[openib-general] How to support IOMMUs for ipath driver

[Or Gerlitz]

Ralph Campbell wrote:
> +static inline dma_addr_t ib_dma_map_sg(struct ib_device *dev,
> +				       struct scatterlist *sg, int nents,
> +				       enum dma_data_direction direction)
> +{
> +	return dev->map_sg ?
> +		dev->map_sg(dev, sg, nents, direction) :
> +		dma_map_sg(dev->dma_device, sg, nents, direction);
> +}

As SG dma mapping happens in place and you don't want to change struct 
scatterlist for every arch, i think you would need to keep some mapping 
(hash) from each struct scatterlist to its ipath buddy...

Also you would need to implement the sg_dma_address() and sg_dma_len() 
macros used by ULP code when page/s is/are to be input-ed for the IB 
verbs layer eg to get an SG FMR-ed or send/recv from/into a page and use 
queries into the ipath scatterlist buddy.

Or.