Re: [PATCH v2 1/1] s390/vfio-ap: fix circular lockdep when setting/clearing crypto masks

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 15 Feb 2021 20:15:47 -0500
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> This patch fixes a circular locking dependency in the CI introduced by
> commit f21916ec4826 ("s390/vfio-ap: clean up vfio_ap resources when KVM
> pointer invalidated"). The lockdep only occurs when starting a Secure
> Execution guest. Crypto virtualization (vfio_ap) is not yet supported for
> SE guests; however, in order to avoid CI errors, this fix is being
> provided.
> 
> The circular lockdep was introduced when the masks in the guest's APCB
> were taken under the matrix_dev->lock. While the lock is definitely
> needed to protect the setting/unsetting of the KVM pointer, it is not
> necessarily critical for setting the masks, so this will not be done under
> protection of the matrix_dev->lock.
> 
> Fixes: f21916ec4826 ("s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 119 +++++++++++++++++++++---------
>  1 file changed, 84 insertions(+), 35 deletions(-)

I've been looking at the patch for a bit now and tried to follow down
the various paths; and while I think it's ok, I do not really have
enough confidence about that for a R-b. But have an

Acked-by: Cornelia Huck <cohuck@redhat.com>