From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B49CC43381 for ; Mon, 18 Feb 2019 18:32:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3736E217F5 for ; Mon, 18 Feb 2019 18:32:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727929AbfBRScl (ORCPT ); Mon, 18 Feb 2019 13:32:41 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45752 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726235AbfBRSck (ORCPT ); Mon, 18 Feb 2019 13:32:40 -0500 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1IITJ7q018544 for ; Mon, 18 Feb 2019 13:32:39 -0500 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2qqxynj0ub-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 18 Feb 2019 13:32:39 -0500 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 18 Feb 2019 18:32:32 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1IIWVNT59834440 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 18 Feb 2019 18:32:31 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 47FB511C04C; Mon, 18 Feb 2019 18:32:31 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9FF6E11C058; Mon, 18 Feb 2019 18:32:30 +0000 (GMT) Received: from [9.145.70.2] (unknown [9.145.70.2]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 18 Feb 2019 18:32:30 +0000 (GMT) Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH v3 4/9] s390: ap: tools to find a queue with a specific APQN To: Cornelia Huck , Tony Krowiak Cc: borntraeger@de.ibm.com, alex.williamson@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com References: <1550152269-6317-1-git-send-email-pmorel@linux.ibm.com> <1550152269-6317-5-git-send-email-pmorel@linux.ibm.com> <56f583e7-fb41-ec54-ccf9-585a3e51b1c4@linux.ibm.com> <20190218132111.3684b1f1.cohuck@redhat.com> From: Pierre Morel Date: Mon, 18 Feb 2019 19:32:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190218132111.3684b1f1.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19021818-0012-0000-0000-000002F72D87 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19021818-0013-0000-0000-0000212EB7C1 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-18_14:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=852 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902180137 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/02/2019 13:21, Cornelia Huck wrote: > On Fri, 15 Feb 2019 17:13:21 -0500 > Tony Krowiak wrote: > >> On 2/14/19 8:51 AM, Pierre Morel wrote: >>> We need to find the queue with a specific APQN during the >>> handling of the interception of the PQAP/AQIC instruction. >>> >>> To handle the AP associated device reference count we keep >>> track of it in the vfio_ap_queue until we put the device. >>> >>> Signed-off-by: Pierre Morel >>> --- >>> drivers/s390/crypto/vfio_ap_ops.c | 54 +++++++++++++++++++++++++++++++++++ >>> drivers/s390/crypto/vfio_ap_private.h | 1 + >>> 2 files changed, 55 insertions(+) > >>> +/** >>> + * 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 associated to the vfio_ap_driver. >>> + * >>> + * The vfio_ap_queue has been already associated with the device >>> + * during the probe. >>> + * Store the associated device for reference counting >>> + * >>> + * Returns the pointer to the associated vfio_ap_queue >>> + */ >>> +static __attribute__((unused)) >>> + struct vfio_ap_queue *vfio_ap_get_queue(int apqn) >> >> I think you should change this signature for the reasons I stated >> below: >> >> struct device *vfio_ap_get_queue_dev(int apqn) >> >>> +{ >>> + struct device *dev; >>> + struct vfio_ap_queue *q; >>> + >>> + dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL, &apqn, >>> + vfio_ap_check_apqn); >>> + if (!dev) >>> + return NULL; >>> + q = dev_get_drvdata(dev); >>> + q->dev = dev; >> >> Why store the device with the vfio_ap_queue object? Why not just return >> the device. The caller can get the vfio_ap_queue from the device's >> driver data. It seems the only reason for the 'dev' field is to >> temporarily hold a ref to the device so it can be put later. Why not >> just put the device. > > Having looked at the remainder of the patches, I tend to agree that we > don't really need the backlink; we walk the driver's list of devices in > any case IIUC. > > We *might* want a mechanism to grab the queue quickly (i.e. without > walking the list) if there's anything performance sensitive in there; > but from the patch descriptions, I don't think anything is done in a > hot path, so it should be fine. > OK you are right, I ll drop it -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany