netdev - Re: [Intel-wired-lan] [PATCH] i40e: avoid redundant VF link state updates

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Message-ID: <0c62b505-abe7-474e-9859-a301f4104eeb@molgen.mpg.de>
Date: Wed, 22 Oct 2025 13:49:22 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Robert Malz <robert.malz@...onical.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
 Jamie Bainbridge <jamie.bainbridge@...il.com>,
 Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
 Dennis Chen <dechen@...hat.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Lukasz Czapnik <lukasz.czapnik@...el.com>,
 Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, Eric Dumazet <edumazet@...gle.com>,
 Tony Nguyen <anthony.l.nguyen@...el.com>, Simon Horman <horms@...nel.org>,
 Jacob Keller <jacob.e.keller@...el.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, "David S . Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH] i40e: avoid redundant VF link state
 updates

Dear Robert,

Thank you for your patch.

Am 21.10.25 um 17:44 schrieb Robert Malz:
> From: Jay Vosburgh <jay.vosburgh@...onical.com>
> 
> Multiple sources can request VF link state changes with identical
> parameters. For example, Neutron may request to set the VF link state to

What is Neutron?

> IFLA_VF_LINK_STATE_AUTO during every initialization or user can issue:
> `ip link set <ifname> vf 0 state auto` multiple times. Currently, the i40e
> driver processes each of these requests, even if the requested state is
> the same as the current one. This leads to unnecessary VF resets and can
> cause performance degradation or instability in the VF driver - particularly
> in DPDK environment.

What is DPDK?

> With this patch i40e will skip VF link state change requests when the
> desired link state matches the current configuration. This prevents
> unnecessary VF resets and reduces PF-VF communication overhead.

Add a test (with `ip link …`) case to show, that it works now.

> Co-developed-by: Robert Malz <robert.malz@...onical.com>
> Signed-off-by: Robert Malz <robert.malz@...onical.com>
> Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>
> ---
>   drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> index 081a4526a2f0..0fe0d52c796b 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> @@ -4788,6 +4788,7 @@ int i40e_ndo_set_vf_link_state(struct net_device *netdev, int vf_id, int link)
>   	unsigned long q_map;
>   	struct i40e_vf *vf;
>   	int abs_vf_id;
> +	int old_link;
>   	int ret = 0;
>   	int tmp;
>   
> @@ -4806,6 +4807,17 @@ int i40e_ndo_set_vf_link_state(struct net_device *netdev, int vf_id, int link)
>   	vf = &pf->vf[vf_id];
>   	abs_vf_id = vf->vf_id + hw->func_caps.vf_base_id;
>   
> +	/* skip VF link state change if requested state is already set */
> +	if (!vf->link_forced)
> +		old_link = IFLA_VF_LINK_STATE_AUTO;
> +	else if (vf->link_up)
> +		old_link = IFLA_VF_LINK_STATE_ENABLE;
> +	else
> +		old_link = IFLA_VF_LINK_STATE_DISABLE;
> +
> +	if (link == old_link)
> +		goto error_out;

Should a debug message be added?

> +
>   	pfe.event = VIRTCHNL_EVENT_LINK_CHANGE;
>   	pfe.severity = PF_EVENT_SEVERITY_INFO;
>   

Kind regards,

Paul