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Wed, 08 Apr 2020 15:38:10 +0000 Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 038Fc8tr53346708 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 8 Apr 2020 15:38:08 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 695D1AE05C; Wed, 8 Apr 2020 15:38:08 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 961BFAE062; Wed, 8 Apr 2020 15:38:07 +0000 (GMT) Received: from cpe-172-100-173-215.stny.res.rr.com (unknown [9.85.151.56]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 8 Apr 2020 15:38:07 +0000 (GMT) Subject: Re: [PATCH v7 01/15] s390/vfio-ap: store queue struct in hash table for quick access To: Cornelia Huck Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, mjrosato@linux.ibm.com, pmorel@linux.ibm.com, pasic@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, jjherne@linux.ibm.com, fiuczy@linux.ibm.com References: <20200407192015.19887-1-akrowiak@linux.ibm.com> <20200407192015.19887-2-akrowiak@linux.ibm.com> <20200408124801.2d61bc5b.cohuck@redhat.com> From: Tony Krowiak Message-ID: Date: Wed, 8 Apr 2020 11:38:07 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200408124801.2d61bc5b.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-07_10:2020-04-07,2020-04-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 mlxscore=0 malwarescore=0 priorityscore=1501 clxscore=1015 adultscore=0 mlxlogscore=999 suspectscore=3 spamscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004080122 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/8/20 6:48 AM, Cornelia Huck wrote: > On Tue, 7 Apr 2020 15:20:01 -0400 > Tony Krowiak wrote: > >> Rather than looping over potentially 65535 objects, let's store the >> structures for caching information about queue devices bound to the >> vfio_ap device driver in a hash table keyed by APQN. > This also looks like a nice code simplification. > >> Signed-off-by: Tony Krowiak >> --- >> drivers/s390/crypto/vfio_ap_drv.c | 28 +++------ >> drivers/s390/crypto/vfio_ap_ops.c | 90 ++++++++++++++------------- >> drivers/s390/crypto/vfio_ap_private.h | 10 ++- >> 3 files changed, 60 insertions(+), 68 deletions(-) >> > (...) > >> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c >> index 5c0f53c6dde7..134860934fe7 100644 >> --- a/drivers/s390/crypto/vfio_ap_ops.c >> +++ b/drivers/s390/crypto/vfio_ap_ops.c >> @@ -26,45 +26,16 @@ >> >> 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 >> - * @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. >> - * >> - * Returns the pointer to the associated vfio_ap_queue > Any reason you're killing this comment, instead of adapting it? The > function is even no longer static... I can update and restore the comment and the function should be static. > >> - */ >> -static struct vfio_ap_queue *vfio_ap_get_queue( >> - struct ap_matrix_mdev *matrix_mdev, >> - int apqn) >> +struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn) >> { >> 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)) >> - return NULL; > These were just optimizations and therefore can be dropped now? The purpose of this function has changed from its previous incarnation. This function was originally called from the handle_pqap() function and served two purposes: It retrieved the struct vfio_ap_queue as driver data and linked the matrix_mdev to the  vfio_ap_queue. The linking of the matrix_mdev and the vfio_ap_queue are now done when queue devices are probed and when adapters and domains are assigned; so now, the handle_pqap() function calls this function to retrieve both the vfio_ap_queue as well as the matrix_mdev to which it is linked. Consequently, the above code is no longer needed. > >> - >> - 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); >> >> - return q; >> + hash_for_each_possible(matrix_dev->qtable, q, qnode, apqn) { >> + if (q && (apqn == q->apqn)) >> + return q; >> + } > Do we need any serialization here? Previously, the driver core made > sure we could get a reference only if the device was still registered; > not sure if we need any further guarantees now. The vfio_ap_queue structs are created when the queue device is probed and removed when the queue device is removed. > >> + >> + return NULL; >> } >> >> /** > (...) >