I looked at this in a bit more detail, and I think we need both. For PAGE_SIZE or smaller SG entries you're correct, and we don't need the offset for dma_addr. But it doesn't harm either.
I think it can harm us.
But for lager SG entries we need it to calculate the correct base address.
I'm not sure if this is true either. Can you explain why? The Memory region mapping is described by: 1. page vector: [addr0, addr1, addr2,...] 2. iova: the first byte offset 3. length: the total byte count of the mr 4. page_size: size of each page in the page vector This means that the HCA assumes that each address in the page vector has the size of page_size, also the region can start at some offset (iova - addr0), and it has some length. So say the HCA wants to write 8k to the MR: first page_size (4k) will be written starting from addr0, and the next page_size (4k) will be written starting from addr1. If you set addr0 = page_addr + offset then the HW will assume it can access addr0 + page_size which is not what we want. I think that the page vectors should contain page addresses and not incorporate offsets. Thoughts? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
