Messages in this thread | | | Subject | Re: [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices | From | "Kuppuswamy, Sathyanarayanan" <> | Date | Thu, 21 May 2020 12:31:33 -0700 |
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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 <sathyanarayanan.kuppuswamy@linux.intel.com> >>>> >>>> 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 <jay.vosburgh@canonical.com> >>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> >>>> --- >>>> 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. > > 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) { >>> >> . >> >
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