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=-3.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLACK, USER_AGENT_SANE_1 autolearn=no 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 44FA9C00523 for ; Wed, 8 Jan 2020 07:35:13 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B7354206DA for ; Wed, 8 Jan 2020 07:35:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B7354206DA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47t1HK5zP4zDqPn for ; Wed, 8 Jan 2020 18:35:09 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=ajd@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47t1FJ6x2RzDqQg for ; Wed, 8 Jan 2020 18:33:23 +1100 (AEDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0087WdE8049306 for ; Wed, 8 Jan 2020 02:33:20 -0500 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xb8unj47k-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 08 Jan 2020 02:33:20 -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) Wed, 8 Jan 2020 07:33:16 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0087XFdu46071938 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 8 Jan 2020 07:33:15 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0B245AE045; Wed, 8 Jan 2020 07:33:15 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AF1BCAE058; Wed, 8 Jan 2020 07:33:14 +0000 (GMT) Received: from ozlabs.au.ibm.com (unknown [9.192.253.14]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 8 Jan 2020 07:33:14 +0000 (GMT) Received: from [9.102.44.133] (unknown [9.102.44.133]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id D7F32A0193; Wed, 8 Jan 2020 18:33:10 +1100 (AEDT) Subject: Re: [PATCH v2 01/11] powerpc/powernv/ioda: Fix ref count for devices with their own PE To: Frederic Barrat , linuxppc-dev@lists.ozlabs.org, clombard@linux.ibm.com References: <20191121134918.7155-1-fbarrat@linux.ibm.com> <20191121134918.7155-2-fbarrat@linux.ibm.com> From: Andrew Donnellan Date: Wed, 8 Jan 2020 18:33:10 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191121134918.7155-2-fbarrat@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20010807-0012-0000-0000-0000037B6827 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20010807-0013-0000-0000-000021B785D4 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-01-08_01:2020-01-07, 2020-01-08 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 bulkscore=0 priorityscore=1501 impostorscore=0 suspectscore=18 adultscore=0 phishscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxlogscore=922 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001080064 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: aik@ozlabs.ru, oohall@gmail.com, groug@kaod.org, alastair@au1.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 22/11/19 12:49 am, Frederic Barrat wrote: > The pci_dn structure used to store a pointer to the struct pci_dev, so > taking a reference on the device was required. However, the pci_dev > pointer was later removed from the pci_dn structure, but the reference > was kept for the npu device. > See commit 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary > pcidev from pci_dn"). > > We don't need to take a reference on the device when assigning the PE > as the struct pnv_ioda_pe is cleaned up at the same time as > the (physical) device is released. Doing so prevents the device from > being released, which is a problem for opencapi devices, since we want > to be able to remove them through PCI hotplug. > > Now the ugly part: nvlink npu devices are not meant to be > released. Because of the above, we've always leaked a reference and > simply removing it now is dangerous and would likely require more > work. There's currently no release device callback for nvlink devices > for example. So to be safe, this patch leaks a reference on the npu > device, but only for nvlink and not opencapi. > > CC: aik@ozlabs.ru > CC: oohall@gmail.com > Signed-off-by: Frederic Barrat It took me a while to parse exactly what you're doing here. - In pnv_ioda_setup_dev_PE(), we take a reference on the pci_dev, this is to protect a pointer in the pci_dn structure, but not to protect the pointer in the pci_dev structure (which doesn't need to be protected by taking a reference, because the lifetime of the pnv_ioda_pe is the same as the pci_dev). - The pointer in the pci_dn structure has now been removed, so we should remove the pci_dev_get() accordingly. This seems okay to me, though anything PE-related is irritatingly hairy so one can never be truly certain... Reviewed-by: Andrew Donnellan -- Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited