[ewg] Re: [ofa-general] Toward next OFED release (1.3)

[Roland Dreier]

 > > Sorry... I've been remiss in posting about this.  I would actually
 > > prefer to see an extension to the dma_map_sg() interface (a new flag
 > > perhaps?) that would set the right magic bit in the DMA address on
 > > altix.  The refactoring of ib_umem_get() to be called by low-level
 > > drivers makes this a fairly clean approach, and it avoids the problems
 > > with using dma_alloc_coherent() to allocate userspace buffers (for
 > > example, dma_alloc_coherent() uses up kernel virtual addresses, which
 > > may be scarce on 32 bit architectures).

 > While this make sense it would be hard to push into the kernel proper.
 > Or no? Are you going to do that?

I don't think I'm willing to merge a fix that uses dma_alloc_coherent()
inside the kernel so this alternate fix is probably easier to merge.
Yes, it does mean an extension to the DMA mapping API but I think
getting that right will be useful in terms of making sure what we're
doing really makes sense.

 - R.