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

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Date:   Fri, 19 Feb 2021 15:49:57 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, stable@...r.kernel.org,
        borntraeger@...ibm.com, kwankhede@...dia.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pasic@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 1/1] s390/vfio-ap: fix circular lockdep when
 setting/clearing crypto masks



On 2/19/21 8:45 AM, Cornelia Huck wrote:
> On Mon, 15 Feb 2021 20:15:47 -0500
> Tony Krowiak <akrowiak@...ux.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@...r.kernel.org
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.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@...hat.com>

Thanks for the review.

>