net/mlx5: fix meter EIR calculation

Before the yellow color policy was supported, the only supported
profile of metering is RFC2697 and EIR is not part of the profile.
When creating a meter with this profile, the EIR part was always
zero.

After the yellow color policy supported and RFC2698 & 4115 support
was introduced, EIR is relevant and should be calculated. Usually
the EIR could not be zero and the formula for calculating CIR
mantissa & exponent could be reused.

The EIR could be 0 and then only green and red colors will be
supported from the specification. Both the mantissa and exponent
parts should be set to 0. Currently, the formula wrongly sets
non-zero values for the EIR=0 case.

Setting the mantissa and the exponent parts to zeros when EIR is 0
will solve the issue.

Fixes: 33a7493c8df8 ("net/mlx5: support meter for trTCM profiles")
Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>

diff --git a/drivers/net/mlx5/mlx5_flow_meter.c b/drivers/net/mlx5/mlx5_flow_meter.c
index 0f51710907d205c37e1d8e1dd98a7a27d5076a90..a24bd9c7ae167a902563efa827e4936a2f0568da 100644 (file)
--- a/drivers/net/mlx5/mlx5_flow_meter.c
+++ b/drivers/net/mlx5/mlx5_flow_meter.c
@@ -245,17 +245,23 @@ mlx5_flow_meter_profile_validate(struct rte_eth_dev *dev,
 static inline void
 mlx5_flow_meter_xir_man_exp_calc(int64_t xir, uint8_t *man, uint8_t *exp)
 {
-       int64_t _cir;
+       int64_t _xir;
        int64_t delta = INT64_MAX;
        uint8_t _man = 0;
        uint8_t _exp = 0;
        uint64_t m, e;
 
+       /* Special case xir == 0 ? both exp and matissa are 0. */
+       if (xir == 0) {
+               *man = 0;
+               *exp = 0;
+               return;
+       }
        for (m = 0; m <= 0xFF; m++) { /* man width 8 bit */
                for (e = 0; e <= 0x1F; e++) { /* exp width 5bit */
-                       _cir = (1000000000ULL * m) >> e;
-                       if (llabs(xir - _cir) <= delta) {
-                               delta = llabs(xir - _cir);
+                       _xir = (1000000000ULL * m) >> e;
+                       if (llabs(xir - _xir) <= delta) {
+                               delta = llabs(xir - _xir);
                                _man = m;
                                _exp = e;
                        }