Re: [bug report] vdpa/mlx5: Support different address spaces for control and data

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Aug 11, 2022 at 12:40:09PM +0000, Eli Cohen wrote:
> > From: Dan Carpenter <dan.carpenter@oracle.com>
> > Sent: Thursday, August 11, 2022 1:40 PM
> > To: Eli Cohen <elic@nvidia.com>
> > Cc: virtualization@lists.linux-foundation.org
> > Subject: [bug report] vdpa/mlx5: Support different address spaces for control and data
> > 
> > Hello Eli Cohen,
> > 
> > The patch d5358cd0e369: "vdpa/mlx5: Support different address spaces
> > for control and data" from Jul 14, 2022, leads to the following
> > Smatch static checker warning:
> > 
> > 	drivers/vdpa/mlx5/net/mlx5_vnet.c:2676 mlx5_vdpa_set_map()
> > 	error: uninitialized symbol 'err'.
> > 
> > drivers/vdpa/mlx5/net/mlx5_vnet.c
> >     2657 static int mlx5_vdpa_set_map(struct vdpa_device *vdev, unsigned int asid,
> >     2658                              struct vhost_iotlb *iotlb)
> >     2659 {
> >     2660         struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> >     2661         struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> >     2662         int err;
> >     2663
> >     2664         down_write(&ndev->reslock);
> >     2665         if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
> >     2666                 err = set_map_data(mvdev, iotlb);
> >     2667                 if (err)
> >     2668                         goto out;
> >     2669         }
> >     2670
> >     2671         if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid)
> >     2672                 err = set_map_control(mvdev, iotlb);
> > 
> > err not initialized on else path.  My guess is that one or both of these
> > conditions has to be true and this is a false positive but I don't know
> > the code well enough to be sure.
> 
> Thanks for reporting this.
> I think it would be better to return an error if the provided asid is not recognized.
> 
> Therefore I am thinking about adding something like this:
> 
>         if (asid != mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] &&
>             asid != mvdev->group2asid[MLX5_VDPA_CVQ_GROUP]) {
>                 err = -EINVAL;
>                 goto out;
>         }

I would probably chain the conditions:

if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
} else if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid) {
} else {
                 err = -EINVAL;
                 goto out;
}


or alternatively initialize err with -EINVAL and be done with it.


> > 
> >     2673
> >     2674 out:
> >     2675         up_write(&ndev->reslock);
> > --> 2676         return err;
> >     2677 }
> > 
> > regards,
> > dan carpenter

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