iavf: Fix max_rate limiting

Fix max_rate option in TC, check for proper quanta boundaries.
Check for minimum value provided and if it fits expected 50Mbps
quanta.

Without this patch, iavf could send settings for max_rate limiting
that would be accepted from by PF even the max_rate option is less
than expected 50Mbps quanta. It results in no rate limiting
on traffic as rate limiting will be floored to 0.

Example:
tc qdisc add dev $vf root mqprio num_tc 3 map 0 2 1 queues \
2@0 2@2 2@4 hw 1 mode channel shaper bw_rlimit \
max_rate 50Mbps 500Mbps 500Mbps

Should limit TC0 to circa 50 Mbps

tc qdisc add dev $vf root mqprio num_tc 3 map 0 2 1 queues \
2@0 2@2 2@4 hw 1 mode channel shaper bw_rlimit \
max_rate 0Mbps 100Kbit 500Mbps

Should return error

Fixes: d5b33d02 ("i40evf: add ndo_setup_tc callback to i40evf")
Signed-off-by: Przemyslaw Patynowski <przemyslawx.patynowski@intel.com>
Signed-off-by: Jun Zhang <xuejun.zhang@intel.com>
Tested-by: Bharathi Sreenivas <bharathi.sreenivas@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/iavf/iavf.h

@@ -92,6 +92,7 @@ struct iavf_vsi {
 #define IAVF_HKEY_ARRAY_SIZE ((IAVF_VFQF_HKEY_MAX_INDEX + 1) * 4)
 #define IAVF_HLUT_ARRAY_SIZE ((IAVF_VFQF_HLUT_MAX_INDEX + 1) * 4)
 #define IAVF_MBPS_DIVISOR	125000 /* divisor to convert to Mbps */
+#define IAVF_MBPS_QUANTA	50
 
 #define IAVF_VIRTCHNL_VF_RESOURCE_SIZE (sizeof(struct virtchnl_vf_resource) + \
 					(IAVF_MAX_VF_VSI * \

drivers/net/ethernet/intel/iavf/iavf_main.c

@@ -3322,6 +3322,7 @@ static int iavf_validate_ch_config(struct iavf_adapter *adapter,
 				   struct tc_mqprio_qopt_offload *mqprio_qopt)
 {
 	u64 total_max_rate = 0;
+	u32 tx_rate_rem = 0;
 	int i, num_qps = 0;
 	u64 tx_rate = 0;
 	int ret = 0;
@@ -3336,12 +3337,32 @@ static int iavf_validate_ch_config(struct iavf_adapter *adapter,
 			return -EINVAL;
 		if (mqprio_qopt->min_rate[i]) {
 			dev_err(&adapter->pdev->dev,
-				"Invalid min tx rate (greater than 0) specified\n");
+				"Invalid min tx rate (greater than 0) specified for TC%d\n",
+				i);
 			return -EINVAL;
 		}
-		/*convert to Mbps */
+
+		/* convert to Mbps */
 		tx_rate = div_u64(mqprio_qopt->max_rate[i],
 				  IAVF_MBPS_DIVISOR);
+
+		if (mqprio_qopt->max_rate[i] &&
+		    tx_rate < IAVF_MBPS_QUANTA) {
+			dev_err(&adapter->pdev->dev,
+				"Invalid max tx rate for TC%d, minimum %dMbps\n",
+				i, IAVF_MBPS_QUANTA);
+			return -EINVAL;
+		}
+
+		(void)div_u64_rem(tx_rate, IAVF_MBPS_QUANTA, &tx_rate_rem);
+
+		if (tx_rate_rem != 0) {
+			dev_err(&adapter->pdev->dev,
+				"Invalid max tx rate for TC%d, not divisible by %d\n",
+				i, IAVF_MBPS_QUANTA);
+			return -EINVAL;
+		}
+
 		total_max_rate += tx_rate;
 		num_qps += mqprio_qopt->qopt.count[i];
 	}