xen: initialize legacy backends from xen_bus_init()

Prepare for moving the calls to xen_be_register() under the
control of xen_bus_init(), using the normal xen_backend_init()
method that is used by the "modern" backends.

This requires the xenstore global variable to be initialized,
which is done by xen_be_init().  To ensure that everything is
ready at the time the xen_backend_init() functions are called,
remove the xen_be_init() function from all the boards and
place it directly in xen_bus_init().

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240509170044.190795-7-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/i386/pc.c

@@ -1250,7 +1250,6 @@ void pc_basic_device_init(struct PCMachineState *pcms,
             pci_create_simple(pcms->pcibus, -1, "xen-platform");
         }
         xen_bus_init();
-        xen_be_init();
     }
 #endif
 

hw/xen/xen-bus.c

@@ -13,6 +13,7 @@
 #include "hw/sysbus.h"
 #include "hw/xen/xen.h"
 #include "hw/xen/xen-backend.h"
+#include "hw/xen/xen-legacy-backend.h" /* xen_be_init() */
 #include "hw/xen/xen-bus.h"
 #include "hw/xen/xen-bus-helper.h"
 #include "monitor/monitor.h"
@@ -329,6 +330,9 @@ static void xen_bus_realize(BusState *bus, Error **errp)
         goto fail;
     }
 
+    /* Initialize legacy backend core & drivers */
+    xen_be_init();
+
     if (xs_node_scanf(xenbus->xsh, XBT_NULL, "", /* domain root node */
                       "domid", NULL, "%u", &domid) == 1) {
         xenbus->backend_id = domid;

hw/xen/xen-hvm-common.c

@@ -872,8 +872,6 @@ void xen_register_ioreq(XenIOState *state, unsigned int max_cpus,
 
     xen_bus_init();
 
-    xen_be_init();
-
     return;
 
 err:

hw/xenpv/xen_machine_pv.c

@@ -34,8 +34,7 @@ static void xen_init_pv(MachineState *machine)
 {
     setup_xen_backend_ops();
 
-    /* Initialize backend core & drivers */
-    xen_be_init();
+    xen_bus_init();
 
     switch (xen_mode) {
     case XEN_ATTACH:
@@ -60,8 +59,6 @@ static void xen_init_pv(MachineState *machine)
         vga_interface_created = true;
     }
 
-    xen_bus_init();
-
     /* config cleanup hook */
     atexit(xen_config_cleanup);
 }