net/mlx5: Add support for configuring max device MTU

Allow an admin creating a vdpa device to specify the max MTU for the
net device.

For example, to create a device with max MTU of 1000, the following
command can be used:

$ vdpa dev add name vdpa-a mgmtdev auxiliary/mlx5_core.sf.1 mtu 1000

This configuration mechanism assumes that vdpa is the sole real user of
the function. mlx5_core could theoretically change the mtu of the
function using the ip command on the mlx5_core net device but this
should not be done.

Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220221121927.194728-1-elic@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index d0f9107..5d7f3e8 100644 (file)
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2565,6 +2565,28 @@ static int event_handler(struct notifier_block *nb, unsigned long event, void *p
        return ret;
 }
 
+static int config_func_mtu(struct mlx5_core_dev *mdev, u16 mtu)
+{
+       int inlen = MLX5_ST_SZ_BYTES(modify_nic_vport_context_in);
+       void *in;
+       int err;
+
+       in = kvzalloc(inlen, GFP_KERNEL);
+       if (!in)
+               return -ENOMEM;
+
+       MLX5_SET(modify_nic_vport_context_in, in, field_select.mtu, 1);
+       MLX5_SET(modify_nic_vport_context_in, in, nic_vport_context.mtu,
+                mtu + MLX5V_ETH_HARD_MTU);
+       MLX5_SET(modify_nic_vport_context_in, in, opcode,
+                MLX5_CMD_OP_MODIFY_NIC_VPORT_CONTEXT);
+
+       err = mlx5_cmd_exec_in(mdev, modify_nic_vport_context, in);
+
+       kvfree(in);
+       return err;
+}
+
 static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
                             const struct vdpa_dev_set_config *add_config)
 {
@@ -2624,6 +2646,13 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
        init_mvqs(ndev);
        mutex_init(&ndev->reslock);
        config = &ndev->config;
+
+       if (add_config->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU)) {
+               err = config_func_mtu(mdev, add_config->net.mtu);
+               if (err)
+                       goto err_mtu;
+       }
+
        err = query_mtu(mdev, &mtu);
        if (err)
                goto err_mtu;
@@ -2741,7 +2770,8 @@ static int mlx5v_probe(struct auxiliary_device *adev,
        mgtdev->mgtdev.device = mdev->device;
        mgtdev->mgtdev.id_table = id_table;
        mgtdev->mgtdev.config_attr_mask = BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MACADDR) |
-                                         BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP);
+                                         BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP) |
+                                         BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU);
        mgtdev->mgtdev.max_supported_vqs =
                MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues) + 1;
        mgtdev->mgtdev.supported_features = get_supported_features(mdev);