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 91766C433E0 for ; Thu, 21 May 2020 10:58:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63F11206F6 for ; Thu, 21 May 2020 10:58:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728348AbgEUK6V (ORCPT ); Thu, 21 May 2020 06:58:21 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:4834 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727864AbgEUK6V (ORCPT ); Thu, 21 May 2020 06:58:21 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id A83EBD3A61E79073949C; Thu, 21 May 2020 18:58:18 +0800 (CST) Received: from [10.65.58.147] (10.65.58.147) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.487.0; Thu, 21 May 2020 18:58:13 +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> CC: , , , From: Yicong Yang Message-ID: <8dd2233c-a636-59fa-4c6e-5da08556d09e@hisilicon.com> Date: Thu, 21 May 2020 18:58:22 +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: <2569c75c-41a6-d0f3-ee34-0d288c4e0b61@linux.intel.com> 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 2020/5/21 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. 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) { >> > . >