On Tue, 13 Aug 2024 04:39:47 -0400 Mina Almasry wrote: > On Mon, Aug 12, 2024 at 8:15 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > BTW, Mina, the core should probably also check that XDP isn't installed > > before / while the netmem is bound to a queue. > > Sorry if noob question, but what is the proper check for this? if (dev_xdp_prog_count(netdev)) > I tried adding this to net_devmem_bind_dmabuf_to_queue(): > > if (xdp_rxq_info_is_reg(&rxq->xdp_rxq)) > return -EEXIST; > > But quickly found out that in netif_alloc_rx_queues() we initialize > all the rxq->xdp_rxq to state REGISTERED regardless whether xdp is > installed or not, so this check actually fails. > > Worthy of note is that GVE holds an instance of xdp_rxq_info in > gve_rx_ring, and seems to use that for its xdp information, not the > one that hangs off of netdev_rx_queue in core. > > Additionally, my understanding of XDP is limited, but why do we want > to disable it? My understanding is that XDP is a kernel bypass that > hands the data directly to userspace. In theory at least there should > be no issue binding dmabuf to a queue, then getting the data in the > queue via an XDP program instead of via TCP sockets or io uring. Is > there some fundamental reason why dmabuf and XDP are incompatible? You're conflating XDP with AF_XDP, two different things, slightly related but different.
