On Tue, Dec 18, 2018 at 10:45:21AM -0700, Stephen Warren wrote: > There are two allocation paths; one using dma_alloc_coherent and one using > alloc_pages. (The hns driver only has the dma_alloc_coherent path.) These > both store allocations into an sg list which is stored in a table, and that > table is searched by a single function mlx4_table_find() irrespective of > which allocation path was used, so if one of the allocation paths is updated > to store the CPU virtual address differently, then both paths need to be > updated so they match, so that the single table search path can continue to > have a single implementation. So the problem here is that on some arches sg_set_buf(sg, dma_coherent_buf, size) p = sg_virt(sg); assert(p == dma_coherent_buf); Doesn't work or crashes? Is this how sgl should work? But if you accept this and don't do the sg_set_buf then the scatterlist is substantially broken, many of the APIs related to it will not work as expected at all. So, I don't think drivers should create such a broken scatterlist or arches should not have this problem (ie the mathematical transformation to struct page * and back to virtual address should work in the coherent space even if there are no backing struct pages allocated)? What do you think CH? Jason
