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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 BF4EBC28CBC for ; Sat, 9 May 2020 06:35:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C89C2495A for ; Sat, 9 May 2020 06:35:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728821AbgEIGfE (ORCPT ); Sat, 9 May 2020 02:35:04 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:4365 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726115AbgEIGfE (ORCPT ); Sat, 9 May 2020 02:35:04 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id ED15481B88DF56C8D873; Sat, 9 May 2020 14:35:01 +0800 (CST) Received: from [10.65.58.147] (10.65.58.147) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.487.0; Sat, 9 May 2020 14:34:58 +0800 Subject: Re: [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery To: Jay Vosburgh , "Kuppuswamy, Sathyanarayanan" References: <12115.1588207324@famine> <18897ceb-2263-1101-ae43-918a66794e14@linux.intel.com> <14682.1588279297@famine> CC: , Bjorn Helgaas From: Yicong Yang Message-ID: Date: Sat, 9 May 2020 14:35:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <14682.1588279297@famine> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.65.58.147] X-CFilter-Loop: Reflected Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hi Jay, Kuppuswamy On 2020/5/1 4:41, Jay Vosburgh wrote: > "Kuppuswamy, Sathyanarayanan" wrote: > >> Hi Jay, >> >> On 4/29/20 6:15 PM, Kuppuswamy, Sathyanarayanan wrote: >>> >>> On 4/29/20 5:42 PM, Jay Vosburgh wrote: >>>> Commit 6d2c89441571 ("PCI/ERR: Update error status after >>>> reset_link()"), introduced a regression, as pcie_do_recovery will >>>> discard the status result from report_frozen_detected. This can cause a >>>> failure to recover if _NEED_RESET is returned by report_frozen_detected >>>> and report_slot_reset is not invoked. >>>> >>>> Such an event can be induced for testing purposes by reducing >>>> the Max_Payload_Size of a PCIe bridge to less than that of a device >>>> downstream from the bridge, and then initating I/O through the device, >>>> resulting in oversize transactions. In the presence of DPC, this >>>> results in a containment event and attempted reset and recovery via >>>> pcie_do_recovery. After 6d2c89441571 report_slot_reset is not invoked, >>>> and the device does not recover. >>> I think this issue is related to the issue discussed in following >>> thread (DPC non-hotplug support). >>> >>> https://lkml.org/lkml/2020/3/28/328 >>> >>> If my assumption is correct, you are dealing with devices which are >>> not hotplug capable. If the devices are hotplug capable then you don't >>> need to proceed to report_slot_reset(), since hotplug handler will >>> remove/re-enumerate the devices correctly. > Correct, this particular device (a network card) is in a > non-hotplug slot. > >> Can you check whether following fix works for you? > Yes, it does. > > I fixed up the whitespace and made a minor change to add braces > in what look like the correct places around the "if (reset_link)" block; > the patch I tested with is below. I'll also install this on another > machine with hotplug capable slots to test there as well. > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c > index 14bb8f54723e..db80e1ecb2dc 100644 > --- a/drivers/pci/pcie/err.c > +++ b/drivers/pci/pcie/err.c > @@ -165,13 +165,24 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > pci_dbg(dev, "broadcast error_detected message\n"); > if (state == pci_channel_io_frozen) { > pci_walk_bus(bus, report_frozen_detected, &status); > - status = reset_link(dev); > - if (status != PCI_ERS_RESULT_RECOVERED) { > + status = PCI_ERS_RESULT_NEED_RESET; > + } else { > + pci_walk_bus(bus, report_normal_detected, &status); > + } > + > + if (status == PCI_ERS_RESULT_NEED_RESET) { > + if (reset_link) { > + if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED) > + status = PCI_ERS_RESULT_DISCONNECT; > + } else { > + if (pci_bus_error_reset(dev)) > + status = PCI_ERS_RESULT_DISCONNECT; > + } > + The PCI_ERS_RESULT_NEED_RESET may indicate that the driver requires a *slot* reset. With this patch, seems later slot reset broadcast may not be performed. if (status == PCI_ERS_RESULT_NEED_RESET) { status = PCI_ERS_RESULT_RECOVERED; pci_dbg(dev, "broadcast slot_reset message\n"); pci_walk_bus(bus, report_slot_reset, &status); } One minor question, currently the callers of pcie_do_recovery() will always pass a reset_link pointer, so is the condition necessary? Yicong > + if (status == PCI_ERS_RESULT_DISCONNECT) { > pci_warn(dev, "link reset failed\n"); > goto failed; > } > - } else { > - pci_walk_bus(bus, report_normal_detected, &status); > } > > if (status == PCI_ERS_RESULT_CAN_RECOVER) { > > > -J > >> This includes support for bus_reset in recovery function itself. >> >> index 14bb8f54723e..c9eaab68ab7a 100644 >> --- a/drivers/pci/pcie/err.c >> +++ b/drivers/pci/pcie/err.c >> @@ -165,13 +165,23 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, >> pci_dbg(dev, "broadcast error_detected message\n"); >> if (state == pci_channel_io_frozen) { >> if (state == pci_channel_io_frozen) { >> pci_walk_bus(bus, report_frozen_detected, &status); >> - status = reset_link(dev); >> - if (status != PCI_ERS_RESULT_RECOVERED) { >> + status = PCI_ERS_RESULT_NEED_RESET; >> + } else { >> + pci_walk_bus(bus, report_normal_detected, &status); >> + } >> + >> + if (status == PCI_ERS_RESULT_NEED_RESET) { >> + if (reset_link) >> + if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED) >> + status = PCI_ERS_RESULT_DISCONNECT; >> + else >> + if (pci_bus_error_reset(dev)) >> + status = PCI_ERS_RESULT_DISCONNECT; >> + >> + if (status == PCI_ERS_RESULT_DISCONNECT) { >> pci_warn(dev, "link reset failed\n"); >> goto failed; >> } >> - } else { >> - pci_walk_bus(bus, report_normal_detected, &status); >> } >> >> if (status == PCI_ERS_RESULT_CAN_RECOVER) { >> >> >>>> Inspection shows a similar path is plausible for a return of >>>> _CAN_RECOVER and the invocation of report_mmio_enabled. >>>> >>>> Resolve this by preserving the result of report_frozen_detected if >>>> reset_link does not return _DISCONNECT. >>>> >>>> Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()") >>>> Signed-off-by: Jay Vosburgh >>>> >>>> --- >>>> drivers/pci/pcie/err.c | 11 +++++++++-- >>>> 1 file changed, 9 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c >>>> index 14bb8f54723e..e4274562f3a0 100644 >>>> --- a/drivers/pci/pcie/err.c >>>> +++ b/drivers/pci/pcie/err.c >>>> @@ -164,10 +164,17 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev >>>> *dev, >>>> pci_dbg(dev, "broadcast error_detected message\n"); >>>> if (state == pci_channel_io_frozen) { >>>> + pci_ers_result_t status2; >>>> + >>>> pci_walk_bus(bus, report_frozen_detected, &status); >>>> - status = reset_link(dev); >>>> - if (status != PCI_ERS_RESULT_RECOVERED) { >>>> + /* preserve status from report_frozen_detected to >>>> + * insure report_mmio_enabled or report_slot_reset are >>>> + * invoked even if reset_link returns _RECOVERED. >>>> + */ >>>> + status2 = reset_link(dev); >>>> + if (status2 != PCI_ERS_RESULT_RECOVERED) { >>>> pci_warn(dev, "link reset failed\n"); >>>> + status = status2; >>>> goto failed; >>>> } >>>> } else { >>>> > --- > -Jay Vosburgh, jay.vosburgh@canonical.com > . >