Subject: Re: [PATCH v2 2/3] vdpa/mlx5: reuse common function for MAC address updates

From: Simon Horman <[email-masked]>
Date: Wed, 7 Jan 2026 12:24:18 +0000

On Mon, Dec 29, 2025 at 03:16:13PM +0800, Cindy Lu wrote:
> Factor out MAC address update logic and reuse it from handle_ctrl_mac().
> 
> This ensures that old MAC entries are removed from the MPFS table
> before adding a new one and that the forwarding rules are updated
> accordingly. If updating the flow table fails, the original MAC and
> rules are restored as much as possible to keep the software and
> hardware state consistent.
> 
> Signed-off-by: Cindy Lu <[email-masked]>
> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 95 +++++++++++++++++--------------
>  1 file changed, 53 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 6e42bae7c9a1..c87e6395b060 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2125,62 +2125,48 @@ static void teardown_steering(struct mlx5_vdpa_net *ndev)
>  	mlx5_destroy_flow_table(ndev->rxft);
>  }
>  
> -static virtio_net_ctrl_ack handle_ctrl_mac(struct mlx5_vdpa_dev *mvdev, u8 cmd)
> +static int mlx5_vdpa_change_new_mac(struct mlx5_vdpa_net *ndev,
> +				    struct mlx5_core_dev *pfmdev,
> +				    const u8 *new_mac)
>  {
> -	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> -	struct mlx5_control_vq *cvq = &mvdev->cvq;
> -	virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
> -	struct mlx5_core_dev *pfmdev;
> -	size_t read;
> -	u8 mac[ETH_ALEN], mac_back[ETH_ALEN];
> -
> -	pfmdev = pci_get_drvdata(pci_physfn(mvdev->mdev->pdev));
> -	switch (cmd) {
> -	case VIRTIO_NET_CTRL_MAC_ADDR_SET:
> -		read = vringh_iov_pull_iotlb(&cvq->vring, &cvq->riov, (void *)mac, ETH_ALEN);
> -		if (read != ETH_ALEN)
> -			break;
> -
> -		if (!memcmp(ndev->config.mac, mac, 6)) {
> -			status = VIRTIO_NET_OK;
> -			break;
> -		}
> +	struct mlx5_vdpa_dev *mvdev = &ndev->mvdev;
> +	u8 old_mac[ETH_ALEN];
>  
> -		if (is_zero_ether_addr(mac))
> -			break;
> +	if (is_zero_ether_addr(new_mac))
> +		return -EINVAL;
>  
> -		if (!is_zero_ether_addr(ndev->config.mac)) {
> -			if (mlx5_mpfs_del_mac(pfmdev, ndev->config.mac)) {
> -				mlx5_vdpa_warn(mvdev, "failed to delete old MAC %pM from MPFS table\n",
> -					       ndev->config.mac);
> -				break;
> -			}
> +	if (!is_zero_ether_addr(ndev->config.mac)) {
> +		if (mlx5_mpfs_del_mac(pfmdev, ndev->config.mac)) {
> +			mlx5_vdpa_warn(mvdev, "failed to delete old MAC %pM from MPFS table\n",
> +				       ndev->config.mac);
> +			return -EIO;
>  		}
> +	}
>  
> -		if (mlx5_mpfs_add_mac(pfmdev, mac)) {
> -			mlx5_vdpa_warn(mvdev, "failed to insert new MAC %pM into MPFS table\n",
> -				       mac);
> -			break;
> -		}
> +	if (mlx5_mpfs_add_mac(pfmdev, (u8 *)new_mac)) {
> +		mlx5_vdpa_warn(mvdev, "failed to insert new MAC %pM into MPFS table\n",
> +			       new_mac);
> +		return -EIO;
> +	}
>  
>  		/* backup the original mac address so that if failed to add the forward rules
>  		 * we could restore it
>  		 */
> -		memcpy(mac_back, ndev->config.mac, ETH_ALEN);
> +		memcpy(old_mac, ndev->config.mac, ETH_ALEN);
>  
> -		memcpy(ndev->config.mac, mac, ETH_ALEN);
> +		memcpy(ndev->config.mac, new_mac, ETH_ALEN);

...

Hi Cindy,

I realise that this makes the diffstat significantly more verbose.
And hides material changes. So perhaps there is a nicer way to do this.

But with the current arrangement of this patch, I think that
the indentation from just above, until the end of this function
needs to be updated.

I.e. the following incremental patch on top of this one.

This was flagged by Smatch.

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index c87e6395b060..c796f502b604 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2149,48 +2149,48 @@ static int mlx5_vdpa_change_new_mac(struct mlx5_vdpa_net *ndev,
 		return -EIO;
 	}
 
-		/* backup the original mac address so that if failed to add the forward rules
-		 * we could restore it
-		 */
-		memcpy(old_mac, ndev->config.mac, ETH_ALEN);
+	/* backup the original mac address so that if failed to add the forward rules
+	 * we could restore it
+	 */
+	memcpy(old_mac, ndev->config.mac, ETH_ALEN);
 
-		memcpy(ndev->config.mac, new_mac, ETH_ALEN);
+	memcpy(ndev->config.mac, new_mac, ETH_ALEN);
 
-		/* Need recreate the flow table entry, so that the packet could forward back
-		 */
-		mac_vlan_del(ndev, old_mac, 0, false);
+	/* Need recreate the flow table entry, so that the packet could forward back
+	 */
+	mac_vlan_del(ndev, old_mac, 0, false);
 
-		if (mac_vlan_add(ndev, ndev->config.mac, 0, false)) {
-			mlx5_vdpa_warn(mvdev, "failed to insert forward rules, try to restore\n");
+	if (mac_vlan_add(ndev, ndev->config.mac, 0, false)) {
+		mlx5_vdpa_warn(mvdev, "failed to insert forward rules, try to restore\n");
 
-			/* Although it hardly run here, we still need double check */
-			if (is_zero_ether_addr(old_mac)) {
-				mlx5_vdpa_warn(mvdev, "restore mac failed: Original MAC is zero\n");
-				return -EIO;
-			}
+		/* Although it hardly run here, we still need double check */
+		if (is_zero_ether_addr(old_mac)) {
+			mlx5_vdpa_warn(mvdev, "restore mac failed: Original MAC is zero\n");
+			return -EIO;
+		}
 
-			/* Try to restore original mac address to MFPS table, and try to restore
-			 * the forward rule entry.
-			 */
-			if (mlx5_mpfs_del_mac(pfmdev, ndev->config.mac)) {
-				mlx5_vdpa_warn(mvdev, "restore mac failed: delete MAC %pM from MPFS table failed\n",
-					       ndev->config.mac);
-			}
+		/* Try to restore original mac address to MFPS table, and try to restore
+		 * the forward rule entry.
+		 */
+		if (mlx5_mpfs_del_mac(pfmdev, ndev->config.mac)) {
+			mlx5_vdpa_warn(mvdev, "restore mac failed: delete MAC %pM from MPFS table failed\n",
+				       ndev->config.mac);
+		}
 
-			if (mlx5_mpfs_add_mac(pfmdev, old_mac)) {
-				mlx5_vdpa_warn(mvdev, "restore mac failed: insert old MAC %pM into MPFS table failed\n",
-					       old_mac);
-			}
+		if (mlx5_mpfs_add_mac(pfmdev, old_mac)) {
+			mlx5_vdpa_warn(mvdev, "restore mac failed: insert old MAC %pM into MPFS table failed\n",
+				       old_mac);
+		}
 
-			memcpy(ndev->config.mac, old_mac, ETH_ALEN);
+		memcpy(ndev->config.mac, old_mac, ETH_ALEN);
 
-			if (mac_vlan_add(ndev, ndev->config.mac, 0, false))
-				mlx5_vdpa_warn(mvdev, "restore forward rules failed: insert forward rules failed\n");
+		if (mac_vlan_add(ndev, ndev->config.mac, 0, false))
+			mlx5_vdpa_warn(mvdev, "restore forward rules failed: insert forward rules failed\n");
 
-			return -EIO;
-		}
+		return -EIO;
+	}
 
-		return 0;
+	return 0;
 }
 
 static virtio_net_ctrl_ack handle_ctrl_mac(struct mlx5_vdpa_dev *mvdev, u8 cmd)