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Fri, 30 Oct 2020 20:53:05 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A434112061; Fri, 30 Oct 2020 20:53:05 +0000 (GMT) Received: from cpe-66-24-58-13.stny.res.rr.com (unknown [9.85.162.174]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 30 Oct 2020 20:53:05 +0000 (GMT) Subject: Re: [PATCH v11 01/14] s390/vfio-ap: No need to disable IRQ after queue reset 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, hca@linux.ibm.com, gor@linux.ibm.com References: <20201022171209.19494-1-akrowiak@linux.ibm.com> <20201022171209.19494-2-akrowiak@linux.ibm.com> <20201027074846.30ee0ddc.pasic@linux.ibm.com> <7a2c5930-9c37-8763-7e5d-c08a3638e6a1@linux.ibm.com> <20201030185406.7fa13fbe.pasic@linux.ibm.com> From: Tony Krowiak Message-ID: Date: Fri, 30 Oct 2020 16:53:04 -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: <20201030185406.7fa13fbe.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=2020-10-30_10:2020-10-30,2020-10-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 suspectscore=11 lowpriorityscore=0 impostorscore=0 mlxscore=0 spamscore=0 mlxlogscore=955 bulkscore=0 clxscore=1015 phishscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010300147 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/30/20 1:54 PM, Halil Pasic wrote: > On Thu, 29 Oct 2020 19:29:35 -0400 > Tony Krowiak wrote: > >>>> @@ -1177,7 +1166,10 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev) >>>> */ >>>> if (ret) >>>> rc = ret; >>>> - vfio_ap_irq_disable_apqn(AP_MKQID(apid, apqi)); >>>> + q = vfio_ap_get_queue(matrix_mdev, >>>> + AP_MKQID(apid, apqi)); >>>> + if (q) >>>> + vfio_ap_free_aqic_resources(q); > [..] > >>> Under what circumstances do we expect !q? If we don't, then we need to >>> complain one way or another. >> In the current code (i.e., prior to introducing the subsequent hot >> plug patches), an APQN can not be assigned to an mdev unless it >> references a queue device bound to the vfio_ap device driver; however, >> there is nothing preventing a queue device from getting unbound >> while the guest is running (one of the problems mostly resolved by this >> series). In that case, q would be NULL. > But if the queue does not belong to us any more it does not make sense > call vfio_ap_mdev_reset_queue() on it's APQN, or? This is precisely why we prevent a queue from being taken away from vfio_ap (the in-use callback) when its APQN is assigned to an mdev in this patch series. On the other hand, this is a very good point. > > I think we should have > > if(!q) > continue; > at the very beginning of the loop body, or we want to be sure that q is > not null. I agree, I'll go ahead and make this change. > >