On Fri, Sep 16, 2016 at 09:03:40PM +0200, Jesper Dangaard Brouer wrote: > Hi Brenden, > > I've discovered a bug with XDP_TX recycling of pages in the mlx4 driver. > > If I increase the number of RX and TX queues/channels via ethtool cmd: > ethtool -L mlx4p1 rx 10 tx 10 > > Then when running the xdp2 program, which does XDP_TX, the kernel will > crash with page errors, because the page refcnt goes to zero or even > minus. I've noticed pages delivered to mlx4_en_rx_recycle() can have > a page refcnt of zero, which is wrong, they should always have 1 (for > XDP). > > Debugging it further, I find that this can happen when mlx4_en_rx_recycle() > is called from mlx4_en_recycle_tx_desc(). This is the TX cleanup function, > associated with TX ring queues used for XDP_TX only. No others than the > XDP_TX action should be able to place packets into these TX rings > which call mlx4_en_recycle_tx_desc().
Sounds pretty straightforward, let me look into it. > > Do you have any idea of what could be going wrong in this case? > > -- > Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > Author of http://www.iptv-analyzer.org > LinkedIn: http://www.linkedin.com/in/brouer > >
