From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Date: Thu, 4 Mar 2021 09:53:56 +0100 Subject: [Intel-wired-lan] [PATCH intel-net 1/3] i40e: move headroom initialization to i40e_configure_rx_ring In-Reply-To: <20210303153928.11764-2-maciej.fijalkowski@intel.com> References: <20210303153928.11764-1-maciej.fijalkowski@intel.com> <20210303153928.11764-2-maciej.fijalkowski@intel.com> Message-ID: <20210304095356.054a8778@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On Wed, 3 Mar 2021 16:39:26 +0100 Maciej Fijalkowski wrote: > i40e_rx_offset(), that is supposed to initialize the Rx buffer headroom, > relies on I40E_RXR_FLAGS_BUILD_SKB_ENABLED flag. > > Currently, the callsite of mentioned function is placed incorrectly > within i40e_setup_rx_descriptors() where Rx ring's build skb flag is not > set yet. This causes the XDP_REDIRECT to be partially broken due to > inability to create xdp_frame in the headroom space, as the headroom is > 0. > > For the record, below is the call graph: > > i40e_vsi_open > i40e_vsi_setup_rx_resources > i40e_setup_rx_descriptors > i40e_rx_offset() <-- sets offset to 0 as build_skb flag is set below > > i40e_vsi_configure_rx > i40e_configure_rx_ring > set_ring_build_skb_enabled(ring) <-- set build_skb flag > > Fix this by moving i40e_rx_offset() to i40e_configure_rx_ring() after > the flag setting. > > Fixes: f7bb0d71d658 ("i40e: store the result of i40e_rx_offset() onto i40e_ring") > Reported-by: Jesper Dangaard Brouer > Co-developed-by: Jesper Dangaard Brouer > Signed-off-by: Jesper Dangaard Brouer > Signed-off-by: Maciej Fijalkowski > --- > drivers/net/ethernet/intel/i40e/i40e_main.c | 13 +++++++++++++ > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 12 ------------ > 2 files changed, 13 insertions(+), 12 deletions(-) Acked-by: Jesper Dangaard Brouer Tested-by: Jesper Dangaard Brouer I'm currently looking at extending samples/bpf/ xdp_redirect_map to detect the situation. As with this bug the redirect tests/sample programs will just report really high performance numbers (because packets are dropped earlier due to err). Knowing what performance numbers to expect, I could see that they were out-of-spec, and investigated the root-cause. I assume Intel QA tested XDP-redirect and didn't find the bug due to this. Red Hat QA also use samples/bpf/xdp* and based on the reports I get from them, I could not blame them if this bug would slip through, as the tool reports "good" results. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer