Re: [PATCH v3 1/2] vfio: Fix unbalanced vfio_df_close call in no-iommu mode

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 10 Jul 2025 11:40:25 -0700
Jacob Pan <jacob.pan@linux.microsoft.com> wrote:

> Hi Alex et al,
> 
> Just wondering if there are more comments?

Seems not.  Sorry for the delay, these just fell early in the cycle and
other patches are going through various re-spins.  Applied to vfio next
branch for v6.17.  Thanks,

Alex
 
> On Wed, 18 Jun 2025 16:46:17 -0700
> Jacob Pan <jacob.pan@linux.microsoft.com> wrote:
> 
> > For devices with no-iommu enabled in IOMMUFD VFIO compat mode, the
> > group open path skips vfio_df_open(), leaving open_count at 0. This
> > causes a warning in vfio_assert_device_open(device) when
> > vfio_df_close() is called during group close.
> > 
> > The correct behavior is to skip only the IOMMUFD bind in the device
> > open path for no-iommu devices. Commit 6086efe73498 omitted
> > vfio_df_open(), which was too broad. This patch restores the previous
> > behavior, ensuring the vfio_df_open is called in the group open path.
> > 
> > Fixes: 6086efe73498 ("vfio-iommufd: Move noiommu compat validation
> > out of vfio_iommufd_bind()") Suggested-by: Alex Williamson
> > <alex.williamson@redhat.com> Suggested-by: Jason Gunthorpe
> > <jgg@nvidia.com> Signed-off-by: Jacob Pan
> > <jacob.pan@linux.microsoft.com> ---
> > v3: Apply a concise fix from Alex
> > v2: Use a fix from Jason
> > ---
> >  drivers/vfio/group.c   | 7 +++----
> >  drivers/vfio/iommufd.c | 4 ++++
> >  2 files changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> > index c321d442f0da..c376a6279de0 100644
> > --- a/drivers/vfio/group.c
> > +++ b/drivers/vfio/group.c
> > @@ -192,11 +192,10 @@ static int vfio_df_group_open(struct
> > vfio_device_file *df)
> >  		 * implies they expected translation to exist
> >  		 */
> >  		if (!capable(CAP_SYS_RAWIO) ||
> > -		    vfio_iommufd_device_has_compat_ioas(device,
> > df->iommufd))
> > +		    vfio_iommufd_device_has_compat_ioas(device,
> > df->iommufd)) { ret = -EPERM;
> > -		else
> > -			ret = 0;
> > -		goto out_put_kvm;
> > +			goto out_put_kvm;
> > +		}
> >  	}
> >  
> >  	ret = vfio_df_open(df);
> > diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
> > index c8c3a2d53f86..a38d262c6028 100644
> > --- a/drivers/vfio/iommufd.c
> > +++ b/drivers/vfio/iommufd.c
> > @@ -25,6 +25,10 @@ int vfio_df_iommufd_bind(struct vfio_device_file
> > *df) 
> >  	lockdep_assert_held(&vdev->dev_set->lock);
> >  
> > +	/* Returns 0 to permit device opening under noiommu mode */
> > +	if (vfio_device_is_noiommu(vdev))
> > +		return 0;
> > +
> >  	return vdev->ops->bind_iommufd(vdev, ictx, &df->devid);
> >  }
> >    
>