PCI: Avoid slot reset if bridge itself is broken

When checking to see if a PCI slot can safely be reset, we previously
checked to see if any of the children had their PCI_DEV_FLAGS_NO_BUS_RESET
flag set.

Some PCIe root port bridges do not behave well after a slot reset, and may
cause the device in the slot to become unusable.

Add a check for PCI_DEV_FLAGS_NO_BUS_RESET being set in the bridge device
to prevent the slot from being reset.
Signed-off-by: NJan Glauber <jglauber@cavium.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NAlex Williamson <alex.williamson@redhat.com>

drivers/pci/pci.c

@@ -4424,6 +4424,10 @@ static bool pci_slot_resetable(struct pci_slot *slot)
 {
 	struct pci_dev *dev;
 
+	if (slot->bus->self &&
+	    (slot->bus->self->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET))
+		return false;
+
 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
 		if (!dev->slot || dev->slot != slot)
 			continue;