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Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 49E49A405C; Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Received: from sig-9-145-36-222.uk.ibm.com (unknown [9.145.36.222]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Message-ID: <0c9326c943c0e6aa572cc132ee2deb952bf41c7f.camel@linux.ibm.com> Subject: Re: [PATCH 0/5] s390/pci: automatic error recovery From: Niklas Schnelle To: "Oliver O'Halloran" Cc: Bjorn Helgaas , Linas Vepstas , Russell Currey , linuxppc-dev , Linux Kernel Mailing List , linux-s390@vger.kernel.org, Matthew Rosato , Pierre Morel Date: Tue, 07 Sep 2021 14:21:17 +0200 In-Reply-To: References: <20210906094927.524106-1-schnelle@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-16.el8) X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: SkUon7ztrKqjkeIh7btB_xV5c0wMpkDT X-Proofpoint-GUID: qZD9o8qgwlzYyZe-rDOYlYcLItkcgiQA Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-09-07_04:2021-09-07,2021-09-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 bulkscore=0 spamscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 suspectscore=0 mlxlogscore=904 phishscore=0 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109070080 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2021-09-07 at 10:45 +0200, Niklas Schnelle wrote: > On Tue, 2021-09-07 at 12:04 +1000, Oliver O'Halloran wrote: > > On Mon, Sep 6, 2021 at 7:49 PM Niklas Schnelle wrote: > > > Patch 3 I already sent separately resulting in the discussion below but without > > > a final conclusion. > > > > > > https://lore.kernel.org/lkml/20210720150145.640727-1-schnelle@linux.ibm.com/ > > > > > > I believe even though there were some doubts about the use of > > > pci_dev_is_added() by arch code the existing uses as well as the use in the > > > final patch of this series warrant this export. > > > > The use of pci_dev_is_added() in arch/powerpc was because in the past > > pci_bus_add_device() could be called before pci_device_add(). That was > > fixed a while ago so It should be safe to remove those calls now. > > Hmm, ok that confirms Bjorns suspicion and explains how it came to be. > I can certainly sent a patch for that. This would then leave only the > existing use in s390 which I added because of a dead lock prevention > and explained here: > https://lore.kernel.org/lkml/87d15d5eead35c9eaa667958d057cf4a81a8bf13.camel@linux.ibm.com/ > > Plus the need to use it in the recovery code of this series. I think in > the EEH code the need for a similar check is alleviated by the checks > in the beginning of > arch/powerpc/kernel/eeh_driver.c:eeh_handle_normal_event() especially > eeh_slot_presence_check() which checks presence via the hotplug slot. > I guess we could use our own state tracking in a similar way but felt > like pci_dev_is_added() is the more logical choice. Looking into this again, I think we actually can't easily track this state ourselves outside struct pci_dev. The reason for this is that when e.g. arch/s390/pci/pci_sysfs.c:recover_store() removes the struct pci_dev and scans it again the new struct pci_dev re-uses the same struct zpci_dev because from a platform point of view the PCI device was never removed but only disabled and re-enabled. Thus we can only distinguish the stale struct pci_dev by looking at things stored in struct pci_dev itself. That said, I think for the recovery case we might be able to drop the pci_dev_is_added() and rely on pdev->driver != NULL which we check anyway and that should catch any PCI device that was already removed. 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Tue, 7 Sep 2021 08:21:24 -0400 Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 3ax78m96kx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 07 Sep 2021 08:21:24 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 187CC3DU028211; Tue, 7 Sep 2021 12:21:22 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma04ams.nl.ibm.com with ESMTP id 3av0e9eyhh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 07 Sep 2021 12:21:22 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 187CH60t60752128 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 7 Sep 2021 12:17:06 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C7255A4054; Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 49E49A405C; Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Received: from sig-9-145-36-222.uk.ibm.com (unknown [9.145.36.222]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 7 Sep 2021 12:21:18 +0000 (GMT) Message-ID: <0c9326c943c0e6aa572cc132ee2deb952bf41c7f.camel@linux.ibm.com> Subject: Re: [PATCH 0/5] s390/pci: automatic error recovery From: Niklas Schnelle To: "Oliver O'Halloran" Date: Tue, 07 Sep 2021 14:21:17 +0200 In-Reply-To: References: <20210906094927.524106-1-schnelle@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-16.el8) X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: SkUon7ztrKqjkeIh7btB_xV5c0wMpkDT X-Proofpoint-GUID: qZD9o8qgwlzYyZe-rDOYlYcLItkcgiQA Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-09-07_04:2021-09-07, 2021-09-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 bulkscore=0 spamscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 suspectscore=0 mlxlogscore=904 phishscore=0 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109070080 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: linux-s390@vger.kernel.org, Pierre Morel , Matthew Rosato , Linux Kernel Mailing List , Bjorn Helgaas , Linas Vepstas , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 2021-09-07 at 10:45 +0200, Niklas Schnelle wrote: > On Tue, 2021-09-07 at 12:04 +1000, Oliver O'Halloran wrote: > > On Mon, Sep 6, 2021 at 7:49 PM Niklas Schnelle wrote: > > > Patch 3 I already sent separately resulting in the discussion below but without > > > a final conclusion. > > > > > > https://lore.kernel.org/lkml/20210720150145.640727-1-schnelle@linux.ibm.com/ > > > > > > I believe even though there were some doubts about the use of > > > pci_dev_is_added() by arch code the existing uses as well as the use in the > > > final patch of this series warrant this export. > > > > The use of pci_dev_is_added() in arch/powerpc was because in the past > > pci_bus_add_device() could be called before pci_device_add(). That was > > fixed a while ago so It should be safe to remove those calls now. > > Hmm, ok that confirms Bjorns suspicion and explains how it came to be. > I can certainly sent a patch for that. This would then leave only the > existing use in s390 which I added because of a dead lock prevention > and explained here: > https://lore.kernel.org/lkml/87d15d5eead35c9eaa667958d057cf4a81a8bf13.camel@linux.ibm.com/ > > Plus the need to use it in the recovery code of this series. I think in > the EEH code the need for a similar check is alleviated by the checks > in the beginning of > arch/powerpc/kernel/eeh_driver.c:eeh_handle_normal_event() especially > eeh_slot_presence_check() which checks presence via the hotplug slot. > I guess we could use our own state tracking in a similar way but felt > like pci_dev_is_added() is the more logical choice. Looking into this again, I think we actually can't easily track this state ourselves outside struct pci_dev. The reason for this is that when e.g. arch/s390/pci/pci_sysfs.c:recover_store() removes the struct pci_dev and scans it again the new struct pci_dev re-uses the same struct zpci_dev because from a platform point of view the PCI device was never removed but only disabled and re-enabled. Thus we can only distinguish the stale struct pci_dev by looking at things stored in struct pci_dev itself. That said, I think for the recovery case we might be able to drop the pci_dev_is_added() and rely on pdev->driver != NULL which we check anyway and that should catch any PCI device that was already removed.