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Date: Wed, 16 May 2018 11:19:57 +0530
From: poza@...eaurora.org
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Philippe Ombredanne <pombredanne@...b.com>,
Thomas Gleixner <tglx@...utronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kate Stewart <kstewart@...uxfoundation.org>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
Dongdong Liu <liudongdong3@...wei.com>,
Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
Sinan Kaya <okaya@...eaurora.org>,
Timur Tabi <timur@...eaurora.org>,
linux-pci-owner@...r.kernel.org
Subject: Re: [PATCH v16 3/9] PCI/AER: Handle ERR_FATAL with removal and
re-enumeration of devices
On 2018-05-16 05:29, Bjorn Helgaas wrote:
> On Fri, May 11, 2018 at 06:43:22AM -0400, Oza Pawandeep wrote:
>> This patch alters the behavior of handling of ERR_FATAL, where removal
>> of devices is initiated, followed by reset link, followed by
>> re-enumeration.
>>
>> So the errors are handled in a different way as follows:
>> ERR_NONFATAL => call driver recovery entry points
>> ERR_FATAL => remove and re-enumerate
>>
>> please refer to Documentation/PCI/pci-error-recovery.txt for more
>> details.
>>
>> Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
>> Reviewed-by: Keith Busch <keith.busch@...el.com>
>>
>> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c
>> b/drivers/pci/pcie/aer/aerdrv_core.c
>> index 0ea5acc..649dd1f 100644
>> --- a/drivers/pci/pcie/aer/aerdrv_core.c
>> +++ b/drivers/pci/pcie/aer/aerdrv_core.c
>> @@ -20,6 +20,7 @@
>> #include <linux/slab.h>
>> #include <linux/kfifo.h>
>> #include "aerdrv.h"
>> +#include "../../pci.h"
>>
>> #define PCI_EXP_AER_FLAGS (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE
>> | \
>> PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
>> @@ -475,35 +476,84 @@ static pci_ers_result_t reset_link(struct
>> pci_dev *dev)
>> }
>>
>> /**
>> - * do_recovery - handle nonfatal/fatal error recovery process
>> + * do_fatal_recovery - handle fatal error recovery process
>> + * @dev: pointer to a pci_dev data structure of agent detecting an
>> error
>> + *
>> + * Invoked when an error is fatal. Once being invoked, removes the
>> devices
>> + * benetah this AER agent, followed by reset link e.g. secondary bus
>> reset
>> + * followed by re-enumeration of devices.
>> + */
>> +
>> +static void do_fatal_recovery(struct pci_dev *dev)
>> +{
>> + struct pci_dev *udev;
>> + struct pci_bus *parent;
>> + struct pci_dev *pdev, *temp;
>> + pci_ers_result_t result = PCI_ERS_RESULT_RECOVERED;
>> + struct aer_broadcast_data result_data;
>> +
>> + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
>> + udev = dev;
>> + else
>> + udev = dev->bus->self;
>> +
>> + parent = udev->subordinate;
>> + pci_lock_rescan_remove();
>> + list_for_each_entry_safe_reverse(pdev, temp, &parent->devices,
>> + bus_list) {
>> + pci_dev_get(pdev);
>> + pci_dev_set_disconnected(pdev, NULL);
>> + if (pci_has_subordinate(pdev))
>> + pci_walk_bus(pdev->subordinate,
>> + pci_dev_set_disconnected, NULL);
>> + pci_stop_and_remove_bus_device(pdev);
>> + pci_dev_put(pdev);
>> + }
>> +
>> + result = reset_link(udev);
>
> I don't like the fact that for DPC, the link reset happens before we
> call
> the driver .remove() methods, while for AER, the reset happens *after*
> the
> .remove() methods. That means the .remove() methods may work
> differently
> for AER vs. DPC, e.g., they may be able to access the device if AER is
> handling the error, but they would not be able to access it if DPC is
> handling it.
>
> I don't know how to fix this, and I think we can keep this patch as it
> is
> for now, but I think we should fix it eventually.
point noted, will see to this eventually.
>
>> + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>> + /*
>> + * If the error is reported by a bridge, we think this error
>> + * is related to the downstream link of the bridge, so we
>> + * do error recovery on all subordinates of the bridge instead
>> + * of the bridge and clear the error status of the bridge.
>> + */
>> + pci_walk_bus(dev->subordinate, report_resume, &result_data);
>> + pci_cleanup_aer_uncorrect_error_status(dev);
>> + }
>> +
>> + if (result == PCI_ERS_RESULT_RECOVERED) {
>> + if (pcie_wait_for_link(udev, true))
>> + pci_rescan_bus(udev->bus);
>> + } else {
>> + pci_uevent_ers(dev, PCI_ERS_RESULT_DISCONNECT);
>> + pci_info(dev, "AER: Device recovery failed\n");
>> + }
>> +
>> + pci_unlock_rescan_remove();
>> +}
>> +
>> +/**
>> + * do_nonfatal_recovery - handle nonfatal error recovery process
>> * @dev: pointer to a pci_dev data structure of agent detecting an
>> error
>> - * @severity: error severity type
>> *
>> * Invoked when an error is nonfatal/fatal. Once being invoked,
>> broadcast
>> * error detected message to all downstream drivers within a
>> hierarchy in
>> * question and return the returned code.
>> */
>> -static void do_recovery(struct pci_dev *dev, int severity)
>> +static void do_nonfatal_recovery(struct pci_dev *dev)
>> {
>> - pci_ers_result_t status, result = PCI_ERS_RESULT_RECOVERED;
>> + pci_ers_result_t status;
>> enum pci_channel_state state;
>>
>> - if (severity == AER_FATAL)
>> - state = pci_channel_io_frozen;
>> - else
>> - state = pci_channel_io_normal;
>> + state = pci_channel_io_normal;
>>
>> status = broadcast_error_message(dev,
>> state,
>> "error_detected",
>> report_error_detected);
>>
>> - if (severity == AER_FATAL) {
>> - result = reset_link(dev);
>> - if (result != PCI_ERS_RESULT_RECOVERED)
>> - goto failed;
>> - }
>> -
>> if (status == PCI_ERS_RESULT_CAN_RECOVER)
>> status = broadcast_error_message(dev,
>> state,
>> @@ -562,8 +612,10 @@ static void handle_error_source(struct
>> pcie_device *aerdev,
>> if (pos)
>> pci_write_config_dword(dev, pos + PCI_ERR_COR_STATUS,
>> info->status);
>> - } else
>> - do_recovery(dev, info->severity);
>> + } else if (info->severity == AER_NONFATAL)
>> + do_nonfatal_recovery(dev);
>> + else if (info->severity == AER_FATAL)
>> + do_fatal_recovery(dev);
>> }
>>
>> #ifdef CONFIG_ACPI_APEI_PCIEAER
>> @@ -627,8 +679,10 @@ static void aer_recover_work_func(struct
>> work_struct *work)
>> continue;
>> }
>> cper_print_aer(pdev, entry.severity, entry.regs);
>> - if (entry.severity != AER_CORRECTABLE)
>> - do_recovery(pdev, entry.severity);
>> + if (entry.severity == AER_NONFATAL)
>> + do_nonfatal_recovery(pdev);
>> + else if (entry.severity == AER_FATAL)
>> + do_fatal_recovery(pdev);
>> pci_dev_put(pdev);
>> }
>> }
>> --
>> 2.7.4
>>
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