Subject: Re: [PATCH net-next v2] octeontx2-pf: persist netdev stats across routine operations

From: Jakub Kicinski <[email-masked]>
Date: Mon, 11 May 2026 17:12:46 -0700

On Mon, 11 May 2026 15:12:05 +0530 Anshumali Gaur wrote:
> Currently netdev driver is not retaining ethtool stats during
> interface up and down, as per kernel driver standard netdev driver
> must keep stats constant to avoid race conditions with user space
> trying to read them. Stats must persist across routine
> operations like bringing the interface down and up.

I think you're confusing the value of the stats with the list of stats.
Retaining values thru down/up is probably the most common behavior but
that's not what the doc is likely talking about.

> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> index 971fcab1c248..0ffcc613a4b2 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> @@ -139,19 +139,21 @@ void otx2_get_stats64(struct net_device *netdev,
>  		      struct rtnl_link_stats64 *stats)
>  {
>  	struct otx2_nic *pfvf = netdev_priv(netdev);
> -	struct otx2_dev_stats *dev_stats;
> +	struct otx2_dev_stats *dev_stats, *old_stats;
>  
>  	otx2_get_dev_stats(pfvf);
>  
>  	dev_stats = &pfvf->hw.dev_stats;
> -	stats->rx_bytes = dev_stats->rx_bytes;
> -	stats->rx_packets = dev_stats->rx_frames;
> -	stats->rx_dropped = dev_stats->rx_drops;
> -	stats->multicast = dev_stats->rx_mcast_frames;
> -
> -	stats->tx_bytes = dev_stats->tx_bytes;
> -	stats->tx_packets = dev_stats->tx_frames;
> -	stats->tx_dropped = dev_stats->tx_drops;
> +	old_stats = &pfvf->hw.old_stats;
> +
> +	stats->rx_bytes = old_stats->rx_bytes + dev_stats->rx_bytes;
> +	stats->rx_packets = old_stats->rx_frames + dev_stats->rx_frames;
> +	stats->rx_dropped = old_stats->rx_drops + dev_stats->rx_drops;
> +	stats->multicast = old_stats->rx_mcast_frames + dev_stats->rx_mcast_frames;
> +
> +	stats->tx_bytes = old_stats->tx_bytes + dev_stats->tx_bytes;
> +	stats->tx_packets = old_stats->tx_frames + dev_stats->tx_frames;
> +	stats->tx_dropped = old_stats->tx_drops + dev_stats->tx_drops;
>  }
>  EXPORT_SYMBOL(otx2_get_stats64);
>  
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.h b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.h
> index eecee612b7b2..ad65aa19b80d 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.h
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.h
> @@ -255,6 +255,7 @@ struct otx2_hw {
>  
>  	/* Stats */
>  	struct otx2_dev_stats	dev_stats;
> +	struct otx2_dev_stats	old_stats;
>  	struct otx2_drv_stats	drv_stats;
>  	u64			cgx_rx_stats[CGX_RX_STATS_COUNT];
>  	u64			cgx_tx_stats[CGX_TX_STATS_COUNT];
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> index ee623476e5ff..9606c8cb8c82 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c
> @@ -2158,10 +2158,28 @@ int otx2_stop(struct net_device *netdev)
>  	struct otx2_qset *qset = &pf->qset;
>  	int qidx, vec, wrk;
>  
> +	struct otx2_dev_stats *dev = &pf->hw.dev_stats;
> +	struct otx2_dev_stats *old_stats = &pf->hw.old_stats;

Please format your code according to kernel coding style.

>  	/* If the DOWN flag is set resources are already freed */
>  	if (pf->flags & OTX2_FLAG_INTF_DOWN)
>  		return 0;
>  
> +	/* Accumulate old stats */
> +	old_stats->rx_bytes     += dev->rx_bytes;
> +	old_stats->rx_drops     += dev->rx_drops;
> +	old_stats->rx_bcast_frames      += dev->rx_bcast_frames;
> +	old_stats->rx_mcast_frames      += dev->rx_mcast_frames;
> +	old_stats->rx_ucast_frames      += dev->rx_ucast_frames;
> +	old_stats->rx_frames            += dev->rx_frames;
> +
> +	old_stats->tx_bytes             += dev->tx_bytes;
> +	old_stats->tx_drops             += dev->tx_drops;
> +	old_stats->tx_bcast_frames      += dev->tx_bcast_frames;
> +	old_stats->tx_mcast_frames      += dev->tx_mcast_frames;
> +	old_stats->tx_ucast_frames      += dev->tx_ucast_frames;
> +	old_stats->tx_frames            += dev->tx_frames;
> +
>  	netif_carrier_off(netdev);
>  	netif_tx_stop_all_queues(netdev);
>