2 files changed, 28 insertions, 4 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index a8752c2c2b53..2ae921f84bd3 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -46,6 +46,30 @@ static inline void pci_iov_set_numvfs(struct pci_dev *dev, int nr_virtfn)
         pci_read_config_word(dev, iov->pos + PCI_SRIOV_VF_STRIDE, &iov->stride);
 }
 
+/*
+ * The PF consumes one bus number.  NumVFs, First VF Offset, and VF Stride
+ * determine how many additional bus numbers will be consumed by VFs.
+ *
+ * Iterate over all valid NumVFs and calculate the maximum number of bus
+ * numbers that could ever be required.
+ */
+static inline u8 virtfn_max_buses(struct pci_dev *dev)
+{
+        struct pci_sriov *iov = dev->sriov;
+        int nr_virtfn;
+        u8 max = 0;
+        u8 busnr;
+
+        for (nr_virtfn = 1; nr_virtfn <= iov->total_VFs; nr_virtfn++) {
+                pci_iov_set_numvfs(dev, nr_virtfn);
+                busnr = virtfn_bus(dev, nr_virtfn - 1);
+                if (busnr > max)
+                        max = busnr;
+        }
+
+        return max;
+}
+
 static struct pci_bus *virtfn_add_bus(struct pci_bus *bus, int busnr)
 {
         struct pci_bus *child;
@@ -427,6 +451,7 @@ found:
 
         dev->sriov = iov;
         dev->is_physfn = 1;
+        iov->max_VF_buses = virtfn_max_buses(dev);
 
         return 0;
 
@@ -556,15 +581,13 @@ void pci_restore_iov_state(struct pci_dev *dev)
 int pci_iov_bus_range(struct pci_bus *bus)
 {
         int max = 0;
-        u8 busnr;
         struct pci_dev *dev;
 
         list_for_each_entry(dev, &bus->devices, bus_list) {
                 if (!dev->is_physfn)
                         continue;
-                busnr = virtfn_bus(dev, dev->sriov->total_VFs - 1);
-                if (busnr > max)
-                        max = busnr;
+                if (dev->sriov->max_VF_buses > max)
+                        max = dev->sriov->max_VF_buses;
         }
 
         return max ? max - bus->number : 0;
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 57329645dd01..bae593c04541 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -243,6 +243,7 @@ struct pci_sriov {
         u16 stride;             /* following VF stride */
         u32 pgsz;               /* page size for BAR alignment */
         u8 link;                /* Function Dependency Link */
+        u8 max_VF_buses;        /* max buses consumed by VFs */
         u16 driver_max_VFs;     /* max num VFs driver supports */
         struct pci_dev *dev;    /* lowest numbered PF */
         struct pci_dev *self;   /* this PF */