net/mlx4_core: Fix slave id computation for single port VF

The code that deals with computing the slave id based on a given GID
gave wrong results when the number of single port VFs wasn't the
same for port 1 vs. port 2 and the relevant VF is single ported on
port 2. As a result, incoming CM MADs were dispatched to the wrong VF.
Fixed that and added documentation to clarify the computation steps.

Fixes: 449fc48 ('net/mlx4: Adapt code for N-Port VF')
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/mellanox/mlx4/port.c b/drivers/net/ethernet/mellanox/mlx4/port.c
index cfcad26ed40f60b0e5b992195339d8c12c0e68d7..b5b3549b0c8d30e9878249c502af4d18e5162a25 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/port.c
+++ b/drivers/net/ethernet/mellanox/mlx4/port.c
@@ -1106,6 +1106,9 @@ int mlx4_get_slave_from_roce_gid(struct mlx4_dev *dev, int port, u8 *gid,
        }
 
        if (found_ix >= 0) {
+               /* Calculate a slave_gid which is the slave number in the gid
+                * table and not a globally unique slave number.
+                */
                if (found_ix < MLX4_ROCE_PF_GIDS)
                        slave_gid = 0;
                else if (found_ix < MLX4_ROCE_PF_GIDS + (vf_gids % num_vfs) *
@@ -1118,41 +1121,43 @@ int mlx4_get_slave_from_roce_gid(struct mlx4_dev *dev, int port, u8 *gid,
                          ((vf_gids % num_vfs) * ((vf_gids / num_vfs + 1)))) /
                         (vf_gids / num_vfs)) + vf_gids % num_vfs + 1;
 
+               /* Calculate the globally unique slave id */
                if (slave_gid) {
                        struct mlx4_active_ports exclusive_ports;
                        struct mlx4_active_ports actv_ports;
                        struct mlx4_slaves_pport slaves_pport_actv;
                        unsigned max_port_p_one;
-                       int num_slaves_before = 1;
+                       int num_vfs_before = 0;
+                       int candidate_slave_gid;
 
+                       /* Calculate how many VFs are on the previous port, if exists */
                        for (i = 1; i < port; i++) {
                                bitmap_zero(exclusive_ports.ports, dev->caps.num_ports);
-                               set_bit(i, exclusive_ports.ports);
+                               set_bit(i - 1, exclusive_ports.ports);
                                slaves_pport_actv =
                                        mlx4_phys_to_slaves_pport_actv(
                                                        dev, &exclusive_ports);
-                               num_slaves_before += bitmap_weight(
+                               num_vfs_before += bitmap_weight(
                                                slaves_pport_actv.slaves,
                                                dev->num_vfs + 1);
                        }
 
-                       if (slave_gid < num_slaves_before) {
-                               bitmap_zero(exclusive_ports.ports, dev->caps.num_ports);
-                               set_bit(port - 1, exclusive_ports.ports);
-                               slaves_pport_actv =
-                                       mlx4_phys_to_slaves_pport_actv(
-                                                       dev, &exclusive_ports);
-                               slave_gid += bitmap_weight(
-                                               slaves_pport_actv.slaves,
-                                               dev->num_vfs + 1) -
-                                               num_slaves_before;
-                       }
-                       actv_ports = mlx4_get_active_ports(dev, slave_gid);
+                       /* candidate_slave_gid isn't necessarily the correct slave, but
+                        * it has the same number of ports and is assigned to the same
+                        * ports as the real slave we're looking for. On dual port VF,
+                        * slave_gid = [single port VFs on port <port>] +
+                        * [offset of the current slave from the first dual port VF] +
+                        * 1 (for the PF).
+                        */
+                       candidate_slave_gid = slave_gid + num_vfs_before;
+
+                       actv_ports = mlx4_get_active_ports(dev, candidate_slave_gid);
                        max_port_p_one = find_first_bit(
                                actv_ports.ports, dev->caps.num_ports) +
                                bitmap_weight(actv_ports.ports,
                                              dev->caps.num_ports) + 1;
 
+                       /* Calculate the real slave number */
                        for (i = 1; i < max_port_p_one; i++) {
                                if (i == port)
                                        continue;