Re: [RFC PATCH v1 18/18] nvme-pci: use new dma API

Leon Romanovsky
2024-07-05T18:48:51Z

On Fri, Jul 05, 2024 at 07:58:06AM +0200, Christoph Hellwig wrote:
> > This is exactly how dma_map_sg() works.
>
> Which dma_map_sg? swiotlb handling is implemented in the underlying
> ops, dma-direct and dma-iommu specifically.
>
> dma-direct just iterates over the entries and calls dma_direct_map_page,
> which does a per-entry decision to bounce based on
> is_swiotlb_force_bounce, dma_capable and dma_kmalloc_needs_bounce.

dma-direct is not going to have "use_iova" flag. Robin pointed to
dma-iommu path.

In that case the flow is dma_map_sg()->iommu_dma_map_sg()->dev_use_sg_swiotlb().

Thanks

>
>