PCI/ERR: Handle fatal error recovery

We don't need to be paranoid about the topology changing while handling an
error.  If the device has changed in a hotplug capable slot, we can rely on
the presence detection handling to react to a changing topology.

Restore the fatal error handling behavior that existed before merging DPC
with AER with 7e9084b3 ("PCI/AER: Handle ERR_FATAL with removal and
re-enumeration of devices").
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>

Documentation/PCI/pci-error-recovery.txt

@@ -110,7 +110,7 @@ The actual steps taken by a platform to recover from a PCI error
 event will be platform-dependent, but will follow the general
 sequence described below.
 
-STEP 0: Error Event: ERR_NONFATAL
+STEP 0: Error Event
 -------------------
 A PCI bus error is detected by the PCI hardware.  On powerpc, the slot
 is isolated, in that all I/O is blocked: all reads return 0xffffffff,
@@ -228,7 +228,13 @@ proceeds to either STEP3 (Link Reset) or to STEP 5 (Resume Operations).
 If any driver returned PCI_ERS_RESULT_NEED_RESET, then the platform
 proceeds to STEP 4 (Slot Reset)
 
-STEP 3: Slot Reset
+STEP 3: Link Reset
+------------------
+The platform resets the link.  This is a PCI-Express specific step
+and is done whenever a fatal error has been detected that can be
+"solved" by resetting the link.
+
+STEP 4: Slot Reset
 ------------------
 
 In response to a return value of PCI_ERS_RESULT_NEED_RESET, the
@@ -314,7 +320,7 @@ Failure).
 >>> However, it probably should.
 
 
-STEP 4: Resume Operations
+STEP 5: Resume Operations
 -------------------------
 The platform will call the resume() callback on all affected device
 drivers if all drivers on the segment have returned
@@ -326,7 +332,7 @@ a result code.
 At this point, if a new error happens, the platform will restart
 a new error recovery sequence.
 
-STEP 5: Permanent Failure
+STEP 6: Permanent Failure
 -------------------------
 A "permanent failure" has occurred, and the platform cannot recover
 the device.  The platform will call error_detected() with a
@@ -349,27 +355,6 @@ errors. See the discussion in powerpc/eeh-pci-error-recovery.txt
 for additional detail on real-life experience of the causes of
 software errors.
 
-STEP 0: Error Event: ERR_FATAL
--------------------
-PCI bus error is detected by the PCI hardware. On powerpc, the slot is
-isolated, in that all I/O is blocked: all reads return 0xffffffff, all
-writes are ignored.
-
-STEP 1: Remove devices
---------------------
-Platform removes the devices depending on the error agent, it could be
-this port for all subordinates or upstream component (likely downstream
-port)
-
-STEP 2: Reset link
---------------------
-The platform resets the link.  This is a PCI-Express specific step and is
-done whenever a fatal error has been detected that can be "solved" by
-resetting the link.
-
-STEP 3: Re-enumerate the devices
---------------------
-Initiates the re-enumeration.
 
 Conclusion; General Remarks
 ---------------------------

drivers/pci/pci.h

@@ -433,8 +433,8 @@ static inline int pci_dev_specific_disable_acs_redir(struct pci_dev *dev)
 #endif
 
 /* PCI error reporting and recovery */
-void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service);
-void pcie_do_nonfatal_recovery(struct pci_dev *dev);
+void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
+		      u32 service);
 
 bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
 #ifdef CONFIG_PCIEASPM

drivers/pci/pcie/aer.c

@@ -1010,9 +1010,11 @@ static void handle_error_source(struct pci_dev *dev, struct aer_err_info *info)
 					info->status);
 		pci_aer_clear_device_status(dev);
 	} else if (info->severity == AER_NONFATAL)
-		pcie_do_nonfatal_recovery(dev);
+		pcie_do_recovery(dev, pci_channel_io_normal,
+				 PCIE_PORT_SERVICE_AER);
 	else if (info->severity == AER_FATAL)
-		pcie_do_fatal_recovery(dev, PCIE_PORT_SERVICE_AER);
+		pcie_do_recovery(dev, pci_channel_io_frozen,
+				 PCIE_PORT_SERVICE_AER);
 	pci_dev_put(dev);
 }
 
@@ -1048,9 +1050,11 @@ static void aer_recover_work_func(struct work_struct *work)
 		}
 		cper_print_aer(pdev, entry.severity, entry.regs);
 		if (entry.severity == AER_NONFATAL)
-			pcie_do_nonfatal_recovery(pdev);
+			pcie_do_recovery(pdev, pci_channel_io_normal,
+					 PCIE_PORT_SERVICE_AER);
 		else if (entry.severity == AER_FATAL)
-			pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_AER);
+			pcie_do_recovery(pdev, pci_channel_io_frozen,
+					 PCIE_PORT_SERVICE_AER);
 		pci_dev_put(pdev);
 	}
 }

drivers/pci/pcie/dpc.c

@@ -216,7 +216,7 @@ static irqreturn_t dpc_handler(int irq, void *context)
 
 	reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN) >> 1;
 	ext_reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT) >> 5;
-	dev_warn(dev, "DPC %s detected, remove downstream devices\n",
+	dev_warn(dev, "DPC %s detected\n",
 		 (reason == 0) ? "unmasked uncorrectable error" :
 		 (reason == 1) ? "ERR_NONFATAL" :
 		 (reason == 2) ? "ERR_FATAL" :
@@ -233,7 +233,7 @@ static irqreturn_t dpc_handler(int irq, void *context)
 	}
 
 	/* We configure DPC so it only triggers on ERR_FATAL */
-	pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_DPC);
+	pcie_do_recovery(pdev, pci_channel_io_frozen, PCIE_PORT_SERVICE_DPC);
 
 	return IRQ_HANDLED;
 }

drivers/pci/pcie/err.c

@@ -271,83 +271,20 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
 	return result_data.result;
 }
 
-/**
- * pcie_do_fatal_recovery - handle fatal error recovery process
- * @dev: pointer to a pci_dev data structure of agent detecting an error
- *
- * Invoked when an error is fatal. Once being invoked, removes the devices
- * beneath this AER agent, followed by reset link e.g. secondary bus reset
- * followed by re-enumeration of devices.
- */
-void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service)
-{
-	struct pci_dev *udev;
-	struct pci_bus *parent;
-	struct pci_dev *pdev, *temp;
-	pci_ers_result_t result;
-
-	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
-		udev = dev;
-	else
-		udev = dev->bus->self;
-
-	parent = udev->subordinate;
-	pci_walk_bus(parent, pci_dev_set_disconnected, NULL);
-
-	pci_lock_rescan_remove();
-	pci_dev_get(dev);
-	list_for_each_entry_safe_reverse(pdev, temp, &parent->devices,
-					 bus_list) {
-		pci_stop_and_remove_bus_device(pdev);
-	}
-
-	result = reset_link(udev, service);
-
-	if ((service == PCIE_PORT_SERVICE_AER) &&
-	    (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)) {
-		/*
-		 * If the error is reported by a bridge, we think this error
-		 * is related to the downstream link of the bridge, so we
-		 * do error recovery on all subordinates of the bridge instead
-		 * of the bridge and clear the error status of the bridge.
-		 */
-		pci_aer_clear_fatal_status(dev);
-		pci_aer_clear_device_status(dev);
-	}
-
-	if (result == PCI_ERS_RESULT_RECOVERED) {
-		if (pcie_wait_for_link(udev, true))
-			pci_rescan_bus(udev->bus);
-		pci_info(dev, "Device recovery from fatal error successful\n");
-	} else {
-		pci_uevent_ers(dev, PCI_ERS_RESULT_DISCONNECT);
-		pci_info(dev, "Device recovery from fatal error failed\n");
-	}
-
-	pci_dev_put(dev);
-	pci_unlock_rescan_remove();
-}
-
-/**
- * pcie_do_nonfatal_recovery - handle nonfatal error recovery process
- * @dev: pointer to a pci_dev data structure of agent detecting an error
- *
- * Invoked when an error is nonfatal/fatal. Once being invoked, broadcast
- * error detected message to all downstream drivers within a hierarchy in
- * question and return the returned code.
- */
-void pcie_do_nonfatal_recovery(struct pci_dev *dev)
+void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
+		      u32 service)
 {
 	pci_ers_result_t status;
-	enum pci_channel_state state;
-
-	state = pci_channel_io_normal;
 
 	status = broadcast_error_message(dev,
 			state,
 			"error_detected",
 			report_error_detected);
 
+	if (state == pci_channel_io_frozen &&
+	    reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
+		goto failed;
+
 	if (status == PCI_ERS_RESULT_CAN_RECOVER)
 		status = broadcast_error_message(dev,
 				state,