On Wed, Mar 06, 2019 at 05:55:11PM +0200, Gal Pressman wrote: > Looks like some of the drivers operate on the scatterlist itself (no chaining), > while others (such as the one you cited) operate on a sg table. I wonder if we > should convert all to use scatterlist or sg tables? sg table is generally simpler for cases that don't need extreme efficiency > Also, EFA is special in the sense that all sg functions use PAGE_SIZE while EFA > needs EFA_PAGE_SIZE. I guess it could be solved by passing that as a parameter, > but that'll probably require some changes in existing API functions > (__sg_alloc_table_from_pages for example)? No, you are supposed to build up the sgl in large chunks and then fragment it into whatever the HW requires after DMA mapping. The code as written is wrong, as the IOMMU is free to consolidate the carefully broken up SGL into a single entry after doing dma_map. Fragementation for HW page size limitations must be done after mapping to use the APIs correctly. Shiraz is working on a function to iterate over a sgl in specified fixed size blocks (ie EFA_PAGE_SIZE), you should work with him as it is exactly what is needed here as well. > Would you consider keeping efa_vmalloc_buf_to_sg() as a temporary solution? > The scope of this change is a bit bigger than just RDMA and I'd like to split > these changes. You still have to make what you have right.. I'd suggest you write the full function you'd like to propose for lib/scatterlist.c in EFA and commit to move it out later. Jason
