include/hw/xen/xen_common: return error from xen_create_ioreq_server

This is done to prepare for enabling xenpv support for ARM architecture.
On ARM it is possible to have a functioning xenpv machine with only the
PV backends and no IOREQ server. If the IOREQ server creation fails,
continue to the PV backends initialization.

Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Paul Durrant <paul@xen.org>

include/hw/xen/xen_native.h

@@ -463,21 +463,23 @@ static inline void xen_unmap_pcidev(domid_t dom,
                                                   PCI_FUNC(pci_dev->devfn));
 }
 
-static inline void xen_create_ioreq_server(domid_t dom,
-                                           ioservid_t *ioservid)
+static inline int xen_create_ioreq_server(domid_t dom,
+                                          ioservid_t *ioservid)
 {
     int rc = xendevicemodel_create_ioreq_server(xen_dmod, dom,
                                                 HVM_IOREQSRV_BUFIOREQ_ATOMIC,
                                                 ioservid);
 
     if (rc == 0) {
         trace_xen_ioreq_server_create(*ioservid);
-        return;
+        return rc;
     }
 
     *ioservid = 0;
     use_default_ioreq_server = true;
     trace_xen_default_ioreq_server();
+
+    return rc;
 }
 
 static inline void xen_destroy_ioreq_server(domid_t dom,