Re: [PATCH 1/3] s390/vfio-ap: clean up mdev resources when remove callback invoked

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Jun 09, 2021 at 06:46:32PM -0400, Tony Krowiak wrote:
> The mdev remove callback for the vfio_ap device driver bails out with
> -EBUSY if the mdev is in use by a KVM guest (i.e., the KVM pointer in the
> struct ap_matrix_mdev is not NULL). The intended purpose was
> to prevent the mdev from being removed while in use. There are two
> problems with this scenario:
> 
> 1. Returning a non-zero return code from the remove callback does not
>    prevent the removal of the mdev.
> 
> 2. The KVM pointer in the struct ap_matrix_mdev will always be NULL because
>    the remove callback will not get invoked until the mdev fd is closed.
>    When the mdev fd is closed, the mdev release callback is invoked and
>    clears the KVM pointer from the struct ap_matrix_mdev.
> 
> Let's go ahead and remove the check for KVM in the remove callback and
> allow the cleanup of mdev resources to proceed.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 10 ----------
>  1 file changed, 10 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason