[PATCH AUTOSEL for 4.9 050/100] i40e: Do not enable NAPI on q_vectors that have no rings

[alexander . levin]

From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>

[ Upstream commit 13a8cd191a2b470cfd435b3b57dbd21aa65ff78c ]

When testing the epoll w/ busy poll code I found that I could get into a
state where the i40e driver had q_vectors w/ active NAPI that had no rings.
This was resulting in a divide by zero error.  To correct it I am updating
the driver code so that we only support NAPI on q_vectors that have 1 or
more rings allocated to them.

Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
Tested-by: Andrew Bowers <andrewx.bowers@xxxxxxxxx>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 2caafebb0295..becffd15c092 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -4217,8 +4217,12 @@ static void i40e_napi_enable_all(struct i40e_vsi *vsi)
 	if (!vsi->netdev)
 		return;
 
-	for (q_idx = 0; q_idx < vsi->num_q_vectors; q_idx++)
-		napi_enable(&vsi->q_vectors[q_idx]->napi);
+	for (q_idx = 0; q_idx < vsi->num_q_vectors; q_idx++) {
+		struct i40e_q_vector *q_vector = vsi->q_vectors[q_idx];
+
+		if (q_vector->rx.ring || q_vector->tx.ring)
+			napi_enable(&q_vector->napi);
+	}
 }
 
 /**
@@ -4232,8 +4236,12 @@ static void i40e_napi_disable_all(struct i40e_vsi *vsi)
 	if (!vsi->netdev)
 		return;
 
-	for (q_idx = 0; q_idx < vsi->num_q_vectors; q_idx++)
-		napi_disable(&vsi->q_vectors[q_idx]->napi);
+	for (q_idx = 0; q_idx < vsi->num_q_vectors; q_idx++) {
+		struct i40e_q_vector *q_vector = vsi->q_vectors[q_idx];
+
+		if (q_vector->rx.ring || q_vector->tx.ring)
+			napi_disable(&q_vector->napi);
+	}
 }
 
 /**
-- 
2.11.0