[PATCH] PCIe AER: report non fatal errors only to the functions of the same device

[Dongdong Liu <liudongdong3@huawei.com>]

From: Gabriele Paoloni <gabriele.paoloni@huawei.com>

Currently if an uncorrectable error is reported by an EP the AER
driver walks over all the devices connected to the upstream port
bus and in turns call the report_error_detected() callback.
If any of the devices connected to the bus does not implement
dev->driver->err_handler->error_detected() do_recovery() will fail.

However for non fatal errors the PCIe link should not be considered
compromised, therefore it makes sense to report the error only to
all the functions of a multifunction device.
This patch implements this new behaviour for non fatal errors.

Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
---
 drivers/pci/bus.c                  | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/pci/pcie/aer/aerdrv_core.c | 13 ++++++++++++-
 include/linux/pci.h                |  3 ++-
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index bc56cf1..bc8f8b2 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -364,6 +364,44 @@ void pci_bus_add_devices(const struct pci_bus *bus)
 }
 EXPORT_SYMBOL(pci_bus_add_devices);
 
+/** pci_walk_mf_dev - walk all functions of a multi-function
+ *  device calling callback.
+ *  @dev      a function in a multi-function device
+ *  @cb       callback to be called for each device found
+ *  @userdata arbitrary pointer to be passed to callback.
+ *
+ *  Walk, on a given bus, only the adjacent functions of a
+ *  multi-function device. Call the provided callback on each
+ *  device found.
+ *
+ *  We check the return of @cb each time. If it returns anything
+ *  other than 0, we break out.
+ *
+ */
+void pci_walk_mf_dev(struct pci_dev *dev, int (*cb)(struct pci_dev *, void *),
+		  void *userdata)
+{
+	int retval;
+	struct pci_bus *bus;
+	struct pci_dev *pdev;
+	int ndev;
+
+	bus = dev->bus;
+	ndev = PCI_SLOT(dev->devfn);
+
+	down_read(&pci_bus_sem);
+	/* call cb for all the functions of the mf device */
+	list_for_each_entry(pdev, &bus->devices, bus_list) {
+		if (PCI_SLOT(pdev->devfn) == ndev) {
+			retval = cb(pdev, userdata);
+			if (retval)
+				break;
+		}
+	}
+	up_read(&pci_bus_sem);
+}
+EXPORT_SYMBOL_GPL(pci_walk_mf_dev);
+
 /** pci_walk_bus - walk devices on/under bus, calling callback.
  *  @top      bus whose devices should be walked
  *  @cb       callback to be called for each device found
diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index b1303b3..67c3dc0 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -390,7 +390,18 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
 		 * If the error is reported by an end point, we think this
 		 * error is related to the upstream link of the end point.
 		 */
-		pci_walk_bus(dev->bus, cb, &result_data);
+		if ((state == pci_channel_io_normal) &&
+				(!pci_ari_enabled(dev->bus)))
+			/*
+			 * the error is non fatal so the bus is ok, just walk
+			 * through all the functions in a multifunction device.
+			 * if ARI is enabled on the bus then there can be only
+			 * one device under that bus (so walk all the functions
+			 * under the bus).
+			 */
+			pci_walk_mf_dev(dev, cb, &result_data);
+		else
+			pci_walk_bus(dev->bus, cb, &result_data);
 	}
 
 	return result_data.result;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 4869e66..69e77bb 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1269,7 +1269,8 @@ const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
 					 struct pci_dev *dev);
 int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 		    int pass);
-
+void pci_walk_mf_dev(struct pci_dev *dev, int (*cb)(struct pci_dev *, void *),
+		  void *userdata);
 void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
 		  void *userdata);
 int pci_cfg_space_size(struct pci_dev *dev);
-- 
1.9.1