[PATCH v3 1/1] PCI/ERR: don't clobber status after reset_link()

[Hedi Berriche <hedi.berriche@hpe.com>]

Commit 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
broke pcie_do_recovery(): updating status after reset_link() has the ill
side effect of causing recovery to fail if the error status is
PCI_ERS_RESULT_CAN_RECOVER or PCI_ERS_RESULT_NEED_RESET as the following
code will *never* run in the case of a successful reset_link()

   177         if (status == PCI_ERS_RESULT_CAN_RECOVER) {
   ...
   181         }

   183         if (status == PCI_ERS_RESULT_NEED_RESET) {
   ...
   192         }

For instance in the case of PCI_ERS_RESULT_NEED_RESET we end up not
calling ->slot_reset() (because we skip report_slot_reset()) thus
breaking driver (re)initialisation.

Don't clobber status with the return value of reset_link(); set status
to PCI_ERS_RESULT_RECOVERED, in case of successful link reset, if and
only if the initial value of error status is PCI_ERS_RESULT_DISCONNECT
or PCI_ERS_RESULT_NO_AER_DRIVER.

Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
Signed-off-by: Hedi Berriche <hedi.berriche@hpe.com>
Cc: Russ Anderson <rja@hpe.com>
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Joerg Roedel <jroedel@suse.com>

Cc: stable@kernel.org # v5.7+
---
 drivers/pci/pcie/err.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index c543f419d8f9..2730826cfd8a 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -165,10 +165,13 @@ 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) {
+		if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED) {
 			pci_warn(dev, "link reset failed\n");
 			goto failed;
+		} else {
+			if (status == PCI_ERS_RESULT_DISCONNECT ||
+			    status == PCI_ERS_RESULT_NO_AER_DRIVER)
+				status = PCI_ERS_RESULT_RECOVERED;
 		}
 	} else {
 		pci_walk_bus(bus, report_normal_detected, &status);
-- 
2.28.0