Re: [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery

["Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>]

Hi Jay,

On 4/29/20 6:15 PM, Kuppuswamy, Sathyanarayanan wrote:
> 
> 
> On 4/29/20 5:42 PM, Jay Vosburgh wrote:
>>     Commit 6d2c89441571 ("PCI/ERR: Update error status after
>> reset_link()"), introduced a regression, as pcie_do_recovery will
>> discard 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 initating 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.
> 
> I think this issue is related to the issue discussed in following
> thread (DPC non-hotplug support).
> 
> https://lkml.org/lkml/2020/3/28/328
> 
> If my assumption is correct, you are dealing with devices which are
> not hotplug capable. If the devices are hotplug capable then you don't
> need to proceed to report_slot_reset(), since hotplug handler will
> remove/re-enumerate the devices correctly.

Can you check whether following fix works for you?

This includes support for bus_reset in recovery function itself.

index 14bb8f54723e..c9eaab68ab7a 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -165,13 +165,23 @@ 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) {
         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)
+                               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) {


> 
>>
>>     Inspection shows a similar path is plausible for a return of
>> _CAN_RECOVER and the invocation of report_mmio_enabled.
>>
>>     Resolve this by preserving the result of report_frozen_detected if
>> reset_link does not return _DISCONNECT.
>>
>> Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
>> Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
>>
>> ---
>>   drivers/pci/pcie/err.c | 11 +++++++++--
>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 14bb8f54723e..e4274562f3a0 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -164,10 +164,17 @@ 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_ers_result_t status2;
>> +
>>           pci_walk_bus(bus, report_frozen_detected, &status);
>> -        status = reset_link(dev);
>> -        if (status != PCI_ERS_RESULT_RECOVERED) {
>> +        /* preserve status from report_frozen_detected to
>> +         * insure report_mmio_enabled or report_slot_reset are
>> +         * invoked even if reset_link returns _RECOVERED.
>> +         */
>> +        status2 = reset_link(dev);
>> +        if (status2 != PCI_ERS_RESULT_RECOVERED) {
>>               pci_warn(dev, "link reset failed\n");
>> +            status = status2;
>>               goto failed;
>>           }
>>       } else {
>>