RE: [EXTERNAL] [PATCH net] netvsc: transfer lower device max tso size during VF transition

[Haiyang Zhang]

> -----Original Message-----
> From: Li Tian <litian@xxxxxxxxxx>
> Sent: Wednesday, March 25, 2026 12:50 AM
> To: netdev@xxxxxxxxxxxxxxx; linux-hyperv@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>;
> Wei Liu <wei.liu@xxxxxxxxxx>; Dexuan Cui <DECUI@xxxxxxxxxxxxx>; Long Li
> <longli@xxxxxxxxxxxxx>; Andrew Lunn <andrew+netdev@xxxxxxx>; Eric Dumazet
> <edumazet@xxxxxxxxxx>; Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>; Paolo Abeni
> <pabeni@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Jason Wang
> <jasowang@xxxxxxxxxx>; Li Tian <litian@xxxxxxxxxx>
> Subject: [EXTERNAL] [PATCH net] netvsc: transfer lower device max tso size
> during VF transition
> 
> When netvsc is accelerated by the lower device, we can advertise the
> lower device max tso size in order to get better performance.
> While a long-term migration to user-space bonding is planned, current
> users on RHEL 10 / Azure are experiencing significant performance
> regressions in 802.3ad environments. This patch provides a localized,
> safe fix within netvsc without introducing new core networking helpers.
> 
> Signed-off-by: Li Tian <litian@xxxxxxxxxx>
> ---
>  drivers/net/hyperv/netvsc_drv.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c
> b/drivers/net/hyperv/netvsc_drv.c
> index ee5ab5ceb2be..971607c7406f 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -2428,10 +2428,14 @@ static int netvsc_vf_changed(struct net_device
> *vf_netdev, unsigned long event)
>  		 * This value is only increased for netvsc NIC when datapath
> is
>  		 * switched over to the VF
>  		 */
> -		if (vf_is_up)
> +		if (vf_is_up) {
>  			netif_set_tso_max_size(ndev, vf_netdev->tso_max_size);
> -		else
> +			WRITE_ONCE(ndev->gso_max_size, READ_ONCE(vf_netdev-
> >gso_max_size));
> +			WRITE_ONCE(ndev->gso_ipv4_max_size,
> +				   READ_ONCE(vf_netdev->gso_ipv4_max_size));
> +		} else {
>  			netif_set_tso_max_size(ndev, netvsc_dev-
> >netvsc_gso_max_size);
> +		}
>  	}
> 
>  	return NOTIFY_OK;
Thanks.

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>