0534@codeaurora.org>
From: okaya@codeaurora.org
Date: Mon, 18 Apr 2016 01:06:27 -0400
> On 2016-04-18 00:00, David Miller wrote:
>> From: Sinan Kaya <okaya@codeaurora.org>
>> Date: Sat, 16 Apr 2016 18:23:32 -0400
>>
>>> Current code is assuming that the address returned by
>>> dma_alloc_coherent
>>> is a logical address. This is not true on ARM/ARM64 systems. This
>>> patch
>>> replaces dma_alloc_coherent with dma_map_page API. The address
>>> returned
>>> can later by virtually mapped from the CPU side with vmap API.
>>> Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
>> You can't do this.
>> The DMA map page API gives non-coherent mappings, and thus requires
>> proper flushing.
>> So a straight conversion like this is never legitimate.
>
> I would agree on proper dma api usage. However, the code is already
> assuming coherent architecture by mapping the cpu pages as
> page_kernel.
>
> Dma_map_page returns cached buffers and you don't need cache flushes
> on coherent architecture to make the data visible.
All you are telling me is that there are two bugs instead of one, so now
both need to be fixed.
next prev parent reply other threads:[~2016-04-18 15:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-16 22:23 [PATCH V2] net: ethernet: mellanox: correct page conversion Sinan Kaya
2016-04-18 4:00 ` David Miller
2016-04-18 5:06 ` okaya
2016-04-18 15:59 ` David Miller [this message]
2016-04-18 16:06 ` Sinan Kaya
2016-04-18 6:54 ` Eli Cohen
2016-04-18 13:53 ` Sinan Kaya
2016-04-18 14:05 ` Eli Cohen
2016-04-18 14:32 ` Christoph Hellwig
2016-04-18 14:39 ` Eli Cohen
2016-04-18 15:17 ` Christoph Hellwig
2016-04-18 15:21 ` Sinan Kaya
2016-04-18 15:40 ` Christoph Hellwig
2016-04-18 17:47 ` Sinan Kaya
2016-04-19 7:50 ` Sinan Kaya
2016-04-18 12:12 ` Christoph Hellwig
2016-04-18 13:06 ` okaya
2016-04-18 13:10 ` Christoph Hellwig
2016-04-18 13:49 ` Sinan Kaya
2016-04-18 13:59 ` Christoph Hellwig
2016-04-18 15:15 ` Timur Tabi
2016-04-18 15:22 ` Sinan Kaya
2016-04-19 18:22 ` Christoph Hellwig
2016-04-19 18:37 ` Sinan Kaya
2016-04-20 11:08 ` Eran Ben Elisha
2016-04-20 13:35 ` Sinan Kaya
2016-04-20 13:38 ` Sinan Kaya
2016-04-20 13:41 ` Timur Tabi
2016-04-20 18:40 ` Eran Ben Elisha
2016-04-20 18:42 ` Sinan Kaya
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