From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pierre Morel <pmorel@linux.ibm.com>
Subject: Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP
 device driver
Date: Wed, 16 May 2018 10:21:55 +0200
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To: Tony Krowiak <akrowiak@linux.vnet.ibm.com>, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com
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On 07/05/2018 17:11, Tony Krowiak wrote:
> Introduces a new AP device driver. This device driver
> is built on the VFIO mediated device framework. The framework
> provides sysfs interfaces that facilitate passthrough
> access by guests to devices installed on the linux host.
...snip...
> +static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
> +{

You should take care of the ap devices when they are added or removed
from the matrix.
I suggest you add a remove callback to avoid unbinding a queue while
it is assigned to a guest.

> +	return 0;
> +}
> +
> +static void vfio_ap_matrix_dev_release(struct device *dev)
> +{
> +	struct ap_matrix *ap_matrix = dev_get_drvdata(dev);
> +
> +	kfree(ap_matrix);
> +}
...snip...

-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany