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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E5F8AC63798 for ; Tue, 24 Nov 2020 17:17:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E6362151B for ; Tue, 24 Nov 2020 17:17:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ys7p0VlQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390759AbgKXRRt (ORCPT ); Tue, 24 Nov 2020 12:17:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:51874 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390255AbgKXRRs (ORCPT ); Tue, 24 Nov 2020 12:17:48 -0500 Received: from localhost (129.sub-72-107-112.myvzw.com [72.107.112.129]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 963B8206F7; Tue, 24 Nov 2020 17:17:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606238268; bh=yKPTzHntmG3todINsm3YIWKJ8EZMzP+0TRmukNQeEfg=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=Ys7p0VlQ3pSBuRRJRSuUng9/D09E8iVuacSyIy0hvqVf6+t1nlP86rjurboVbNh9e ItJ4XbG5t/tV3NjccYTOEQwrpsVCK4serhVxryId/m6iN49yj2FXjdMbEKxJ/ngDrt tG/478uOA6oD01Z/UljAP+YQ8qNsMcdkdP25dUGs= Date: Tue, 24 Nov 2020 11:17:46 -0600 From: Bjorn Helgaas To: "Kelley, Sean V" Cc: "bhelgaas@google.com" , Jonathan Cameron , "xerces.zhao@gmail.com" , "Wysocki, Rafael J" , "Raj, Ashok" , "Luck, Tony" , "Kuppuswamy, Sathyanarayanan" , "Zhuo, Qiuxu" , Linux PCI , Linux Kernel Mailing List Subject: Re: [PATCH v12 10/15] PCI/ERR: Limit AER resets in pcie_do_recovery() Message-ID: <20201124171746.GA565099@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <93D815E0-3100-4AAC-B9EE-AA6736A0419F@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Nov 23, 2020 at 11:57:35PM +0000, Kelley, Sean V wrote: > > On Nov 23, 2020, at 3:28 PM, Bjorn Helgaas wrote: > > On Fri, Nov 20, 2020 at 04:10:31PM -0800, Sean V Kelley wrote: > >> In some cases a bridge may not exist as the hardware controlling may be > >> handled only by firmware and so is not visible to the OS. This scenario is > >> also possible in future use cases involving non-native use of RCECs by > >> firmware. > >> > >> Explicitly apply conditional logic around these resets by limiting them to > >> Root Ports and Downstream Ports. > > > > Can you help me understand this? The subject says "Limit AER resets" > > and here you say "limit them to RPs and DPs", but it's not completely > > obvious how the resets are being limited, i.e., the patch doesn't add > > anything like: > > > > + if (type == PCI_EXP_TYPE_ROOT_PORT || > > + type == PCI_EXP_TYPE_DOWNSTREAM) > > reset_subordinates(bridge); > > > > It *does* add checks around pcie_clear_device_status(), but that also > > includes RC_EC. And that's not a reset, so I don't think that's > > explicitly mentioned in the commit log. > > The subject should have referred to the clearing of the device status rather than resets. > It originally came from this simpler patch in which I made use of reset instead of clear: > > https://lore.kernel.org/linux-pci/20201002184735.1229220-8-seanvk.dev@oregontracks.org/ > > So a rephrase of clearing in place of resets would be more appropriate. > > Then we added the notion of bridges…below > > > > > Also see the question below. > > > >> Link: https://lore.kernel.org/r/20201002184735.1229220-8-seanvk.dev@oregontracks.org > >> Signed-off-by: Sean V Kelley > >> Signed-off-by: Bjorn Helgaas > >> Acked-by: Jonathan Cameron > >> --- > >> drivers/pci/pcie/err.c | 31 +++++++++++++++++++++++++------ > >> 1 file changed, 25 insertions(+), 6 deletions(-) > >> > >> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c > >> index 8b53aecdb43d..7883c9791562 100644 > >> --- a/drivers/pci/pcie/err.c > >> +++ b/drivers/pci/pcie/err.c > >> @@ -148,13 +148,17 @@ static int report_resume(struct pci_dev *dev, void *data) > >> > >> /** > >> * pci_walk_bridge - walk bridges potentially AER affected > >> - * @bridge: bridge which may be a Port > >> + * @bridge: bridge which may be a Port, an RCEC with associated RCiEPs, > >> + * or an RCiEP associated with an RCEC > >> * @cb: callback to be called for each device found > >> * @userdata: arbitrary pointer to be passed to callback > >> * > >> * If the device provided is a bridge, walk the subordinate bus, including > >> * any bridged devices on buses under this bus. Call the provided callback > >> * on each device found. > >> + * > >> + * If the device provided has no subordinate bus, call the callback on the > >> + * device itself. > >> */ > >> static void pci_walk_bridge(struct pci_dev *bridge, > >> int (*cb)(struct pci_dev *, void *), > >> @@ -162,6 +166,8 @@ static void pci_walk_bridge(struct pci_dev *bridge, > >> { > >> if (bridge->subordinate) > >> pci_walk_bus(bridge->subordinate, cb, userdata); > >> + else > >> + cb(bridge, userdata); > >> } > >> > >> pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> @@ -174,10 +180,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> > >> /* > >> * Error recovery runs on all subordinates of the bridge. If the > >> - * bridge detected the error, it is cleared at the end. > >> + * bridge detected the error, it is cleared at the end. For RCiEPs > >> + * we should reset just the RCiEP itself. > >> */ > >> if (type == PCI_EXP_TYPE_ROOT_PORT || > >> - type == PCI_EXP_TYPE_DOWNSTREAM) > >> + type == PCI_EXP_TYPE_DOWNSTREAM || > >> + type == PCI_EXP_TYPE_RC_EC || > >> + type == PCI_EXP_TYPE_RC_END) > >> bridge = dev; > >> else > >> bridge = pci_upstream_bridge(dev); > >> @@ -185,6 +194,12 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> pci_dbg(bridge, "broadcast error_detected message\n"); > >> if (state == pci_channel_io_frozen) { > >> pci_walk_bridge(bridge, report_frozen_detected, &status); > >> + if (type == PCI_EXP_TYPE_RC_END) { > >> + pci_warn(dev, "subordinate device reset not possible for RCiEP\n"); > >> + status = PCI_ERS_RESULT_NONE; > >> + goto failed; > >> + } > >> + > >> status = reset_subordinates(bridge); > >> if (status != PCI_ERS_RESULT_RECOVERED) { > >> pci_warn(bridge, "subordinate device reset failed\n"); > >> @@ -217,9 +232,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> pci_dbg(bridge, "broadcast resume message\n"); > >> pci_walk_bridge(bridge, report_resume, &status); > >> > >> - if (pcie_aer_is_native(bridge)) > >> - pcie_clear_device_status(bridge); > >> - pci_aer_clear_nonfatal_status(bridge); > >> + if (type == PCI_EXP_TYPE_ROOT_PORT || > >> + type == PCI_EXP_TYPE_DOWNSTREAM || > >> + type == PCI_EXP_TYPE_RC_EC) { > >> + if (pcie_aer_is_native(bridge)) > >> + pcie_clear_device_status(bridge); > >> + pci_aer_clear_nonfatal_status(bridge); > > > > This is hard to understand because "type" is from "dev", but "bridge" > > is not necessarily the same device. Should it be this? > > > > type = pci_pcie_type(bridge); > > if (type == PCI_EXP_TYPE_ROOT_PORT || > > ...) > > Correct, it would be better if the type was based on the ‘bridge’. OK. This is similar to https://lore.kernel.org/linux-pci/20201002184735.1229220-8-seanvk.dev@oregontracks.org/, which you cited above except for the bridge/dev question and the addition here of RC_EC. I tried to split that back into its own patch and started with the commit message from that patch. But I got stuck on the commit message. I got as far as: In some cases an error may be reported by a device not visible to the OS, e.g., if firmware manages the device and passes error information to the OS via ACPI APEI. But I still can't quite connect that to the patch. "bridge" is clearly a device visible to Linux. I guess we're trying to assert that if "bridge" is not a Root Port, Downstream Port, or RCEC, we shouldn't clear the error status because the error came from a device Linux doesn't know about. But I think "bridge" is *always* either a Root Port or a Downstream Port: if (type == PCI_EXP_TYPE_ROOT_PORT || type == PCI_EXP_TYPE_DOWNSTREAM) bridge = dev; else bridge = pci_upstream_bridge(dev); pci_upstream_bridge() returns either NULL (in which case previous uses dereference a NULL pointer), or dev->bus->self, which is always a Root Port, Switch Downstream Port, or Switch Upstream Port (or NULL for the special case of VFs). > >> + } > >> pci_info(bridge, "device recovery successful\n"); > >> return status; > >> > >> -- > >> 2.29.2 >