Ajit Khaparde wrote:

On 24/11/09 17:20 -0800, Alexander Duyck wrote:

quoted

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.

If this is the case can the members related to the dma mapping stuff
(skb_shinfo(skb)->dma_maps) be moved out of this shared info structure and
we retain this "good" abstraction provided by this skb_dma_map/unmap api?

I had submitted a patch on November 5th that tried to move the maps out 
of the shared info structure and into the sk_buff itself.  That was 
rejected and it was suggested to go back to what was there before since 
not enough drivers were using the skb_dma_map/unmap calls to justify 
increasing the size of an sk_buff.

The biggest issue is that you end up needing to retain a copy of the DMA 
mapping output each time it is called and so the easiest place to retain 
the information is within the transmit buffer driver specific data 
structure.

quoted

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.

quoted

      be2net: remove use of skb_dma_map/unmap

 drivers/net/benet/be_main.c    |   37 ++++++---

We have pulled the be2net specific patch for testing and review.
We will send an update once done with it.

-Ajit

Thanks for taking a look at this.

Alex