[PATCH net v2] qed: fix division by zero in qed_init_wfq_param when all vports are configured

[Evgenii Burenchev <evg28bur@yandex.ru>]

In qed_init_wfq_param(), variable non_requested_count can become zero
when the number of vports with the configured flag set (including the
current vport being configured) equals total num_vports. This happens
when configuring the last unconfigured vport or when re-configuring
an already configured vport.

The function then calculates left_rate_per_vp = total_left_rate /
non_requested_count, which causes division by zero.

Fix this by skipping the division when non_requested_count is zero.
In that case, there is no remaining bandwidth to distribute, so just
record the configuration for the current vport and return success.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: bcd197c81f63 ("qed: Add vport WFQ configuration APIs")
Signed-off-by: Evgenii Burenchev <evg28bur@yandex.ru>
---
Changes in v2:
- Return success instead of -EINVAL when non_requested_count is zero
- Add Fixes tag
- Clarify commit message: explain both scenarios that lead to non_requested_count == 0
---
 drivers/net/ethernet/qlogic/qed/qed_dev.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_dev.c b/drivers/net/ethernet/qlogic/qed/qed_dev.c
index 42c6dcfb1f0f..dd75c47758e1 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_dev.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_dev.c
@@ -5103,6 +5103,13 @@ static int qed_init_wfq_param(struct qed_hwfn *p_hwfn,
 		return -EINVAL;
 	}
 
+	/* All vports are already or become configured, nothing to distribute */
+	if (non_requested_count == 0) {
+		p_hwfn->qm_info.wfq_data[vport_id].min_speed = req_rate;
+		p_hwfn->qm_info.wfq_data[vport_id].configured = true;
+		return 0;
+	}
+
 	total_left_rate	= min_pf_rate - total_req_min_rate;
 
 	left_rate_per_vp = total_left_rate / non_requested_count;
-- 
2.43.0