[RFC,V3,03/12] xen: Introduce --enable-xen command options.

diff --git a/Makefile.target b/Makefile.target
index f112e66..1984f58 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -2,6 +2,7 @@ 
 
 GENERATED_HEADERS = config-target.h
 CONFIG_NO_KVM = $(if $(subst n,,$(CONFIG_KVM)),n,y)
+CONFIG_NO_XEN = $(if $(subst n,,$(CONFIG_XEN)),n,y)
 
 include ../config-host.mak
 include config-devices.mak
@@ -182,6 +183,8 @@  QEMU_CFLAGS += $(VNC_PNG_CFLAGS)
 
 # xen backend driver support
 obj-$(CONFIG_XEN) += xen_machine_pv.o xen_domainbuild.o
+obj-$(CONFIG_XEN) += xen-all.o
+obj-$(CONFIG_NO_XEN) += xen-stub.o
 
 # xen full virtualized machine
 obj-$(CONFIG_XEN) += xen_machine_fv.o
diff --git a/hw/xen.h b/hw/xen.h
index 780dcf7..14bbb6e 100644
--- a/hw/xen.h
+++ b/hw/xen.h
@@ -18,4 +18,14 @@  enum xen_mode {
 extern uint32_t xen_domid;
 extern enum xen_mode xen_mode;
 
+extern int xen_allowed;
+
+#if defined CONFIG_XEN
+#define xen_enabled() (xen_allowed)
+#else
+#define xen_enabled() (0)
+#endif
+
+int xen_init(int smp_cpus);
+
 #endif /* QEMU_HW_XEN_H */
diff --git a/qemu-options.hx b/qemu-options.hx
index a0b5ae9..457ca32 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1904,6 +1904,15 @@  Enable KVM full virtualization support. This option is only available
 if KVM support is enabled when compiling.
 ETEXI
 
+DEF("enable-xen", 0, QEMU_OPTION_enable_xen, \
+    "-enable-xen     enable Xen full virtualization support\n", QEMU_ARCH_ALL)
+STEXI
+@item -enable-xen
+@findex -enable-xen
+Enable Xen full virtualization support. This option is only available
+if Xen support is enabled when compiling.
+ETEXI
+
 DEF("xen-domid", HAS_ARG, QEMU_OPTION_xen_domid,
     "-xen-domid id   specify xen guest domain id\n", QEMU_ARCH_ALL)
 DEF("xen-create", 0, QEMU_OPTION_xen_create,
diff --git a/vl.c b/vl.c
index 3f45aa9..6948703 100644
--- a/vl.c
+++ b/vl.c
@@ -243,6 +243,7 @@  static NotifierList exit_notifiers =
     NOTIFIER_LIST_INITIALIZER(exit_notifiers);
 
 int kvm_allowed = 0;
+int xen_allowed = 0;
 uint32_t xen_domid;
 enum xen_mode xen_mode = XEN_EMULATE;
 
@@ -2448,6 +2449,9 @@  int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_enable_kvm:
                 kvm_allowed = 1;
                 break;
+            case QEMU_OPTION_enable_xen:
+                xen_allowed = 1;
+                break;
             case QEMU_OPTION_usb:
                 usb_enabled = 1;
                 break;
@@ -2756,6 +2760,18 @@  int main(int argc, char **argv, char **envp)
         }
     }
 
+    if (xen_allowed) {
+        int ret = xen_init(smp_cpus);
+        if (ret < 0) {
+            if (!xen_available()) {
+                printf("Xen not supported for this target\n");
+            } else {
+                fprintf(stderr, "failed to initialize Xen: %s\n", strerror(-ret));
+            }
+            exit(1);
+        }
+    }
+
     if (qemu_init_main_loop()) {
         fprintf(stderr, "qemu_init_main_loop failed\n");
         exit(1);
diff --git a/xen-all.c b/xen-all.c
new file mode 100644
index 0000000..f505563
--- /dev/null
+++ b/xen-all.c
@@ -0,0 +1,25 @@ 
+/*
+ * Copyright (C) 2010       Citrix Ltd.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "config.h"
+
+#include "hw/xen_common.h"
+#include "hw/xen_backend.h"
+
+/* Initialise Xen */
+
+int xen_init(int smp_cpus)
+{
+    xen_xc = xc_interface_open(NULL, NULL, 0);
+    if (xen_xc == NULL) {
+        xen_be_printf(NULL, 0, "can't open xen interface\n");
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/xen-stub.c b/xen-stub.c
new file mode 100644
index 0000000..0fa9c51
--- /dev/null
+++ b/xen-stub.c
@@ -0,0 +1,17 @@ 
+/*
+ * Copyright (C) 2010       Citrix Ltd.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "config.h"
+
+#include "qemu-common.h"
+#include "hw/xen.h"
+
+int xen_init(int smp_cpus)
+{
+    return -ENOSYS;
+}