From: Jason Gunthorpe <jgg@nvidia.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
Harald Freudenberger <freude@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Jason Herne <jjherne@linux.ibm.com>,
linux-s390@vger.kernel.org, Halil Pasic <pasic@linux.ibm.com>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>, Christoph Hellwig <hch@lst.de>,
kvm@vger.kernel.org
Subject: Re: [PATCH v3] vfio/ap_ops: Add missed vfio_uninit_group_dev()
Date: Wed, 22 Sep 2021 10:11:50 -0300 [thread overview]
Message-ID: <20210922131150.GP327412@nvidia.com> (raw)
In-Reply-To: <4a50ed05-c60c-aad0-bceb-de9665602aed@linux.ibm.com>
On Wed, Sep 22, 2021 at 09:05:06AM -0400, Tony Krowiak wrote:
>
>
> On 9/21/21 8:11 AM, Jason Gunthorpe wrote:
> > Without this call an xarray entry is leaked when the vfio_ap device is
> > unprobed. It was missed when the below patch was rebased across the
> > dev_set patch. Keep the remove function in the same order as the error
> > unwind in probe.
> >
> > Fixes: eb0feefd4c02 ("vfio/ap_ops: Convert to use vfio_register_group_dev()")
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > Tested-by: Tony Krowiak <akrowiak@linux.ibm.com>
> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> > drivers/s390/crypto/vfio_ap_ops.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > v3:
> > - Keep the remove sequence the same as remove to avoid a lockdep splat
> > v2: https://lore.kernel.org/r/0-v2-25656bbbb814+41-ap_uninit_jgg@nvidia.com/
> > - Fix corrupted diff
> > v1: https://lore.kernel.org/r/0-v1-3a05c6000668+2ce62-ap_uninit_jgg@nvidia.com/
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> > index 118939a7729a1e..623d5269a52ce5 100644
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -361,6 +361,7 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
> > mutex_lock(&matrix_dev->lock);
> > list_del(&matrix_mdev->node);
> > mutex_unlock(&matrix_dev->lock);
> > + vfio_uninit_group_dev(&matrix_mdev->vdev);
> > kfree(matrix_mdev);
> > err_dec_available:
> > atomic_inc(&matrix_dev->available_instances);
> > @@ -376,9 +377,10 @@ static void vfio_ap_mdev_remove(struct mdev_device *mdev)
> > mutex_lock(&matrix_dev->lock);
> > vfio_ap_mdev_reset_queues(matrix_mdev);
> > list_del(&matrix_mdev->node);
> > + mutex_unlock(&matrix_dev->lock);
> > + vfio_uninit_group_dev(&matrix_mdev->vdev);
> > kfree(matrix_mdev);
> > atomic_inc(&matrix_dev->available_instances);
>
> I think the above line of code should be done under the
> matrix_dev->lock after removing the matrix_mdev from
> the list since it is changing a value in matrix_dev.
No, the read-side doesn't hold the lock
if ((atomic_dec_if_positive(&matrix_dev->available_instances) < 0))
return -EPERM;
I think it is just a leftover from the atomic conversion that Alex
did to keep it under the matrix_dev struct.
If we were going to hold the lock then it wouldn't need to be an
atomic.
Jason
next prev parent reply other threads:[~2021-09-22 13:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 12:11 [PATCH v3] vfio/ap_ops: Add missed vfio_uninit_group_dev() Jason Gunthorpe
2021-09-22 13:05 ` Tony Krowiak
2021-09-22 13:11 ` Jason Gunthorpe [this message]
2021-09-23 20:10 ` Alex Williamson
2021-09-24 2:24 ` Tony Krowiak
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