diff --git a/src/config/cloud/ioapi.h b/src/config/cloud/ioapi.h
index bcd245981..3ab05082f 100644
--- a/src/config/cloud/ioapi.h
+++ b/src/config/cloud/ioapi.h
@@ -8,3 +8,13 @@
 #define PCIAPI_RUNTIME_PCBIOS
 #define PCIAPI_RUNTIME_DIRECT
 #endif
+
+/* Work around missing PCI host bridge drivers in the cut-down UEFI found
+ * in some AWS EC2 instances.
+ */
+#ifdef PLATFORM_efi
+#undef PCIAPI_EFI
+#define PCIAPI_CLOUD
+#define PCIAPI_RUNTIME_EFI
+#define PCIAPI_RUNTIME_ECAM
+#endif
diff --git a/src/config/config_pci.c b/src/config/config_pci.c
index 8ed9f6603..b2adae995 100644
--- a/src/config/config_pci.c
+++ b/src/config/config_pci.c
@@ -45,3 +45,6 @@ REQUIRE_OBJECT ( pcibios );
 #ifdef PCIAPI_RUNTIME_DIRECT
 REQUIRE_OBJECT ( pcidirect );
 #endif
+#ifdef PCIAPI_RUNTIME_EFI
+REQUIRE_OBJECT ( efi_pci );
+#endif
diff --git a/src/include/ipxe/pci_io.h b/src/include/ipxe/pci_io.h
index 0d32adf81..7ac09efb0 100644
--- a/src/include/ipxe/pci_io.h
+++ b/src/include/ipxe/pci_io.h
@@ -192,9 +192,10 @@ struct pci_api {
 #endif
 
 /* PCI runtime selectable API priorities */
-#define PCIAPI_PRIORITY_ECAM	01	/**< ACPI ECAM */
-#define PCIAPI_PRIORITY_PCBIOS	02	/**< PCI BIOS calls */
-#define PCIAPI_PRIORITY_DIRECT	03	/**< Direct Type 1 accesses */
+#define PCIAPI_PRIORITY_EFI	01	/**< EFI PCI I/O protocols */
+#define PCIAPI_PRIORITY_ECAM	02	/**< ACPI ECAM */
+#define PCIAPI_PRIORITY_PCBIOS	03	/**< PCI BIOS calls */
+#define PCIAPI_PRIORITY_DIRECT	04	/**< Direct Type 1 accesses */
 
 /** Provide a runtime selectable PCI I/O API */
 #define PROVIDE_PCIAPI_RUNTIME( subsys, priority )			   \
diff --git a/src/interface/efi/efi_pci.c b/src/interface/efi/efi_pci.c
index fbf06300b..f4853c234 100644
--- a/src/interface/efi/efi_pci.c
+++ b/src/interface/efi/efi_pci.c
@@ -436,6 +436,7 @@ PROVIDE_PCIAPI_INLINE ( efi, pci_write_config_byte );
 PROVIDE_PCIAPI_INLINE ( efi, pci_write_config_word );
 PROVIDE_PCIAPI_INLINE ( efi, pci_write_config_dword );
 PROVIDE_PCIAPI ( efi, pci_ioremap, efipci_ioremap );
+PROVIDE_PCIAPI_RUNTIME ( efi, PCIAPI_PRIORITY_EFI );
 
 /******************************************************************************
  *