On Thu, Nov 07, 2024 at 09:28:08AM -0400, Jason Gunthorpe wrote: > Once we are freed from scatterlist we can explore a design that would > pass the P2P routing information directly. For instance imagine > something like: > > dma_map_p2p(dev, phys, p2p_provider); > > Then dma_map_page(dev, page) could be something like > > if (is_pci_p2pdma_page(page)) > dev_map_p2p(dev, page_to_phys(page), page->pgmap->p2p_provider) One thing that this series does is to move the P2P mapping decisions out of the low-level dma mapping helpers and into the caller (again) for the non-sg callers and moves the special switch based bus mapping into a routine that can be called directly. Take a look at blk_rq_dma_map_iter_start, which now literally uses dma_map_page for the no-iommu, no-switch P2P case. It also is a good use case for the proposed dma_map_phys. > GPU driver > > https://lore.kernel.org/dri-devel/20240117221223.18540-7-oak.zeng@xxxxxxxxx/ Eww, that's horrible. Converting this to Leon's new hmm helpers would be really nice (and how that they are useful for more than mlx5).
