Re: [PATCH v6 19/24] vfio-iommufd: Add detach_ioas support for emulated VFIO devices

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, Mar 08, 2023 at 05:28:58AM -0800, Yi Liu wrote:
> External email: Use caution opening links or attachments
> 
> 
> this prepares for adding DETACH ioctl for emulated VFIO devices.
> 
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Tested-by: Terrence Xu <terrence.xu@intel.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  drivers/gpu/drm/i915/gvt/kvmgt.c  |  1 +
>  drivers/s390/cio/vfio_ccw_ops.c   |  1 +
>  drivers/s390/crypto/vfio_ap_ops.c |  1 +
>  drivers/vfio/iommufd.c            | 14 +++++++++++++-
>  include/linux/vfio.h              |  3 +++
>  5 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index de675d799c7d..9cd9e9da60dd 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1474,6 +1474,7 @@ static const struct vfio_device_ops intel_vgpu_dev_ops = {
>         .bind_iommufd   = vfio_iommufd_emulated_bind,
>         .unbind_iommufd = vfio_iommufd_emulated_unbind,
>         .attach_ioas    = vfio_iommufd_emulated_attach_ioas,
> +       .detach_ioas    = vfio_iommufd_emulated_detach_ioas,
>  };
> 
>  static int intel_vgpu_probe(struct mdev_device *mdev)
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
> index 5b53b94f13c7..cba4971618ff 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -632,6 +632,7 @@ static const struct vfio_device_ops vfio_ccw_dev_ops = {
>         .bind_iommufd = vfio_iommufd_emulated_bind,
>         .unbind_iommufd = vfio_iommufd_emulated_unbind,
>         .attach_ioas = vfio_iommufd_emulated_attach_ioas,
> +       .detach_ioas = vfio_iommufd_emulated_detach_ioas,
>  };
> 
>  struct mdev_driver vfio_ccw_mdev_driver = {
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 72e10abb103a..9902e62e7a17 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -1844,6 +1844,7 @@ static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
>         .bind_iommufd = vfio_iommufd_emulated_bind,
>         .unbind_iommufd = vfio_iommufd_emulated_unbind,
>         .attach_ioas = vfio_iommufd_emulated_attach_ioas,
> +       .detach_ioas = vfio_iommufd_emulated_detach_ioas,
>  };
> 
>  static struct mdev_driver vfio_ap_matrix_driver = {
> diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
> index c06494e322f9..8a9457d0a33c 100644
> --- a/drivers/vfio/iommufd.c
> +++ b/drivers/vfio/iommufd.c
> @@ -218,8 +218,20 @@ int vfio_iommufd_emulated_attach_ioas(struct vfio_device *vdev, u32 *pt_id)
>  {
>         lockdep_assert_held(&vdev->dev_set->lock);
> 
> -       if (!vdev->iommufd_access)
> +       if (WARN_ON(!vdev->iommufd_access))
>                 return -ENOENT;
>         return iommufd_access_set_ioas(vdev->iommufd_access, *pt_id);
>  }
>  EXPORT_SYMBOL_GPL(vfio_iommufd_emulated_attach_ioas);
> +
> +void vfio_iommufd_emulated_detach_ioas(struct vfio_device *vdev)
> +{
> +       lockdep_assert_held(&vdev->dev_set->lock);
> +
> +       if (WARN_ON(!vdev->iommufd_access))
> +               return;
> +
[...]
> +       iommufd_access_destroy(vdev->iommufd_access);
> +       vdev->iommufd_access = NULL;

After moving access allocation/destroy to bind/unbind, here it
should be:
	iommufd_access_set_ioas(vdev->iommufd_access, 0);

Thanks
Nic