In commit 'ixgbe: let the xdpdrv work with more than 64 cpus' (4fe815850bdc8d4cc94e06fe1de069424a895826), support was added to allow XDP programs to run on systems with more than 64 CPUs by locking the XDP TX rings and indexing them using cpu % 64 (IXGBE_MAX_XDP_QS). Upon trying this out patch via the Intel 5.18.6 out of tree driver on a system with more than 64 cores, the kernel paniced with an array-index-out-of-bounds at the return in ixgbe_determine_xdp_ring in ixgbe.h, which means ixgbe_determine_xdp_q_idx was just returning the cpu instead of cpu % IXGBE_MAX_XDP_QS. I think this is how it happens: Upon loading the first XDP program on a system with more than 64 CPUs, ixgbe_xdp_locking_key is incremented in ixgbe_xdp_setup. However, immediately after this, the rings are reconfigured by ixgbe_setup_tc. ixgbe_setup_tc calls ixgbe_clear_interrupt_scheme which calls ixgbe_free_q_vectors which calls ixgbe_free_q_vector in a loop. ixgbe_free_q_vector decrements ixgbe_xdp_locking_key once per call if it is non-zero. Commenting out the decrement in ixgbe_free_q_vector stopped my system from panicing. I suspect to make the original patch work, I would need to load an XDP program and then replace it in order to get ixgbe_xdp_locking_key back above 0 since ixgbe_setup_tc is only called when transitioning between XDP and non-XDP ring configurations, while ixgbe_xdp_locking_key is incremented every time ixgbe_xdp_setup is called. Also, ixgbe_setup_tc can be called via ethtool --set-channels, so this becomes another path to decrement ixgbe_xdp_locking_key to 0 on systems with greater than 64 CPUs. For this patch, I have changed static_branch_inc to static_branch_enable in ixgbe_setup_xdp. We aren't counting references and I don't see any reason to turn it off, since all the locking appears to be in the XDP_TX path, which isn't run if a XDP program isn't loaded. Signed-off-by: John Hickey <jjh@xxxxxxxxxxxx> --- drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c | 3 --- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 2 +- 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c index f8156fe4b1dc..0ee943db3dc9 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c @@ -1035,9 +1035,6 @@ static void ixgbe_free_q_vector(struct ixgbe_adapter *adapter, int v_idx) adapter->q_vector[v_idx] = NULL; __netif_napi_del(&q_vector->napi); - if (static_key_enabled(&ixgbe_xdp_locking_key)) - static_branch_dec(&ixgbe_xdp_locking_key); - /* * after a call to __netif_napi_del() napi may still be used and * ixgbe_get_stats64() might access the rings on this vector, diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c index ab8370c413f3..cd2fb72c67be 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -10283,7 +10283,7 @@ static int ixgbe_xdp_setup(struct net_device *dev, struct bpf_prog *prog) if (nr_cpu_ids > IXGBE_MAX_XDP_QS * 2) return -ENOMEM; else if (nr_cpu_ids > IXGBE_MAX_XDP_QS) - static_branch_inc(&ixgbe_xdp_locking_key); + static_branch_enable(&ixgbe_xdp_locking_key); old_prog = xchg(&adapter->xdp_prog, prog); need_reset = (!!prog != !!old_prog); -- 2.37.2
