[PATCH v5 1/5] PCI/AER: Fix pci_ops return NULL in pci_read/write_aer

[Yijing Wang <wangyijing@huawei.com>]

When we injected aer errors to the pcie device by aer_inject module, pci_ops of the pci
bus the device on will be assigned to pci_ops_aer.So if the target pci device
is a bridge, once we hot-remove and hot-add the bridge, the newly created child bus's pci_ops
will be assigned to pci_ops_aer too.Now every access to the child bus's device will cause the
system panic, because it will get a NULL pci_ops in pci_read_aer/pci_write_aer.

Reviewed-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Reviewed-by: Sven Dietrich <Sven.Dietrich@huawei.com>
---
 drivers/pci/pcie/aer/aer_inject.c |   26 +++++++++++++++++++++++++-
 1 files changed, 25 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
index 4e24cb8..fdab3bb 100644
--- a/drivers/pci/pcie/aer/aer_inject.c
+++ b/drivers/pci/pcie/aer/aer_inject.c
@@ -109,6 +109,26 @@ static struct aer_error *__find_aer_error_by_dev(struct pci_dev *dev)
 	return __find_aer_error((u16)domain, dev->bus->number, dev->devfn);
 }
 
+/* find pci_ops of the nearest parent bus */
+static struct pci_ops *__find_pci_bus_ops_parent(struct pci_bus *bus)
+{
+	struct pci_bus_ops *bus_ops;
+	struct pci_bus *pbus = bus->parent;
+
+	if (!pbus)
+		return NULL;
+
+	while (pbus) {
+		list_for_each_entry(bus_ops, &pci_bus_ops_list, list)
+			if (bus_ops->bus == pbus)
+				return bus_ops->ops;
+
+		pbus = pbus->parent;
+	}
+
+	return NULL;
+}
+
 /* inject_lock must be held before calling */
 static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
 {
@@ -118,7 +138,9 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
 		if (bus_ops->bus == bus)
 			return bus_ops->ops;
 	}
-	return NULL;
+
+	/* can't find bus_ops, fall back to get bus_ops of parent bus */
+	return __find_pci_bus_ops_parent(bus);
 }
 
 static struct pci_bus_ops *pci_bus_ops_pop(void)
@@ -208,6 +230,7 @@ static int pci_read_aer(struct pci_bus *bus, unsigned int devfn, int where,
 	}
 out:
 	ops = __find_pci_bus_ops(bus);
+	BUG_ON(!ops);
 	spin_unlock_irqrestore(&inject_lock, flags);
 	return ops->read(bus, devfn, where, size, val);
 }
@@ -243,6 +266,7 @@ int pci_write_aer(struct pci_bus *bus, unsigned int devfn, int where, int size,
 	}
 out:
 	ops = __find_pci_bus_ops(bus);
+	BUG_ON(!ops);
 	spin_unlock_irqrestore(&inject_lock, flags);
 	return ops->write(bus, devfn, where, size, val);
 }
-- 
1.7.1