netdev - RE: [RFC PATCH 00/10] Remove skb_dma

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Date:	Mon, 30 Nov 2009 17:03:25 -0800
From:	"Duyck, Alexander H" <alexander.h.duyck@...el.com>
To:	David Miller <davem@...emloft.net>
CC:	"mcarlson@...adcom.com" <mcarlson@...adcom.com>,
	"mchan@...adcom.com" <mchan@...adcom.com>,
	"sathyap@...verengines.com" <sathyap@...verengines.com>,
	"subbus@...verengines.com" <subbus@...verengines.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [RFC PATCH 00/10] Remove skb_dma_map/unmap calls

David Miller wrote:
> From: Alexander Duyck <alexander.h.duyck@...el.com>
> Date: Tue, 24 Nov 2009 17:20:12 -0800
> 
>> This patch series removes the skb_dma_map and skb_dma_unmap function
>> calls. The reason for this change is because the use of
>> skb_dma_map/unmap can lead to serious issues when HW IOMMU is
>> enabled.  This is because each mapping 
>> of the skb with a HW IOMMU enabled results in a new set of DMA
>> mappings. 
>> This in turn leads to issues when skbs are cloned for uses such as
>> bridging or pktgen because each transmitting device will update the
>> skb shared info structure resulting in some mappings being
>> overwritten, and others being freed multiple times. 
>> 
>> I am looking for input specifically on the tg3, be2net, and bnx2
>> driver patches as I am not very familiar with them and I am not
>> certain if additional changes are required.
>> 
>> I have included the changes for the Intel wired Ethernet drivers as a
>> reference.
> 
> These changes look good, but at least one of them does not apply
> to current net-2.6
> 
> Can you respin this against current sources?
> 
> Thanks a lot for doing this work Alexander.

Due to the fact that nobody else had reported the issue and it existed in previous kernel versions I figured it would be easier to just drop it into net-next-2.6.

If you want I can change the patches to net-2.6 though if that is what you would prefer.

Thanks,

Alex--
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