Re: [PATCH v6 1/2] s390/vfio-ap: clean up mdev resources when remove callback invoked

[Jason Gunthorpe]

On Mon, Jun 21, 2021 at 06:04:54PM +0200, Christian Borntraeger wrote:
> 
> 
> On 21.06.21 17:57, 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@xxxxxxxxxxxxx>
> > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> 
> This one is already queued on
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/log/?h=fixes
> 
> Jason. Do you want this in stable? Then we should write a mail after
> merging.

It is fine as is, we are already at rc7, so long as it goes to some
tree for this merge window

Jason