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Tue, 29 Sep 2020 20:57:35 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D22B913604F; Tue, 29 Sep 2020 20:57:33 +0000 (GMT) Received: from localhost.localdomain (unknown [9.85.170.177]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 29 Sep 2020 20:57:33 +0000 (GMT) Subject: Re: [PATCH v10 02/16] s390/vfio-ap: use new AP bus interface to search for queue devices To: Halil Pasic Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, mjrosato@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, fiuczy@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, kernel test robot References: <20200821195616.13554-1-akrowiak@linux.ibm.com> <20200821195616.13554-3-akrowiak@linux.ibm.com> <20200925042729.3b9d5704.pasic@linux.ibm.com> <20200929153755.20bdd94f.pasic@linux.ibm.com> From: Tony Krowiak Message-ID: <020af9d9-33d7-2e32-5253-74aa7a36f3ed@linux.ibm.com> Date: Tue, 29 Sep 2020 16:57:33 -0400 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: <20200929153755.20bdd94f.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=2.50.10434:6.0.235,18.0.687 definitions=2020-09-29_13:2020-09-29,2020-09-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 impostorscore=0 malwarescore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 mlxlogscore=999 bulkscore=0 suspectscore=0 phishscore=0 spamscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009290169 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 9/29/20 9:37 AM, Halil Pasic wrote: > On Tue, 29 Sep 2020 09:07:40 -0400 > Tony Krowiak wrote: > >> >> On 9/24/20 10:27 PM, Halil Pasic wrote: >>> On Fri, 21 Aug 2020 15:56:02 -0400 >>> Tony Krowiak wrote: >>> >>>> --- a/drivers/s390/crypto/vfio_ap_ops.c >>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c >>>> @@ -26,43 +26,26 @@ >>>> >>>> static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev); >>>> >>>> -static int match_apqn(struct device *dev, const void *data) >>>> -{ >>>> - struct vfio_ap_queue *q = dev_get_drvdata(dev); >>>> - >>>> - return (q->apqn == *(int *)(data)) ? 1 : 0; >>>> -} >>>> - >>>> /** >>>> - * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a list >>>> - * @matrix_mdev: the associated mediated matrix >>>> + * vfio_ap_get_queue: Retrieve a queue with a specific APQN. >>>> * @apqn: The queue APQN >>>> * >>>> - * Retrieve a queue with a specific APQN from the list of the >>>> - * devices of the vfio_ap_drv. >>>> - * Verify that the APID and the APQI are set in the matrix. >>>> + * Retrieve a queue with a specific APQN from the AP queue devices attached to >>>> + * the AP bus. >>>> * >>>> - * Returns the pointer to the associated vfio_ap_queue >>>> + * Returns the pointer to the vfio_ap_queue with the specified APQN, or NULL. >>>> */ >>>> -static struct vfio_ap_queue *vfio_ap_get_queue( >>>> - struct ap_matrix_mdev *matrix_mdev, >>>> - int apqn) >>>> +static struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn) >>>> { >>>> + struct ap_queue *queue; >>>> struct vfio_ap_queue *q; >>>> - struct device *dev; >>>> >>>> - if (!test_bit_inv(AP_QID_CARD(apqn), matrix_mdev->matrix.apm)) >>>> - return NULL; >>>> - if (!test_bit_inv(AP_QID_QUEUE(apqn), matrix_mdev->matrix.aqm)) >>>> + queue = ap_get_qdev(apqn); >>>> + if (!queue) >>>> return NULL; >>>> >>>> - dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL, >>>> - &apqn, match_apqn); >>>> - if (!dev) >>>> - return NULL; >>>> - q = dev_get_drvdata(dev); >>>> - q->matrix_mdev = matrix_mdev; >>>> - put_device(dev); >>>> + q = dev_get_drvdata(&queue->ap_dev.device); >>> Is this cast here safe? (I don't think it is.) >> In the probe, we execute: >> dev_set_drvdata(&queue->ap_dev.device, q); >> >> I don't get any compile nor execution errors. Why wouldn't it be safe? >> > Because the queue may or may not be bound to the vfio_ap driver. AFAICT > this function can be called with an arbitrary APQN. > > If it is bound to another driver then drvdata is not likely to hold a > struct vfio_ap_queue. Then the function will return NULL. All callers must check for NULL before using it which is the case in all places where this function is called. > > >>>> + put_device(&queue->ap_dev.device); >>>> >>>> return q; >>>> }