PCI/MSI: Skip disabling disconnected devices

Check the device connected state prior to executing device shutdown
operations or writing MSI messages so that tear down on disconnected
devices completes quicker.
Tested-by: NKrishna Dhulipala <krishnad@fb.com>
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NWei Zhang <wzhang@fb.com>

drivers/pci/msi.c

@@ -298,7 +298,7 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
 	struct pci_dev *dev = msi_desc_to_pci_dev(entry);
 
-	if (dev->current_state != PCI_D0) {
+	if (dev->current_state != PCI_D0 || pci_dev_is_disconnected(dev)) {
 		/* Don't touch the hardware now */
 	} else if (entry->msi_attrib.is_msix) {
 		void __iomem *base = pci_msix_desc_addr(entry);
@@ -1001,6 +1001,11 @@ void pci_msix_shutdown(struct pci_dev *dev)
 	if (!pci_msi_enable || !dev || !dev->msix_enabled)
 		return;
 
+	if (pci_dev_is_disconnected(dev)) {
+		dev->msix_enabled = 0;
+		return;
+	}
+
 	/* Return the device with MSI-X masked as initial states */
 	for_each_pci_msi_entry(entry, dev) {
 		/* Keep cached states to be restored */