On Wed, Feb 05, 2020 at 05:58:31AM +0100, Maciej Fijalkowski wrote: > Cameron reported [0] that on fresh bpf-next he could not run multiple > xdpsock instances in Tx-only mode on single network interface with i40e > driver. > > Turns out that Maxim's series [1] which was adding RCU protection around > ndo_xsk_wakeup added check against the __I40E_CONFIG_BUSY being set on > pf->state within i40e_xsk_wakeup() - if it's set, return -ENETDOWN. > Since this bit is set per PF when UMEM is being enabled/disabled, the > situation Cameron stumbled upon was that when he launched second xdpsock > instance, second UMEM was being registered, hence set __I40E_CONFIG_BUSY > which is now observed by first xdpsock and therefore xdpsock's kick_tx() > gets -ENETDOWN as errno. > > -ENETDOWN currently is not allowed in kick_tx(), so we were exiting the > first application. Such exit means also XDP program being unloaded and > its dedicated resources, which caused an -ENXIO being return in the > second xdpsock instance. > > Let's fix the issue from both sides - protect ourselves from future > xdpsock crashes by allowing for -ENETDOWN errno being set in kick_tx() > (patch 3) and from driver side, return -EAGAIN for the case where PF is > busy (patch 1). > > Remove also doubled variable from xdpsock_user.c (patch 2). > > Note that ixgbe seems not to be affected since UMEM registration sets > the busy/disable bit per ring, not per PF. > > Thanks! > Maciej > > [0]: https://www.spinics.net/lists/xdp-newbies/msg01558.html > [1]: https://lore.kernel.org/netdev/20191217162023.16011-1-maximmi@xxxxxxxxxxxx/ Applied, thanks!
