i40e: consolidate maximum frame size calculation for vsi

Introduce new helper function to calculate max frame size for validating
and setting of vsi frame size. This is used while configuring vsi,
changing the MTU and attaching an XDP program to the vsi.

This is in preparation of the legacy rx and multi-buffer changes to be
introduced in later patches.

Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
Tested-by: Chandan Kumar Rout <chandanx.rout@intel.com> (A Contingent Worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -2896,15 +2896,35 @@ static void i40e_sync_filters_subtask(struct i40e_pf *pf)
 }
 
 /**
- * i40e_max_xdp_frame_size - returns the maximum allowed frame size for XDP
+ * i40e_calculate_vsi_rx_buf_len - Calculates buffer length
+ *
+ * @vsi: VSI to calculate rx_buf_len from
+ */
+static u16 i40e_calculate_vsi_rx_buf_len(struct i40e_vsi *vsi)
+{
+	if (!vsi->netdev || (vsi->back->flags & I40E_FLAG_LEGACY_RX))
+		return I40E_RXBUFFER_2048;
+
+	return PAGE_SIZE < 8192 ? I40E_RXBUFFER_3072 : I40E_RXBUFFER_2048;
+}
+
+/**
+ * i40e_max_vsi_frame_size - returns the maximum allowed frame size for VSI
  * @vsi: the vsi
+ * @xdp_prog: XDP program
  **/
-static int i40e_max_xdp_frame_size(struct i40e_vsi *vsi)
+static int i40e_max_vsi_frame_size(struct i40e_vsi *vsi,
+				   struct bpf_prog *xdp_prog)
 {
-	if (PAGE_SIZE >= 8192 || (vsi->back->flags & I40E_FLAG_LEGACY_RX))
-		return I40E_RXBUFFER_2048;
+	u16 rx_buf_len = i40e_calculate_vsi_rx_buf_len(vsi);
+	u16 chain_len;
+
+	if (xdp_prog)
+		chain_len = 1;
 	else
-		return I40E_RXBUFFER_3072;
+		chain_len = I40E_MAX_CHAINED_RX_BUFFERS;
+
+	return min_t(u16, rx_buf_len * chain_len, I40E_MAX_RXBUFFER);
 }
 
 /**
@@ -2919,12 +2939,13 @@ static int i40e_change_mtu(struct net_device *netdev, int new_mtu)
 	struct i40e_netdev_priv *np = netdev_priv(netdev);
 	struct i40e_vsi *vsi = np->vsi;
 	struct i40e_pf *pf = vsi->back;
+	int frame_size;
 
-	if (i40e_enabled_xdp_vsi(vsi)) {
-		int frame_size = new_mtu + I40E_PACKET_HDR_PAD;
-
-		if (frame_size > i40e_max_xdp_frame_size(vsi))
-			return -EINVAL;
+	frame_size = i40e_max_vsi_frame_size(vsi, vsi->xdp_prog);
+	if (new_mtu > frame_size - I40E_PACKET_HDR_PAD) {
+		netdev_err(netdev, "Error changing mtu to %d, Max is %d\n",
+			   new_mtu, frame_size - I40E_PACKET_HDR_PAD);
+		return -EINVAL;
 	}
 
 	netdev_dbg(netdev, "changing MTU from %d to %d\n",
@@ -3693,24 +3714,6 @@ static int i40e_vsi_configure_tx(struct i40e_vsi *vsi)
 	return err;
 }
 
-/**
- * i40e_calculate_vsi_rx_buf_len - Calculates buffer length
- *
- * @vsi: VSI to calculate rx_buf_len from
- */
-static u16 i40e_calculate_vsi_rx_buf_len(struct i40e_vsi *vsi)
-{
-	if (!vsi->netdev || (vsi->back->flags & I40E_FLAG_LEGACY_RX))
-		return I40E_RXBUFFER_2048;
-
-#if (PAGE_SIZE < 8192)
-	if (!I40E_2K_TOO_SMALL_WITH_PADDING && vsi->netdev->mtu <= ETH_DATA_LEN)
-		return I40E_RXBUFFER_1536 - NET_IP_ALIGN;
-#endif
-
-	return PAGE_SIZE < 8192 ? I40E_RXBUFFER_3072 : I40E_RXBUFFER_2048;
-}
-
 /**
  * i40e_vsi_configure_rx - Configure the VSI for Rx
  * @vsi: the VSI being configured
@@ -3722,13 +3725,15 @@ static int i40e_vsi_configure_rx(struct i40e_vsi *vsi)
 	int err = 0;
 	u16 i;
 
-	vsi->max_frame = I40E_MAX_RXBUFFER;
+	vsi->max_frame = i40e_max_vsi_frame_size(vsi, vsi->xdp_prog);
 	vsi->rx_buf_len = i40e_calculate_vsi_rx_buf_len(vsi);
 
 #if (PAGE_SIZE < 8192)
 	if (vsi->netdev && !I40E_2K_TOO_SMALL_WITH_PADDING &&
-	    vsi->netdev->mtu <= ETH_DATA_LEN)
-		vsi->max_frame = I40E_RXBUFFER_1536 - NET_IP_ALIGN;
+	    vsi->netdev->mtu <= ETH_DATA_LEN) {
+		vsi->rx_buf_len = I40E_RXBUFFER_1536 - NET_IP_ALIGN;
+		vsi->max_frame = vsi->rx_buf_len;
+	}
 #endif
 
 	/* set up individual rings */
@@ -13316,14 +13321,14 @@ static netdev_features_t i40e_features_check(struct sk_buff *skb,
 static int i40e_xdp_setup(struct i40e_vsi *vsi, struct bpf_prog *prog,
 			  struct netlink_ext_ack *extack)
 {
-	int frame_size = vsi->netdev->mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN;
+	int frame_size = i40e_max_vsi_frame_size(vsi, prog);
 	struct i40e_pf *pf = vsi->back;
 	struct bpf_prog *old_prog;
 	bool need_reset;
 	int i;
 
 	/* Don't allow frames that span over multiple buffers */
-	if (frame_size > i40e_calculate_vsi_rx_buf_len(vsi)) {
+	if (vsi->netdev->mtu > frame_size - I40E_PACKET_HDR_PAD) {
 		NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP");
 		return -EINVAL;
 	}