linux-kernel - Re: [PATCH v4] s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated

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Date:   Tue, 22 Dec 2020 16:57:06 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     Halil Pasic <pasic@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        stable@...r.kernel.org, borntraeger@...ibm.com,
        kwankhede@...dia.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pasic@...ux.vnet.ibm.com
Subject: Re: [PATCH v4] s390/vfio-ap: clean up vfio_ap resources when KVM
 pointer invalidated

On Tue, 22 Dec 2020 10:37:01 -0500
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> On 12/21/20 11:05 PM, Halil Pasic wrote:
> > On Mon, 21 Dec 2020 13:56:25 -0500
> > Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> >>   static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> >>   				       unsigned long action, void *data)
> >>   {
> >> -	int ret;
> >> +	int ret, notify_rc = NOTIFY_DONE;
> >>   	struct ap_matrix_mdev *matrix_mdev;
> >>   
> >>   	if (action != VFIO_GROUP_NOTIFY_SET_KVM)
> >>   		return NOTIFY_OK;
> >>   
> >>   	matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
> >> +	mutex_lock(&matrix_dev->lock);
> >>   
> >>   	if (!data) {
> >> -		matrix_mdev->kvm = NULL;
> >> -		return NOTIFY_OK;
> >> +		if (matrix_mdev->kvm)
> >> +			vfio_ap_mdev_unset_kvm(matrix_mdev);
> >> +		notify_rc = NOTIFY_OK;
> >> +		goto notify_done;
> >>   	}
> >>   
> >>   	ret = vfio_ap_mdev_set_kvm(matrix_mdev, data);
> >>   	if (ret)
> >> -		return NOTIFY_DONE;
> >> +		goto notify_done;
> >>   
> >>   	/* If there is no CRYCB pointer, then we can't copy the masks */
> >>   	if (!matrix_mdev->kvm->arch.crypto.crycbd)
> >> -		return NOTIFY_DONE;
> >> +		goto notify_done;
> >>   
> >>   	kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
> >>   				  matrix_mdev->matrix.aqm,
> >>   				  matrix_mdev->matrix.adm);
> >>   
> >> -	return NOTIFY_OK;  
> > Shouldn't there be an
> >   +	notify_rc = NOTIFY_OK;
> > here? I mean you initialize notify_rc to NOTIFY_DONE, in the !data branch
> > on success you set notify_rc to NOTIFY_OK, but in the !!data branch it
> > just stays NOTIFY_DONE. Or am I missing something?  
> 
> I don't think it matters much since NOTIFY_OK and NOTIFY_DONE have
> no further effect on processing of the notification queue, but I believe
> you are correct, this is a change from what we originally had. I can
> restore the original return values if you'd prefer.

Even if they have the same semantics now, that might change in the
future; restoring the original behaviour looks like the right thing to
do.

> 
> >
> > Otherwise LGTM!

Same here.

> >
> > Regards,
> > Halil
> >  
> >> +notify_done:
> >> +	mutex_unlock(&matrix_dev->lock);
> >> +	return notify_rc;
> >>   }
> >>  
> > [..]  
>