On Tue, Sep 06, 2022 at 08:48:28AM -0300, Jason Gunthorpe wrote: > Right, this whole thing is the "standard" that dmabuf has adopted > instead of the struct pages. Once the AMD GPU driver started doing > this some time ago other drivers followed. But it is simple wrong. The scatterlist requires struct page backing. In theory a physical address would be enough, but when Dan Williams sent patches for that Linus shot them down. That being said the scatterlist is the wrong interface here (and probably for most of it's uses). We really want a lot-level struct with just the dma_address and length for the DMA side, and leave it separate from that what is used to generate it (in most cases that would be a bio_vec). > Now we have struct pages, almost, but I'm not sure if their limits are > compatible with VFIO? This has to work for small bars as well. Why would small BARs be problematic for the pages? The pages are more a problem for gigantic BARs do the memory overhead.
