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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 DFB05C433E0 for ; Fri, 22 May 2020 02:55:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF775207E8 for ; Fri, 22 May 2020 02:55:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727779AbgEVCzs (ORCPT ); Thu, 21 May 2020 22:55:48 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:4836 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727770AbgEVCzr (ORCPT ); Thu, 21 May 2020 22:55:47 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 158A475D5FA2F00C5850; Fri, 22 May 2020 10:55:45 +0800 (CST) Received: from [10.65.58.147] (10.65.58.147) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.487.0; Fri, 22 May 2020 10:55:41 +0800 Subject: Re: [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices To: "Kuppuswamy, Sathyanarayanan" , References: <18609.1588812972@famine> <2569c75c-41a6-d0f3-ee34-0d288c4e0b61@linux.intel.com> <8dd2233c-a636-59fa-4c6e-5da08556d09e@hisilicon.com> CC: , , , From: Yicong Yang Message-ID: Date: Fri, 22 May 2020 10:56:03 +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: Content-Type: text/plain; charset="windows-1252" 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 On 2020/5/22 3:31, Kuppuswamy, Sathyanarayanan wrote: > > > On 5/21/20 3:58 AM, Yicong Yang wrote: >> On 2020/5/21 1:04, Kuppuswamy, Sathyanarayanan wrote: >>> >>> >>> On 5/20/20 1:28 AM, Yicong Yang wrote: >>>> On 2020/5/7 11:32, sathyanarayanan.kuppuswamy@linux.intel.com wrote: >>>>> From: Kuppuswamy Sathyanarayanan >>>>> >>>>> If there are non-hotplug capable devices connected to a given >>>>> port, then during the fatal error recovery(triggered by DPC or >>>>> AER), after calling reset_link() function, we cannot rely on >>>>> hotplug handler to detach and re-enumerate the device drivers >>>>> in the affected bus. Instead, we will have to let the error >>>>> recovery handler call report_slot_reset() for all devices in >>>>> the bus to notify about the reset operation. Although this is >>>>> only required for non hot-plug capable devices, doing it for >>>>> hotplug capable devices should not affect the functionality. >>>>> >>>>> Along with above issue, this fix also applicable to following >>>>> issue. >>>>> >>>>> Commit 6d2c89441571 ("PCI/ERR: Update error status after >>>>> reset_link()") added support to store status of reset_link() >>>>> call. Although this fixed the error recovery issue observed if >>>>> the initial value of error status is PCI_ERS_RESULT_DISCONNECT >>>>> or PCI_ERS_RESULT_NO_AER_DRIVER, it also discarded 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 initiating 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. >>>>> >>>>> [original patch is from jay.vosburgh@canonical.com] >>>>> [original patch link https://lore.kernel.org/linux-pci/18609.1588812972@famine/] >>>>> Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()") >>>>> Signed-off-by: Jay Vosburgh >>>>> Signed-off-by: Kuppuswamy Sathyanarayanan >>>>> --- >>>>> drivers/pci/pcie/err.c | 19 +++++++++++++++---- >>>>> 1 file changed, 15 insertions(+), 4 deletions(-) >>>>> >>>>> 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) >>>> >>>> we'll call reset_link() only if link is frozen. so it may have problem here. >>> you mean before this change right? >>> After this change, reset_link() will be called as long as status is >>> PCI_ERS_RESULT_NEED_RESET. >> >> Yes. I think we should reset the link only if the io is blocked as before. There's >> no reason to reset a normal link. > Currently, only AER and DPC driver uses pcie_do_recovery() call. So the > possible reset_link options are dpc_reset_link() and aer_root_reset(). > > In dpc_reset_link() case, the link is already disabled and hence we > don't need to do another reset. In case of aer_root_reset() it > uses pci_bus_error_reset() to reset the slot. Not exactly. In pci_bus_error_reset(), we call pci_slot_reset() only if it's hotpluggable. But we always call pci_bus_reset() to perform a secondary bus reset for the bridge. That's what I think is unnecessary for a normal link, and that's what reset link indicates us to do. The slot reset is introduced in the process only to solve side effects. (c4eed62a2143, PCI/ERR: Use slot reset if available) PCI_ERS_RESULT_NEED_RESET indicates that the driver wants a platform-dependent slot reset and its ->slot_reset() method to be called then. I don't think it's same as slot reset mentioned above, which is only for hotpluggable ones. Previously, if link is normal and the driver reports PCI_ERS_RESULT_NEED_RESET, we'll only call ->slot_reset() without slot reset in reset_link(). Maybe it's better to perform just like before. Thanks. >> >> Furthermore, PCI_ERS_RESULT_NEED_RESET means device driver requires a slot reset rather >> than a link reset, so it maybe improper to use it to judge whether a link reset is needed. >> We decide whether to do a link reset only by the io state. >> >> Thanks, >> Yicong >> >> >>>> >>>> Thanks, >>>> Yicong >>>> >>>> >>>>> + 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) { >>>> >>> . >>> >> > . >