linux-kernel - Re: [PATCH v10 05/16] s390/vfio-ap: implement in-use callback for vfio

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Message-ID: <20200925112941.71589591.pasic@linux.ibm.com>
Date:   Fri, 25 Sep 2020 11:29:41 +0200
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, mjrosato@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v10 05/16] s390/vfio-ap: implement in-use callback for
 vfio_ap driver

On Fri, 21 Aug 2020 15:56:05 -0400
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> +
> +bool vfio_ap_mdev_resource_in_use(unsigned long *apm, unsigned long *aqm)
> +{
> +	bool in_use;
> +
> +	mutex_lock(&matrix_dev->lock);
> +	in_use = !!vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm);
> +	mutex_unlock(&matrix_dev->lock);

See also my comment for patch 4. AFAIU as soon as you release the lock
the in_use may become outdated in any moment.

> +
> +	return in_use;
> +}