On Tue, Oct 15, 2024 at 09:49:30PM -0700, Christoph Hellwig wrote: > > + /* > > + * Used for private (un-addressable) device memory only. Return a > > + * corresponding struct page, that can be mapped to device > > + * (e.g using dma_map_page) > > + */ > > + struct page *(*get_dma_page_for_device)(struct page *private_page); > > We are talking about P2P memory here. How do you manage to get a page > that dma_map_page can be used on? All P2P memory needs to use the P2P > aware dma_map_sg as the pages for P2P memory are just fake zone device > pages. FWIW, I've been expecting this series to be rebased on top of Leon's new DMA API series so it doesn't have this issue.. I think this series is at RFC quality, but shows more of the next steps. I'm guessing they got their testing done so far on a system without an iommu translation? > which also makes it clear that returning a page from the method is > not that great, a PFN might work a lot better, e.g. > > unsigned long (*device_private_dma_pfn)(struct page *page); Ideally I think we should not have the struct page * at all through these APIs if we can avoid it.. Jason
