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Subject: Re: [PATCH v2 1/1] s390/vfio-ap: fix circular lockdep when
 setting/clearing crypto masks
To:     Cornelia Huck <cohuck@redhat.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, stable@vger.kernel.org,
        borntraeger@de.ibm.com, kwankhede@nvidia.com, pbonzini@redhat.com,
        alex.williamson@redhat.com, pasic@linux.vnet.ibm.com
References: <20210216011547.22277-1-akrowiak@linux.ibm.com>
 <20210216011547.22277-2-akrowiak@linux.ibm.com>
 <20210219144554.3857a034.cohuck@redhat.com>
From:   Tony Krowiak <akrowiak@linux.ibm.com>
Message-ID: <567bb57c-1b3d-721e-b622-4026a8df2d31@linux.ibm.com>
Date:   Fri, 19 Feb 2021 15:49:57 -0500
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On 2/19/21 8:45 AM, Cornelia Huck wrote:
> 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>

Thanks for the review.

>