netdev - [PATCH net] idpf: fix idpf_vport_splitq_napi

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Message-ID: <20250520124030.1983936-1-edumazet@google.com>
Date: Tue, 20 May 2025 12:40:30 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Tony Nguyen <anthony.l.nguyen@...el.com>, 
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Peter Newman <peternewman@...gle.com>, 
	Joshua Hay <joshua.a.hay@...el.com>, Alan Brady <alan.brady@...el.com>, 
	Madhu Chittim <madhu.chittim@...el.com>, Phani Burra <phani.r.burra@...el.com>, 
	Pavan Kumar Linga <pavan.kumar.linga@...el.com>
Subject: [PATCH net] idpf: fix idpf_vport_splitq_napi_poll()

idpf_vport_splitq_napi_poll() can incorrectly return @budget
after napi_complete_done() has been called.

This violates NAPI rules, because after napi_complete_done(),
current thread lost napi ownership.

Move the test against POLL_MODE before the napi_complete_done().

Fixes: c2d548cad150 ("idpf: add TX splitq napi poll support")
Reported-by: Peter Newman <peternewman@...gle.com>
Closes: https://lore.kernel.org/netdev/20250520121908.1805732-1-edumazet@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Joshua Hay <joshua.a.hay@...el.com>
Cc: Alan Brady <alan.brady@...el.com>
Cc: Madhu Chittim <madhu.chittim@...el.com>
Cc: Phani Burra <phani.r.burra@...el.com>
Cc: Pavan Kumar Linga <pavan.kumar.linga@...el.com>
---
 drivers/net/ethernet/intel/idpf/idpf_txrx.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
index bdf52cef3891b8ff1d919b7024d42d024299215e..2d5f5c9f91ce1ef331e577848d91b0d130dcce8c 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
@@ -4025,6 +4025,14 @@ static int idpf_vport_splitq_napi_poll(struct napi_struct *napi, int budget)
 		return budget;
 	}
 
+	/* Switch to poll mode in the tear-down path after sending disable
+	 * queues virtchnl message, as the interrupts will be disabled after
+	 * that.
+	 */
+	if (unlikely(q_vector->num_txq && idpf_queue_has(POLL_MODE,
+							 q_vector->tx[0])))
+		return budget;
+
 	work_done = min_t(int, work_done, budget - 1);
 
 	/* Exit the polling mode, but don't re-enable interrupts if stack might
@@ -4035,15 +4043,7 @@ static int idpf_vport_splitq_napi_poll(struct napi_struct *napi, int budget)
 	else
 		idpf_vport_intr_set_wb_on_itr(q_vector);
 
-	/* Switch to poll mode in the tear-down path after sending disable
-	 * queues virtchnl message, as the interrupts will be disabled after
-	 * that
-	 */
-	if (unlikely(q_vector->num_txq && idpf_queue_has(POLL_MODE,
-							 q_vector->tx[0])))
-		return budget;
-	else
-		return work_done;
+	return work_done;
 }
 
 /**
-- 
2.49.0.1101.gccaa498523-goog