On Thu, 23 May 2019 21:20:35 +0300 Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote: > Add XDP support based on rx page_pool allocator, one frame per page. > Page pool allocator is used with assumption that only one rx_handler > is running simultaneously. DMA map/unmap is reused from page pool > despite there is no need to map whole page. When using page_pool for DMA-mapping, your XDP-memory model must use 1-page per packet, which you state you do. This is because __page_pool_put_page() fallback mode does a __page_pool_clean_page() unmapping the DMA. Ilias and I are looking at options for removing this restriction as Mlx5 would need it (when we extend the SKB to return pages to page_pool). Unfortunately, I've found another blocker for drivers using the DMA mapping feature of page_pool. We don't properly handle the case, where a remote TX-driver have xdp_frame's in-flight, and simultaneously the sending driver is unloaded and take down the page_pool. Nothing crash, but we end-up calling put_page() on a page that is still DMA-mapped. I'm working on different solutions for fixing this, see here: https://github.com/xdp-project/xdp-project/blob/master/areas/mem/page_pool03_shutdown_inflight.org -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
