1 files changed, 21 insertions, 1 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index cd7b6de9376c..fe5b50bd7536 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -170,7 +170,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
 {
         u32 l, sz, mask;
         u16 orig_cmd;
-        struct pci_bus_region region;
+        struct pci_bus_region region, inverted_region;
         bool bar_too_big = false, bar_disabled = false;
 
         mask = type ? PCI_ROM_ADDRESS_MASK : ~0;
@@ -266,6 +266,26 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
         }
 
         pcibios_bus_to_resource(dev, res, &region);
+        pcibios_resource_to_bus(dev, &inverted_region, res);
+
+        /*
+         * If "A" is a BAR value (a bus address), "bus_to_resource(A)" is
+         * the corresponding resource address (the physical address used by
+         * the CPU.  Converting that resource address back to a bus address
+         * should yield the original BAR value:
+         *
+         *     resource_to_bus(bus_to_resource(A)) == A
+         *
+         * If it doesn't, CPU accesses to "bus_to_resource(A)" will not
+         * be claimed by the device.
+         */
+        if (inverted_region.start != region.start) {
+                dev_info(&dev->dev, "reg 0x%x: initial BAR value %pa invalid; forcing reassignment\n",
+                         pos, &region.start);
+                res->flags |= IORESOURCE_UNSET;
+                res->end -= res->start;
+                res->start = 0;
+        }
 
         goto out;