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@xxxxxxxxxxxxxxx wrote:
>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxxxxx]
>>> [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@xxxxxxxxxxxxx>
>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
>>> ---
>>> 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) {
>>
> .
>
