[PATCH iwl-net 10/10] ice: allow setting min_tx_rate to 0 to resolve VF bandwidth oversubscription

[Aleksandr Loktionov <aleksandr.loktionov@intel.com>]

ice_set_vf_bw() refuses to accept any min_tx_rate value when the
total guaranteed bandwidth is already oversubscribed, even when the
requested value is 0. This makes it impossible to recover from an
oversubscribed state via "ip link set <pf> vf <id> min_tx_rate 0".

Allow a zero min_tx_rate to bypass the oversubscription check so
users can always clear the guaranteed rate. Additionally print an
informational message when the oversubscription guard fires to help
diagnose why a non-zero request was rejected.

Fixes: 4ecc8633056b ("ice: Add support for VF rate limiting")
Cc: stable@vger.kernel.org
Signed-off-by: Sudheer Mogilappagari <sudheer.mogilappagari@intel.com>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_sriov.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_sriov.c b/drivers/net/ethernet/intel/ice/ice_sriov.c
index 7e00e09..6e3bec7 100644
--- a/drivers/net/ethernet/intel/ice/ice_sriov.c
+++ b/drivers/net/ethernet/intel/ice/ice_sriov.c
@@ -1507,6 +1507,12 @@ ice_min_tx_rate_oversubscribed(struct ice_vf *vf, int min_tx_rate)
 	all_vfs_min_tx_rate -= vf->min_tx_rate;
 
 	if (all_vfs_min_tx_rate + min_tx_rate > link_speed_mbps) {
+		if (ice_calc_all_vfs_min_tx_rate(vf->pf) > link_speed_mbps) {
+			dev_info(ice_pf_to_dev(vf->pf),
+				 "The sum of min_tx_rate for all VFs is greater than the link speed\n");
+			dev_info(ice_pf_to_dev(vf->pf),
+				 "Set min_tx_rate to 0 on VFs to resolve oversubscription\n");
+		}
 		dev_err(ice_pf_to_dev(vf->pf), "min_tx_rate of %d Mbps on VF %u would cause oversubscription of %d Mbps based on the current link speed %d Mbps\n",
 			min_tx_rate, vf->vf_id,
 			all_vfs_min_tx_rate + min_tx_rate - link_speed_mbps,
@@ -1556,7 +1562,7 @@ ice_set_vf_bw(struct net_device *netdev, int vf_id, int min_tx_rate,
 		goto out_put_vf;
 	}
 
-	if (ice_min_tx_rate_oversubscribed(vf, min_tx_rate)) {
+	if (min_tx_rate && ice_min_tx_rate_oversubscribed(vf, min_tx_rate)) {
 		ret = -EINVAL;
 		goto out_put_vf;
 	}
-- 
2.52.0