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

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Message-ID: <IA3PR11MB89860CA0245498E6FF720E48E5F3A@IA3PR11MB8986.namprd11.prod.outlook.com>
Date: Wed, 22 Oct 2025 12:06:12 +0000
From: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>, Robert Malz
	<robert.malz@...onical.com>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Jamie Bainbridge
	<jamie.bainbridge@...il.com>, Michal Swiatkowski
	<michal.swiatkowski@...ux.intel.com>, Dennis Chen <dechen@...hat.com>,
	"Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>, "Czapnik, Lukasz"
	<lukasz.czapnik@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, Eric Dumazet
	<edumazet@...gle.com>, "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
	Simon Horman <horms@...nel.org>, "Keller, Jacob E"
	<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



> -----Original Message-----
> From: Paul Menzel <pmenzel@...gen.mpg.de>
> Sent: Wednesday, October 22, 2025 1:49 PM
> 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>;
> Kitszel, Przemyslaw <przemyslaw.kitszel@...el.com>; Czapnik, Lukasz
> <lukasz.czapnik@...el.com>; Loktionov, Aleksandr
> <aleksandr.loktionov@...el.com>; Andrew Lunn <andrew+netdev@...n.ch>;
> Eric Dumazet <edumazet@...gle.com>; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; Simon Horman <horms@...nel.org>; Keller,
> Jacob E <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?
> 
I think Robert needs:
- to expand acronyms in the commit message (Neutron → OpenStack Neutron, DPDK → Data Plane Development Kit).
- to fix the comment style as per coding guidelines.
- add a short note in the commit message about how to reproduce the issue.
@Paul Menzel right?

> > 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?
> 
I think adding one would be redundant since skipping identical state changes is expected behavior. 

Thank you
Alex

> > +
> >   	pfe.event = VIRTCHNL_EVENT_LINK_CHANGE;
> >   	pfe.severity = PF_EVENT_SEVERITY_INFO;
> >
> 
> 
> Kind regards,
> 
> Paul