bootindex: add check bootindex function

Determine whether a given bootindex exists or not.
If exists, we report an error.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

bootdevice.c

@@ -36,6 +36,21 @@ struct FWBootEntry {
 static QTAILQ_HEAD(, FWBootEntry) fw_boot_order =
     QTAILQ_HEAD_INITIALIZER(fw_boot_order);
 
+void check_boot_index(int32_t bootindex, Error **errp)
+{
+    FWBootEntry *i;
+
+    if (bootindex >= 0) {
+        QTAILQ_FOREACH(i, &fw_boot_order, link) {
+            if (i->bootindex == bootindex) {
+                error_setg(errp, "The bootindex %d has already been used",
+                           bootindex);
+                return;
+            }
+        }
+    }
+}
+
 void add_boot_device_path(int32_t bootindex, DeviceState *dev,
                           const char *suffix)
 {

include/sysemu/sysemu.h

@@ -213,6 +213,7 @@ void add_boot_device_path(int32_t bootindex, DeviceState *dev,
 char *get_boot_devices_list(size_t *size, bool ignore_suffixes);
 
 DeviceState *get_boot_device(uint32_t position);
+void check_boot_index(int32_t bootindex, Error **errp);
 
 QemuOpts *qemu_get_machine_opts(void);