linux-kernel - Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated

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Date:   Thu, 3 Dec 2020 18:01:41 +0100
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Tony Krowiak <akrowiak@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        borntraeger@...ibm.com, alex.williamson@...hat.com,
        kwankhede@...dia.com, david@...hat.com
Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM
 pointer invalidated

On Thu, 3 Dec 2020 11:19:07 +0100
Cornelia Huck <cohuck@...hat.com> wrote:

> > @@ -1095,7 +1106,7 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> >  	matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
> >  
> >  	if (!data) {
> > -		matrix_mdev->kvm = NULL;
> > +		vfio_ap_mdev_put_kvm(matrix_mdev);  
> 
> Hm. I'm wondering whether you need to hold the maxtrix_dev lock here as
> well?

In v12 we eventually did come along and patch "s390/vfio-ap: allow hot
plug/unplug of AP resources using mdev device" made this a part of a
critical section protected by the matrix_dev->lock.

IMHO the cleanup should definitely happen with the matrix_dev->lock held.

Regards,
Halil