i40e: Fix VF set max MTU size

Max MTU sent to VF is set to 0 during memory allocation. It cause
that max MTU on VF is changed to IAVF_MAX_RXBUFFER and does not
depend on data from HW.

Set max_mtu field in virtchnl_vf_resource struct to inform
VF in GET_VF_RESOURCES msg what size should be max frame.

Fixes: dab86af ("i40e/i40evf: Change the way we limit the maximum frame size for Rx")
Signed-off-by: Michal Jaron <michalx.jaron@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c

@@ -2038,6 +2038,25 @@ static void i40e_del_qch(struct i40e_vf *vf)
 	}
 }
 
+/**
+ * i40e_vc_get_max_frame_size
+ * @vf: pointer to the VF
+ *
+ * Max frame size is determined based on the current port's max frame size and
+ * whether a port VLAN is configured on this VF. The VF is not aware whether
+ * it's in a port VLAN so the PF needs to account for this in max frame size
+ * checks and sending the max frame size to the VF.
+ **/
+static u16 i40e_vc_get_max_frame_size(struct i40e_vf *vf)
+{
+	u16 max_frame_size = vf->pf->hw.phy.link_info.max_frame_size;
+
+	if (vf->port_vlan_id)
+		max_frame_size -= VLAN_HLEN;
+
+	return max_frame_size;
+}
+
 /**
  * i40e_vc_get_vf_resources_msg
  * @vf: pointer to the VF info
@@ -2139,6 +2158,7 @@ static int i40e_vc_get_vf_resources_msg(struct i40e_vf *vf, u8 *msg)
 	vfres->max_vectors = pf->hw.func_caps.num_msix_vectors_vf;
 	vfres->rss_key_size = I40E_HKEY_ARRAY_SIZE;
 	vfres->rss_lut_size = I40E_VF_HLUT_ARRAY_SIZE;
+	vfres->max_mtu = i40e_vc_get_max_frame_size(vf);
 
 	if (vf->lan_vsi_idx) {
 		vfres->vsi_res[0].vsi_id = vf->lan_vsi_id;