platform/mellanox: mlxbf-tmfifo: Drop jumbo frames

This commit drops over-sized network packets to avoid tmfifo
queue stuck.

Fixes: 1357dfd7 ("platform/mellanox: Add TmFifo driver for Mellanox BlueField Soc")
Signed-off-by: Liming Sun <limings@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/9318936c2447f76db475c985ca6d91f057efcd41.1693322547.git.limings@nvidia.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/mellanox/mlxbf-tmfifo.c

@@ -224,7 +224,7 @@ static u8 mlxbf_tmfifo_net_default_mac[ETH_ALEN] = {
 static efi_char16_t mlxbf_tmfifo_efi_name[] = L"RshimMacAddr";
 
 /* Maximum L2 header length. */
-#define MLXBF_TMFIFO_NET_L2_OVERHEAD	36
+#define MLXBF_TMFIFO_NET_L2_OVERHEAD	(ETH_HLEN + VLAN_HLEN)
 
 /* Supported virtio-net features. */
 #define MLXBF_TMFIFO_NET_FEATURES \
@@ -642,13 +642,14 @@ static void mlxbf_tmfifo_rxtx_word(struct mlxbf_tmfifo_vring *vring,
  * flag is set.
  */
 static void mlxbf_tmfifo_rxtx_header(struct mlxbf_tmfifo_vring *vring,
-				     struct vring_desc *desc,
+				     struct vring_desc **desc,
 				     bool is_rx, bool *vring_change)
 {
 	struct mlxbf_tmfifo *fifo = vring->fifo;
 	struct virtio_net_config *config;
 	struct mlxbf_tmfifo_msg_hdr hdr;
 	int vdev_id, hdr_len;
+	bool drop_rx = false;
 
 	/* Read/Write packet header. */
 	if (is_rx) {
@@ -668,8 +669,8 @@ static void mlxbf_tmfifo_rxtx_header(struct mlxbf_tmfifo_vring *vring,
 			if (ntohs(hdr.len) >
 			    __virtio16_to_cpu(virtio_legacy_is_little_endian(),
 					      config->mtu) +
-			    MLXBF_TMFIFO_NET_L2_OVERHEAD)
-				return;
+					      MLXBF_TMFIFO_NET_L2_OVERHEAD)
+				drop_rx = true;
 		} else {
 			vdev_id = VIRTIO_ID_CONSOLE;
 			hdr_len = 0;
@@ -684,16 +685,25 @@ static void mlxbf_tmfifo_rxtx_header(struct mlxbf_tmfifo_vring *vring,
 
 			if (!tm_dev2)
 				return;
-			vring->desc = desc;
+			vring->desc = *desc;
 			vring = &tm_dev2->vrings[MLXBF_TMFIFO_VRING_RX];
 			*vring_change = true;
 		}
+
+		if (drop_rx && !IS_VRING_DROP(vring)) {
+			if (vring->desc_head)
+				mlxbf_tmfifo_release_pkt(vring);
+			*desc = &vring->drop_desc;
+			vring->desc_head = *desc;
+			vring->desc = *desc;
+		}
+
 		vring->pkt_len = ntohs(hdr.len) + hdr_len;
 	} else {
 		/* Network virtio has an extra header. */
 		hdr_len = (vring->vdev_id == VIRTIO_ID_NET) ?
 			   sizeof(struct virtio_net_hdr) : 0;
-		vring->pkt_len = mlxbf_tmfifo_get_pkt_len(vring, desc);
+		vring->pkt_len = mlxbf_tmfifo_get_pkt_len(vring, *desc);
 		hdr.type = (vring->vdev_id == VIRTIO_ID_NET) ?
 			    VIRTIO_ID_NET : VIRTIO_ID_CONSOLE;
 		hdr.len = htons(vring->pkt_len - hdr_len);
@@ -742,7 +752,7 @@ static bool mlxbf_tmfifo_rxtx_one_desc(struct mlxbf_tmfifo_vring *vring,
 
 	/* Beginning of a packet. Start to Rx/Tx packet header. */
 	if (vring->pkt_len == 0) {
-		mlxbf_tmfifo_rxtx_header(vring, desc, is_rx, &vring_change);
+		mlxbf_tmfifo_rxtx_header(vring, &desc, is_rx, &vring_change);
 		(*avail)--;
 
 		/* Return if new packet is for another ring. */