[PATCH v2] iommu: Streamline iommu_iova_to_phys()

[Christoph Hellwig]

On Thu, Jul 15, 2021 at 03:16:08PM +0100, Robin Murphy wrote:
> On 2021-07-15 15:07, Christoph Hellwig wrote:
> > On Thu, Jul 15, 2021 at 02:04:24PM +0100, Robin Murphy wrote:
> > > If people are going to insist on calling iommu_iova_to_phys()
> > > pointlessly and expecting it to work,
> > 
> > Maybe we need to fix that?
> 
> Feel free to try, but we didn't have much luck pushing back on it
> previously, so playing whack-a-mole against netdev now is a game I'm
> personally happy to stay away from ;)

One thing I've done with symbols I want people to not use it to
unexport them.  But what about vfio?

While we're talking about iommu_iova_to_phys: __iommu_dma_unmap_swiotlb
calls it unconditionally, despite only needed ing the physical address.
Can we optimize that somehow by splitting out the bounce buffering case
out?