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 A6A4BC28CBC for ; Sat, 9 May 2020 17:55:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B95F21582 for ; Sat, 9 May 2020 17:55:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728162AbgEIRzw (ORCPT ); Sat, 9 May 2020 13:55:52 -0400 Received: from mga06.intel.com ([134.134.136.31]:12245 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726214AbgEIRzw (ORCPT ); Sat, 9 May 2020 13:55:52 -0400 IronPort-SDR: ea98B2T+53kFY2tNpOtxMbLm1dg5NETRmIgZl96ETtNz1REm3o0eT3ydJb1gi83a+GQta02fO5 rsYRDwgwMQiw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 May 2020 10:55:51 -0700 IronPort-SDR: pLn0YEtLaf+QDcD8Vo6LNKiwCq/Ntvm78P5riRcDHB1pHLjnsQLcJ5dDn+gWUHuT/AjFeDdGWK QW6TkiftXJHA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,372,1583222400"; d="scan'208";a="297262818" Received: from stnguye1-mobl.amr.corp.intel.com (HELO [10.255.228.45]) ([10.255.228.45]) by orsmga008.jf.intel.com with ESMTP; 09 May 2020 10:55:51 -0700 Subject: Re: [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery To: Yicong Yang , Jay Vosburgh Cc: linux-pci@vger.kernel.org, Bjorn Helgaas References: <12115.1588207324@famine> <18897ceb-2263-1101-ae43-918a66794e14@linux.intel.com> <14682.1588279297@famine> From: "Kuppuswamy, Sathyanarayanan" Message-ID: <818a6db3-f97e-83cf-83d9-7a0a2bd1dff7@linux.intel.com> Date: Sat, 9 May 2020 10:55:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 5/8/20 11:35 PM, Yicong Yang wrote: > 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. Slot reset wont be performed only if reset_link or pci_bus_error_reset returns error. Otherwise, we will still call pci_slot_reset later. > > 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? Yes, currently we don't need it. I added it to cover future use cases. But we can remove it if not needed. > > 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) { >> >>pci_bus_error_reset >> -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 >> . >> >