On Fri, 4 Sep 2020 10:30:48 -0600 David Ahern <dsahern@xxxxxxxxx> wrote: > On 9/4/20 9:59 AM, Jesper Dangaard Brouer wrote: > >> dev_rx for example seems like it could just be the netdev > >> index rather than a pointer or perhaps can be removed completely. I > >> believe it is only used for 1 use case (redirects to CPUMAP); maybe that > >> code can be refactored to handle the dev outside of xdp_frame. > > > > The dev_rx is needed when creating an SKB from a xdp_frame (basically > > skb->dev = rx_dev). Yes, that is done in cpumap, but I want to > > generalize this. The veth also creates SKBs from xdp_frame, but use > > itself as skb->dev. > > > > And yes, we could save some space storing the index instead, and trade > > space for cycles in a lookup. > > I think this can be managed without adding a reference to the xdp_frame. > I'll start a separate thread on that. > > >> > >> As for frame_sz, why does it need to be larger than a u16? > > > > Because PAGE_SIZE can be 64KiB on some archs. > > I also believe syzbot managed to create packets for generic-XDP with frame_sz 128KiB, which was a bit weird (it's on my todo list to investigate and fix). > ok, is there any alignment requirement? can frame_sz be number of 32-bit > words? I believe bit shifts are cheap. No that is not possible, because some drivers and generic-XDP have a fully dynamic frame_sz. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
