RE: [Intel-wired-lan] [PATCH intel-net 1/3] i40e: move headroom initialization to i40e_configure_rx_ring

-----Original Message-----
From: Intel-wired-lan <redacted> On Behalf Of
Maciej Fijalkowski
Sent: Wednesday, March 3, 2021 9:09 PM
To: intel-wired-lan@lists.osuosl.org
Cc: netdev@vger.kernel.org; brouer@redhat.com; kuba@kernel.org;
bpf@vger.kernel.org; Topel, Bjorn [off-list ref]; Karlsson,
Magnus [off-list ref]
Subject: [Intel-wired-lan] [PATCH intel-net 1/3] i40e: move headroom
initialization to i40e_configure_rx_ring

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 <redacted>
Co-developed-by: Jesper Dangaard Brouer <redacted>
Signed-off-by: Jesper Dangaard Brouer <redacted>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 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(-)

Tested-by: Kiran Bhandare <redacted>  A Contingent Worker at Intel