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Fri, 4 Dec 2020 16:48:25 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1DDB8B2064; Fri, 4 Dec 2020 16:48:25 +0000 (GMT) Received: from cpe-66-24-58-13.stny.res.rr.com (unknown [9.85.195.249]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 4 Dec 2020 16:48:24 +0000 (GMT) Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated To: Halil Pasic Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, alex.williamson@redhat.com, kwankhede@nvidia.com, david@redhat.com References: <20201202234101.32169-1-akrowiak@linux.ibm.com> <20201203185514.54060568.pasic@linux.ibm.com> From: Tony Krowiak Message-ID: Date: Fri, 4 Dec 2020 11:48:24 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20201203185514.54060568.pasic@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-04_05:2020-12-04,2020-12-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 phishscore=0 spamscore=0 impostorscore=0 adultscore=0 malwarescore=0 clxscore=1015 suspectscore=3 mlxscore=0 priorityscore=1501 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012040090 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/3/20 12:55 PM, Halil Pasic wrote: > On Wed, 2 Dec 2020 18:41:01 -0500 > Tony Krowiak wrote: > >> The vfio_ap device driver registers a group notifier with VFIO when the >> file descriptor for a VFIO mediated device for a KVM guest is opened to >> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM >> event). When the KVM pointer is set, the vfio_ap driver stashes the pointer >> and calls the kvm_get_kvm() function to increment its reference counter. >> When the notifier is called to make notification that the KVM pointer has >> been set to NULL, the driver should clean up any resources associated with >> the KVM pointer and decrement its reference counter. The current >> implementation does not take care of this clean up. >> >> Signed-off-by: Tony Krowiak > Do we need a Fixes tag? Do we need this backported? In my opinion > this is necessary since the interrupt patches. I'll put in a fixes tag: Fixes: 258287c994de (s390: vfio-ap: implement mediated device open callback) Yes, this should probably be backported. > >> --- >> drivers/s390/crypto/vfio_ap_ops.c | 21 +++++++++++++-------- >> 1 file changed, 13 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c >> index e0bde8518745..eeb9c9130756 100644 >> --- a/drivers/s390/crypto/vfio_ap_ops.c >> +++ b/drivers/s390/crypto/vfio_ap_ops.c >> @@ -1083,6 +1083,17 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb, >> return NOTIFY_DONE; >> } >> >> +static void vfio_ap_mdev_put_kvm(struct ap_matrix_mdev *matrix_mdev) > I don't like the name. The function does more that put_kvm. Maybe > something like _disconnect_kvm()? Since the vfio_ap_mdev_set_kvm() function is called by the notifier when the KVM pointer is set, how about: vfio_ap_mdev_unset_kvm() for when the KVM pointer is nullified? > >> +{ >> + if (matrix_mdev->kvm) { >> + (matrix_mdev->kvm); >> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; > Is a plain assignment to arch.crypto.pqap_hook apropriate, or do we need > to take more care? > > For instance kvm_arch_crypto_set_masks() takes kvm->lock before poking > kvm->arch.crypto.crycb. > >> + vfio_ap_mdev_reset_queues(matrix_mdev->mdev); >> + kvm_put_kvm(matrix_mdev->kvm); >> + matrix_mdev->kvm = NULL; >> + } >> +} >> + >> static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, >> unsigned long action, void *data) >> { >> @@ -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); > The lock question was already raised. > > What are the exact circumstances under which this branch can be taken? > >> return NOTIFY_OK; >> } >> >> @@ -1222,13 +1233,7 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev) >> struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); >> >> mutex_lock(&matrix_dev->lock); >> - if (matrix_mdev->kvm) { >> - kvm_arch_crypto_clear_masks(matrix_mdev->kvm); >> - matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; >> - vfio_ap_mdev_reset_queues(mdev); >> - kvm_put_kvm(matrix_mdev->kvm); >> - matrix_mdev->kvm = NULL; >> - } >> + vfio_ap_mdev_put_kvm(matrix_mdev); >> mutex_unlock(&matrix_dev->lock); >> >> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,