Replace -no-virtio-balloon by -balloon

We want to do (at least) two things to the virtio-balloon device:
suppress it, and control its PCI address.  Option -no-virtio-balloon
lets us do only the former.  To get the latter, replace
-no-virtio-balloon with

    -balloon none   disable balloon device
    -balloon virtio[,addr=str]
                    enable virtio balloon device (default)

Syntax suggested by Anthony Liguori.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index 9d1fe87..7b7489c 100644
--- a/vl.c
+++ b/vl.c
@@ -242,7 +242,8 @@
 const char *vnc_display;
 int acpi_enabled = 1;
 int no_hpet = 0;
-int no_virtio_balloon = 0;
+int virtio_balloon = 1;
+const char *virtio_balloon_devaddr;
 int fd_bootchk = 1;
 int no_reboot = 0;
 int no_shutdown = 0;
@@ -4762,6 +4763,29 @@
     }
 }
 
+#ifdef TARGET_I386
+static int balloon_parse(const char *arg)
+{
+    char buf[128];
+    const char *p;
+
+    if (!strcmp(arg, "none")) {
+        virtio_balloon = 0;
+    } else if (!strncmp(arg, "virtio", 6)) {
+        virtio_balloon = 1;
+        if (arg[6] == ',')  {
+            p = arg + 7;
+            if (get_param_value(buf, sizeof(buf), "addr", p)) {
+                virtio_balloon_devaddr = strdup(buf);
+            }
+        }
+    } else {
+        return -1;
+    }
+    return 0;
+}
+#endif
+
 #ifdef _WIN32
 static BOOL WINAPI qemu_ctrl_handler(DWORD type)
 {
@@ -5578,8 +5602,11 @@
             case QEMU_OPTION_no_hpet:
                 no_hpet = 1;
                 break;
-            case QEMU_OPTION_no_virtio_balloon:
-                no_virtio_balloon = 1;
+            case QEMU_OPTION_balloon:
+                if (balloon_parse(optarg) < 0) {
+                    fprintf(stderr, "Unknown -balloon argument %s\n", optarg);
+                    exit(1);
+                }
                 break;
 #endif
             case QEMU_OPTION_no_reboot: