"Kuppuswamy, Sathyanarayanan" wrote:
>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.
Correct, this particular device (a network card) is in a
non-hotplug slot.
>Can you check whether following fix works for you?
Yes, it does.
I fixed up the whitespace and made a minor change to add braces
in what look like the correct places around the "if (reset_link)" block;
the patch I tested with is below. I'll also install this on another
machine with hotplug capable slots to test there as well.
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)
+ 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) {
-J
>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@xxxxxxxxxxxxx>
>>>
>>> ---
>>> 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 {
>>>
---
-Jay Vosburgh, jay.vosburgh@xxxxxxxxxxxxx
