linux-kernel - Re: [PATCH 1/3] s390/vfio-ap: clean up mdev resources when remove callback invoked

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Date:   Tue, 15 Jun 2021 09:43:44 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        cohuck@...hat.com, pasic@...ux.vnet.ibm.com, jjherne@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
        hca@...ux.ibm.com
Subject: Re: [PATCH 1/3] s390/vfio-ap: clean up mdev resources when remove
 callback invoked



On 11.06.21 18:48, Jason Gunthorpe wrote:
> On Wed, Jun 09, 2021 at 06:46:32PM -0400, Tony Krowiak wrote:
>> The mdev remove callback for the vfio_ap device driver bails out with
>> -EBUSY if the mdev is in use by a KVM guest (i.e., the KVM pointer in the
>> struct ap_matrix_mdev is not NULL). The intended purpose was
>> to prevent the mdev from being removed while in use. There are two
>> problems with this scenario:
>>
>> 1. Returning a non-zero return code from the remove callback does not
>>     prevent the removal of the mdev.
>>
>> 2. The KVM pointer in the struct ap_matrix_mdev will always be NULL because
>>     the remove callback will not get invoked until the mdev fd is closed.
>>     When the mdev fd is closed, the mdev release callback is invoked and
>>     clears the KVM pointer from the struct ap_matrix_mdev.
>>
>> Let's go ahead and remove the check for KVM in the remove callback and
>> allow the cleanup of mdev resources to proceed.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 10 ----------
>>   1 file changed, 10 deletions(-)
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason, I guess you want this patch still in 5.13, the other 2 can be 5.14?