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Mon, 28 Jun 2021 18:27:30 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CC96D788E2; Mon, 28 Jun 2021 18:27:27 +0000 (GMT) Received: from cpe-172-100-179-72.stny.res.rr.com (unknown [9.85.148.87]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 28 Jun 2021 18:27:27 +0000 (GMT) Subject: Re: [PATCH] s390/vfio-ap: do not use open locks during VFIO_GROUP_NOTIFY_SET_KVM notification To: Jason Gunthorpe Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com References: <20210625220758.80365-1-akrowiak@linux.ibm.com> <20210628173448.GG4459@nvidia.com> <20210628182248.GH4459@nvidia.com> From: Tony Krowiak Message-ID: Date: Mon, 28 Jun 2021 14:27:26 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210628182248.GH4459@nvidia.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-GUID: Nv96jAtlyoKi5Tc2FgpF9Z1TjRAVqDqe X-Proofpoint-ORIG-GUID: gng92e5pMiaR7jyLm9gPHSGWaVH_OnzP X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-28_14:2021-06-25,2021-06-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 mlxscore=0 spamscore=0 impostorscore=0 priorityscore=1501 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106280118 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/28/21 2:22 PM, Jason Gunthorpe wrote: > On Mon, Jun 28, 2021 at 02:20:55PM -0400, Tony Krowiak wrote: >> >> On 6/28/21 1:34 PM, Jason Gunthorpe wrote: >>> On Fri, Jun 25, 2021 at 06:07:58PM -0400, Tony Krowiak wrote: >>>> static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) >>>> { >>>> + mutex_lock(&matrix_dev->lock); >>>> + if ((matrix_mdev->kvm) && (matrix_mdev->kvm->arch.crypto.crycbd)) { >>>> mutex_unlock(&matrix_dev->lock); >>>> + down_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); >>>> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; >>>> + up_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); >>>> + kvm_arch_crypto_clear_masks(matrix_mdev->kvm); >>>> mutex_lock(&matrix_dev->lock); >>>> vfio_ap_mdev_reset_queues(matrix_mdev->mdev); >>>> kvm_put_kvm(matrix_mdev->kvm); >>>> matrix_mdev->kvm = NULL; >>>> + mutex_unlock(&matrix_dev->lock); >>>> } >>> Doesn't a flow exit the function with matrix_dev->lock held he Yes, you are correct. Stupid mistake. >> How can that happen? What flow? > When the if isn't taken > >>> Write it with 'success oriented flow' >> I'm not sure what you mean, can you clarify this statement? > Basically, don't write the bulk of the function under an if statement > > mutex_lock(&matrix_dev->lock); > if (!matrix_mdev->kvm || !matrix_mdev->kvm->arch.crypto.crycbd) { > mutex_unlock(&matrix_dev->lock); > return; > } Sure. > > Jason >