RE: [Intel-wired-lan] [PATCH iwl-next v5 02/13] idpf: fix Rx descriptor ready check barrier in splitq

-----Original Message-----
From: Intel-wired-lan <redacted> On Behalf Of
Alexander Lobakin
Sent: Tuesday, August 26, 2025 9:25 PM
To: intel-wired-lan@lists.osuosl.org
Cc: Lobakin, Aleksander <aleksander.lobakin@intel.com>; Kubiak, Michal
[off-list ref]; Fijalkowski, Maciej
[off-list ref]; Nguyen, Anthony L
[off-list ref]; Kitszel, Przemyslaw
[off-list ref]; Andrew Lunn [off-list ref];
David S. Miller [off-list ref]; Eric Dumazet
[off-list ref]; Jakub Kicinski [off-list ref]; Paolo Abeni
[off-list ref]; Alexei Starovoitov [off-list ref]; Daniel
Borkmann [off-list ref]; Simon Horman [off-list ref];
NXNE CNSE OSDT ITP Upstreaming
[off-list ref]; bpf@vger.kernel.org;
netdev@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: [Intel-wired-lan] [PATCH iwl-next v5 02/13] idpf: fix Rx descriptor
ready check barrier in splitq

No idea what the current barrier position was meant for. At that point,
nothing is read from the descriptor, only the pointer to the actual one is
fetched.
The correct barrier usage here is after the generation check, so that only the
first qword is read if the descriptor is not yet ready and we need to stop
polling. Debatable on coherent DMA as the Rx descriptor size is <= cacheline
size, but anyway, the current barrier position only makes the codegen worse.

Fixes: 3a8845af66ed ("idpf: add RX splitq napi poll support")
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 drivers/net/ethernet/intel/idpf/idpf_txrx.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Tested-by: R,Ramu <redacted>