Re: [PATCH iwl-next v3 3/5] i40e: Add helpers to find VSI and VEB by SEID and use them

[Ivan Vecera]

On 20. 11. 23 12:42, Simon Horman wrote:
> On Thu, Nov 16, 2023 at 04:21:12PM +0100, Ivan Vecera wrote:
> > Add two helpers i40e_(veb|vsi)_get_by_seid() to find corresponding
> > VEB or VSI by their SEID value and use these helpers to replace
> > existing open-coded loops.
> >
> > Reviewed-by: Wojciech Drewek <wojciech.drewek@xxxxxxxxx>
> > Signed-off-by: Ivan Vecera <ivecera@xxxxxxxxxx>
>
> Hi Ivan,
>
> some minor feedback from my side.
>
> ...
>
> > diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
> > index 1e9266de270b..ca8997d29c02 100644
> > --- a/drivers/net/ethernet/intel/i40e/i40e.h
> > +++ b/drivers/net/ethernet/intel/i40e/i40e.h
> > @@ -1360,4 +1360,38 @@ static inline struct i40e_pf *i40e_hw_to_pf(struct i40e_hw *hw)
> >   
> >   struct device *i40e_hw_to_dev(struct i40e_hw *hw);
> >   
> > +/**
> > + * i40e_pf_get_vsi_by_seid - find VSI by SEID
> > + * @pf: pointer to a PF
>
> nit: @seid is missing here
>
> > + **/
> > +static inline struct i40e_vsi *
> > +i40e_pf_get_vsi_by_seid(struct i40e_pf *pf, u16 seid)
> > +{
> > +	struct i40e_vsi *vsi;
> > +	int i;
> > +
> > +	i40e_pf_for_each_vsi(pf, i, vsi)
> > +		if (vsi->seid == seid)
> > +			return vsi;
> > +
> > +	return NULL;
> > +}
> > +
> > +/**
> > + * i40e_pf_get_veb_by_seid - find VEB by SEID
> > + * @pf: pointer to a PF
>
> Ditto
>
> ...
>
> > diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
>
> ...
>
> > @@ -14848,23 +14831,16 @@ struct i40e_veb *i40e_veb_setup(struct i40e_pf *pf, u16 flags,
> >   	}
> >   
> >   	/* make sure there is such a vsi and uplink */
> > -	i40e_pf_for_each_vsi(pf, vsi_idx, vsi)
> > -		if (vsi->seid == vsi_seid)
> > -			break;
> > -
> > -	if (vsi_idx == pf->num_alloc_vsi && vsi_seid != 0) {
> > -		dev_info(&pf->pdev->dev, "vsi seid %d not found\n",
> > -			 vsi_seid);
> > -		return NULL;
> > +	if (vsi_seid) {
> > +		vsi = i40e_pf_get_vsi_by_seid(pf, vsi_seid);
> > +		if (!vsi) {
> > +			dev_err(&pf->pdev->dev, "vsi seid %d not found\n",
> > +				vsi_seid);
> > +			return NULL;
> > +		}
> >   	}
> > -
> >   	if (uplink_seid && uplink_seid != pf->mac_seid) {
> > -		i40e_pf_for_each_veb(pf, veb_idx, veb) {
> > -			if (veb->seid == uplink_seid) {
> > -				uplink_veb = veb;
> > -				break;
> > -			}
> > -		}
> > +		uplink_veb = i40e_pf_get_veb_by_seid(pf, uplink_seid);
> >   		if (!uplink_veb) {
> >   			dev_info(&pf->pdev->dev,
> >   				 "uplink seid %d not found\n", uplink_seid);
>
> The next part of this function looks like this:
>
> 		if (!uplink_veb) {
> 			dev_info(&pf->pdev->dev,
> 				 "uplink seid %d not found\n", uplink_seid);
> 			return NULL;
> 		}
> 	}
> 	/* get veb sw struct */
> 	veb_idx = i40e_veb_mem_alloc(pf);
> 	if (veb_idx < 0)
> 		goto err_alloc;
> 	veb = pf->veb[veb_idx];
> 	veb->flags = flags;
> 	veb->uplink_seid = uplink_seid;
> 	veb->veb_idx = (uplink_veb ? uplink_veb->idx : I40E_NO_VEB);
> 	veb->enabled_tc = (enabled_tc ? enabled_tc : 0x1);
>
> 	/* create the VEB in the switch */
> 	ret = i40e_add_veb(veb, vsi);
>
> Smatch complains that vsi may be used uninitialised here.
> Which does seem possible to me if vsi_seid is 0.

Yes, the support for floating VEBs is and WAS broken prior this patch 
and it is fixed by the following patch.

Prior this patch... Let's vsi_seid == 0:

	/* make sure there is such a vsi and uplink */
	i40e_pf_for_each_vsi(pf, vsi_idx, vsi)
		if (vsi->seid == vsi_seid)
			break;
-> here vsi_idx == pf->num_alloc_vsi because there cannot be VSI with 
SEID == 0... and VSI points after the pf->vsi[] array.

	if (vsi_idx == pf->num_alloc_vsi && vsi_seid != 0) {
		dev_info(&pf->pdev->dev, "vsi seid %d not found\n",
			 vsi_seid);
		return NULL;
	}

This condition is not met, although vsi_idx == pf->num_alloc_vsi but 
vsi_seid == 0 so the rest of code ended by:

	ret = i40e_add_veb(veb, vsi);

and vsi pointer points to invalid area (item after the last one from 
pf->vsi).

As I mentioned the broken floating VEB functionality (where vsi_seid == 
0 and uplink_seid == 0) is fixed by the following patch.

Thanks,
Ivan