netdev - RE: [PATCH] i40e: avoid redundant VF link state updates

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Message-ID: <CO1PR11MB5089A29DFDC077EDE6E535BAD6F2A@CO1PR11MB5089.namprd11.prod.outlook.com>
Date: Tue, 21 Oct 2025 20:35:00 +0000
From: "Keller, Jacob E" <jacob.e.keller@...el.com>
To: Robert Malz <robert.malz@...onical.com>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC: "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S
 . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>, "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>,
	"Czapnik, Lukasz" <lukasz.czapnik@...el.com>, Jamie Bainbridge
	<jamie.bainbridge@...il.com>, Jay Vosburgh <jay.vosburgh@...onical.com>,
	Dennis Chen <dechen@...hat.com>, Michal Swiatkowski
	<michal.swiatkowski@...ux.intel.com>
Subject: RE: [PATCH] i40e: avoid redundant VF link state updates



> -----Original Message-----
> From: Robert Malz <robert.malz@...onical.com>
> Sent: Tuesday, October 21, 2025 8:45 AM
> To: intel-wired-lan@...ts.osuosl.org; netdev@...r.kernel.org
> Cc: Nguyen, Anthony L <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@...el.com>; Andrew Lunn <andrew+netdev@...n.ch>; David
> S . Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>;
> Jakub Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Simon
> Horman <horms@...nel.org>; Loktionov, Aleksandr
> <aleksandr.loktionov@...el.com>; Czapnik, Lukasz <lukasz.czapnik@...el.com>;
> Robert Malz <robert.malz@...onical.com>; Jamie Bainbridge
> <jamie.bainbridge@...il.com>; Jay Vosburgh <jay.vosburgh@...onical.com>;
> Dennis Chen <dechen@...hat.com>; Keller, Jacob E <jacob.e.keller@...el.com>;
> Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
> Subject: [PATCH] i40e: avoid redundant VF link state updates
> 
> 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
> 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.
> 
> 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.
> 
> 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;
> +

This seems reasonable to me. We should check if ice needs something similar as well.

Thanks,
Jake

>  	pfe.event = VIRTCHNL_EVENT_LINK_CHANGE;
>  	pfe.severity = PF_EVENT_SEVERITY_INFO;
> 
> --
> 2.34.1