PCI: Don't try to restore VF BARs

VF BARs are read-only zero, so updating VF BARs will not have any effect.
See the SR-IOV spec r1.1, sec 3.4.1.11.

Don't update VF BARs in pci_restore_bars().

This avoids spurious "BAR %d: error updating" messages that we see when
doing vfio pass-through after 6eb7018705de ("vfio-pci: Move idle devices to
D3hot power state").

[bhelgaas: changelog, fix whitespace]
Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -484,7 +484,7 @@ int pci_wait_for_pending(struct pci_dev *dev, int pos, u16 mask)
 }
 
 /**
- * pci_restore_bars - restore a devices BAR values (e.g. after wake-up)
+ * pci_restore_bars - restore a device's BAR values (e.g. after wake-up)
  * @dev: PCI device to have its BARs restored
  *
  * Restore the BAR values for a given device, so as to make it
@@ -494,6 +494,10 @@ static void pci_restore_bars(struct pci_dev *dev)
 {
 	int i;
 
+	/* Per SR-IOV spec 3.4.1.11, VF BARs are RO zero */
+	if (dev->is_virtfn)
+		return;
+
 	for (i = 0; i < PCI_BRIDGE_RESOURCES; i++)
 		pci_update_resource(dev, i);
 }

drivers/pci/setup-res.c

@@ -36,6 +36,11 @@ void pci_update_resource(struct pci_dev *dev, int resno)
 	enum pci_bar_type type;
 	struct resource *res = dev->resource + resno;
 
+	if (dev->is_virtfn) {
+		dev_warn(&dev->dev, "can't update VF BAR%d\n", resno);
+		return;
+	}
+
 	/*
 	 * Ignore resources for unimplemented BARs and unused resource slots
 	 * for 64 bit BARs.