linux-kernel - Re: [PATCH v3 2/2] s390/vfio-ap: fix unlinking of queues from the mdev

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Message-ID: <7c222f64-3f06-5184-31c3-be557051c6fa@linux.ibm.com>
Date:   Tue, 13 Sep 2022 10:53:49 -0400
From:   Anthony Krowiak <akrowiak@...ux.ibm.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, jjherne@...ux.ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, mjrosato@...ux.ibm.com,
        alex.williamson@...hat.com, stable@...r.kernel.org
Subject: Re: [PATCH v3 2/2] s390/vfio-ap: fix unlinking of queues from the
 mdev


On 9/13/22 10:07 AM, Halil Pasic wrote:
> On Tue, 23 Aug 2022 11:06:43 -0400
> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>
>> The vfio_ap_mdev_unlink_adapter and vfio_ap_mdev_unlink_domain functions
>> add the associated vfio_ap_queue objects to the hashtable that links them
>> to the matrix mdev to which their APQN is assigned. In order to unlink
>> them, they must be deleted from the hashtable; if not, they will continue
>> to be reset whenever userspace closes the mdev fd or removes the mdev.
>> This patch fixes that issue.
> I'm not so sure about that!
>
>> Cc: stable@...r.kernel.org
>> Fixes: 70aeefe574cb ("s390/vfio-ap: reset queues after adapter/domain unassignment")
>> Reported-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 6 ++----
>>   1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index ee82207b4e60..2493926b5dfb 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -1049,8 +1049,7 @@ static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
>>   		if (q && qtable) {
>>   			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
>>   			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
>> -				hash_add(qtable->queues, &q->mdev_qnode,
>> -					 q->apqn);
> Careful qtable->queues is not supposed to be the same as
> matrix_mdev->qtable.queues it is rather a function local
> qtable that you use to know which queues were unlinked and
> need resetting.


You are correct. This patch is unnecessary.


>
> Have a look at vfio_ap_mdev_hot_unplug_adapter()
>
>> +				vfio_ap_unlink_queue_fr_mdev(q);
> IMHO this change is completely bogous. BTW
> vfio_ap_unlink_apqn_fr_mdev() a couple of lines above in the source
> (not seen in diff context) calls vfio_ap_unlink_queue_fr_mdev().


After further review, this patch is not only bogus, it is not necessary.


>
>>   		}
>>   	}
>>   }
>> @@ -1236,8 +1235,7 @@ static void vfio_ap_mdev_unlink_domain(struct ap_matrix_mdev *matrix_mdev,
>>   		if (q && qtable) {
>>   			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
>>   			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
>> -				hash_add(qtable->queues, &q->mdev_qnode,
>> -					 q->apqn);
>> +				vfio_ap_unlink_queue_fr_mdev(q);
> Same as above...
>
> Regards,
> Halil
>
>>   		}
>>   	}
>>   }