diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 3c1ff63..a599a6b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2362,12 +2362,20 @@
 static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
 {
 	int pos;
-	u16 ctrl;
+	u16 cap, ctrl;
 
 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
 	if (!pos)
 		return false;
 
+	/*
+	 * Except for egress control, capabilities are either required
+	 * or only required if controllable.  Features missing from the
+	 * capability field can therefore be assumed as hard-wired enabled.
+	 */
+	pci_read_config_word(pdev, pos + PCI_ACS_CAP, &cap);
+	acs_flags &= (cap | PCI_ACS_EC);
+
 	pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
 	return (ctrl & acs_flags) == acs_flags;
 }
@@ -2442,9 +2450,6 @@
 		if (!pdev->multifunction)
 			break;
 
-		acs_flags &= (PCI_ACS_RR | PCI_ACS_CR |
-			      PCI_ACS_EC | PCI_ACS_DT);
-
 		return pci_acs_flags_enabled(pdev, acs_flags);
 	}